Contributions to economic geology (short papers and preliminary reports) 1920

Ransome, F. L · 1921 · Historical

Contributions to economic geology (short papers and preliminary reports) 1920 by Ransome, F. L (1921). Full text and reference in the Mountain Man Mining…

Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.

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Contents.

[The letters in parentheses preceding the titles are those used to designate the liMipers for

advance publication.]

Page.

iDtroductioD vn

(A) Potash deposits in Spain, by H. S. Gale (published June 5, 1920).. 1

(B) The potash deposits of Alsace, by H. S. Gale (published June 5,

1920) 17

(C) A deposit of manganese ore in Wyoming, by E. L. Jones, Jr. (pub-

lished Sept. 18, 1920)-. 57

(D) Some deposits of manganese ore in Colorado, by E. L. Jones, Jr.

(published Sept. 17, 1920) 61

(E) Geology of the Yellow Pine cinnabar-mining district, Idaho, by E. S.

Larsen and D. C. Livingston (published Sept. 15, 1920) 73

(F) Deposits of iron ore near Stanford, Mont., by L. G. Westgate (pub-

lished Sept. 16, 1920) . 85

(G) Preliminary report on the deposits of manganese ore in the Bates-

ville district. Ark., by H. D. Miser (published Nov. 15, 1920) 93

(H) Omitted.

(I) Potash resources of Nebraska, by W. B. Hicks (published Feb. 8,

1920. ) 125

(J) Phosphate rock near MaxviUe, Granite County, Mont, by J. T. Pardee

(published Feb. 7, 1921) 141

(K) The Divide silver district, Nev., by Adolph Knopf (published Feb.

12, 1921) 147

(L) The Mogollon district, N. Mex.,*by H. G. Ferguson (published Feb.

8, 1921 ) 171

(M) Permian salt deposits of the south-central United States, by N. H.

I>arton (published April 28, 1921) . 205

Index 225

Illustrations.

Page. Platk I. A, Ootcrop of rock salt by the roadside at the foot of the bluff

helow the old castle, Cardona, Spain; B, The salt moun- tain at Cardona, Spain, from the castle, overlooking the

salt basin 4

II. Af Outcrop of tilted sandstones and gypsum overlying the light- colored shale and salt beds, as exposed in the bluff below the old castle at Cardona, Spain ; B, Contorted bedding of the salt in the cliffs at the head of the salt basin, Cardona, Spain ' 6

ni

Iv Illustrations.

Page.

Plate III. The Monserrat escarpment near Manresa, Spain 12

IV. A, Storage and refinery buildings at Am<lie shaft 1, Wlttels- heim, Alsace; B, Shaft house and head frame at Am61ie

shaft 1 30

V. Af Max mine, near Wittelsheim, Alsace; B, Reichsland mine,

Wittenheim, Alsace : 34

VI. Geologic map of the Batesville district, Ark 04

VII. Generalized lections of the Paleozoic rocks of the Batesville

district, Ark 98

VIII. Section through the Lassiter, Polk Southard, and Blue Ridge mines, Batesville district, Ark., illustrating the occurrence

of their manganese-ore deposits 100

IX-XII. Omitted.

XIII. Map and section of the northern part of the Phllipsburg phos- phate field, Mont- 142

XIV. Geologic map of the Divide district, Nev . 150

XV. Geologic map of the Mogollon district, Socorro County, N.

Mex. 174

XVI. Geologic sections across the Mogollon district, N. Mex 184

XVII. Map showing outcrops of faults in Mogollon district, N. 184 XVIII. Sections showing assumed position of surface In Mogollon

district, N. Mex., after faulting 194

XIX. Vertical projection of Little Fanney mine, Mogollon district,

N. Mex 198

XX. Vertical projection of Last Chance and Confidence mines,

Mogollon district, N. Mex 202

XXI. Map of salt basin in Texas, New Mexico, Oklahoma, and

Kansas 206

XXII. Sections across the salt deposits of central Kansas 208

XXIII. Records of deep borings in southern Kansas and northwest-

ern Oklahoma 210

XXIV. Records of borings in Woods and Alfalfa counties, Okla 212

FiousE 1. Index map of Spain showing the situation of the potash de- posits of Catalonia 2

2. Sketch map of the " salina de Cardona," Spain 6

3. Map of the northeastern part of Spain, with geology general-

ized from the Carte glogique Internationale de TEurope— 12

4. Map showing potash field and valley of the Rhine in the

vicinity of Mulhouse, Alsace 18

5. Diagram representing lower potash bed in Amlie shaft 1,

Wlttelshelm, Alsace 31

6. Claim map of cinnabar camp in Yellow Pine mining district.

Valley County, Idaho 74

7. Reconnaissance geologic sketch map of Yellow Pine cinnabar

district, Valley County, Idaho 78

8. Map of a part of north-central Montana showing the location

of the hematite deposits near Stanford 85

9. Geologic map of the vicinity of the hematite deposits near

Stanford, Mont 86

10. Map showing claims on the hematite deposits near Stanford,

Mont 88

11. Section of the ore body on the Snowbird claim, near Stan-

ford, Mont 90

Illustrations. V

FiouRB 12. Index map of Arkansas sbowlng the location of tbe Bates-

ville manganese-ore district 98

13. Section near the central part of the Cason mine, Batesville

district. Ark . 103

14. Sketch section at the Club House mine, Batesville district,

Ark 113

15. Section through the Searcy mine, Batesville district, Ark 114

ie-25. Omitted.

26. Map showing potash-lake district in western Nebraska 128

2T. Index map showing location of Pbilipsburg phosphate field,

Mont 141

Generalized columnar section of the rocks of the Divide dis- trict. Nev 147

Map of southwestern New Mexico showing the location of

the Mogollon district 171

30. Transverse sections across Fanney vein, Mogollon district, N. Mex 1&7

31. Record of boring at McPherson, Kans 208

32. Records of borings in central Kansas 209

33. Records of borings in south -central Kansas 211

34. Records of deep borings in northwestern Texas 215

35. Record of boring at Childress, Tex 217

36. Record of boring near Shamrock, Tex 217

37- Record of Hapgood boring, 28 miles north of AmariUo, Tex— 218

38. Section across southeastern New Mexico from the Sacramento Mountains through Carlsbad 220

39. Record of boring 8 miles east of Carlsbad, N. Mex 221

40. Record of boring 13 miles north-northeast of Roswell, N. Mex. 222

Contributions to Economic Geology, 1920,

Part I. METALS AND NONMETALS EXCEPT FUELS.

F. L. Baksome, H. S. Gale, and E. F. Burchard, Oeologists in charge.

Introduction.

The Survey's Contributions to economic geology " have been pub- lished annually since 1902. In 1906 the increase in the number of papers coming imder this classification made it necessary to divide the contributions into two parts, oiie iiicluding papers on metals and nonmetals except fuels and the other including papers on mineral fuels. In 1915 the year included in the title was changed from the year in which the field work reported in these papers was done to the year of publication, and in consequence there was no volume entitled " Contributions to economic geology, 1914." The subjoined table gives a summary of these bulletins.

United Staten Geological Survey " Contributions to economic gedtogyy

Date in title.

19Q2

I9M

190ft Put I.

Faitn

1907, Parti.

Partn I9Q8y Parti.

Partn

1909, Parti. Partn

1910, Part I. Partn

1911, Parti. Partn

Dateol

publica-

tion.a

Bulletin No.

19M

DateintlUe.

1912, Part I. PartH

1913, Parti. Part II

1915, Part I. Partn

1916, Part I. Part II

1917, Parti. Partn

1918, Parti. Partn

1919, Parti. Partn

1020, Part I. Partn

Date of

publi(-

tioa.a

BnUetlll No.

no ni

file date given ia that of the complete volame; beginning with Bulletin 285, the papers have been advance chaptefs aa soon as tney were ready.

As the subtitle indicates, most of the papers in these volumes are of three classes — (1) short papers describing as thoroughlv as con- ditions will permit areas or deposits oA which no other report is likely

vn

Vm INTRODUCTION,

to be prepared; (2) brief notes on mining: districts or economic de- posits whose examination has been merely incidental to other work; and (3) preliminary reports on economic investigations the results of which are to be published later in more detailed form.

Although these papers set forth mainly the practical results of economic investigations they include brief theoretical discussions and summary statements of conclusions if these appear to require prompt publication.

Beginning in the spring of 1917 and continuing throughout the period of the war the United States Geological Survey made special field explorations, surveys, and laboratory studies of deposits of ores of metals used in the manufacture of ferroalloys, pig iron, and steel, including manganese, chromium, tungsten, molybdenum, titanium, uranium, vanadium, zirconium, and iron.

Summaries of the data were promptly published by the Geological Survey in the form of press bulletins, and several longer papers on these subjects were published in Survey Bulletin 710* and in the Transactions of the American Institute of Mining and Metallurgical Engineers.* Other papers prepared largely by Federal Survey geolo- gists have been published by several State surveys." The papers on manganese and iron ore in this bulletin are some of the results of this war work, and other papers, now in preparation, will be pub- lished in " Contributions to economic geology, 1921."

Jonefly E. It,, Jr., A reconnalBsanoe of thQ Pine Creek district, Idaho : U. S. Geol. Sur- vey Bull. 710, pp. 1--36, 1910 ; Deposits of manganese ore in New Mexico : Idem, pp. 37-60 ; Deposits of manganese ore in southeastern California : Idem, pp. 185-208. Sears, J. D., Deposits of manganese ore in Costa Rica : Idem, pp. 61-84 ; Deposits of manganese ore near Boqueron River, Panama : Idem, pp. 85-92. Jones, E. L., Jr., and Ransome, F. L., Deposits of manganese ore in Arisona: Idem, pp. 93-184. Pardee, J. T., and Jones, B. U, Jr., Deposits of manganese ore in Nevada : Idem, pp. 200-242.

Harder, B. C, and Hewett, D. F., Recent stndies of domestic manganese deposits : Am. Inst Min. and Met. Eng. Trans., September, 1019, 48 pp. Diller, J. 8., Recent studies of domestic chromite deposits : Idem, 44 pp. Burchard, E. F., Manganese-ore de- posits in Culm : Idem, 62 pp. Burchard, E. F., Chrome-ore deposits in Cuba : Idem, 23 pp.

Stose, O. W., and Schrader, C, Manganese deposits of east Tennessee : Resources of Tennessee, vol. 8, Nos. 3 and 4, 631 pp., Tennessee State Geol. Survey, 1919. Stose, G. W., Miser, H. D., Kata, F. J., and Hewett, D. F., Manganese deposits of the west foot of the Blue Ridge, Va. : Virginia Geol. Survey Bull. 17, 166 pp., 1919. Hull, J. P. D., LaForge, Laurence, and Crane, W. R., Manganese deposits of Georgia : Georgia Geol. Sur- vey Bull. 85, 295 pp., 1919.

.

Potash Deposits In Spain.

By HoYT S. Gale.

Introduction.

The announcement of the discovery of potash in deposits in the Province of Barcelona, in Catalonia, in the northeast comer of Spain, appeared in print in 1913 with the publication of the first of two excellent reports on the subject by engineers of the Instituto geol6gico de Espana. There has been much discussion of the salt deposits of the region, which have long attracted attention as show- ing very remarkable features, and the series of publications concern- ing them includes papers by Trail in 1814, Cordier in 1817, Duf rfinoy in 1831, Toschi in 1845, and numerous others in a series reaching down to the present time. The potash associated with these salt de- posits was recognized in 1912, and then only by accident as a result of development to enlarge the production of salt.

Location And Access.

The Spanish potash field, as now defined, lies north to northwest of Barcelona, in an area extending approximately from east to west between the towns of Vich and Balaguer. The area thus defined is about 75 miles long, and the claims or concessions, though of irregu- lar shape, form a practically continuous belt with a maximum width between Manresa and Cardona of about 15 to 18 miles. The general situation of the field is represented on the accompanying index map

The principal discoveries of potash have been made in the im- mediate vicinity of the villages of Cardona and Suria. These places are 40 to 45 miles in a direct line northwest of Barcelona. One of the two main lines of railway between Barcelona and Zaragoza, which are the direct routes between Barcelona and Madrid, is the Ferrocarril del Norte, which skirts the southern border of the potash field. This line runs northward from Barcelona through Sabadell

>Bublo, Csap, and Martn, AgustTn, Sales potfisicas en CataluBa : Inst. geol. Hspafia BoL, r€h a4, pp. 178-280, 1913 ; Sales pot&sicas de Catalufia : Idem, vol, 39, pp, 1-38.

2 Contributions To Economic Geology, 1930, Part I.

and Tarrasa to Manresa, all impoi:ti!nt cotton-weaving and manu- facturing communities. At/JM&\nresa the railway turns west, passing through Lerida. Both'ar3mia and Suria, where the potash has been found, lie in .tlife' Valley of Cardoner River and jar© reached by motor omnibus/6r* ldiligence " over an ordinary country road fol- lowing tlje rivek'* Manresa is 40 miles by rail from Barcelona, and train, aeipyice* is frequent and fairly satisfactory. Suria is 9 miles aiid'Cai'dona about 20 miles north of Manresa. A branch railway is

FiQUBB 1. — Index nuip of Spain 8howln£r the situation of tlie potaah deposits of Catalonia.

now under construction from Manresa to Suria, put in primarily on account of the potash developments now going on at Suria.

There is a comfortable hotel of the local country type at Manresa, and a similar smaller one at Cardona. In 1919 automobiles were to be hired at Manresa for 1.25 to 1.50 pesetas a kilometer, which is equivalent to about 40 cents or more in United States money for each mile traveled, no account being taken of the time required for stops if these are not considered out of proportion to the length of the trip. Boads through the country are passable for automobiles, but that is about as far as a recommendation can go.

Potash Deposits Ut Spain. 8

Ownership.

A large area of concessions has already been ceded to private claimants by the Spanish Government, After the first rush to ap- propriate these mineral lands restriction was put on the granting of further rights. A tract reserved by the State is defined as that in- cluded by straight boundaries joining the towns of Vich, Berga, Isona, Balaguer, Tarrega, Igualada, and Manresa. This includes a total area of about 1,800 square miles. Much of this tract is undoubt- edly not potash bearing, but it includes in a general way the forma- tions similar to those containing the salts at Cardona and Suria and is a provisionally outlined field reserved for further exploration. An area of 350 to 400 square miles is outlined in the map of concessions already granted. Private interests or foreign governments are in- vited to participate in the development or operation of the field, under specific regulations of the State and local governments as to manner and regularity of operation and the price and distribution of the product. This phase of the subject is discussed more at length in the section entitled "Spanish legislation" (p. 15).

The principal owners of concessions in the Spanish potash field are as follows:

Solyay & Cie., 33 Rne du Prince Albert, Brussels, Belgium. This is the well- known Franco-Belgian syndicate which already operates in Spain in the sub- Rldlary soda works at Santa nder. The local representatives of the potash prop- erties are EMdoro 6. Lef&vre, Belgian consul at Barcelona, and Luis Dupont, local director of the property at Suria.

La Sociedad Fodlna, which has engaged in exploring concessions ceded to Francisco Ripoll and Ignaclo Marlnello, of Barcelona. Tliis concern is under- stood to be a subsidiary of or closely allied to the Sociedad Electro-Qulnilca de FUx, Galle de la Princesa 21, Barcelona. The last-named company is listed as a manufacturer of caustic and industrial chemical products, presumably fer- tilizer materials, and is said to have strong German affiliations.

Ia Sociedad General de Industrla y Comerclo, a Spanish and French company, with headquarters at VlUanueva 11, Madrid. This company is engaged In the manufacture of fertilizers, explosives, and other chemical prod- ucts, and has plants at Balboa, Barcelona, and in other parts of Spain.

Ia Gompafifa de la Sallna de Cardona is the old snit company that has been mining and shipping rock salt for many years from the celebrated salt mountain of Cardona. The property belongs to the Duque de Tarlfa. The local admlnls- trador is Juan Ratera Cendra, at Cardona.

La Miners, a German organization, is reported to be a subsidiary of one of the potash companies in Germany and therefore allied to the German Kali- syndikat. La Minera controls an extensive area of concessions In various parts of the Spanish field.

The American Agricultural Chemical Co., 92 State Street, Boston, Mass., holds concessions in the name of Roberto Sturz Bradley. Two properties called the Flladelfia and the Boston cover territory adjacent io or Intermediate be- tween areas in which the recorded discoveries of potash salts have been made.

4 Contributions To Economic Geology, 1930, Part I.

Besides those Darned above there are other less extensive holdings, listed under the names of Juan Valves, Ren Pnulus, and Demetrlo Castellana Moreno, and there are also some concessions originally held for coal that may Include potash.

A quotation from a royal order of December 14, 1918,* gives a list of concessionaires containing only three names, one of which is not included in the foregoing record, as follows :

Solvay & Cle., Mlnas de Suria, Santander, Si)ain. Sociedad Andnima Fodina, Laurla 21, Barcelona. Spain. Sociedad Andnima La Sevillana, Trafalgar 11, Barcelona, Spain.

It is not clear whether this is a revision or curtailment of the lidt of concessionaires or whether the quotation referred to is incomplete.

The Salt Mountain At Cardona.

'La montaiia de sal de Cardona," described by Calder6n' as a veritable mountain of salt 80 meters high and 4 kilometers in cir- cumference, has been one of the renowned natural features of Cata- lonia since a very early date. (See PI. I, B.) Baedeker says that this phenomenon is mentioned by Strabo, quoting a reference to Book III of his geographic works, which the writer has not been able to verify. The occurrence of mineral salt in Turdetania is men- tioned by Strabo also, but this is the region about Cordoba and Cadiz. The mining of salt from the Cardona deposit is a very old industry and is still carried on, both for local consumption and for export. The title to this property is apparently a local hereditary right, hav- ing recently passed from the Duque de Medinacelli to the Duque de Tarifa.

Cardona (judicial district of Berga, Province of Barcelona) is an old fortified town perched on the summit of an almost isolated hill in a bend of Cardoner River, 600 feet above the river level. The town is surrounded by a wall and dominated at the very summit by an interesting old castle (el Castillo). (See PI. I, The wagon road encircles the base of the hill and climbs the steep north slope, entering the town through a gate. Trails descend the precipitous south slope from a gate in the wall on the south side. In dear weather there is a wonderful view from the old castle, with Cardoner River stretching away in either direction in the foreground, and beyond it, to the north, the distant snow-capped peaks of the Pyre- nees. To the south and southwest the town overlooks, at the very foot of the hill on which it is situated, a peculiar depression, which is the salt basin, the salina de Cardona.' At the farther end of this basin is a great whitish-looking scar lying against the mountain side, and this is the famous mountain of salt. It is a great natural out-

1 Commerce Bepts., Apr. 10, 1919.

2 jg mlnerales de Espana, vol. 1. p. 385, 1910.

. a, (1IOI.O0ICAI. BDRTB* BVL1.BTIN 715 FLATS I

nlliB rinnca aboi brnMtaUa.

iwA Hit, ihs biuia haLui tbe enaralioD by lolutiDB of the nil aiDwd aliHW

Potash Deposits In Spain. 5

crop of rock salt which occurs as an interstratified part of the sedi- mentary rock section. It is brought to the surface along the crest of a distinct anticlinal fold, the structure of which is perfectly evi- dent in the dip and stratification of the series of sandstones and shales which overlie it and whose outcrops encircle the basin in reg- ular form. Smaller exposures of rock salt occur at many places in the bottom or on the lower slopes of the basin. Just at the foot of the hill below the castle is a large funnel-shax)ed sink hole.

The salt is mined in solid form and is sawed or hewn into regular- sized blocks for shipment. The Spanish yearbook (Anuario general de Espana) for 1917 says in reference to Cardona: "It owes its re- nown to its famous mountains of salt, from which there are extracted 40,000 quintals annually." The salt blocks are said to be chiefly ex- ported to Africa, where salt is prized in this form. The industry is limited, however, by the cost of transportation. Salt from this source was supplied to the American x\rmy in France during the re- cent war, and it is said that production was pushed to the capacity of the equipment.

The upper layers of the deposit are a composite of relatively thin . bands of variously colored salts and interstratified layers of gypsum and clay. Red and white are the prevailing colors, but there is much gray and some orange or salmon-yellow. (See p. 8.) These upper layers appear in a strangely contorted mass. Under them there is a great compact mass of white transparent salt which is very pure. The salt mined is obtained from the lower layers. According to report, the mining was formerly done in a large open pit, the salt being cut in steps or terraces, but now it is obtained by underground mining. These workings now have a depth of 50 meters, and the whole depth, it is claimed, is cut in solid salt without the intercala- tion of any other substance.

The accompanying sketch map (fig. 2) was prepared by the writer from a pocket-compass traverse made at the time of his visit. It shows the general outline of the outcrop of the salt and the situation of the basin with respect to the valley of Cardoner River and the town of Cardona.

The salt basin is the eroded axis of a well-defined anticline. Apparently the massive rock salt is the lowest member of the sec- tion exposed by erosion and solution along the axis of this fold. The center of the valley is to a considerable extent covered by detritus of red clay, but the salt shows at the surface in many places. The topographic basin thus formed is almost surrounded by rugged walls exhibiting the dark-red sandstone ledges, which dip outward in all directions from the axis. At the east end the valley opens by a relatively narrow gap into the valley of the Cardoner, which is almost a gorge at this place. The axis of the fold apparently

6 Contributions To Economic Geology, 1920, Part I.

plunges here, but the outcrop of the salts clearly has been inter- sected by the river channel, where the salt has of course been dis- solved away. Singularly, however, the salt is exposed in masve ledges at the base of the hill below the castle, just above the level of the river. The Cardoner is a full-flowing stream of fresh water, and the region is very far from having the appearance of a desert. The river derives its water mainly from the higher mountains to the north, and the rainfall in this particular region must be slight, or so much salt would not be preserved at the surface. A small

FiouEiB 2.— Kkctcli map of the " ullna de Cardona," Si1a.

stream, which is a saturated solution of salts, flows from the salt outcrops down through the salt basin and enters Cardoner River.

The view in Plate II, A, shows the outcrops of salt and the over- lying shales, gypsum, and sandstone in the bluff at the base of the hill below the castle, at the outlet to the salt basin.

The stratigraphic section exposed in the bluff below the castle is represented in the cross section attached to the sketch map of the salt basin. This section apparently represents at least those mem- bers numlwrocl 4 to 8, inclusive, of the general section given on pnge 13. By rough computation from the data obtained in making the sketch map, the section exposed here totals about 1,800 feet of

I. QMOtMaiCM, 8URVET BCLLKTIN 715

J. OUTCROP OF TILTED SANDSTONES OVERLYING THE LIGHT-COLORED SHALE AND SALT BEDS, AS EXPOSED IN THE BLUFF BELOW THE OLD CASTLE AT CARDONA. SPAIN.

fsw from the tna on lent with tlia lonr put cf town Jut oaulda Uw walh (Mo.

T The Head Of The

Potash Deposits In Spain. 7

stratigraphic thickness, but the thickness can be obtained very much more accurately with more careful measurements.

Little seems to be known about the total thickness of the salt beds. The cliff at the head of the salt basin is made up of banded salts in a strangely contorted mass. The convolutions of the bedding of the salt are exhibited by distinct color banding of the salt layers and by the interlaminated seams of clay and gypsum, so that in parts of the mass the display is very fantastic. This contortion illustrates the plasticity of salt under such compression as has been exerted on it in the folding of these rocks. No estimate of the normal thickness of the whole could be obtained from such a mass. Such folding is probably extreme in the axis of the fold and possibly would not ex- tend far on either flank of the simple anticline. The sandstones and interbedded shales that overlie the salt appear to be quite normal and regular at either side of the valley.

Plate II, 5, is a view of the contorted bedding in the salt cliffs at the head of the salt basin. It also shows farther in the distance the profile of the slope bordering the south side of the basin, with the salt and soft shale below the cap of the more resistant sandstones above.

The evidence of the existence of potash in the Cardona deposit is not very definite. This may be because of lack of adequate investi- gation at this locality or the potash may not be present in large amount in this part of the field. As has been said, this exposure gives one of the most favorable opportunities in the field for observation of the general relations of the salt and the overlying beds. It is an epitome of the Spanish field, whether the potash is found in commer- cial quantity at this locality or not.

Rubio, in his report already referred to, quotes some analyses of samples from both red and white specimens from the Cardona de- posit, which shows the existence of very pure chloride of potassium at this locality. He states, however, that these were found only in a small area, and it was said locally that the potash. had so far been found only in very thin seams in this deposit. Analysis of the salts in solution in the little brine stream that flows from the big salt cliff is stated to have shown 81.65 grams of potassium chloride per liter of the solution. This seems to be saturation with respect to potassium chloride, but in any solution this depends on the amount and nature of the other salts present, particularly magnesium chloride, the amount of which is not stated in this analysis. The amount of the potash indicated is high in any case. Samples of the rusty-red and white banded salts (B in the following table) collected by the writer have given no significant test for potash, and the same is true of a sample of a clear granular salmon-colored salt (A in the fo lowing table) which is conspicuous in the outcroj)S.

Contributions To Economkj Gkology, 1920, Part I.

CMni>08itv)n of two samples from upper colored part of the salt depasit at

Cardona.

(Collected by Hoyt S. Gale; analyzed by E. Theodore Erirkson.]

Detenninalloiui.

CalcaUted Mlta.

A.

B.

A.

B.

K

KCl

Na

NaCl

Co

MrCIs

Mg

NaiSOf

CaSOf

So4

Undetermined (moisture and in- soluble matter).

Undetermined (moisture and in- soluble matter).

These samples are therefore without special significance of posi- tive value. They show that some of the red and white banded salts so conspicuous in the deposit at Cardona and some of the clear salmon-colored bands are essentially sodium chloride, the red and white salts carrying a little gypsum and insoluble matter.

The value and workability of the potash beds in the Cardona region are therefore still problematic, but there is an excellent pros- pect at this locality that seems worthy of exploration.

Potash Prospects At Suria.

The discovery of potash in the Spanish field was first made at Suria in 1912, by accident. In attempting to open a mine for com- mon salt, at a site where there had been some ancient salt workings, Macary & Viader sunk some borings and a shaft that revealed the potash salts, and it appears that these were very shortly recognized as potash. An investigation carried out in 1913-14 by a French association resulted in the application for and granting of a conces- sion near the village of Suria, which was later enlarged, and con- cessions in other parts of the field were added to it. This group com- bined interest with the Belgian Solvay Co., and the subsequent ex- plorations in the field have been conducted by the Solvay Co., prin- cipally in the immediate vicinity of Suria. The discoveries at Suria, of which there are now available only the records of the old shaft sunk for salt, and the borings sunk on the Solvay Co.'s concessions constitute about the only evidence of the existence of potash in quan- tity in the Spanish field. These holes have been filled and carefully sealed to prevent damage to the deposit by water, and no new evi- dence is to be had from them. The records available have been pub- lished in the reports of Kubio and Marin already referred to. Such records are difficult to interpret correctly, even when all the evidence concerning them is at hand, but there is no doubt that the existence of potash in considerable masses has been demonstrated.

POTASH DEPOSITS IN SPAIlir. 9

The valley of Cardoner River broadens in the vicinity of Suria in a way that is very clearly related to the structural geology. The gentle undulations of the strata bordering the valley below Suria give place to a marked flexure with steeply tilted bedding as the town is approached from the south. Sharp folds and an overthrust fault, the axes of which lie directly in the channel of the river or branch from that channel as a center, have brought the lower part of the Ter- tiary section, including the gypsum and the salts, together with the potash salts, close to the surface. The southern flank of the southern of two anticlines, which is itself a somewhat cross- folded structure, overrides a distinct and regular anticlinal axis to the north. The overthrust on the south is the greater of the two uplifts and would undoubtedly reveal the salt and potash beds in natural outcrops in much the same way as at Cardona, except that at Suria the river has had much more effective access to the axes of these folds and has naturally dissolved and carried off practically all the evidence of the salt at the surface. The broadening of the valley of Cardoner River at Suria, as also of the valley of its little tributary the Rivera de Ter- dell, is the result of the removal of the salts and the soft shales over- lying them through solution and erosion by the river water.

The description of the old shaft sunk for salt and the record that has been published and repeatedly quoted are complete, so far as that evidence goes. This shaft was sunk at the edge of the river- bottom lands, only a few yards above the water level. It is surpris- ing that the strata cut were so impervious that water did not at once filter into the hole, but on the contrary the shaft remained open long enough for the cutting of a cross gallery and the later boring of drill holes to extend the exploration in the bottom and at the end of the gallery. The shaft was subsequently flooded from some unknown cause and has now been filled and sealed.

This working is near an axis of prominent folding of the strata, and it is to be expected that the salts encountered would be found to be extremely contorted, as they are in the axis of the fold at Cardona. The record of the old shaft and of the adjacent borings bears out this supposition, as illustrated by the following quotation :

The principal pit cut the salt at 68 meters. At 66 meters a cross gaUery was started in the direction N. 25" W. Thus far the shaft was cut through shale, as also was the first 2 meters of the gallery. Beyond the shale, In the gallery, there was encountered 2 meters of salt and anhydrite, and then 6 to 8 meters of Impure common salt mixed with anhydrite, and beyond this the first portion of potash salts. In the plan [accompanying the report referred to) the details of this section are given, but it should be explained that these are by no means regular or susceptible of being exactly gaged. They are found at places in bands, and at other places in irregularly folded bands, and In many places they appear as a cement between fragments of salt. In the

*BoUo. Ctear, and Main, Agustfn, op. cit (vol. 34), p. 192.

10 Contributions To Economic Geoloqt, 1920, Part I.

latter the carnalllte has filled ap the crevices in the salt, showing the existence of areas of secondary deposition. The formation in the cross gallery has a very pronounced dip to the south of ahout 70*", which is tielieved to be due to undulations or secondary folds like those at Oardona

This shaft has now been supplemented by sonae 15 borings, mostly in the immediate vicinity of Suria, and nearly all of these are re- ported to have shown sylvinite and caxnallite in fairly regular beds, eo that in the main these beds could be correlated from place to place. The contorted beds, it is said, are confined to the axes of the folds. There are in general two beds of camallite and a lower bed, in some places two, of sylvinite. The camallite zone, containing workable beds 3 meters or more in thickness, averages 12 per cent potash (KjO) as shown by taking a weighted average from the core samples so as to represent all the material removed from the section indicated. The sylvinite, in beds of 2 meters or more in thickness, is reported as averaging at least 20 per cent potash, and certain portions containing much purer material were found. Ton- nage estimates of the reserve supply in the concession at Suria have been based on the evidence that is summarized above. The evidence was deemed sufficiently good to justify a company with a reputation for competence and conservatism in proceeding with some rather extensive plans for actual commercial operation in its property.

At the time of the writer's visit, in May, 1919, a standard mining shaft, which was begun in April, 1918, had reached a depth of about 60. meters. Permanent foundations for a refining plant and sub- stantial dwellings and offices for staff and employees were also being erected. The shaft has not yet reached the depth at which it was expected to encounter the potash, but water was flowing from a zone at about the level of the river, and the work going on at the time con- sisted chiefly in the attempt to seal this out.

The new shaft at Suria is about 1,500 feet a little west of north from the old shaft but is started farther from the river and on higher ground. It lies in approximately the same stratigraphic position as the old working and probably encounters a similar section, with some variation in detail. This work is being started on the border of the zone of most intensive folding, near the axes of the anticlines, and the salt beds may be expected to show more or less folded and contorted structure. Probably it will be possible to extend the workings under- ground laterally until areas of more regular structure are reached, if complications are foimd to interfere with the mining of the potash.

The area at Suria considered as proved by these prospects is about 8,500 hectares (8,648.6 acres), which according to optimistic reports of interested engineers establishes the existence of potash-bearing strata of an aggregate thickness of 80 to 200 meters, having a poten- tial Droduction of 200,000,000 tons of pure potash (KgO).

Potash Deposits In Spain. 11

OTfiER DEPOSITS.

Aside from the two localities at Suria and Cardona, which are only 7 or 8 miles apart in an air line, the field covered by concessions reaches about 30 miles to the east and 45 miles to the west, the loca- tions being based rather on the extension of similar geologic forma- tions with some evidence of salt, gypsum, and the shales associated with the salt, than on specific discoveries of the potash. A good deal of boring has already been done throughout this area, mostly with essentially negative results, but a few more positive indications have been found. The principal evidence of the existence of potash out- side the valley of Cardoner River is at Villanueva de la Aguda, a village situated near a locally well-known brine spring a little over 20 miles west of Cardona. The brine is reported to carry 4.1 grams of potassium chloride per liter, which is not necessarily an excep- tional indication. However, a boring put down by La Sociedad Fodina is reported to have cut two layers of potash salts, the first at a depth of 303 meters and the second at 654 meters. The boring was continued to a depth of 737 meters and was discontinued while still penetrating massive salt. The information as to the thickness or character of the potash seems to be rather meager.

Many of the borings have shown the extension of the massive rock salt deposits or of gypsum and salt mixed, and there is always the possibility that the record is incomplete through failure to reach sufficient depth or for other reasons.

GENERAL OEOIiOGY OF THE FIEU>.

An extensive basin of Tertiary sediments in northeastern Spain is limited on the north the east-west axis of the Pyrenees Moun- tains, which is a well-defined anticlinal fold exposing the Paleozoic rocks, gneisses, and granitic rocks along its crest. This great low area extends eastward from the valley of Ebro River and is sharply delimited on the south by the coast ranges of Catalonia. The Medi- terranean coast is bordered by a belt of low but rugged mountains, which is clearly an upfaulted mass of the older sediments and igneous rocks, complex in details but forming a distinct structural unit. The interior basin is bounded on the west by the midland plateau of Spain, but it reaches far to the northwest up the present valley of the Ebro. This area of the younger (Tertiary) sediments reaches east- ward into a triangular apex north of Barcelona, practically inclosed between the two mountain belts of older rocks. The drainage of this great interior basin combines along its axis into a few major streams, ▼hich break through the coast ranges in narrow channels, to the Mediterranean. These features are represented on the accompanying Dttap (fig. 3) showing in a generalized way the geology of this re'

12 CONTRIBTmONa TO ECONOMIC GEOLOQT, 1920, PAET I.

From these conditions it seems quite likely that during some por- tion of earlier Tertiary time in this region the Ebro basin may have been occupied either by a continental sea or by a great gulf with narrow passages connecting it with the ocean. According to the observations of European geologists the uplifting of the great an- ticlinal folds that give rise to the Pyrenees Mountains began in the Eocene but took place principally in Oligocene time. Thick salt and gypsum deposits are found among the sediments laid down in this basin during Eocene and Oligocene time. Thus the earth move- ments gave rise to inclosed areas where the evaporation of saline waters left thick deposits of crystallized salts, and in at least some

parts of these areas this process was continued to a stage at which tlie potash and mAgnesian residues of the mother liquor brines were also crystallized. The historical record seems fairly clear in its major aspects.

The section of Tertiary rocks, which is well exhibited, includes near its base a great mass of thick-bedded sandstones and con- glomerates with interbedded shales. These are conspicuously ex- posed in the Monserrat, a prominent landmark northwest of Barce- lona, This escarpment of massive beds dipping gently toward the north is the approximate southern margin of the basin of Tertiary rocks. On the south slope of the Monserrat the rocks tilt up sharply to a vertical position and the section is cut off by the fault-

5£

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pi

I'OTASa DEPOSITS spaht. 13

ing up of the older schists and formations involved in the coast belt. From Monistrol, on the railway between Barcelona and Manresa, a fine view of the Monserrat is obtained, showing an extensive cross section of the massive sandstone and conglomerates. (See PI. III.)

The base of this whole series is found at Olesa, where the Monser- rat sandstones, conglomerates, and red shales bend sharply into a vertical position and grade downward into ribs of massive lime- stone and intervening bands of deep maroon-red shale, which trav- erse the hills from east to west and evidently terminate against a fault From the Monserrat to Manresa the section seems to be con- tinuous. Tlie summit topography, formed on the massive sandstone section, gradually dips with the dip of the strata, and the strata of the Monserrat summit reach and dip below the level of the river. The conglomerates grade into finer materials towtffd the north, in- dicating that the source of these sediments was to the south, and the Monserrat cliffs are evidently an enlarged development which may be represented by a much thinner section of sediments in the in- terior of the basin of deposition.

In order to identify the position of the salt beds and the associated potash, and to trace the extent of the field in which they will be found, it seems necessary that the section beginning with the sand- stones and shales exposed at Manresa as a base and extending to the top of the series represented in the field should be studied in detail. The following section is given as it is published by the Spanish geologists and paleontologists. The youngest beds are at the top of the section.

Stratiffraphic section in potash region of Spain,

L "MoIaBas," soft gray and red shales, as represented by an exposure at Lerida.

2. 'Molasas" and limestone with fossil bones, as represented by an exposure

at Tarrega.

3. Reddish sandstones, with brown coal and fossils, represented by an exposure

at Calaf. 1 "Uolasas," limestones, shales with fossil Melania, Ptanorhis Limnea, and

a layer with Melanoides alMgensia, 5. Sandstone, conglomerate, shale, and red clay. G. Red gypsiferous shale and gypsum.

7. Bluish-gray shale, which overlies the salts at Surla and Cardona and is

also exposed at Tora and Villanueva de la Aguda.

8. Massive rock salt, with portions consisting of salts of potash and magnesia,

the latter perhaps less extensively distributed than the salt and pre- sumably found on the upper part of this section. 0. Shales, defined as marine Eocene, represented in ex];)osures at Manresa, Vich, Igualada, and other places.

Rnbio. Csar, and Marin, Agustfn, Sales pot&alcas en Catalufia: Inst geol. Bspafia BoL. ToL 84, ppu 173-230, 1913; Sales pot&sicas de Catalufia; Idem, vol. 39, pp. 1-38,

14 COKTBIBUnOXS TO ECONOMIC GEOUOOT, 1990, PABT I.

The brief time spent by the writer in this field was not sufficient to permit the compilation of an independent stratigraphic classification, but it would undoubtedly be possible to trace and map certain litho- logic units which would give valuable dues as to the depth and dis- tribution of the salts. Figures showing thickness of the units in this section are not given and could not be obtained but are important now for practical considerations.

The section of these Tertiary rocks is made conspicuous by a pre- vailing deep-red color in the weathered surfaces, so that the series superficially resembles the so-called red beds of the Triassic or Permo-Triassic of the United States. Aside from the general simi- larity of the rocks and their manner of exposure, both periods were characterized by the deposition of salts and gjrpsum.

As will be seen from the detailed stratigraphic section, the salt, in- cluding the potash, occurs rather low in a complex series of sand- stones, conglomerates, shales, clays, and some limestone and gypsum. Several of these zones are convenient markers by which to trace from the surface the position of the underlying salt& Inmiediately over the salt beds is a section of 50 to 100 feet or more of bluish-gray shale, that readily disintegrates on exposure into a very light colored, al- most white mud, and where this shale crops out the proximity of the salt may be assumed. In the rocks overlying this shale there is, at both Suria and Cardona and apparently elsewhere, a prominent bed of gypsum, and above that a bed of fossiliferous limestone. The whole section overlying the salts is made conspicuous by the presence of many massive sandstone members, and these chiefly determine the topography of the region. The structure as a whole is that of gently dipping beds with slight undulations, so that the higher sandstones and conglomerates, by their resistance to erosion, have produced an upland of generally level tops, divided by the steep-sided valley walls, which are rimmed with outcropping ledges. There is seldom found a more favorable field for the study of both structure and stratig- raphy.

Although there appears to be little information about the total thickness of the beds overlying the salts, it seems likely that this section is thick enough to bury the salts very deeply in a great part of the Tertiary basin. There are, however, several belts of sharp folding and overthrust faulting, which are described by the Spanish geologists as continuous from east to west across the area outlined as the potash field. In at least the two places that have been described these folds have brought the salts to the surface along the Gardener River channel, and the salts are relatively shallow in other parts of the field. The Cardona and Suria districts have been described, but structure of the same sort occurs elsewhere, although apparently it is of suflBcient intensity to cause the salt beds to crop out.

Potash Deposits In Spain. 15

SPANISH ILiBOISIiATION CONCERNING THE POTASH

Lands.

Soon after the general announcement of the discovery of potash in Catalonia, efforts were made to put through special legislation concerning these deposits. This was in principle a perfectly natural and appropriate step, as applications for extensive areas and rights of a class without precedent in the country would naturally require special consideration.

In 1915 a bill was presented to the Cortes, the national legislature of Spain, by the minister of public works. This bill seemed to place such restrictions on ownership, development, and operations that it aroused protest, and apparently was not passed. It was replaced, however, by a royal order dated June 10, 1915, which was in harmony with the general provisions of the bill still pending. It provided that the concessionaires in the potash field must work uninterruptedly either in exploration or by mining. According to this order, if regu- lar production had been established under it, the concessionaires would have been obliged to reserve for consumption in Spain such part of the potash recovered as the Government might Require.

Another royal decree, published October 1, 1914, permitted the Spanish Grovemment to reserve the right of private concession in the potash field until investigations by the technical departments of the Government had been carried out. This also granted a right for per- manent withholding of land in the field for operation by the Gov- ernment, if that should seem desirable. Rewards for further discov- eries of value in this field were offered.

These orders remained in force until increasing activity in the developments at Suria during the early part of 1918 again attracted attention to the subject, and on May 2, 1918, another potash bill was published in the Gaceta de Madrid. This contained much of the original bill of 1915, including the obligation on the part of concessionaires to continuous operation, protective measures in favor of internal consmnption of potash, a provision that export prices for the potash produced shall be greater than the domestic, and annual regulation of the maximum price for the home market and the minimum price for export. The Government is also directed to fix the. maximum and minimum annual output of each mine. The Spanish Government assumes supervisory control of all mining con- cessions granted or to be granted, and work on such properties must be under the supervision of the mining inspector of the district in which the concessions are located. Provision is made that the Gov- ernment shall own a share in a syndicate of owners of the mines and shall have a voice in the administration of this syndicate — regula- tions evidently patterned after those of the German Kalisyndikat.

16 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 19aD, PART I.

Quotations from a royal order dated December 14, 1918, ste that conditions have been specified under which foreign and Spanish com- panies can compete for concessions to work the potash deposits.

The restrictions placed by the acts of the Spanish Government have undoubtedly impeded progress in the development of the field, and the price-fixing feature of the present act must prove a deterrent to foreign capitalists desiring to enter the field. It is of course fair that Spain should safeguard her own interests, as, for instance, in providing against passing the ownership of these properties too largely into foreign hands and in insuring preferential treatment for domestic potash requirements from these deposits. However, assurance is needed that the conditions under which de- velopments in the field are undertaken will be stable.

Prospects For Production.

Production of potash for commercial use from the Spanish field was not expected during 1919, and even with good fortune attending the work now going on it seems unlikely that potash will be shipped from these deposits before the middle of 1920 at the earliest. It is still too early to estimate with much confidence what the future of the Spanish field as a factor in the world production of potash will be. The prospects of production to meet Spanish needs seem promis- ing, particularly as the lower grades of crude salts that may be ob- tained at first may be available locally before it may be possible to carry out the refining processes successfully.

Statements estimating tonnage reserves are accepted with con- siderable reservation until some verification is obtained from under- ground development by mining. Well records in regions of such structural complications as are exhibited in these salt deposits must be very difiicult of interpretation, and the thicknesses recorded for the potash beds encountered must be largely dependent upon the angle at which these beds are penetrated, which is often not de- terminable. It appears that the more regular parts of the deposits, if such exist, have not been explored.

For the reasons stated above, it still seems necessary to reserve

judgment as' to the magnitude or importance of the Spanish potash field. The prospects are excellent, and the development now going on should settle the matter in a practical way very soon. Although there is abundant potash in both the German and the Alsatian potash fields and in other possible sources to supply the world's needs for as long as there is now need of estimating, it is far to be preferred that the world should be supplied from numerous and abundant sources than that there should be any danger of monopolizing this resource. Further news of the success attending the development of this field is awaited with interest.

The Potash Deposits Of Alsace,

By HoYT S. Gamj.*

Introduction.

When potash was discovered in Alsace in 1904 the monopoly of the potash industry that had rested with the owners of the great deposits in north-central Germany since 1860 was broken. The new field, although less extensive than that of Germany, was very soon recog- nized as having several important advantages over the older developed field. The Alsatian deposits underlie a large area in exceedingly regular beds, and the salts are on the average remarkably rich in potash* The deposits consist of a simple mixture of potassium and sodium chlorides, known as sylvinite, with very little other soluble materiaL This mixture of crude salts requires only the simple chemi- cal treatment in order to purify it into the higher grades of potash salta The field itself is somewhat farther from ocean port than the north-oentral German region, but as it lies in a well-developed part of the Rhine Valley, directly on the routes of main-line water and rail transportation, this difference is not a serious handicap. It is natural, therefore, that the first mine opened in the new Alsatian field at once took third or fourth rank as a producer with all the older Ger- man mines, a position it has since been well able to maintain.

It has seemed a strange coincidence that the only two really large deposits of soluble potash salts that have been found in the whole world should have been opened within the domain controlled by a single empire. The return of Alsace to France now divides the monopoly of this important natural resource, and general interest in the details of the Alsatian field and its prospects for the future has increased.

Many excellent descriptions of the geology and the conditions of the Alsatian potash deposits have already been published. Most of these descriptions, naturally, are written in either French or German and from the viewpoint of those having a special local interest. It is the writer's good fortune to have had the opportunity to visit all

The writer visited the potash mines in Alsace as the est of the French Government, going there an an authorized representative from the Department of the Interior and representiiig both the United States Geological Survey and the Bureau of Mines in an inTestigatlon of foreign potash resources.

18 Contributions To Economic Geology, 190), Pabt I.

the properties accessible in this field during the spring of 1919 and to be able to give from his own viewpoint not only an abstract of what has already been published but some original account of recent developments. A list and brief summaries of most of the important published references to the geology or deposits of this immediate region are given in the bibliography at the end of this report.

liOCATION AND ACCESS.

The potash deposits lie beneath the open valley of the Bhine in the southern part of Alsace, about 20 to 25 miles north of the

Swiss border. This re gion, known as Upper Alsace, is about equally divided between the slopes of the Vosges Mountains on the west and the broad level floor of the Bhine and its tributaries on the east. The whole region is one of old settlement and intensive cultiva- tion. Mulhouse is an important manufactur- ing centeRy being the seat of large cotton and woolen goods mills and calico printing, paper, and other in- dustrial establishments. The region is well sup- plied with railways, which include the main line of the State rail- way that extends along the Bhine Valley and many branch lines. The valley is also intersected by many canals, the largest of which, the Bhine-Bhone Canal, is an important water- way available for the shipment of potash if needed..

The general situation of the potash field with respect to the main valley, railways, and some of the larger settlements in the region is shown by the accompanying index map (fig. 4). The Vosges Mountains present a steep and rugged front toward the Bhine, largely forest covered, the lower slopes cultivated in vineyards.

FiauBB 4. — Map showing potash field and valley of the Rhine In the ylcinlty of the Mulhouse, Alsace.

The Potash Deposits Of Alsace. 19

East of the Ehine, in Baden, Germany, the Black Forest similarly presents a rugged westward-facing front toward the Rhine Valley, with the river close at its foot. The valley is a broad expanse of meadows and wooded areas, with many towns scattered throughout and large tracts under cultivation.

No evidence of either the potash or the large masses of common salt that are associated with it is to be found at the surface of the ground in this region, and the salts were discovered only by boring in a search for other things. Soon after the presence of the valuable potash was recognized, an association for exploration put down more than 100 deep borings, of which 95 penetrated rock salt and 17 found the potash layers, and in this way the general outline of the deposit as indicated on the accompanying map (fig. 4) was made known. The deposit is found in two beds, of surprising regularity, both of which seem to thin out or to be faulted off at the edges of the basin." It is reported, however, that an extension of these deposits has been found by some borings on the east side of the Rhine, near Buggingen and Zienken, in Baden, but it is now sup- posed that this extension is not of conmiercial importance. The area of the main field as outlined is about 65 square miles, and throughout this field the lower and thicker of the two beds of potash is practically continuous. The upper and thinner bed is less ex- tensive, and, included within the same outline, occupies an area of about 33 square miles. These are the areas used in the computations of reserves of the field given on page 27.

History And Ownership.

The most complete account of the history of the discovery and de- velopment of these deposits is given by M. F61ix Binder, with whom the writer had the pleasure of being associated in his recent examination of the field and from whom the following summary was obtained. M. Binder is an Alsatian, long prominent in industrial affairs in Alsace, and as he has made an enthusiastic study of the whole problem of the Alsatian deposits he is especially qualified to give the record, much of which is from personal or first-hand knowledge.

The existence of common salt in deposits underneath the Bhine Valley near Mulhouse has been known since 1869, when it was en- countered by a boring put down at Domach to a depth of about 300 feet. However, it was not until much later that the eidstence of potash in association with this salt was discovered. Early in 1903, some croppings of coal having attracted the attention of J. B. Grisez, he sunk a small shaft to explore for the deposit. This work was not successful, but nevertheless M. Grisez interested Joseph Vogt, chiefly because of the interest M. Vogt held in property concerned. An association was formed in March, 1904, through the initiation of

20 CONTRIBtmoKS TO ECONOMIC OEOLOOY. 190), PABT I.

M. Vogt, including three other persons besides himself and M. Grisez, which provided the necessary funds for sinking an explora- tory boring. This work was commenced June 13, 1904', at a point a little over 2 miles south of Wittelsheim, near the railway from Lut- terbach to Cemay. This boring reached a depth of 3,700 feet on November 1, 1904. It passed through the potash, which was not at first recognized, but later M. Vogt, noticing its red color, submitted samples for analysis, and the discovery was made. In spite of the seeming importance of such a discovery, some time was lost in an attempt to enlist local support for a project to extend these explora- tions, and it was not until the matter was presented to those already familiar with the potash industry in Germany that the needed funds were readily forthcoming. A consortium created by M. Vogt under the name Socit4 Aralie transferred all its shares to the Deutsche Kaliwerke, one of the large German operating concerns having headquarters at Bemterode, in the north-central Grerman potash field. An extensive system of exploration by drilling was soon carried out and this association acquired large interests in the southern two-thirds of the field. M. Vogt then arranged to continue the exploration to the north, forming a new company of exclusively French and Alsatian capital under the name of Soci6t6 Anonyme des Mines de Kali Ste.-Th&fese.

The German ownership was later divided, presumably by the sale of stock, to finance the development of the several mines, but by far the largest interest remained with the Deutsche Kaliwerke. The principal German owners were the Aktiengesellschaft Deutsche Kaliwerke, of Bernterode (Untereichsfeld) ; the Gewerkschaft Wintershall, of Heringen, on Werra River; and the Gewerkschaft Hohenzollern, of Freden, on Leine River. The other properties remained in French-Alsatian ownership. This general condition has been maintained since 1911, except that in 1913 the government of Alsace-Lorraine purchased shares in the Reichsland, Theodor, and Prinz Eugen properties.

At present ownership or control of all the potash properties in Alsace is represented by P. A. Helmer, squestre gfinral des mines de potasse, and Femand Vogt, directeur genferal de la mine Ste.- Therese. The local ofiice of the squestre is the Bureau provisoire de vente de la potasse d' Alsace, 1 rue des Fabriques, Mulhouse, Alsace.

Output From Alsatian Field.

According to reports, the first mining shaft was completed in 1909, and a total production of 37,000 metric tons of crude salts was obtained in 1910. The production in 1911 is reported as 102,644

Frankfurter Zeitung, Apr. 3, 1913.

The Potash Deposits Of Alsace. 21

tons of crude salts, which was reduced to 66,760 tons as actually

marketed. Reports for 1912 give 137,243 tons of crude salts as

the gross output from three shafts operating in the Alsatian potash

field, which was marketed as 88,756 tons of potash and raw salts,

equivalent to 17,963 tons of pure potash (KjO). Similar statistics

for 1913 show 350,341 tons of crude salts taken from the 17 shafts,

of which 219,912 tons of potash and raw salts, equivalent to 40,707

tons of KgO, were sold. In 1913 most of the output was of 12 to 15

per cent grade, which was sold in Grermany, France, and the United

States, with a considerable production of 40 to 50 per cent pure

chloride of potassium distributed in about the same way.

The complete records of production during the war are not at hand, but details concerning the output from the Amelie and some of the other mines are given in the mine descriptions on subsequent

pages.

Shipping Facilities.

The Rhine is navigable for boats of 1,200 tons or less from Rotter- dam as far as Kehl, the port of Strasbourg, which is about 70 miles by rail or canal north of Mulhouse. The State railway west of the Rhine affords direct connection from Mulhouse to Strasbourg or Kehl and beyond, and there is also a system of canals the largest of which, known as the Rhine-Rhone Canal, furnishes a direct water- way for shipment. The shipping facilities are therefore ample. Several of the potash plants are near the main line of the State rail- way, and the others have direct rail connections.

The usual route for export from the potash mines is by rail to Kehl and by river boat thence to Rotterdam or Antwerp, whence the salts may be transshipped to any foreign coimtry. Rail con- nection may of course be had to other ports or to any other part of Europe. Strasbourg is about 375 miles by the river route from Rotterdam. The distance from the Alsatian potash field to the ocean is somewhat longer than that from the potash field of north- central Germany, but as the transfers of cargo from rail to canal boat and from canal boat to ocean vessel must be made from either district, the difference in distance is not a serious handicap.

Geology Of The Deposits.

The Rhine Valley from Basel, on the Swiss border, to Mainz or Frankfort, in Germany, at the north, is a broad, level floor bordered by the abrupt and rugged fronts of the Vosges Mountains on the west and the Black Forest (Schwarz Wald) on the east. A broad, rounding arch of the sedimentary strata has been broken at the crest by a system of north-south faults, and a long strip in the axis

Daily Consalar and Trade Repts., No. 202, pp. 1126-1127, Aag. 28, 1914.

Contributions To Economic Geology, 1920, Part I.

of the arch has dropped, leaving the escarpments of the present mountain fronts facing inward toward the valley, and the back surface of the arch, forming the outer mountain slope, dipping gradually away on either side. This structural feature is known to German geologists as a graben. The present bottom of the Khine Valley is filled with thick deposits of river sediments, and the river channel follows a meandering course over the surface of this alluvial plain. The bottom lands are fertile and, being open to easy access by rail and water, are the site of important agricul- tural and industrial activity and settlements.

The sediments that lie beneath the floor of the Rhine Valley have little evident relation to those in the adjacent mountains. In the valley, below the river alluvium, are shales, rock salt, gypsum or anhydrite, and other deposits indicating deposition in standing evaporating water. Beds contemporaneous with the deposits under- neath the valley are exposed in some of the foothills at the valley border, i)ut apparently these beds are composed of coarser materials, including conglomerates, as if deposited by running waters over a dry land surface.

The stratigraphy of this basin is classified by Forster as follows:

Section of Tertiary beds represented in the horinffs near WUtelsheim in the

Alsiwe potash field,

Age.

Character.

Thickness (feet).

Upper.

Calcareocu sandstone. " Typical flah shale." " Foraminifera marl"

BluemarL

Middle OHgooene.

Middle.

Gypsom sone. "Limnea" SOD6,

Dolomite, anhydrite, and marl, with rock salt.

Bright-oolored marL

1,875

I/0W6r.

Upper bitmnlnoos sone, with rock

salt and potash salts. Richly fossUiferoos sone. Lower bituminous zone, with rock

salt. Conglomerate cone, with rock salt.

Striped marL

1,700

Lower Oligooene.

Dolomite mar! lone. ! r,,,

fiao

Eocene.

a Wagner, W., Neuere Ergebnisse fiber die Ollederung und Lagerung des Terti&rs im Kalisalzgebiet des Oberelsass, p. 700, 1912.

The borings in the potash field do not extend to the base of the Tertiary, but some holes near Colmar, north of the potash field, pass below the Tertiary into the Jurassic. As interpreted by the local geologists, to whom the original records of the borings have been

The Potash Deposits Of Alsace. 23

available, these records indicate the following as the general history of deposition in the part of the Rhine Valley near Mulhouse.

In late Jurassic time the area of the Vosges-Rhine plain and the Black Forest was covered by the sea, which retreated at the end of the Jurassic. During Cretaceous time these areas were land surfaces. As a result of earth movements Eocene deposits were laid down in certain basins that were developed on the Cretaceous land surfaces, and the records indicate that at the beginning of Oligocene time a general subsidence must have occurred, followed by the deposition of a considerable thickness of sediments. The first deposits were gray or greenish marls, described as calcareous and later dolomitic, con- taining anhydrite, and these deposits are taken by the local geologists as an indication that the period of deposition was initiated by an in- cursion of the sea. It seems to the writer unnecessary to postulate the presence of marine waters to account for the deposition of gyp- sum and anhydrite, as these materials are quite as likely to be thrown down from evaporating natural saline solutions derived from ter- restrial waters in a continental basin as from marine waters. The basin is said to have been deepest near Wittelsheim, where this part of the sedimentary section, known to the local geologists as lower Oligocene,'' is represented by a thickness of about 520 feet.

The greater part of the section represented in the borings in the potash field is called " middle Oligocene." The epoch in which this part was laid down began with the deposition of conglomerate with some anhydrite, dolomitic marl, and rock salt, indicating the drying up of saline solutions, whether derived from a continental water body or an arm of the sea. Here again the axis of greatest depression — that is, the part of the basin that apparently received the greatest thickness of deposits — was in the vicinity of Wittelsheim, well to the west side of the valley of the Rhine. The beds succeeding the con- glomerate, described as " striped marls," include rock salt and at the top of the section the two potash beds. The whole thickness of this division is 1,700 feet in the boring at Wittelsheim. A richly fossil- iferous zone underlies the potash beds, and the fauna derived from this zone has been carefully studied. The fossil zone is considered an excellent horizon marker, as it is widely recognized beyond the limits of the potash basin. Comparison of the sections found within the potash basin and at or beyond its margins shows that while fine sediments or salts were being deposited in the center, coarser mate- rials, in places conglomerates, were being laid down toward the mountains, clearly indicating, in part at least, the limit of the basin of deposition.

The two beds of potash salts are distinct layers included within grayish shales described as dolomitic. Other beds of rock salt and anhydrite are, however, interstratified with the shale, showing a gen-

24 Contributions To Economic Geology, 1920, Part I.

eral condition of concentration of solutions, undoubtedly by evapora- tion in an inclosed basin. The practical absence of soluble sulphate salts or of the soluble compounds of magnesia is worthy of special note, as this feature distinguishes the Alsatian potash deposits from those of the Stassfurt region, in northern Germany.

The colored or variegated marls that overlie the potash beds con- stitute a section aggregating 1,125 to 1,375 feet in the vicinity of Wittelsheim and contain a thick deposit of common salt in the lower part and gypsum or anhydrite both in the lower part and at the top of the section. These beds grade into coarser sediments, in- cluding conglomerates, toward the edge of the basin.

An upper portion of the "middle Oligocene," reported as only about 300 feet thick in the first boring at Wittelsheim but very much thicker elsewhere, is distinguished by several fossiliferous layers and has received the general designation "blue marl." It is described as a deposit laid down in deeper waters. This part of the section is discussed in some detail in the paper by Wagner already cited.

The tectonic or structural geologic record, as interpreted by the local geologists, includes repeated risings and sinkings of portions of the earth's surface in this region, to account for the supposed changes from marine to fresh water and from chemical deposition and fine sediment to coarser deposits accumulated mechanically. Un- doubtedly many oscillations of this sort have occurred, but it is also quite justifiable to assume that a continental basin in the Rhine Valley may have been for a time isolated and without outlet, with perhaps a water supply insufficient to equal the evaporation from the water surfaces as they rose and expanded over the floor of the valley. Slight climatic variations might readily account for alter- nating rise and desiccation of the inclosed waters, as also for the inwash of sometimes coarse and sometimes sparse and finer sedi- ments from adjacent slopes. The assumption of the early existence of the great Rhine graben is fundamental, and it may well be sup- plemented by the further assumption of periodic readjustments of the component elements of the graben. The waters that filled the basin might have been marine, but they might also have been derived from the evaporation of ordinary river and ground waters, such as produce the many continental saline lakes in other parts of the world. The frequent reflooding and interruption of the desiccation process readily accounts for the alternation of chemical precipitates and of mechanically contributed sediments, and it may also account for the dilution and removal of the final mother liquors containing some of the constituents that would normally result from the evapo- ration of a solution of natural salts but that seem to be lacking here.

The Potash Deposits Of Alsace. 25

Nature And Quality Op The Potash Beds.

In the descent into one of the potash mines nothing can be seen of the depasits passed in the shaft, because they are covered by the concrete linmg of the shaft, or, near the top, by a metal oolhir. The first sight of any of the underground deposits is obtained as one steps from the mine cage into the mine workings. Here broad en- tries, well lighted by electricity, have been excavated in the thicker of the two potash beds. The galleries branch in various directions and are closed here and there by doors (brattices) , which are needed to direct the circulation of the air that is forced through the mine for ventilation.

The sight of the potash salts in place is striking. High walls of sparkling crystalline salts are banded in approximately horizontal stripes of red and white, more or less wavy, giving the impression of a portion of an immense flag. On clean mine faces the colors are beautifully clear. Some of the bands are a deep, rusty red or brick red. Other portions are delicately pink, and there is much white and gray granular crystalline material. The belief that the red and BOftnB of the pink salts are directly associated with the richer potash portions of the bed is so generally expressed throughout the field that it must have some foundation in fact, although perfectly white or transparent crystals of almost pure potassium chloride have been found. Examination in detail shows that the coarse crystals, both red and white, are much intermixed, and it is not usually possible to trace a distinct boundary between them, but in general aspect the banding is very distinct.

The top and bottom of the potash beds, where the salts rest against adjacent clay or shale seams, are, however, very clearly delimited. The shale leaves a very smooth clean surface in the roof of the mine, marked by some irregular pits or patches but usually breaking clean from the salts. This is also true of the clearly defined shale seams that occur within the potash bed.

The two beds preserve their individual characteristics, including general thickness and relation to each other, as well as details of the shale partings and chemical character of the constituent members, with remarkable constancy throughout the field. The upper bed, containing about 3 to 5 feet of potassium chloride of richer grade than the lower bed, is the thinner. It is separated from the lower bed by about 60 feet of saline shale which, where exposed in the mine workings, is almost slatelike in appearance. When this shale is ex- posed to air or moisture it swells so much that it breaks up. The lower potash bed, averaging from 10 to 16 feet in thickness, occupies a larger area than the upper bed. In both thickness and quality the two beds are said to vary from place to place throughout the field,

1278*'— 21 3

26 CONTRroUnONS to BCX>1!0M1C geology, 190), PART I.

and it is also reported that where these features are found to vary from the average in one bed they vary also in a corresponding way in the other bed.

Many analyses of the potash salts from these beds migt be quoted, but all show essential uniformity in the general character of the salts. Many specimens taken from the mine carry as reported from 25 to 30 per cent or more of potash (KO), and carefully cut samples from clean faces, unnecessary contamination with dirt be- ing excluded, may yield even high percentages. It has been fre- quently stated that all the salts conmiercially available from this field may be calculated as averaging 22 per cent KO. Nevertheless, the general average of mine-nm material now produced, or that which has been produced under the German regime, is much less than this. Hand sorting at the mouth of the mine yields some material averaging about 22 per cent. The remainder, however, generally runs lower, usually not over 12 to 15 per cent. Thus the various grades in the output of crude salts are obtained. The two samples taken at the Amlie mine, the analyses of which are given on page 82, are doubtless fair representatives of the output from the best and thickest part of the deposit. These samples carried about 15 per cent potash (KO) in ordinary mine-run crushed salts from the lower section of the thicker potash bed, and 21 per cent in a similar product from the thinner upper bed. They also carried from 7 to 8 per cent of insoluble matter, probably clay that adhered to the salts as it was mined, not all of which is it ordinarily practicable to separate. For commercial purposes it seems fair to estimate the average quality of the output over the entire field at about 18 per cent potash (K2O), and even this estimate assumes moderate care for the exclusion of undesirable materials found in the deposits.

The details of the two beds are discussed in the descriptions of some of the individual mines, as the mines are the only places from which such data may be satisfactorily obtained.

Some excellent specimens of the salts collected by the writer in the Amlie mine have been deposited in the United States National Museum. It is difficult to preserve this material so that it will retain the appearance it had when taken from the mine, as the salts, when exposed to the air, collect some moisture which darkens their colors and gives thedr granular crystalline surfaces a more translucent appearance.

Estimated Reserves Of Potash Ix The Alsatian

Field.

Estimates of the reserve supply of potash in the potash field of

have been frequently quoted, and, as these are based on sub-

ly the same data and course of deduction, they are in essential

The Potash Deposits Of Ai£Ace. 27

agreement. Such estimates were apparently made first by Forster. The area of tbe whole field underlain by the lower and thicker of the two beds is stated as 172 square kilometers, and the area underlain by the upper bed as 84 square kilometera The average thickness of the lower bed as determined from all measurements available is stated to be 4.147 meters, but this bed contains some streaks of shale. By tabulating the eight detailed measurements of the lower potash bed, which show the relative proportions of potash salts to shale, the potash is found to make up 84.56 per cent of the whole bed. This factor applied to the average thickness of the whole bed gives 8.507 meters as the estimated thickness of potash salts alone. The upper bed contains no shale partings and the available measurements give an average thickness of 1.164 meters. By simple computation the cubic content of both beds is figured as 700,980,000 cubic meters of potash salts, which at a specific gravity of 2.1 is equivalent to 1,472,- 058,000 metric tons. The usual assumption of the average potash con- tent for the field at 22 per cent K2O would give in round numbers somewhat more than 300,000,000 tons of pure potash (KjO) as the estimated reserve in the ground. This would provide the world's needs at the normal rate of consumption before the war for about 275 years.

Van Werveke ' and later Binder ' and others, using the same fac- tors, obtained the same results. So far as ascertained, there has been no disposition to criticise or dispute either the accuracy of these com- putations, which are easily checked, or the interpretation that is placed on them.

There is, however, a considerable difference between the total re* serve supply of potash believed to exist in the ground and the amount that will probably be recovered in mining. As will be seen by a study of the records of noining operations, much of the mate- rial is wasted in the process of recovery. In many of the first work- ings only the best part of the thickest bed has been taken out, and at least a portion of the salts must be left in place to support the roof. In much of the work that has been done so far more than a mere layer of the valuable salts at the top has been left, and if care is not used and more efficient methods adopted much of this may be wasted. Where pillars or walls are left for support there is to

FSivter, B., Ergebnlsse der Untersuchung von Bobrproben aus den geit 1904 Im Gauge tell ndit Chen zar Aufsuchong yon Steinsalz und Kallsalzen auegefilhrten Tiefbobiningen Im TertUIr OberelsasB : Geol. Landesanstalt Elaass-Lothrlngen Mitt., Band 7, Heft 4, p. 504, 1911.

' Van Wervdse, L., Die Ergebnlsse der geologlschon Forschungen In Elsass-Lothringen nnd ihre Verwendong zii Krlegszwecken : WIss. Gesell. Strassburg Schriften, Heft 28, p. 58. 1916.

'Binder, FAix. Rupport de I'lndustrie de la potasse de la Haute Alsace, p. 11, Paris,

28 Contributions To Economic Geology, 1920, Part I.

be expected a rather high percentage of loss. Faults, sharp folds, or irregularities, though not numerous, lead to the abandonment of certain parts of the deposit. Consequently in estimating the value of the deposit, it would be incorrect to interpret the figure indicat- ing gross weight as if this reprssented the yield to be expected from the field.

Moreover, scrutiny of the results of operation shows that the qual- ity of the raw salts produced in mining operations does not run as high as the figures on which the total tonnage estimates are based. Very probably the higher figures given showing the purity of the deposits in the ground are correct, as is indicated by the analyses of carefully cut and preserved samples. However, in ordinary Tnining operations much dirt is included from within or without the original limits of the deposit, and the crude material as taken from the mines, including both ordinary and hand-sorted grades, prob- ably does not contain over 18 per cent of potash (KO). The accidentally included dirt need not diminish the estimate of total resources of the field, but it does affect the practical interpretation to be given to figures quoted as showing the average quality of the deposit as represented by its average output.

The Mines.

The following pages contain a summary of the records, so far as available at present writing, concerning the individual mines or properties in the Alsatian potash field. The whole area seems to have been subdivided under the Grerman mining law for Alsace into 106 individual minor concession units, which were, however, ceded or granted to private owners in blocks of several units each, making the simple group of about 16 major concessions usually shown on the detailed maps of this potash field. Some of the larger conces- sions were further combined for mining purposes by the building of two shafts near together, but on different properties, so that the two might operate as a single mine. The details of such operations are described in the following text.

AiyrfTTilE MINE. HISTORY.

The Socifite Minifere Am61ie (Gewerkschaft Am61ie), founded June 13, 1906, commenced boring the first shaft in the Alsace potash field in 1908 and first produced potash salts in 1910. The mine was admitted to the Kalisyndikat October 14, 1910, and a quota of 14.66 thousandths of the total German potash production was granted to it, tnus placing the mine at once third in point of pro- duction in the whole German potash industry. The reduced quota

The Potash Deposits Of Aiace. 29

assigned in February, 1918, was 8.32 thousandths for shaft 1 and 2.23 thousandths to shaft 2, a total of 10.55 ; shaft 1 alone then held fourth position in size of output.

The production from the Amelie mine is reported, so far as the record seems available, as follows:

Potash Bold from Amelie mine, Alsace, in metric tons of KtO,

1910 5, 538

1011, 1912 1 Complete records not available.

1913 22, 716

1914 15,551

1915 3, 765

1917 None.

1918 No record.

The Amelie mine was producing about 400 tons of crude salts daily at the time of the writer's visit, in April, 1919. This is practically the equivalent in pure potash of the production under German man- agement in 1913, although the present output consists entirely of crude salts as they come from the mine, the refinery not being in a condition to operate.

The salts from the Amelie have been, like the output from the other properties in Alsace, much in demand because of their high grade and lack of other contaminating salts. It is not known why production from this property was allowed to lapse during the war, but it is assumed that other mines in Alsace, such as the Theodor, were found to be more advantageously workable under stress. There is a large refinery for making potassium chloride at the Amelie mine, which was more or less damaged during the war, mainly by deprecia- tion through use and lack of proper care.

Situation.

The two shafts of the Amelie mine are about 1 mile south to south- east from the town of Wittelsheim, and a little more than 8 miles in a direct course almost due northwest from the center of the town of Mulhouse The mine is connected by a short spur with Richwiller station, on the main line of the State railway between Strasbourg and Mulhouse. The general situation of the mine places it near the center of the southern broader portion of the basin in which the potash salts were deposited. The property belonging to this organi- zation is a square area of 1,800 hectares (4,448 acres).

Ownership.

Originally founded by Joseph Vogt, the Socit Amelie was sold to the Deutsche Kaliwerke for the sum, according to M. Binder, of 32.000,000 marks, payable partly in specie and partly in stock of thf

80 Contributions To Ecjonomic Geologt, Iwo, Part L

concern. In 1918 the capital stock of the Amlie mine was listed at 6,000,000 marks ($1,428,000 at normal exchange). This consisted of 1,000 shares, of which 997 were in x>os8ession of the Aktiengesellschaft Deutsche Kaliwerke. This is a German corporation whose principal property or headquarters is at Bemterode (Untereichsfeld), in the southern Harz potash district in Germany, and which also owned interests — in several cases controlling interests — in other German and Alsatian potash mines. It held important parts of the capital stock of the AmSlie, Marie, Marie-Louise, Anna, Reichsland, Max, Else, and Josef mines in Alsace. This, like all other German owner- ship in Alsatian potash properties, is now under the control of the French s6questre administrar, the final disposition of the title await- ing action by the French Parliament.

GEKERAIi FEATURES.

The two shafts of the Amlie mine are in the Nonnenbruch Woods, which skirt the valley of the Thur south and southeast of Wittel- sheim. Like the rest of the Rhine Valley in the general region of the potash field, the country here is exceedingly flat, with a very low, even slope from the foothills of the Vosges down to the Rhine itself, a distance of 15 miles or more. This includes a portion of the valley of 111 River and its tributaries, which is essentially a part of one broad plain.

The head frames, shaft houses, and mine and refinery buildings, like those of the other potash mines in Alsace, are substantial and mostly well built, constructed according to the most modem stand- ards evolved from the experience of the German potash industry. Considering the comparative simplicity of the mining and refining problems, the equipment seems at first sight unnecessarily heavy and bulky. The two views published herewith (PI. IV) are reproduced from snapshots taken by the writer, showing something of the gen- eral style of construction and arrangement at the Amflie mine.

Shaft 1 was sunk to a depth of 246 feet through the alluvial water-bearing valley fill, a method of freezing the ground frequently being used to seal out the water during construction. The shaft was finally sealed by the insertion of a continuous section of iron tubing, which was set into the cement lining of the lower part of the shaft. The upper of the two potash beds was encountered at a depth of 2,066 feet and has a thickness of 4.26 feet, and the lower or main potash bed was reached at 2,129 feet and has a thickness of 18.4 feet. The base of the main level is at a depth of 2,165 feet. The details of the potash beds are discussed in a subsequent paragraph.

Shaft 2 is about 3,000 feet southwest of shaft 1, and the two are connected in the underground workings. In this shaft the top of

B. Shaft House And Head Frame At Amcue Shaft I

THE I>0TASH deposits OV AIACfi. dl

the upper potash bed was encountered at a depth of 1,699 feet and the lower bed at 1,771 feet; the main working level starts at 1,788 feet. The beds in shaft 2 are similar to those in shaft 1. This second shaft was put into operation toward the end of 1912.

Thx Potash Bedb.

The salts in the two potash beds of the Amflie mine, like those in the other mines of the Alsatian field, present a. striking spectacle underground. The beds are of gently undulating structure and lie in attitudes ranging for the most

, , ." ", . J. . KiO Mewi content

part from horizontal to a dip Ot Thlckna* (per cent) KjO

8° or 10°, with occasional excep- tions showing steeper tilting and zz.q% even faults. The salts are con- solidated into two very distinct beds consisting mostly of crystal- line water-soluble material. The beds consist of alternating lay- ers, mainly of red and white salts, uniformly and distinctly banded. The red ranges from pale pink to a deep brick color. It is generally supposed that the red shades ac- company the potash-rich por- tions of the beds and that the white crystalline layers are mainly common salt. However, some perfectly clear white trans- parent sylvite or potassium chlo- ride is found.

The accompanying section (fig. 5) gives in detail measurements fiouu s.— DUgnm repreaeDtioB lower of the lower and thicker of the E',5SJ" lt';VS,",.'i."'.r two potash beds found at the base

of shaft 1. The record was kindly furnished by M. Louis Bucherer, manager of the Amlie and Max mines under the French suestre regime.

The sections of the potash deposit vary somewhat from place to place, but in genial throughout the greater part of the Alsatian field the main potash bed is divided into a main lower section of salts relatively free from insoluble material and an upper portion con- sisting of two or three potash-bearing members divided by shale bands. The present workings in the lower or main potash bed are confined principally to the recovery of the salt from the portion be- low the conspicuous shale seam near the top. This shale with the

7%

CONTRIBUTIONS TO ECONOMIC GEOLOOYy 190), PART I.

salts above it, the latter being about feet thick, affords a good roof for mining, whereas if the uppermost salts are removed the shale above bulges and falls in great masses, thereby rendering the workings dangerous. In April, 1919, when this miite was visited by the writer, the thick section of potash salts in the center of the main bed, included between the two prominent shale seams, was also being left for later working, and only the lower section of a little more than 6 feet of potash was being mined, because of the inconvenience of working a thicker face at one time.

The interval of about 65 feet between the two potash beds appears to be occupied mainly by shale of fairly uniform, slatelike character, but it contains also some thin beds of salt.

The upper potash bed is mined at the Am61ie shaft 1, where it has a thickness of 5 feet 10 inches of potash salts below an exceedingly regular roof of clay that is almost slaty. This is the richer of the two beds and is taken out in its entirety. The material may be shipped separately or used to enrich the general average grade of the material derived from the lower workings.

Two samples, taken by the writer in the usual systematic way, so that they undoubtedly represent fairly the general run of crude material as it was being produced from these beds, have been ana- lyzed in the chemical laboratory of the United States Geological Survey at Washington, with the following results :

Composition of crude potash produced from the Am4lie mine, Alsace,

[E. Theodore Erickson, analyst.]

Dctormiiuitloiui (pr cnt

Mired).

of aample m re-

CalcBlated lalts.

A

B

A

B

K

KCl

&00

Na

NaCl

Ca

MgCl,

Mg

C&O4

CaCl,

So*

H|0

Insoluble in water

Insoluble. - , . .

Moisture

Sample A was taken in a large stock pile said to be from the lower part of the lower or main bed of potash worked as described above, and sample B was taken in a railroad car partly loaded for shipment, said to be material mainly from the upper potash bed as worked at the Am61ie mine. The potassium reported in sample A is equivalent to 15.18 per cent potash (KjO), and that in sample B to 21.04 per cent KO. These determinations were made by the chlor- jtinate method of determining potash and agree very closely with

The Potash Deposits Of Alsace. 33

the values reported at the mine based on determinations made by the perchloric acid method.

These figures are somewhat lower than the averages shown in the ideal section illustrated oa page 31, but the divergence is probably not more than should be expected. The section on page 31 is based on samples carefully cut and preserved from foreign matter, whereas the ran of mine or crude salts produced in ordinary mining include not only material from the common salt beds but, as shown by the analyses, 7 to 8 per cent of insoluble (earthy) material, which was not included in the calculations made for the ideal section.

Camallite has occasionally been found in the Am61ie mine but is so exceptional that it is pointed out as a curiosity. Camallite is revealed by its tendency to effloresce when exposed, and it has been fomid in small irregular or pockety patches at the very top of the lower or main potash bed. The mineral has been identified by chemi- cal analysis. The magnesia in the material as mined is, however, so low that it may be counted essentially absent.

Refinery.

The refining plant for producing purified potassium chloride was not in operation in April, 1919, having been more or less damaged during the war, mostly by depreciation through neglect, which per- mitted deep rusting of the iron equipment. The equipment is large and of standard design, such as is reviewed in a subsequent section of this report.

Max Mine.

The Max mine is near the Amelie, and these two, which with the Josef and Else shafts form a group, were opened largely under con- trol of the Deutsche Kaliwerke, and are stiU administered through a single management under the French suestre regime. The Max shaft is connected by underground workings with the Amflie shafts.

The Grewerkschaft Max was founded March 3, 1909. The property is a square area of 1,800 hectares (4,448 acres) southeast of the Am61ie concession, to which it is similar in size and form. The shaft reached the depth of the two potash layers about the middle of 1912. The Max mine received an allotment for production under the Kalisyndikat, which was 7.81 thousandths in the list of February,

The mine is immediately adjacent to the mam line of the State railway between Basel, Mulhouse, and Strasbourg, the local station or shipping point being Riehwiller.

Tlie capital stock consisted of 1,000 shares, of which 444 shares were held by the Aktiengesellschaft Deutsche Kaliwerke of Bernte- rode, in Germany. The ownership of the remainder is not reported.

34 CONTRIBUTIONS TO ECONOMIC GBOLOOYy IflO), PART I.

The Max mine was visited April 11, 1919. At that time it was in operation and was reported to be producing at the rate of about 400 tons of crude salts a day, of which about 40 to 50 t<ms averaged 20 to 22 per cent K,0 and the rest averaged 12 to 15 per cent.

The equipment of this mine is of standard type, like that of the Amlie, except that there is only one shaft, and compliance with the double-shaft requirement of the German mining law has been made by establishing connection in the mine workings with Am41ie shaft 1, which is about 4,000 feet distant, northwest of the Max. There is a refining plant for manufacturing purified potassium chloride salts, but it was not in operation in April, 1919. The hier-grade product mentioned in the statement of present output is obtained by hand sorting of the blocks as brought from the mine before the material is crushed. Large storage bins, capable of holding 100,000 tons, were about one-fifth full at the time of this visit.

The upper and thinner potash bed was encountered at a depth of 1,624 feet in the Max shaft, and the lower bed at 1,686 feet The thickness and details of the beds as well as the compoation of the salts are very similar to the same features in the Am£lie.

The following analysis of the salts was furnished at the mine office :

Campoiition of potash salts from Max mine. [Dr. Hont, analyst.]

Kci : 2a 75

NaCl 67. 43

CaSOi -, 1. 92

MgCU .38

CaCU - 1. 26

H*0 .71

Insoluble 11. 23

The working conditions were much the same as at the Amie. At the time of the writer's visit 224 men were employed, and the output was therefore about 2 tons of crude salts per man per day. The view given herewith (PI. V, -4) is a reproduction of a kodak picture taken April 11, 1919, showing the head frame of the Max shaft, a comer of the refinery to the left (north of the shaft house) , and the power house on the right. The Bichwiller railroad siding is just beyond the buildings. Earth piled at the base of the shaft house as a pro- tection against bombardment during the war was in process of re- moval. The buildings are typical of the field and in fact of con- struction at the German potash mines generally.

Josef And Else Kzhe.

The Josef and Else shafts, about 1,600 feet apart, in adjacent con- nons designated by these names, are connected in the underground

"

atmvBT BnLi,ETiN tis

Platz V

rf

,.

J. MAX MINE, NEAIt WITTELSQEIM, ALSACE.

B. nCICHSLAND MINE. WITTENHEtM. ALSACE.

The Potash Deposits Of Alsace.

workings and constitate essentially a single mine. The concessions adjoin and lie west of the Am61ie and Max concessions. The shafts are about a mile west of Am61ie shaft 2, and are thus a part of the Amlie-Max group. The Josef and Else shafts are, however, on the branch of the railroad that runs westward from Mulhouse by way of Lutterbach and Cemay. These shafts are listed as shipping from the same station as the Max (Richwiller) , as thef Cemay line is a branch from the main line of the State railway that runs from Mulhouse direct to Strasbourg.

Both companies, the Grewerkschaft Josef zu Wittelsheim and the Grewerkschaft Else zu Wittelsheim, were owned before the war by the Aktiengesellschaft Deutsche Kaliwerke of Bemterode, a corporation operating in the German potash region, which held 980 of the 1,000 shares of the capital stock of each of these subsidiaries.

The Josef shaft had reached a depth of 1,709 feet when the top of the lower or main potash bed was penetrated in October, 1912, and the top of this bed was cut in the Else shaft at about the same time at a depth of 1,608 feet. The upper potash bed has a thickness of about 3 feet and the lower about 16 feet in both, of these shafts.

The allotment assigned to the Josef by the Kalisyndikat list of February, ldl8, was 1.98 thousandths and that to the Else 2.06 thou- sandths. These shafts were not in operation in April, 1919, and were not visited by the writer.

The following analyses were furnished at the oflSce of the Am61ie and Max workings, to show the character of the salts. These are believed to be essentially of the same character throughout this dis- trict, although the sample from the Else shaft gave somewhat higher potash results than the average. In all the samples from the main potash beds the salts of magnesium and the soluble sulphates are very low.

CompoHtion of crude potash from Josef and Else shafts.

pr. Horet, analyst.]

Kci

Naa

MJOt

CjSOi

H|0

Inaolttble.

Josof.

Else.

&38

Anna Mine.

The Gewerkschaft Anna, of Wittelsheim, is a subsidiary of the Gewerkschaft HohenzoUem, of Freden, south of Hannover, in the north German potash district, which holds 750 shares of a total of

86 CONTRIBUTIONS TO ECONOMIC GBOIiOGY, 192D, PART I.

1,000 shares capital stock. Of the remainder 96 shares are held by the Deutsche Kaliwerke, previously referred to. This is listed as one of the Kalisyndikat properties that is in process of building a shaft." The report to the Kalisyndikat states that shaft 1 on the Anna was started November 1, 1911, and had reached a depth of at least 741 feet, and that shaft 2 was started August 1, 1913, and had reached a depth of 344 feet. The management of this property was evidently closely allied with that of the adjacent Reichsland prop- erty. No production is reported, as the shafts are said to be still incomplete. The workings on the Anna concession were not visited by the writer.

The concession is adjacent to and dirtly northwest of Mulhouse, and so far as present evidence goes is believed to include in greater part lands underlain by only the lower or thicker of the two beds of potash salts. The property consists of about 1,200 hectares (nearly 8,000 acres) , a part of which is probably outside the potash-bearing field. Some of the main routes traversed to and from Mulhouse and the other potash properties pass through the Anna concession just northwest of Mulhouse.

Beighsland Mine.

The Gewerkschaft Reichsland was founded in 1911, with a capital stock of 1,000 shares, of which 600 shares were held by the Gewerk- schaft Anna, which was in turn a subsidiary of the Gewerkschaft HohenzoUem. According to report the Govermiient of Alsace- Lorraine, in 1913, bought interests in the Reichsland as well as in the Theodor and Eugen mines. The Reichsland shafts and equip- ment are much farther advanced than those of the Anna, as this com- pany reported production at least as early as 1916. The sales quota assigned to the Reichsland mine in the Kalisyndikat list of February, 1918, was 8.87 thousandths, which was a reduction from the year preceding but still places this mine well up in the ranks of largest producers in the whole German industry. The sales of potash from the Reichsland mine in 1916 amounted to 10,409 metric tons of KjO and in 1917 to 12,629 metric tons. Its output at the time of visit was reported as about 800 tons of crude salts lifted, a part of which was being used in the production of about 50 tons of refined salts daily. This is considerably more than the reported prewar pro- duction.

The Reichsland mine is near Wittenheim, 4 miles almost due north of Mulhouse, on the left side of 111 River. A provisional con- nection was first made with the minor line of railroad running from Mulhouse to Wittenheim, but later a connection with the main State railway at Richwiller station was established. The mine is

The Potash Deposits Of Alsace. 37

probably readily accessible to the river canals, but shipments are made by rail.

The Beichsland mine is a complete unit, consisting of the two shafts required by the Grerman law, a refining plant for preparing refined grades of potassium chloride salts, and a large storage warehouse. It has a complete steam-power plant, and according to report its stack is the highest chimney in upper Alsace, which contains many manufacturing enterprises. Plate V, B, shows a general view of the plant taken from the public road south of Wittenheim.

The valley lands adjacent to 111 River, north of Mulhouse, are largely cleared fields, cultivated as meadows or in grain and truck crops. The Keichsland mine stands practically alone in these fiat meadows about half a mile southwest of the town of Wittenheim. The shafts, equipment, and refinery were left, at the time of the armistice, in somewhat better repair than those of most of the other potash mines in Alsace, and consequently this property was prompt to respond to French efforts to reestablish the production of potash from this field. The refinery and mine workings were visited by the writer April 10, 1919.

The two shafts, which are about 1,000 feet apart, are near the ex- treme northwest comer of the Beichsland concession, which, being the side of the concession that is toward the center of the field, may be supposed to be in the best or thickest part of the deposit on this property. At present the mining is carried on from the west shaft The underground development is extensive, reaching mostly south- ward from the site of the surface buildings along the border of the adjacent Anna property.

Only the lower of the two potash beds of the Alsatian field is fomid in the workings on the Beichsland property. The top of this bed was reached at a depth of 1,863 feet in the shafts. The overlying beds consist mainly of saline shale, and the potash bed is just below a deposit of common salt 410 feet thick. The potash bed lies in gentle folds, having dips of to 20° in the present workings. The same potash bed is only 1,207 feet deep in a boring just north of nisach, in the southern part of the Beichsland concession and near the extreme edge of the field as now delimited. The potash in the Beichsland mine presents a working face about 7 feet thick. Where exposed more completely, however, it is seen to be between 9 and 10 feet in total thickness but considerably broken by shale partings. As at the Amfilie mine, it is c<Mnposed of an alternation of thin layers of white salt, pink and deep-red sylvite, and clay. One of the inter- bedded layers of clay is used as a roof in the mine. This layer has been cross- fractured and the cross seams filled with crystallized salts of salmon-pink to red colors, said to be mainly sodium chloride. The shale roof in the mine is marked by pits or irregular surface patches,

83 CONTRIBUTIONS TO EOOKOMIO GEOIiOGT, 19, PART I.

presumably impressions of crystal forms against which the mud hardened.

As in the other mines in this field the temperature of the rock is very high (reported 42 to 48 C.) and the galleries are kept cool enough for comfortable working only by forced ventilation. The rocks at mining depth seem to be dry, as no moisture, except that leaking about the upper collars of the mine shafts, was observed in the district

The refining process being carried on here in a commercial way at the time of visit is described in the general section on Surface treat- ment '' (pp. 44"46). The potash works had then been in possession of the French authorities for so short a time that little in the way of regular operation could be considered as established, but much ex- cellent work was being done.

Thsodob Hine.

The Theodor and Prinz Eugen shafts are close together, so that they constitute but a single mine, although opening on two adjacent concessions. This mine is north of the Reichsland, on the same (west) side of the 111 Valley, in the edge of the woods a little farther from the river. The shafts are about 9 miles almost due north of Mulhouse, midway between the towns, of Wittenheim and Pulver- sheim.

The capital stock of the Grewerkschaft Theodor and also that of the Gewerkschaft Eugen consisted of 1,000 shares each, of which 501 were held by the Gewerkschaft Wintershall, of Heringen, in Ger- many, and 334 by the Elsass-Lothringischeti Fiskus, presumably the local government owner that has already been referred to in connec- tion with the Keichsland mine. Both the Theodor and Prinz Eugen organizations were founded April 11, 1911. The Theodor shaft was in process of building from October, 1911, until the later part of 1912. The quotas for production allotted by the Kalisyndikat list of February, 1918, were 7.98 thousandths to the Theodor and 7.01 to the Prinz Eugen, a total of 14.99 thousandths for this mine.

The record of production from the Theodor mine, including both properties, is given in the following tenns:

Potash salts sold from Theodor and Prins Euffen properties in 1916 and 1917,

in metric tons of K%0.

Kalnlt, 12 to 15 per cent K,0 3,041 1,213

Manure salt. 20 to 22 per cent KjO 6,027 25,986

Manure salt, 30 to 82 per cent KfO 3,091 1,869

Manure salt. 40 to 42 per cent KtO 6,827 1,426

Potassium chloride , probably 60 per cent KjO [ 195 499

30,963

The Potash Deposits Of Alsace. 89

The Theodor property was visited by the writer on April 11 and 12, 1919, The underground workings were not examined. They are said to have been badly worked by unskilled Russiai\ prisoners before the end of the war and to have been left in a rather dangerous con- dition. However, an output of about 200 tons of crude salts daily was being made from the mine, and a part of this had been shipped, but much of the crude salts brought to the surface had been used in experimental operations in starting the refinery. The output of re- fined salts was estimated at about 20 tons daily, of which about 500 tons had accumulated in storage.

The top of the upper potash bed is reported to have been encoun- tered at a depth of 1,791 feet, and the top of the lower bed at 1,853 feet. The upper bed is stated to be 4.1 feet thick and to average 26 to 27 per cent KO, and the lower bed to be 13.45 feet thick and to average 28 per cent Kfi. The outline as given for the area in which the upper potash bed is found indicates a southern limit just south of this mine, which may be shown in the mine workings and by borings farther southeast. If so, the upper potash bed seems to terminate abruptly from the recorded thickness of about 4 feet of potash aver- aging 26 to 27 per cent KO.

. The equipment of the refinery was formerly very complete and is being studied in much detail by the present operators. The records of production in 1916 and 1917, showing an output chiefly of lower grades of fertilizer salts, indicate that the refinery equipment was al- lowed to lapse into disuse toward tiie later part of the war, and when the property was taken over by the French the machinery had been largely dismantled, parts of it were scattered, and the extensive iron work was deeply rusted and badly out of repair.

MABIE-IiOXJISE MINE.

The Marie-Louise and Marie shafts, on concessions of the same names and therefore representing two properties, are only 820 feet apart. They constitute but a single mine, and at present operations are carried on through the Marie-Louise shaft, which is the northern of the two. The two shaft houses are connected by a long covered storage building, but there is no refining plant here. The refinery is reported to have been ordered in Germany before the war, which prevented its delivery.

The Grewerkschaft Marie-Louise and Gewerkschaft Marie were organized in 1911. The capital stock of each of these companies is divided into 1,000 shares, of which 501 were held by the Deutsche Kaliwerke, of Bemterode, Germany.

The Marie-Louise shaft cut the potash in 1913 at depths of 2,040 and 2,109 feet. The upper potash bed is reported by a German auUiority to be 4.9 feet thick and to have an average of 32.9 per ce

40 Contributions To Economic Geology, 1920, Part I.

KO, and the lower bed to be 13.1 feet thick and to have an average potash content of 22.6 per cent. The shaft on the Marie concession was sunk at the jsame time as that on the Marie-Louise and reached the two potash beds at depths of 2,191 and 2,230 feet. The upper bed in this shaft is reported (also by German authority) to be 4.9 feet thick and to average 29.2 per cent KjO and the lower bed to be 13.1 feet thick and to average 27.02 per cent KjO. The quota for production assigned by the Kalisyndikat list of February, 1918, allowed 7.52 thousandths to the Marie-Louise shaft and 2.27 to the Marie shaft, a combined output for the mine of 9.79 thousandths. The output from these properties is not reported.

'The mine is 2 miles northeast of Wittelsheim and lies directly alongside the main line of the Strasbourg-Basel Railroad, north of Richwiller. The railroad shipping point is Bolwiller, a town of considerable size 2 miles farther north.

The mine was examined by the writer April 11, 1919. The prin- cipal workings extend north and northeast from the Marie-Louise shaft, where material from both upper and lower beds has been taken out, chiefly, however, along exploratory galleries, so that a large tonnage is definitely blocked out. A north-south drift connects the two shafts, and only a small amount of work has been done from the Marie shaft.

The two potash beds are worked by the room and pillar method at the one place where the exploratory drifts are being extended into regular mine workings. The lower part of the thick lower pot- ash bed, below a shale parting in the salts, such as has been described in the section on the Am61ie mine, is first taken out. It is the inten- tion that the overlying potash shall be removed later. At present it seems necessary to leave large pillars containing about 25 per cent of the original bed for the support of the mine roof, but it is hoped eventually to recover much of this material. In April, 1919, about 500 men were employed, of whom 800 worked underground. The output was stated as 400 tons of crude salts a day.

The potash beds are thick and very uniform or regular in char- acter in this mine, and, to judge from the analyses quoted, this and the Wittelsheim district in general seem to be near the center of deposition of the potash, the beds being of the maximum thickness for the field and the material of excellent grade. There is a marked undulation in the position of the beds, a fold at one place giving a dip as high as 40°. The potash beds in the Marie shaft are 79 feet below the level of the same beds in the Marie-Louise mine, but it is reported that no faulting is visible. The shale beds dividing the principal potash bed into layers make very perfect roofs under which the salts may be removed, and they apparently hold securely throughout the mine, even in old workings. The upper potash bed

The Potash Deposits Of Alsace. 41

is the richer of the two, averagmg, according to analyses reported bj the French operators, 26 to 27 per cent potash.

The lower and thicker bed is found in three principal divisions, similar to those in the section at the Amflie mine, separated by 6 to 10 inches of shale. About feet at the top of this lower bed consists of dark-red and white banded salts. A middle section, about 5 feet thick, is banded red and white; and the lower section, also about 5 feet thick, is more uniformly pink with white bands of salt in it. There is a foot or more of common salt at the base. The pink salt is described as sylvine. The average potash content of these divisions is said by a French authority to be 26 per cent, slightly more or less, for the upper part, 16 per cent for the middle part, and 22 per cent for the lower part, exclusive of the common salt at the base.

The potash is at a lower elevation in the Marie shaft than in the Mari&-Ix>uise, and the galleries at the base of the shaft had been filled by water that dripped through leakage about the collars of the shafts, which had not been drained at the time the property was visited. It appears, however, that water standing in these mines, without drainage or circulation, does not cause serious damage, as several diafts in the district that were allowed to fill in this way during the war and have since been drained show little or no damage.

The mine is as a whole in excellent condition for full operation. The galleries are open and regular and ietre so laid out that develop- ment may proceed according to a regular plan. The quality, regular- ity, and thickness of the beds are favorable, and when both iafts are put into operation this should be a very productive property.

Alex And Budolf Mine.

The Alex and Rudolf mine consists of two shafts on adjacent con- cessions of the same name, which together constitute essentially a single mine. The shafts are about 2,000 feet apart, and each shaft had its own set of buildings, so that operations could be conducted more or less independently. The buildings of the Rudolf were used for storing ammunition during the war and were partly destroyed by fire, so that at the end of the war they were not in condition for operation.

These properties are of original French- Alsatian ownership. The association designated in the German records Gewerkschaft Alex was founded in 1907 as a subsidiary of the Society Ste.-Th6r6se, referred to more specifically in a subsequent paragraph. The capital stock is divided into 100 shares for each concession, the greater part of which is held by the Ste.-Th&*6se association. The work had just been com- pleted at the outbreak of the war, and the property was not operated much thereafter. Preliminary quota figures for production " by the Kalisyndikat in the list of February, 1918, were $ 1278®— 21 i

42 Contributions To Economic Geoloqt, 1930, Part T.

sandths for the Alex shaft and 1.98 thousandths for the Rudolf, a total of 4.17 for the two if considered as a single mine.

The Alex and Rudolf shafts are on the main highway, about half- way between Bolwiller and Pulversheim. They are connected by a short spur track from the main line of the Strasbourg & Basel Rail- way j ust south of Bolwiller. The Alex shaft is miles in a direct line northwest of Mulhouse.

The Alex shaft is reported to be 2,624 feet deep, and this and the Rudolf passed through both potash beds.

The Alex mine was examined by the writer April 12, 1919. It is described as the last shaft sunk in the field before the war, and the equipment is evidently newer or in better condition than at most of the other mines. All is of standard Grerman make. The mine on the Alex concession consists of the shaft and the usual surface buildings, substantially built of concrete, but there is as yet no refining plant for the manufacture of the higher grades of salts. According to report 290 workmen were employed at the time of visit, of whom 210 worked underground. The production at that time was stated to be 350 tons daily of crude salts averaging 15 per cent potash (KjO), and there was in storage about 12,000 tons of crushed and ground crude salts ready for shipment.

The examination of the mine disclosed a system of galleries opened in excellent order as preliminary to the further operation of the mine. The main gallery is lined with concrete near the base of the shaft. Like the others in this field, the mine seemed very warm— in fact, uncomfortably so in the portion beyond the system of ventilation.

The potash beds are less tilted here than in the Marie-Louise property, south of the Alex. The level rises at an angle of about in the direction of the Rudolf shaft, but the gallery following the potash bed is described as passing over a saddle and then down again in that direction. The bedding exposed is exceedingly regular, with the usual succession of red and white banded salts containing partings of clay shale. At present only about 6 feet of the lower part of the main bed is being taken out, except at one place where the whole bed, exclusive of about 1 foot of common salt at the base, was being re- moved. The details of the measurements are similar to those of the Marie-Louise mine.

ste.-th£b1se mine.

The property of the Kaliwerke Sankt Therese Aktiengesellschaft, as designated on the German records, consists of the Ste.-Therftse and Begisheim concessions at Ensisheim, in each of which is a shaft. These concessions and the Alex and Rudolf, described above, are the only properties in the field that were of original French-Alsatian ownership. The titles of these properties have therefore not been

The Potash Deposits Of Alsace. 43

disturbed by the war. The association was formed in 1910, and at the end of 1915 the Ensisheim No. 1 shaft had reached a depth of 2,460 feet, and the Ensisheim No. 2 shaft a depth of 1,804 feet. No record was obtained of the depth or character of the potash beds, as these shafts are said to have been flooded during the war and were inaccessible at the time of the writer's visit.

These shafts are connected by a branch railway which joins the main line of the State railway at Bolwiller.

Technology.

Mines.

The equipment of the mines in Alsace is of standard type, similar to that of mines in the older developed potash fields of north-central Germany. As required by the German mining law, each mine con- sists of at least two connected shafts, a provision doubtless designed for safety in case of accident and to assist ventilation. The shafts are mostly lined with concrete except near the surface, where an iron collar is put down through the loose alluvial and water-bearing beds. The shafts are equipped with two elevator mine cages, apparently of a standard type. The cages are double-decked and carry a num- ber of iron mine cars in which the salts are brought from the mine. Open lights are used, as there is apparently no danger from gas. The rock temperature throughout the region is rather high (reported 42® to 48° C, equivalent to 107.6° to 118.4° F.), and comfortable working conditions are obtained by forced ventilation. The mines are dry except that in some places there is a slow seepage of water from the upper part of the shaft, where it passes through the valley deposits. This water collects in a sump and is removed from the mine in mine cars. Ordinary hand augers and electric drills are used, and the salts are blasted down. The blocks are sorted by hand and the waste is nsed to fiU the spaces mined out. Some timbering is done, mostly in the main galleries, and one gallery was lined with concrete for a short distance from the main shaft. In general the workings stand well, unless the salts are removed in entirety, when large masses of the overlying shale are likely to break down with exposure to the air.

The workings in many of the mines have scarcely advanced beyond the stage of exploratory development, with the extension of main galleries to block out the reserves. In some places a room and pillar system of working has been tried, in which both the necessity of leaving some of the salts for a roof and the large pillars required considerably reduce the percentage of recovery. It is possible that some of this material may be taken out later. In other places a "long-wall" system of mining is employed, whereby a continuous working face is advanced and the space worked out is filled to th"

44 Contributioks To Economic Geology, 190), Pabt I.

rear, generally down the slope, with waste broken out in mining and also with waste salts brought back in the mine cars from the refinery. Where the dip is steep the salts are mined in stopes by the usual manner. In many places the workings on the upper and thinner bed are reached through stopes from the lower level.

From present and past operations it seems fair to assume that each shaft may be counted as capable of bringing to the surface <600 to 750 tons of salts daily, which is equivalent to about 200,000 to 250,000 tons . a year. As the crude salt will probably average on the whole about 14 to 15 per cent, and a smaller amount will be of 20 to 22 per cnt grade, it seems fair to estimate the annual output of a single shaft if worked at approximate capacity as about 80,000 to 40,000 tons of Kfi. This is considerably in excess of the reported past production from any of the mines. For example, the combined output from the two shafts of the Theodor and Prinz Eugen mine was reported as 80,982 tons of K,0 in 1917. However, it is understood that the production of all the properties was much restricted under the man- agement of the Kalisyndikat, so that the estimate given above is thought to be as close as can be obtained from present evidence.

StTBPACE TBSATMENT.

The broken salts that are brought from the mine are passed through a bin to a jaw crusher, where the coarser blocks are brought down to about the size of a man's fist, and the material is then spread on a revolving table, where it is picked over in a hurried way by one or several workers, who remove the larger blocks of waste that happen to come to the surface with the rest. From this table it is fed to a lower level into grinding mills, which are of several types. From these the material either passes into storage for shipment as crude salts or goes into the refinery.

If the material is to be refined, it is elevated and passed through a screen. The fines are relatively cleaner and purer, and the coarse material includes more shale, which is not so readily broken up in the mills. It is then transported, usually by belt, into hoppers, from which at intervals it is fed into boiling vats fitted with agitators. Here the raw salts are heated with liquors derived from previous crystallizations. The liquors and salts from these solution vats are discharged periodically, and the residue is drawn into draining vats which have perforated bottoms and revolving rakes, the latter assisting the draining of the residue while it is still hot. When the free liquor is practically all run off the residue is thrown out at the edge by means of the revolving rakes and goes to the waste, usually beimr returned to the mine to fill old workings. The moist residue 'tains several per cent of potash.

The Potash Deposits Of Alsaoe. 45

The liquor goes to settling vats, where it stays about 15 minutes, beginning to crystallize on the surf ace almost at once. A long glass tube thrust into the solution, then closed at the top and withdrawn, shows the progress of settlement of the muddy slime, and a hinged drainage pipe is let down into the vat, so that its outlet end follows the rather distinct limit of the cleared liquid. At the last the mud and salt left in the bottom of the tank are again washed with hot mother liquor.

The liquor, which is still distinctly muddy, is drawn from the settling tanks through troughs to a battery of iron crystallizing vats of the ordinary type, where as it cools it deposits the crop of muriate (potassium chloride) of varying degrees of purity, the quantity and quality of the product obtained depending somewhat on the care with which the various steps of the process are conducted, the length of time allowed for crystallizing, and the amount of chilling. After the liquor has stood for several days it is withdrawn and returned to the process. There is so much muddy sediment in the liquor that the final product has an earthy color. The salts that crystallize on the sides of the vats are fairly clean, but no effort has yet been made to take these out separately. The crust that forms with each cooling is from 2 to 5 inches thick on the sides of the tanks and somewhat thicker at the bottom. The salt is dug out of the crystallizers by hand and loaded over the sides into tramcars, whence it is taken to a rotary dyer for finishing. The yield was reported to be a little better than 3 tons of crystallized salts pefr crystallizing vat. Thus a plant with 72 crystallizing vats, worked in three groups, would yield about 80 tons of refined product daily.

The mother liquors are used repeatedly, as the accumulation of undesirable constituents in them is slow. This is considered one of the great advantages enjoyed by this field as compared with the German potash regions, where, on account of an excess of soluble magnesian salts in the mother liquor, much of it has to be discarded regularly.

The coal consumption at a plant with 72 crystallizers, producing 80 tons of refined salts daily, was stated as 13 tons a day in the refinery and about 7 tons more for general purposes in the mine, not including electric current used for lighting. The cost of coal was quoted at 56 francs per metric ton.

Some estimates of the cost of producing the salts were compiled by F. K. Cameron* from data given by the operators in April, 1919, which are, however, basd on wage rates lower than those now ob- tained in the field. These estimates, which are given below, include

Potash from Alsace, In HearinB before the Committee on Ways and Means, House Hi BepfesentatlTea, Jaly 28. 1019. ppw 273-278.

46 Coittbibxjtioks To Economic Geology, 190), Part I.

delivery to an ocean port, which might be either Havre, Antwerp, or Botterdam, as all of these are accessible by way of the Bhine and connecting waterways.

Estimated cast per ton of producinff pottish from Alsatian deposits,

1. For potaaslom chloride averaging 18 per cent K/) or

better :

Mining $4.00

Mining . 85

Bagging 1.50

Renewals and repairs 1.00

Office and supervision . . 75

Interest 1.00

Freight 2. 00

CJost per unit of KiO . 617

2. For potassium chloride averaging 45 i)er cent KiO or

better :

Mining 10.00

Milling 4. 12

Bagging 1. 50

Renewals and repairs 4,50

Office and supervision 1. 88

Interest, etc 3. 75

Freight l 3.00

Cost per unit of KaO . 630

These figures do not include a charge for amortization, profit, taxes, and ocean freight It is reasonable to expect some of the above figures to be modi- fled downward with further experience and development of trained and ample working forces. The present freight rates on crude salts from the mine Is 20 francs to Havre, 18 francs to Antwerp, and 16 francs to Botterdam, but there Is a good prospect for early and substantial reduction, especially In the rate to Havre.

Ocean freights at the date of present writing (October, 1919) are about $6.50 a ton from European ports to Atlantic ports in the United States. It is reported that while no objection is made by the carriers to handling the lower grades of crude potash salts, the refined salts muriate) can not be shipped in wooden vessels and, if carried in steel boats, must not be allowed to come into contact with the srteel on account of corrosion. For this reason higher rates are asked by the carriers for the higher-grade salts.

Origin Op The Alsatian Potash Deposit.

Most of the geologists and others who have formulated hypotheses in explanation of the manner in which the deposits of potash in Al- sace came into existence in their present form have assumed as a basis of reasoning that the large deposits of anhydrite and common

The Potash Deposits Of Alsace. 47

salts as well as the potash are the residues left by the drying of sea water. The general assumption is that an arm of the ocean, supposed to have occupied the site of the present Rhine Valley, was partly or wholly cut off by a barrier, and that although there were subsequent incursions of sea water caused by alternate raising and lowering of the barrier, or possibly by waters breaking or flooding over the barrier at intervals, the water in the basin behind the barrier finally dried up and deposited its soluble constituents in the natural order in which such deposition might be assumed to have taken place. This has been a favorite hypothesis used by geologii to account for salt as well as potash deposits in various parts of the world. The process of over* flow of such a barrier by tide and wave action may be seen in opera- tion on a small scale in many places along the seacoast, where barrier bars built by the waves between projecting headlands cut off lagoons of salt water from free access to the sea, and in these lagoons the sea water concentrates and deposits gypsum and salt

Forster is followed by Wagner and others in an assumption of re- peated oscillations of land level in the region, to account for flooding, at times by salt water, as indicated by organic forms of marine types, or by saline deposits, or, as assumed, even by anhydrite, and at times by fresh water.

The writer is inclined to take exception to these as fundamental assumptions for an explanation of the origin of the deposits. The geologic history of the region has been very complex and can hardly be deciphered from the few clues at hand. However, it is a perfectly natural assumption that the Khine graben became in post-Jurassic, probably early Tertiary time a depression without outlet or inlet and not necessarily connected with the sea, although the bottom may have settled to and below sea level. There are many such areas in block-faulted regions, of which the Khine Valley is apparently a good example. Normal drainage tributary to such a basin would have heen impounded there, forming a lake whose surface would expand until evaporation from the surface area became equivalent to the water that flowed into the basin. The concentration of the ordinary saline constituents of river and ground waters would pro- ceed, as is exemplified in many parts of the world, and as a result an inland salt lake would very probably be formed. Slight climatic variation, through seasonal or periodic changes, would raise and lower the water level, and at periods of exceptionally large inflow the salt lake waters would be diluted and sediment would probably be spread over the bottom.

It is well known that many basins in the western United States have held deep lakes which have now entirely dried up. Such evi- dently was the final result in the Ehine graben. It is logical to as- sume in a general way that waters which drained a region r '

48 GOKTBIBUnOISrS to ECOKOHIC GBOLOGYy 1999, PABT I.

limestone, such as the region adjacent to the Rhine Valley, and which undoubtedly carried considerable calcium carbonate, might, with concentration, react with the soluble magnesian and sulphate salts in the concentrating lake water, thereby precipitating CaS04 and both CaCOs and MgCO, as anhydrite and dolomite. As the waters diminished in volume wd the soluticm became more concentrated, common salt in considerable quantity would naturally be deposited, length a solution consisting mainly of sodium and potassium chlorides remained in such proportions that with chilling sylvite began to come down. It happens that the potash-rich salts were de- posited separately from the main mass of sodium chloride, overlain and underlain by deposits of clay. The detailed structure of the de- posit is such as is readily accounted for on this hypothesb, if we assume that the chill of winter would precipitate sylvite in a thin layer, and the evaporation of the following summer would precipitate a corresponding layer of common salt. The process evidently went on for 25 to 60 years or more, until a considerable deposit of the mixture of these two salts, known as sylvinite, had accumulated. Flooding with muddy waters temporarily diluted the brine and stopped the deposition at intervals but at first was not sufficient to break up the process. After the second layer of the potash salts had been formed, for some cause — perhaps the deeper flooding with fresh river waters and the burial of the deposit with silt and possibly the establishment of an overflow outlet — the rest of the solution may have been drained away, and the adjustment of events that produced the potash did not come again.

Earth movements were probably taking place in the region durmg this time, as even now earthquakes are said to indicate a continuance of such phenomena. However, it seems unnecessary to assume an introduction of sea water to account for each deposit of salts, or even to account for the presence of marine types of organic life, for these salts are known to be accumulated in great quantity by the concentration of comparatively fresh waters, and forms of marine types are introduced and live in salt or saline water when conditions there are favorable to their existence. There is nothing catastrophic about this hypothesis, nor any assumption of unusual or very com- plex happenings. It fits with processes that may be observed in various stages to be taking place throughout the world at the present time Many of the details of the history are lacking and probably will never be known. Possibly camallite and other salts would also have been formed if the process had not been interrupted as it was, but this depends on the composition of the residual liquors from which the sylvite was produced, and these residual liquors were evi- dently lost by dilution or overflow, so that this point can not be proved.

The Potash Deposits Of Alsace. 49

1. 1877. Zundel, Ch., and Mleg, Mathleu, Notice sur qnelqaes Bondages anz

environs de Mulhouse et en Alsace [Notes on some borings In the vicinity of Mulhouse and In Alsace] : Soc. Ind. MuUiouse BulL, VOL 47, pp. 631-641.

Gives notes and such record as Is available concerning borings Sn the vicinity of Mulhouse, together with a page of profiles of 13 wells plotted for comparison. The deepest of these wells (240 meters), put down by Gustave DoUfus at DomUch In 1869, en- countered gypsum and salt and gives a basis for some discussion of stratigraphy and correlation, but otherwise this paper has no di- rect bearing on the later discovery of potash In this region.

2. 1888. 3iieg, Mathleu, Note sur un sondage execute H Domach (prte Mul-

house) en 1868 [Note on a boring put down at Domach (near Mulhouse) In 1868] ; Soc. gtol. France BulL, vol. 16, pp. 256-264.

A well put down by Gustave DoUfus in 1868, seeking water, reifbhed a depth of 240 meters (8(X) feet) , the deepest In the vicinity of Mulhouse. The paper gives the results of a detailed study of the section passed through, from the examination of samples, with notes on correlation. The upper part of the section to a depth of 28.6 meters yields fossils, which are identified, but the rest of the section. Including gypsum and some salt at the base, is re- ported as absolutely sterile. & 1906. Togt, Joseph, and Mleg, Mathleu, Note sur la ddcouverte des sels de

potasse en Haute-Alsace [Note on the discovery of salts of potash in Upper Alsace] : Soc. ind. Mulhouse Bull., voL 78, pp. 261-273.

This Is an announcement In some detail of the results of the explorations by boring conducted by the Socl6t6 Bonne Esprance under the direction of M. Vogt* through which the discovery of potash In Alsace was made. A map gives the locatlcm of the borings, with indication of the results attained (whether successful in cutting the potash or finding only salt), shows the depth and location of other borings not yet completed, and presents an inter- pretation of the structure of the potash beds by means of struc- ture contours. Many of the details of the borings are reviewed, and the nature of the deposit and its probable further extension are discussed.

4. 1906. FcSrster. B., Kallsalzlager im Ober-Blsass [Potash salt deposit lii

Upper Alsace] : Zeltschr. prakt. Geologie, Jahrgang 16, pp. 517-518. Review of "Note sur la dficouverte des sels de potasse en Haute-Alsace,** by Joe Vogt and Mathleu Mleg, 1808. (See above.)

5. 1909. FSrster, B., Yorlftuflge Mittellung fiber die Ergebnlsse der Unter-

suchung der Bohrproben aus den aelt 1804 im Gauge beflndllchen Tiefbohrungi im Ollgocftn des Ober-Elsass [Preliminary com- munication on the results of the study of the samples from the deep borings that have been In progress since 1804 in the Oligocene of Upper Alsace] : Geol. Landesanstalt Elsass-Lothrlngen Mitt., Band 7, Heft 1, pp. 127-132.

Referring to the fact as well recognized that the discovery of the large salt deposits with the associated potash layers was made

The writer detlrai to acknowledge friendly cooperation by Messrs. L. M. Prindle r J. M. Kicklee In the rerlew of the German literature.

60 CONTBIBUTIOiS TO ECCITOMIO OEOLOOY, 190, PAKT

since 1004 through the activities of an organization "Gate Hoffnung " under the direction of M. Vogt, of Nlederbruck, explains how the study of the samples from the boring was taken up by the Geological Survey of Alsace-Lorraine. Ck)re material from 33 borings in this district and the profiles from 12 others were avail- able for study In February, 1908, when this work was taken up. The paper is mostly a brief summary concerning the stratigraphy as worked out from these records and the classification made is the basis for that quoted in several subsequent papera (See No. 8 of this list) 6L 1900. Pervinquidre, L., Dcouverte de sels de potasse en Alsace [Discovery of potash salts in Alsace] : Rev. scientifique, Paris, 47* Annee, 1*' Semestre, pp. 434-435.

This is a review of the paper by Vogt and Mieg, "Note sur la dficouverte des sels de potasse en Haute-Alsace,** 1908, referred to above. It concludes by expressing the hope that this basin may extend into France, a hope that Is considered doubtful, because it has been seen that the beds thin toward the south, but as the Oligocene exists about Belfort it would be In order to make an investigation.

7. ]j910. GISrgey, R., Minerale terti&rer Kalisalzlagerst&tten [Minerals of the

Tertiary potash salts deposits] : Min. i)et. Mitt., Neue Folge, Band 29, Heft 6. pp. 517-519.

Brief notes concerning the minerals associated with the potash salts at Kalusz and in Alsace.

8. 1911. FOrster, B., Ergebnlsse der Untersuchung von Bohrproben aus den

seit 1904 Im Gange beflndllchen, zur Aufsuchung von Steinsalz und Kalisalzen ausgeftthrten Tiefbohrungen im Terti&r Oberelsass [Re- sults of the study of well samples from the deep borings in th Tertiary of Upper Alsace, which have been going on since 1904 in the search for rock salt and potash salts] : Geol. Landesonstalt Elsass-Lothringen Mitt, Band 7, Heft 4, pp. 349-24.

After a brief introductory statement as to the origin of the in- vestigations and a list of preceding publications on the subject, describes in detail the core samples from 56 borings and the Wit- telsheim shaft, and gives a tabulation of certain details from 120 borings. A discussion of structure, both folding and faulting, Is supplemented by two text figures which have been reproduced In later papers. The first estimates found of reserve tonnage of the field are made (pp. 503-504). The paper closes with a discus- sion of stratigraphy and with a collection of detailed maps and profiles In colors, which have been repeatedly reproduced in later reports. OL 1011. Wagner, W., Die Kallsalzlager im Tertlftr des Oberelsasses [The pot- ash salt stratum in the Tertiary of Upper Alsace] : Philomath. Gesell. Elsass-Lothrlngen Mitt., Band 4, Heft 4, pp. 471-486.

The paper Is a review, largely by abstract, from the FOrster paper (No. 8 of this list), with an historical geologic interpreta- tion of the stratigraphic data from the Alsace potash region. The substance of the historical record Is reviewed in the present paper under the heading Geology of the deposits." FSrster'g diagrams showing structure in the field are reproduced.

The Potash Deposits Of Alsace. 51

10. 1912. Meisner, , Der oberelsftssische Kalibergbau [The Upper Alsace

potash mining] : Gllickauf, Jahrgang 48, Band 2, pp. 1321-1324.

A rteum of what was known of the Alsace potash deposits, ac- companied by several small bnt clear text maps showing in broadly generalized outline the geology of the upper Rhine basin, the situation and means of access to the potash field, and the relative position of the 11 shafts then in existence.

11. 1912. Bell, C, Die Ausdehnung des oberrheinischen Kalivorkommens [The

extension of the upper Rhine potash occurrence] : Gliickauf Jahrgang 48, Band 2, pp. 1804-1807.

Reviews explorations by borings in various districts about the Alsace potash field and mentions a potash discovery in Baden, Ger- many. Gives a map showing former ownership of the concessions in the Alsace field, on which an area northeast of Mulhouse, lying on both sides of the Rhine, is designated new potash district." The discovery between Buggingen and Zienken of sylvinite of quality similar to that in Alsace is mentioned. However, the area of valley between the Schwarzwald and the Rhine is narrow and is cut off to the north by the Kaiserstuhl and also to the south, so that there is practically no space where such deposits may be found. At Banzenhm, on the west side of the Rhine, two borings and pos- sibly a third have revealed the potash layer, which Is similar in quality to that of the main field but only 1 to 1.5 meters thick. Various considerations make its development impracticable, in part because 160 meters of river sediments would make shaft sinking expensive; the operation at so great a depth of only a very thin deposit and the high temperature observed are also unfavorable.

12. 1912. Binder, Flix, and others. Mines de potasse dans la Haute-Alsace

[Potash mines in Upper Alsace] : Soc. ind. Idulhouse Bull., voL 82 No. 4, pp. 207-800.

This is an important work, combining under one cover a very complete record of the data available at the time concerning the potash deposits in Alsace. It contains chapters on the history by Flix Binder, on the geology and mineralogy by M. Binder and Edm. Boucart, on the borings by E. Rtoy, and on the sinking of shafts and mining by Guy de Place, as well as sections on mechanical equipment and discussions of various aspects of the potash industry by other contributors. It quotes the profiles and . plotted sections, showing the wells and the map of the field from the FOrster report (No. 8 of this list), with French legends. IS. 1912. G((rgey, R., Zur Kenntnls de Kalisalzlager von Wittelsheim im Ober-

Elsass [Knowledge of the potash salt deposit of Wittelsheim in Upper Alsace] : Mln. pet. Mitt., Band 31, pp. 389-468.

An extensive discussion, dealing chiefly with details of the potash salts and associated strata in the deposits of Alsace, baseii on microscopic study and chemical analysis of the materials col lected in the mines. Sections including the potash are described in minute detail, subdivisions a few centimeters each In thickness being reviewed and the results tabulated. From these data is derived a generalization that the sylvite and rock salt were laid down in alternating layers in pairs — an underlying salt deposit over which the sylvite was filled in compactly. The salt was

52 CONTRIBUnOKS TO ECONOMIC OEOLOGY, IMD, PAM 1.

deposited with fine grain at first, and the crystals grew larger and Irregular on the upper surface. Then the sylvite apparently came down abruptly and in fine grain, so as to fill up the irregularities in the salt layer and leave a smooth upper surface. In some places this succession is capped by a thin layer of salt and then some clay. Some good* illustrations showing the banding in the deposits are given. It is concluded, on the whole, that the Upper Alsace potash deposits are quite different in nature from any other known potash deposits and that they must have originated from solutions of distinct character. The paper Includes some colored plates illustrating the relations of the salts in the deposits.

14. 1912. Van Werveke, L., Tektonische Yorgftnge zur Zeit der Bntstehung unaerer

Steinsalx- und KalisalzlagerstEtten [Dynamic processes at the time of the origin of our rock-salt and potash-salt deposits] : Philomat Gesell. Elsass-Lothrlngen Mitt, Band 4, Heft 4, Jahrgang 1911, pp. 575-2.

In the introduction this paper mentions the other salt deposits north of Alsace, with which potash is not known to be associatedt and expresses the belief that an explanation of this difference may be found in reasons based on the structural geology. The bar hy- pothesis as an explanation of the origin of the north German salt and potash deposits is reviewed. After considering the general geologic events preceding the Oligocene, when the sea came into the Rhine Valley out of the Paris Basin, the author discusses the various oscillations of the land levels, which he says took place very irregularly in the different parts of the. Rhine Valley. The hills on the left side of the Rhine about posite the " Sundgau " are said to have formed the bar which, through its movements up and down, so ruled the access of the sea to the Rhine Basin that from time to time different deposits were formed. The basin now occupied by the potash was for the time the deepest part of the whole Rhine Valley. Nowhere north of this basin is there evi- dence of an especially strong rising of the land that would have cut off another potash basin, and therefore it appears that the author draws the conclusion that potash is not to be expected in association with the salt deposits north of the Wlttelsheim region.

15. 1912. Wagner, W., Neuere Brgebnisse tiber die Oliederung und Lagerung des

Tertiftrs im Kallsalzgebiet des Oberelsass [New results on the subdivision and the bedding of the Tertiary in the potash region of Upper Alsace] : Philomath. Gesell. Blsass-Lothilngen Mitt, Band 4, Heft 5, pp. 74a-764.

The author says that the records obtained during the sinking of the mine shafts in the potash region of Alsace have yielded additional details which were not recognizable in the bore logs. A brief review of the general stratlgraphlc classification of F5rster is given. The " Kalksandsteinzone he now finds divisible into three parts, which are named and described. The matter Is, he says, of practical economic significance, as It provided additional clues for the tracing of the extension of the potash field. Other subdivisions, including the Cyrenenmergel and the "Melet- taschlefer," are similarly treated, and a table showing thicknesses of the various members is given. This is followed by a brief review of formations underlying this section. The Dogger, which

The Potash Deposits Of Alsace. 53

Is the foundation of these Tertiary deposits, is equally developed on both sides of the Rhine and must have been evenly deposited over the present Vosges and the Black Forest The paper closes with a short /liscnssion of folds and faults and a profile section (with greatly exaggerated vertical component) across the Rhine Valley, showing the author's interpretation of the geologic struc- ture. 16w 1018. Binder, F., and others, Die Kallbergwerke im Oberelsass ]The potash

mines in Upper Alsace] : Ind. Gesell. Mulhausen Jahresber., pub- llBhed as a parate pamphlet by the Strassburger Druckerei und Yerlagsanstalt, pp. 1-03.

This is a complete translation into German of No. 12 of this list 17. 1013. Harfoort, B., Zur Frage der Genesis der Stelnsalz- und Kalisalzlager-

stfttten im Tertiftr vom Oberelsass und Baden [On the question of the genesis of the rock-salt and potash-salt deposits in the Tertiary of Upper Alsace and Baden] : Zeitschr. prakt Geologic, Band 21, ppi 18&-ld8.

This paper contains at the beginning a list of preceding litera- ture on the Alsace potash deposits. It is in the main a presenta- tion of the arguments contradicting the bar hypothesis as an ex- planation of the origin of the salt and potash deposits in Alsace. In brief, this author believes that an inclosed basin existed in Tertiary time in which a periodic drying up of the waters from Tertiary rivers took place, and that these rivers derived their salt contoit by leaching older salt and potash deposits of the Zech- stein, exposed in areas tributary to the basin.

The paper contains a statement of FOrster*s hypothesis as to the origin of the potash salts, which Van Werveke and Wagner follow in all essential details. This assumes a succession of sinkings and risings of the land, which has been referred to in the reviews of FOrster's papers. Against this hypothesis Harbort offers the fol- lowing objections. The bar theory, he says, does not now find gen- eral acceptance, even as an explanation of the north German potash and salt deposits. The Yon Walther idea is that a mediter- ranean sea existed over the whole of this area, which may not have been connected with the ocean, and that this sea gradually evap- orated so that the salt brine flowed into the lowest parts and finally deposited the salts there. Both these hypotheses presuppose a dry desert climate. Harbort questions if the Ollgooene climate could have been of this sort, citing the brown coal found in these de- posits and other plant remains, including jpalms, as evidence that it was not The bar theory does not agree with the bore profile records, which represent a manifold alternation of fresh-water, brackish-water, and marine fttcles. Therefore he disputes the as- sumption of alternating movements in the earth's crust, up and down, and sees only a major process of sinking with successive fillings by sediments from all sides of the valley. He supposes that only at certain periods was the sinking specially pronounced, so that an Infiow from the sea may have been obtained. The strong predomination of clastic sediments in the basin is said to be evi- dence against the bar theory, as this detritus did not come over a bar but came by rivers from the land, and these were of fresh

54 Contkibutions To Economic Geology, 1920, Pabt I.

water rather than of salt From the chemist'B point of view also he argaes that the salts in the Alsatian deposits are not such as would' have separated from normal sea water. FOrster, he says, recognizes this fact and argues secondary changes in the salt beds to explain their presmit composition, but the stratification of the deposits is original and not secondary and will not admit of such a hypothesis For these reasons Harbort turns away from the bar hypothesis and offers another explanation of the origin of the Al- satian salt and potash deposits, as follows :

In early Tertiary time the graben in the upper hhlne Valley was already formed and had experienced erosion and deposition of sedi- ments. Rivers from adjacent territory flowed into it, carrying salts dissolved from exposed deposits in neighboring reglona There are no salt deposits in the Zechstein in this immediate vicin- ity, but some regions to the north, as for instance north of Heidel- berg, might have had the Zechstein salts, which may have washed out and drained into the Rhine Valley. These river waters prob- ably came In dilute but dried up i)eriodlcally, especially during the summers. Calculations show that the Alsatian deposit is relatively small as compared to even a small part of the Zechstein deposits, so that the washing away of even a small part of the Zechstein might easily account for the whole deposit in the Rhine Valley. This hypothesis as to the origin, therefore, assumes that It is descendant or secondary, derived fkt>m the older deposits of the Zechstein.

The paper contains some good views showing bedding or banding of the deposits.

18. 1918. Wagner, W., Verglelch der Jflngeren Tertiarablagerungen des Kall-

salzgebletes im Oberelsass mlt denen des Mainzer Beckens [Com- parison of the younger Tertiary deposits of the potash region in Upper Alsace with those of the Mainz Basin] : GeoL Landesanstalt Elsass-Lothringen Mitt, Band 8, Heft 2, pp. 273-287.

19. 1914. Van Werveke, L., Die Tektonlk des Sundgaues Ihre Beziehung zu

den Kallsalzvorkommen Im Oberelsass und in Baden und ihre Entstehung [The tectonics of the "Sundgau," its relation to the potash salt occurrences in Upper Alsace and in Baden, and their origin] : Geol. Landesanstalt Elsass-Lothringen Mitt, Band 8, Heft 2, pp. 235-271.

This Is a discussion on lines laid down in previous papers by the same author. The first sections of the paper discuss the folds and faults In the general vicinity of Mulhouse in the Rhine Valley and are followed by a section on the age of the disturbances.

An appendix Is added in which a reply to the Harbort discus- sion (No. 17) is given. Van Werveke does not believe the Alsatian deposits were derived from the Zechstein. There Is abundant In- dication, he says, that fresh water came from the north into the Rhine Basin, but none came from salt deposits. Referring to an argument of Harbort*s about the formation of bitumen in rela- tion to salt de];>osits. Van Werveke says this could not be so be- cause " petroleum is bound to fresh-water strata." Only by sink- ings and mobile bars and closable bays were conditions to be had for the deposition of potash in Alsace. Explaining again in detail the tectonics by which the Rhine graben came into existence, he

The Potash Deposits Of Alsace. 55

concludes with the statement that differential motions of this part of the earth's surface have occurred, resulting in the shutting off or letting in of the sea from time to time, and that through these events the potash and other deposits were formed.

20. 1915. Rozsa, Von M., tber den chemischen Aufbau der KaUsalzablagerungen

im Tertiftr des Oberelsass [On the chemical composition of the potash salts deposits in the Tertiary of Upper Alsace] : Zeitschr. anorg. Chemie, Band 83, pp. 137-160.

Rozsa says that the chemistry of the deposits corroborates the hypothesis, based on geologic evidence, that in the Tertiary history of the Wittelsheim Basin there have been discontinuous periods of evaporation of mixtures of brine derived from Inflows of sea water, residual brines from former crystallizations in the basin, with the added fresh water of tributary drainage. As a result there Was a complete elimination of kalnlte and klserlte, with the precipitation of sulphates and magnesia in dolomite and anhydrite, and the salts deposited were sodium chloride, potas- sium chloride (sylvite), and camalllte. The camallite, according to this writer, suffered in places a secondary change to sylvite. The alternation of salts and sediments is stated to have been caused principally by periodic temperature changes of the evapo- rating brines.

2L 1916. Van Werveke, L., Die Ergebnlsse der geologlschen Forschungen in

Elsass-Lothringen und ihre Verwendung zu Krlegszwecken [The results of the geologic investigations in Alsace-Lorraine and their application to the purposes of the war] : . €resell. Strassburg ., Heft 28.

This paper is introduced with a sununary of the geologic work done in Alsace-Lorraine, including a list and diagrams of maps that have been published. It gives a discussion of the subject of potash in Alsace and (on p. 58) a recalculation of the reserve tonnage of potash salts in the field as 97f million cubic meters of salts in the upper layer and 608i million cubic meters in the lower layer, which, at a specific gravity of 2.1, gives a total of 1,472 million tons of salts.

22. 1916. Wagner, W., Elnpressungen von Salz in Spalten der oberels&ssischen

Salz- mid Kallsalzablageningen. Eln Beitrag zur Frage vom Aufsteigen des Salzgeblrges [The injection by pressure of salt into fissures of the Upper Alsace salt and potash deposits] : GeoL Landesanstalt Elsass-Lothrlngen Mitt., Band 9, Heft 2, pp. 185-159.

Discusses some specific phenomena of compression as evidenced in the salt and potash deposits, and gives some excellent illus- trations of specimens, with identification of the salt and sylvlne parts.

23. 1917. Binder, F61iz, Rapport de Tlndustrie de la potasse de la Haute

Alsace [Report on the potash Industry of Upper Alsace], pp. 1-91, Mlnlstdre de la guerre. Service d'Alsace-Lorralne, Paris.

24. 1918. Kestner, Paul, The Alsace potash deposits: Soc. Chem. Industry

(London) Jour., November 15. 25. .1919- Cameron, Frank K., Potash from Alsace: Hearings before CJom. Ways

and Means, House of Representatives, on H. R. 4870, part 6, pp. 27a-278.

A Deposit Of Manganese Ore In Wyoming-

By Edward L. Jones, Jr.

Introduction.

Few manganese deposits are known in Wyoming, but one deposit in the Laramie Mountains that was reported to the United States Geological Survey was visited by the writer on October 5, 1917. At that time the deposit was being exploited by the Poverty Mining Co., of Liaramie, and 200 tons of ore containing about 40 per cent of manganese was on the dumps, although no ore had been shipped. The deposit is opened by a tunnel and a drift 190 feet in total length, which connect with a shaft 25 feet deep. Six claims constitute the group, which was located April 11, 1916.

Geography.

The deposit of the Poverty Mining Co. lies on a gently sloping mesa on the western flank of the Laramie Mountains, near the head of Sheep Creek, at an altitude of approximately 8,000 feet above sea level. It is accessible from Medicine Bow, on the Union Pacific Railroad, by a fair wagon road 38 miles long. Near the deposit Sheep Creek has eroded in the mesa a channel 250 feet deep, which affords a measure of the relief. The rainfall is moderate, and the vegetation consists principally of grasses and small shrubs. Water level has not been reached in the workings.

Geology.

The core of the Laramie Mountains is a coarse-grained red granite of pre-Cambrian age, but flanking, it on the west side is a series limestones and sandstones which range in age from Carboniferous to Cretaceous. These rocks underlie the mesa toward Medicine Bow. The manganese deposit is interbedded in limestone and sandstone of the Casper formation, of Carboniferous age, which here overlies the granite. In the vicinity of the mine the beds dip generally at low angles to the southwest. Granite crops out a short distance east of the deposit and is exposed in the bed of Sheep Creek half a mile northwest of the deposit, where the stream has eroded its channel through the Casper formation.

1278**— 21-

58 Contributions To Economic Geology, 1930, Part I.

Ore Deposit.

The manganese ore is contained in two beds of chert a few feet apart, each ranging in thickness from 1 to 8 feet, which are intercalated in beds of pink and maroon limestone and thin sandstone. The average thickness of each chert bed is about 6 feet. Chert float occurs abun- dantly over a wide area in the vicinity of the Poverty mine, and prob- ably several beds of manganiferous chert are included in the Casper formation. The extent of the manganiferous chert beds of the Pov- erty mine beyond the workings is not known. The beds are exposed from the portal of the tunnel to a point near the shaft. From the portal the tunnel is driven north for 120 feet, to a point from which a drift to the east 70 feet long connects with the shaft at a depth of 25 feet. Both chert beds are explored by the workings, the upper bed being followed by the tunnel and the lower bed in part by the shaft and in part by the drift. Near the right-angled bend in the tunnel a cave of considerable size was found along an easterly fissure in the limestone. It is reported that the walls of the cave were cov- ered with crusts of manganese oxide and quartz crystals, but the cave is now filled with waste rock.

The ore consists of the manganese oxides manganite and pyrolusite in mammillary crusts and nodular aggregates which have wholly or partly replaced the chert and to a less extent the beds that inclose it. The ore occurs irregularly in the chert beds, though generally most of the high-grade ore is obtained from the upper parts of the beds. The writer estimates that 2 feet of ore could be sorted from each bed ; but the greater part of the manganiferous chert is too siliceous to be valuable unless some economical method of treating the material could be devised. Two varieties, one dark and one light, were noted. The dark chert is a dense, hard material that is believed to have been originally deposited in the limestone, and the light chert is a chalced- onic variety which was deposited secondarily after the dark variety. Masses of the dark chert are incrusted with manganese oxides and fractures in the chert are filled with manganese oxides and second- ary silica. Several cycles of sobition and replacement of the chert are represented, for the light chert is in process of replacement by arborescent growths of manganese oxides, and the chert which they replace is redeposited in cavities of the ore in bluish layers. Small quartz crystals project from the outer layer into the cavity. Quartz crystals were in places deposited over layers of manganite crystals in vugs in the ore, but here and there the process was reversed and scattered small manganite or pyrolusite crystals were deposited on quartz crystals. A thin section of the light chert that was under- going replacement by manganese oxide was studied under the micro- scope. The chert is fine grained, and the silica has been deposited in

A Deposit Of Manganese Ore In Wyoming. 59

laminae and in aggregates of nodules which show radial and con- centric structure. The borders of the growths of manganese oxides are marked by prismatic crystals and minute spindles that extend into the chert.

Manganite and pyrolusite are the oxides of manganese present. The deposit is unusual for the abundance of crystals developed in the ore. Owing to its mode of formation the ore contains many cavities, and these are lined with botryoidal clusters of sparkling small wedge-shaped crystals whose crystal form is that of manganite but which in hardness and streak correspond to pyrolusite. The crystals break down readily into a bluish-black powder which soils the fingers. However, the inner layers of the nodules are manganite, and manganite crystals compose the arborescent growths in the light chert. The pyrolusite is therefore regarded as an alteration product of manganite. Psilomelane was not observed in the ore. Where clay or sandy limestone has been replaced by manganese oxides the ore is a cellular aggregate of small manganite crystals.

Barite occurs in vugs in the ore in large tabular crystals, but it is nowhere abundant, and calcite also occurs sparsely. Iron oxides are probably contained in the dark chert, but they could not be de- tected in association with the manganese oxides.

The source of the manganese oxides is believed to be the dark chert, which was deposited with the limestone and sandstone. By processes of weathering and leaching, probably by carbonated waters, the manganese minerals of the dark chert were dissolved and re- deposited in their present form, replacing the chert and wall rocks.

Some Deposits Of Manganese Ore In Colorado.

By Edward L. Jones Jr.

Introduction.

For many years large quantities of manganiferous silver ore have been mined from the oxidized parts of the lead-silver deposits of the Leadville district, Colo., for use as flux, and from time to time some of this ore has been converted into spiegeleisen by the Colorado Fuel & Iron Co., at Pueblo. The first shipment of high-grade man- ganese ore from Colorado was made in 1915, but the known high- grade deposits are small and not readily accessible, and so far only a few hundred tons has been shipped. Notwithstanding the small production of manganese ores the search for new deposits has been energetically carried on, and to the end of 1918 many discoveries were reported to the United States Geological Survey and to the Colorado Geological Survey. In order to obtain data for an esti- mate of the quantity and grade of manganese ore available in this country, the United States Geological Survey during the war as- signed several geologists to the examination of deposits in the West- em States. In August, 1917, J. B. Umpleby made brief visits to the Leadville and Red Cliffs districts, Colo., and the results of his investigations were made known in articles published in the mining press in the fall of 1917. Other deposits that were on record in the United States Geological Survey — situated in Chaffee County near Salida, Gunnison County near lola, in Saguache County near Moffat, and in western San Miguel County — were visited by the writer early in August, 1917. After that examination many more discoveries were reported, and the deposits were examined by the Colorado Geological Survey in 1918. The new localities examined mclude many in Gunnison and Hinsdale counties; the Ouray dis- trict Ouray County; the Rico district, Dolores County; the West- diffe district, Custer County ; and near Needleton, La Plata County. The present report treats only of the principal features of the man- ganese deposits visited by the writer, but some of the valuable data obtained by the Colorado Geological Survey are incorporated in the descriptions of the types and geologic occurrence of manganese de- posits in the State.

ei

62 Contributions To Economic Geology, 1920, Part I-

Geologic Occurrence.

Deposits of manganese ore occur in Colorado in sedimentary and igneous rocks representing a wide range in geologic age. The sedi- mentary rocks inclosing them range in age from pre-Cambrian slates through Paleozoic, Cretaceous, and Tertiary formations to Quater- nary sandstone, and the igneous rocks range in age from pre-Cam- brian to Tertiary.

Types Op Manganese Deposits.

The manganese deposits of Colorado occur (1) in veins and brec- ciated zones; (2) as replacement deposits; and (3) as probable original bedded deposits.

VEINS Am) BBECCIATED ZOKES.

The veins and brecciated zones constitute by far the most numerous type of manganese deposits in Colorado, but economically they have proved of little importance. They occur in both igneous and sedi- mentary rocks which range from pre-Cambrian to Tertiary in age. The deposits of this type may be further classified into (a) those in which the manganese minerals are of hypogene origin or are the oxidized products of hypogene minerals, and are associated with silver and gold ores, and (6) those in which the manganese minerals are of supergene origin and are associated with no other metallic minerals except iron oxides. The Colorado Geological Survey re- ports deposits of manganese minerals of hypogene origin associated with silver-gold ores in the Cripple Creek, Ouray, and Rico districts, and deposits of supergene origin as widespread in Tertiary lavas in "Gunnison and Hinsdale counties. The origin of manganese oxides in Tertiary lavas is obscure. That the oxides were derived from widely disseminated manganese minerals appears doubtful to the writer.

Beflagekent Deposits.

Replacement deposits of manganese ores occur principally in the oxidized parts of lead-silver deposits in the Leadville district and of deposits containing zinc and iron sulphides in the Red Cliff district. In both localities the deposits are in Carboniferous lime- stone, and the manganese ores are derived from the oxidation of manganiferous siderite. Small replacement deposits occur along the bedding of Paleozoic limestone near Salida, in sandstone and tuff beds associated with Tertiary lava flows in Gunnison and Hins- dale counties, and in sandstone of Upper Triassic age in San Miguel County.

Manganese Ore In Colorado. 63

Bedded Deposit.

A deposit of manganese ore which probably represents the oxidized and enriched part of an original sedimentary bed occurs in sandstone and shale in western San Miguel County.

Manganese Minerals.

The manganese ores are composed dominantly of the oxides pjrro- lusite, manganite, psilomelane, and wad, generally mixed with iron oxides. In the deposit east of Moffat, in Saguache County, haus- mannite was noted. In the most valuable deposits the oxides are the residual products of the weathering of manganiferous siderite, rhodo- chrosite, and manganiferous calcite, but in a number of places they have been deposited at some distance from their source by meteoric waters. According to the Colorado geologists, the oxides in the veins and breccias in Tertiary lavas and in the deposits that replace associated tuff and sand beds were probably laid down by meteoric waters which dissolved the manganese contained in small quantities in ferromagnesium minerals of the lavas.

Deposits.

Chapfee C0T7Ntt. Location.

Several small manganese deposits occur near Salida, in the west- em slope of the Sangre de Cristo Range east of Arkansas Eiver. One deposit, owned by W. Higham & Sons, is 10 miles north of Salida, and the Boyer & Frankenberry property and several other claims are in a small canyon draining to Arkansas River 8 miles south of Salida and a few miles east of Wellsville, a station on the Denver & Rio Grande Railroad. The outcrops of manganese ore have long been known, and claims were staked over them many years ago, but it was not until 1916 that they were exploited as sources of manganese ore. During that year six carloads were shipped from the Higham property and a small quantity from the Boyer & Frankenberry deposit. No work was being done on either property at the time of the writer's visit in August, 1917. The Higham deposit is accessible from Salida by a wagon road 10 miles long, and the Boyer & Frankenberry deposit from Wellsville by a wagon road 2 miles long.

StTBFACB FEATUHES.

The region is high and extremely rugged ; the crest of the Sangre de Cristo Range east of Salida is well above 10,000 feet in altitude,

64 Contributions To Economic Geology, 1930, Part I.

and many of the peaks reach 12,000 feet or more. Barometric read- ings at the manganese deposits gave altitudes from 7,500 to 9,300 feet. The deposits are in canyons that contain intermittent streams draining to Arkansas Biver. In none of them has water level been reached in the workings.

The climate is characterized by short summers and long winters, with heavy snowfall. Cedar and several other varieties of conifer- ous trees are fairly abundant in the higher mountaina

Geology.

The inclosing rocks of most of the manganese deposits are mas- sive, thick-bedded gray Paleozoic limestones, but one deposit occurs in aplite. The limestones are well exposed near Wellsville, where Arkansas River cuts through them, and they extend northward along the Sangre de Cristo Hange to and beyond the Higham property. Sandstone, gritstone, and shale overlie the limestones east of Wells- ville, where the sediments strike a little west of north and dip east- Wfird. At the Higham property the limestones are apparently hori- zontal.

Various kinds of igneous rocks were observed, including diorite, aplite, rhyolite, and andesite, but no attempt was made to determine their relations.

Ore Deposits.

The manganese deposits are fissure fillings in limestone and aplite and replacement deposits in limestone adjacent to fissures. The ore bodies disclosed by the mine developments are small, and the known deposits contain from a few tons to a few thousand tons of ore. The manganese oxides are principally wad, pyrolusite, and psilomelane. These oxides in the limestone are associated with coarsely crystalline carbonates and with much secondary calcite. One of these carbonates is siderite, which decomposes to limonite and wad. Iron oxides are abundant in the ore from the Higham deposit, but in the deposits east of Wellsville only a small percentage of iron is present.

Mines And Prospects. Liberty Hill Olaimb.

The Liberty Hill group of two claims, owned by W. Higham & Sons, of 'jSalida, is 10 miles north of Salida and 1 mile south of the Calumet iron mine, formerly worked by the Colorado Fuel & Iron Co. The claims were located in January, 1916, and in that year six carloads of manganiferous iron ore, containing 20 per cent of man- ganese, were shipped to the Colorado Fuel & Iron Co. at Pueblo, to

Manganese Ore In Colorado. 65

Perth Amboy, N. J., and to Pittsburgh. The workings are on a gently sloping surface at an altitude of 9,200 feet and are several hundred feet lower than the summit of a mountain a short distance east of the claims. They consist of a number of shallow holes and 8 shaft 50 feet deep within an area 150 feet in diameter. The de- posit is contained in a flat bed of massive gray limestone, probably of Paleozoic age. The ore is in lenses and irregular masses from 1 to 4 feet thick, which occur a few feet beneath the surface and adjacent to an irregular vein exploited by the 50-foot shaft. The deposit yields a mixture of soft brown oxides of manganese and iron which contains about 20 per cent of manganese and more iron. The mechanical separation of the manganese and iron oxides does not seem to be possible. The material on the (Jump from the shaft contains a considerable quantity of a coarsely crystalline carbonate that is undergoing decomposition to yellowish iron oxides and there- fore is probably siderite. It is regarded as the source of the man- ganese oxides. Several hundred tons of the manganiferous ore is exposed by the workings. Without some economical method of beneficiation it is doubtful whether any profit can be made from these ores.

Ibov Xovvtaxv Olazicb.

The Iron Mountain group of two claims is in Wells Canyon, 2 miles east of Wellsville, at an altitude of 7,700* feet. The claims are owned by Boyer & Frankenberry and were located January 1, 1916. Two carloads of ore were shipped to the Colorado Fuel & Iron Co., of Pueblo, one in 1916 and the second in June, 1917. The smelter settled for the second carload on the basis of 39.42 per cent of manganese, 3.60 per cent of iron, 3.80 per cent of silica, and 0.03 per cent of phosphorus. The deposit is explored by a tunnel 150 feet long, with short drifts and a raise that extends from the tunnel level 65 feet to the surface on the dip of the vein.

The manganese deposit is contained in beds of a massive gray limestone, which at the outcrop strike N. 20® W. and dip 85° E. At the tunnel level the strata are sharply flexed and broken and the deposit and inclosing beds are flat or dip gently to the north. The ore was formed mainly by the replacement of a bed of coarsely crystalline limestone and clay from 2 to 6 feet thick, but where the strata are broken the ore also extends in irregular masses into the limestone. At the outcrop the ore is a crustiform mass of man- ganese oxides composed of an aggregate of short columnar rods with rounded ends. The center of each colmnn is pyrolusite as a soft black powder, which is surrounded by a thin shell of hard psilome- lane. The ore is of high grade, but tiie deposit is only 1 foot thick.

66 Contributions To Economic Geology, 1920, Part I. .

Much secondary calcite occurs in and above the ore. In the tunnel a section of the deposit is as follows :

Section at Iron Mountain manganeie claim.

Ft. In.

Soft, decomposed limestone or clay 6

Crusted calcite in small white crystals 6

Soft black mangarese oxides 1

Crystalline limestone or carbonates, partly replaced by iron

and manganese oxides or altere<l to them 1

Banded brown clay with streaks of soft black manganese ore and lenses of hard ore 3

The soft black oxides are of high grade and the hard crusts — which are coarse crystals of carbonates partly replaced by manga- nese and iron oxides — are medium or low grade ore. Pyrolusite and wad are the dominant oxides, but psilomelane is also present. Loosely coherent masses of secondary calcite in delicate white crys- tals, some of them 2 feet thick, generally occur above the topmost ore stratum, and smaller masses are scattered through the deposit. The source of the manganese oxides is not apparent. A specimen of coarsely crystalline calcite is impregnated with dendritic growths of manganese oxides and clearly shows that the manganese was not derived from the decomposition of the calcite of the specimen; but in other parts of the deposit coarsely crystalline carbonate is partly replaced by manganese and iron oxides in such a manner as to sug- gest that the oxides were derived from the decomposition of the carbonate.

The ore is prepared for shipment by screening, for the fine mate- rial and a smaller quantity of hand-sorted lumps contain about 40 per cent of manganese. The deposit has been only partly explored, but enough work has been done to show a reserve of 2,000 tons of material containing about 40 per cent of manganese.

Bev Bots& 0Laix8.

Two claims owned by Ben Boyer lie a short distance south of the Iron Mountain group. A tunnel 15 feet long which cuts thick- bedded limestone is the only opening on the claims. The limestone is broken by a north-south fissure, and above the floor of the tunnel small masses of manganese oxides occur in crevices. The manganese oxides form crusted botryoidal masses and short, redlike growths. Pyrolusite or wad forms the center of each rod or concretion, and the outer shell is hard psilomelane. Secondary calcite is abundant in the ore, and it assumes the same concretionary forms as the man- ganese oxides. Only a small quantity of ore is disclosed by the tun- nel, and it is not known to what depths the oxides extend in the frac- tured limestone.

Mangakbse Orb In Colorado. 67

Other small manganese deposits have been found in massive lime- stones on the ridge above the Iron Mountain and Boyer claims, but little development work has been done on them, and in order to market the ore it would be necessary to build a road 2 miles long.

Oalpzv Vbsslavd 0Lazx8.

Two claims owned by Galpin & Vreeland are on a ridge at the head of Potkill Gulch, about miles east of Wellsville. They are at an altitude of 9,300 feet and are miles distant from the nearest road in Wells Canyon. There has been no recent development work, and the location is based on the presence of manganese oxides in material on the dump of an old shaft which is now caved. The country rock is a sheared fine-grained aplite, in which manganese oxides form Teinlets as much as 4 inches thick. The oxides are psilomelane and pyrolusite, and they have not only been deposited in open fissures but also replace the sheared aplite. The width and trend of the deposit could not be ascertained, as the deposit does not crop out.

QTSJsnsnaoN county.

POTTZa OLAZXB.

Several claims located for manganese by J. G. Potter are miles north of lola, in a small canyon which is drained by a stream that flows to Gunnison Kiver. A newly made road extends to lola, a sta- tion on the Denver & Rio Grande Kailroad. Several shallow open cuts and a tunnel 70 feet long constitute the workings on these claims. No ore has been shipped from the property, and the quantity dis- closed by the workings is so small that further work is not advisable.

The claims lie in a canyon several hundred feet below the summit of a hill at an average altitude of 8,600 feet. From the Gimnison Valley a gravel-capped mesa extends northward for about 2 miles along the canyon in which the manganese deposits are situated and merges into the outlying ridges of the higher mountains. The mesa is underlain by sandstone, tuffs, and agglomerate, which are capped by lava flows, and all the rocks are probably of Tertiary age.

The manganese minerals are contained in small seams and fissures, which cut the sandstone and tuff, and in small nodules in the sand- stone.

A vertical fissure vein which strikes N. 15° E. is exposed in an open cut- The vein material is composed of clay gouge 6 inches thick, in which some chert or chalcedonic material contains narrow veinlets of manganese oxides. The veinlets are not persistent, and it is not possible tfi separate a marketable grade of manganese oxides from the siliceous matrix. In another open cut horizontal sand- stone is cut by veinlets of manganese oxides a fraction of an inch

68 GONTBIBUnONS TO ECONOMIC QJ&OIX>QY 1020, PART I.

thick — not think enough for commercial exploitation. In places small sandstone nodules partly replaced by manganese oxides pro- ject from the weathered surface. A tunnel 70 feet long driven on the fissure explored by the open cut disclosed no ore.

SAQITACHE GOXnTTT. 2B0V KZVa 7&0BPX0T.

The Iron King prospect, owned by the Miller Mining & Milling Co., is in Saguache County, about 15 miles east of Moffat, on Cedar Creek, a small stream that flows westward to San Luis Valley. From the prospect to the valley, 8 miles distant, the road is steep and in poor repair, but the remaining 12 miles to Moffat over the level valley floor is good. In August, 1916, the company shipped 10 tons of ore that contained 41 per cent of manganese, 4.75 per cent of iron, 0.0402 per cent of phosphorus, and 16.28 per cent of silica. Since 1916 no work has been done, and the developments disclose little ore. The property is opened by several short tunnels driven in the mountain side at altitudes ranging from 9,200 to 9,700 feet and by open cuts and trenches.

Quartzite, conglomerate, and slate intruded by small masses of granite and rhyolite dikes are the rocks in the vicinity of the prospect. These rocks have been greatly faulted, and the sequence of the sedimentary formations is not apparent. Manganese minerals occur in several localities as replacement deposits in shear zones in the granite and a3 small veins in the sedimentary rocks. The small shipment came from a lenticular body in the granite. In the sedi- mentary rocks the manganese oxide occurs in narrow veins associated with fluorite and quartz. Some specimens show manganese oxides incrusted with fluorite several inches thick, and the fluorite is coated with small quartz crystals. A specimen from a body in the granite is composed of a complex intergrowth of psilomelane and a crystal- line aggregate of hausmannite.

SAN MIGUEL COTTKTY. 0LAZX8 OF OOLOBABO XAVGAVX8S MOnSQ BMZLTXVG 00.

Location. — Deposits of manganese minerals occur in the western part of San Miguel County, in a basin at the head of a gulch that drains to Disappointment Creek near Cedar. The principal out- crops of manganese minerals have been included in a group of five claims owned by the Colorado Manganese Mining & Smelting Co., of Denver. The claims were located in 1914, and in 1915 several small lots of ore aggregating 120 tons were shipped to Chicago. No min- ing has been done on the property since 1915. Most of the develop-

Manganese Ore In Colorado. 69

ment work on the group is centered in the Black Diamond claim, from which the shipments were made, and consists of two tunnels 90 feet apart, driven on the outcrop of the bed. One tunnel is driven eastward 150 feet, and the other tunnel is connected to it by a drift or gallery 65 feet from its portaL About 250 feet of development work has been done.

The deposits are approximately 50 miles by wagon road from Placerville, a station on the Denver & Bio Grande Railroad. The road goes by way of Norwood, 18 miles from Placerville, and to that point it is in excellent condition, but beyond Norwood it is little traveled and in many places is steep and rocky. The road passes within half a mile of the mine, and the material was packed to the road by burros. It is at once apparent that unless more favorable transportation facilities are afforded the deposit can not be worked at a profit.

Surface features, — The deposits of manganese minerals occur in the rim rocks which mark the eastern and southern boundaries of a basin, and in steeply folded rocks in the northern part of the basin. The floor of the basin is about 6,400 feet in altitude, and the highest point on the eastern rim is about 7,100 feet. The western rim is much lower than the eastern, and in two places branches of a gulch have eroded channels through it and find outlet to Disappointment Creek. Within the basin there is a spring, but the nearest perennial stream is Disappointment Creek, 6 miles distant.

The climate is arid, but the rainfall is sufficient to support a growth of pinon and cedar.

Geology. — The rocks in the vicinity of the manganese deposits are all sedimentary and consist of gray, red, and brown sandstone, with interbedded red and green shale, which overlie fossiliferous lime- stone and shale exposed in the floor of the basin. A maximum thick- ness of about 800 feet of sediments is exposed in the eastern rim of the basin. A deposit of gravel 75 feet thick lies on a ridge northeast of the prospect. The series of rocks is known as the Dolores forma- tion, which is of Upper Triassic age.

Structure. — The basin has been formed by the erosion of an anti- cline that plunges toward the southeast On its eastern, southern, and western borders are the hard rim rocks of sandstone, which in places in the eastern rim form cliffs 50 feet high. The floor of the basin is underlain by softer shale, clay, and limestone. From the manganese prospect southwestward across the basin to the opposite sandstone rim the distance is approximately 1 mile. On the eastern rim at the prospect the rocks are flat or dip gently east. Southward from the prospect the dip gradually swings toward the southeast, and at the south end of the basin the beds dip 20° S. The average dip

70 Contributions To Roonomic Geology, 1920, Part I.

of the beds in the western rim is about W. At the north end of the basin the limestones and shales underlying the sandstones are compressed into a sharp fold, with dips of 60 to the northeast and southwest on either side of the axis.

Ore deposits. — Three types of manganese deposits are found here — (1) a thi-bedded deposit between sandstone and shale in the east- em rim of the basin, (2) small irregular lenses and nodules in a brown sandstone bed at the south end of the basin, and (3) small veins in the closely folded shales at the northwest end of the basin.

The bedded deposit is the only one of commercial importance, and from it the shipments were obtained. The bed is overlain by red clay and underlain by red sandstone. In the tunnels it dips about 10 E. or lies flat with local undulations. From the workings the bed can be traced southward for about 1,500 feet, but at no place other than that where the development work was done does it show evidence of yielding ore in commercial quantities.

As it comes from the mine the material is in rather soft lumps of finely granular pyrolusite, though cavities in it are lined with short, minute velvety crystals that are probably manganite. The best mate- rial is said to contain 80 per cent of MnO,, corresponding to about 50 per cent of manganese. Calcite occurs in varying amounts in the de- posit ; small quantities of secondary origin are found in the thoroughly oxidized part of the bed near the portals of the tunnels, but it is in- creasingly abundant toward the faces of the tunnels, where it repre- sents the unweathered part of the bed. The limit, of rich oxides is reached about 100 feet from the portal. At the face, 150 feet from the portal, the bed, which is about 6 inches thick, is only partly decom- posed and replaced by manganese oxides. Here the bed consists of coarsely crystalline calcite in shades that range from white to brown. In a specimen obtained from the face of the tunnel decomposition of the carbonate and replacement by manganese oxide have set in at the top of the bed and extend for 2 inches, yielding a brownish- black substance in which some of the crystal faces of the original carbonate are preserved. Below this decomposition band the calcite is spotted with minute brown needles of manganese oxides, and in a few places nests of manganite crystals are found. A film of man- ganese oxides is locally formed on the cleavage faces of the calcite. Some small calcite fragments which were apparently free from the brown specks were tested and found to yield a small quantity of manganese. Several hundred feet south of the main workings the bed contains barite and here and there stains of copper carbonate in addition to the manganese oxide, but the deposit is too thin and of too low grade to be valuable. Rd and green chert nodules are also associated with the bed at this locality.

Manganese Ore In Colorado. 71

The deposit has been opened for about 100 feet along the outcrop, and the depth of commercial ore is approximately 100 feet. The thickness of the bed ranges from a few inches to 2 feet, with a probable average of 10 inches in the workings. In all, probably 2,000 tons of ore containing about 40 per cent of manganese could be obtained from the deposit. Of this quantity 50 tons would probably yield 50 per cent of manganese.

Origin, — The interbedding of the coarsely crystalline calcite and the manganese oxides suggests that the calcite is of sedimentary origin, but its coarsely crystalline texture would suggest vein filling. Although tests of apparently fresh calcite showed the presence of manganese, the quantity was very small and certainly not enough to account for the richer portions of the deport. Manganese in solu- tion, therefore, probably came from some unknown outside sources and replaced the calcite bed, proceeding from the top downward, as shown by the specimen obtained at the face of the main timnel.

The manganese deposits of the replacement type are found at the south end of the basin, where they are exposed through a vertical distance of 20 feet, and for several hundred feet along a cliff ex- posure of brown sandstone. The deposits yield small irregular masses of manganese oxides, some of which lie along the bedding in tabular form and have a maximum length of 15 feet and thick- ness of feet, vertical tabular masses, chimneys, and boulder-like nodules of various sizes. The line between the ore bodies and unre- placed brown sandstone is sharply marked. The manganese oxides are principally manganite as needle-like crystals about a quarter of an inch long and as short prismatic crystals in granular aggre- gates. Pyrolusite is a minor constituent of the ore. The needle-like crystals were formed in the larger bodies, and barite crystals are commonly found in the centers of the masses. The smaller nodules represent incomplete replacement of the sandstone by manganese oxides, for they contain some unreplaced quartz grains. The man- ganite in these nodules is in short prismatic crystals which usually form cellular masses.

The evidence of the origin of these manganese oxide bodies is obscure, but the most feasible explanation appears to be that the manganese minerals in the form of oxide or carbonate were originally disseminated in the sandstone and through processes of concentration and replacement have attained their present forms. The nodules and masses of manganese ore are so sparsely distributed in the sand- stone beds that it is very doubtful if they can be profitably mined, even under the most favorable conditions.

No manganese deposits have been found on the west side of the basin, although a vein composed principally of coarse-grained calcite

72 Contributions To Economic Qeology, 1920, Part I.

and barite with small amounts of copper carbonates and native copper occurs there.

At the north end of the basin manganese oxides occur in small fissures and yeinlets which strike N. 75 W. and dip steeply north. The inclosing rocks are a grayish or faint purple limestone and un- derlying shale beds which strike N. 80 W. and dip 50 S. One vein whose maximum "width is 8 inches was traced for 76 feet, but there is not enough material in sit to encourage exploitation of the de- posit. The manganese oxides are pyrolusite and manganite, and they are associated with calcite and small amounts of barite.

Geology Of The Yellow Pine Cinnabar-Mining

District, Idaho.

By EfiPEB S. Labsen and D. C. LiviNOffroN.

Introduction.

The Yellow Pine district was visited by Mr. Livingston, of the University of Idaho, early in August, 1918, and by Mr. Larsen, of the United States Geological Survey, a few weeks later. Mr. Liv-r iDgston spent five days in the district and Mr. Larsen three.

Acknowledgments are due from both the authors to Mr. Walter Hovey Hill for claim maps of the district and also for an excellent detailed map of the workings and geology of the Fern mine. Acknowl- edgments are also due to all the operators of the district, especially to Mr. E. H. Van Meter, of the Fern mine, for personal courtesies and valuable assistance.

Three reports on the quicksilver deposits of the Tellow Pine mining district liave been published. The district was first described bjr Robert N. Bell, State mine inspector of Idaho, who also published d later report.' A somewhat more detailed report has been made Mr. Livingston.* [

IiOCATION AND TOPOGRAPHY. i

The Yellow Pine cinnabar district is in that part of Valley County Idaho, which was formerly included in Idaho County. It is about 50 miles northeast of Cascade and about 7 miles from the site, now covered by water, of the town of Roosevelt, the short-lived center of the Thunder Mountain gold district. The cinnabar prospects are in the upper part of the drainage basin of Meadow Creek, a tributary of the East Fork of the South Fork of Salmon River. From Cascade they are reached by a poor mountain road about 70 miles long. An automobile can be taken as far as Knox, 26 miles, but the rest of the road is impassable for an automobile on account of high centers, rocks, steep grades, and general poor surface; it is even difficult for a

i Belly R. N., Qnldksihrer aod antimony dlsooverici In central Idaho: Idaho Mining Dept Bull. 1, 191& Ban, B. N.y Twantleth ammal report of the mining Industry of Idaho for the year 1918, pp 89-100, 1010, s UMbagftoa, D. C, Tnngsten, cinnabar, molybdenmn, and tin depoalts of Idaho: Idaho Uniy. School of Mines Bull. 2, vol 14, pp. 65-65, 1010.

Contributions To Economic Geology, 190, Pabt L

team and wagon. The cost of freighting from Cascade to the mines is about $100 a ton. The district is very nigged ; the highest point is considerably over 8,000 feet above sea level, and the maximum relief is about 4,000 feet. The mountains are well watered and are covered with a good growth of spruce and black pine.

History.

The original discovery of cinnabar in this district was made by Fringle Smith during the Thunder Mountain boom in 1902, in a fork

N

A

mjM§ t ifmum¥i

Appawimate scale wop. P 90 gopo 30pOFc<t

FiouBB O.'-daim map of dnnabar camp in Yellow Pine mining district, Valley County, Idaho. By

Walter Hovey HiU.

of Sugar Creek, afterward named Cinnabar Creek. Mr. Smith located the Hermes group at that time, and for many years he was the only prospector in the district. Prospecting for cinnabar was greatly stimulated by the high prices for the metal that prevailed during the world war, and in 1917 E. H. Van Meter located the Fern group of claims, adjoining the Hermes group on the south. Mr. Van Meter procured Boise capital and organized the Fern Quicksilver

rjsuLOW PINE cnstiTABABrvnsniro distbiot idaho. 75

Mining Co. In 1 9 1 7 this company erected a bench of Johnson-McKay retorts capable of treating 2 tons of ore a day. Since then the whole surface near the cinnabar area has been staked with claims, and sev- eral companies and individuals have carried on active development wort (See fig. 6.)

The cinnabar deposits are practically in the center of the high mountain uplift of central Idalio. This mountain region, according to Umpleby/ is a highly elevated and deeply dissected plateau that was eroded practically to base-level during the Eocene epoch and was subsequently elevated and subjected to profound erosion by both streams and local glaciers.

The divides between the main streams have rather regular, nearly flat tops bordered by steep slopes which continue to the streams, seyeral thousand feet below. The sky line, as seen from the top of any of the divides, is remarkably uniform, and all the divides have about the same elevation. Such a divide, with an elevation of about S,500 feet, lies between Middle and South forks of Salmon River and is followed by the road from Beardon Creek Summit nearly to the quicksilver mines. Many peaks, such as Rainbow Peak, Moimt Logan, and Thunder Mountain, rise several hundred or even a thou- sand feet above the general level of the divides. These axe chiefly monadnocks, hiUs of resistant rock that stood up above the floor of the old peneplain.

The streams flow in canyons from 2,000 to 4,000 feet deep which steepen rapidly toward their heads; hence travel across the drainage lines is very difficult.

Local glaciation has modified the topography near the heads of the streams; many cirques are present, especially on the north and east sides of the ridges, and the upper stream valleys are generally U-shaped, with a broad apron of groimd moraine in the valley bottom. Small grassy flats, the remnants of morainal lakes, exist in many of the cirques.

On the whole, the country in the immediate vicinity of the cin- nabar prospects is moimtainous but not particularly rugged, except where the hard quartzite rocks have been eroded to steep bluffs in the cirque waUs by glaciers. Where the cinnabar occurs the relief is from 1,500 to 2,000 feet, the altitude ranging from a little less than 7,000 feet at Pringle Smith's cabin on Cinnabar Creek to 8,500 or S,600 feet on the ridges separating Fern, Cinnabar, and Sugar creeks. The heads of these three creeks are occupied by cirques, in one of which stand the buildings at the Fern mine.

Hmpleby, J. B., Geology and ore deposits of Lemhi County, Idaho: U. S. Oeol. Survey Bull 628, pp. 2MI), 1913.

76 00Ntbibt7Ti0Ns To Eoonomic Obolooy 1990, Pabt I.

The relief of the oomitry favors the development of most of the cinnabiar prospects by means of tunnels for several hmidred feet below the outcrops.

GEOIiOGT.

Obkeral Obolooy Of Thb Abba.

The cinnabar deposits lie in a body of sedimentary rocks, mostly limestones and qulu*tzites, with considerable schist, that b reported by Bell to be about 2 miles wide and 3 or 4 miles long. These rocks strike about northwest and are nearly vertical. They are intruded by granitic rock and represent an inclusion in the granitic rock or a roof pendant. West of the deposits, as far as Cascade, the bed- rock is made up of granitic rock with a very few small inclusions of sedimentary rock. Between Cascade and the cinnabar deposits the granitic rock seen from the road for many miles east of Cascade appears to be rather tmiformly a light-colored porphyritic biotite granodiorite, but beyond this granodiorite the rock is less uniform and much of it b fine-textured, sugary-grained granitic rock. For some miles west of the cinnabar prospects the rock is a coarse- grained pinkish granodiorite. These granitic rocks are no doubt a part of the great Cretaceous batholith of central Idaho.

South and east of the cinnabar district the granitic rocks and the eroded edges of the sediments are overlain by a considerable thick- ness of Tertiary volcanic rocks, mostly in flows. These rocks are probably quartz latites and andesites, and they are said to extend to the Thunder Moimtain district. Some dikes of rhyolite porphyry and andesite intrude the sedimentary rocks and the granites, and they may be closely related to the volcanic rocks.

Obolooy Of Thb Oinnabab Dbposits.

The cinnabar deposits are in the sedimentary rocks, for the most part in the limestones near their contacts with tlie schists and quartz- ites. The beds are nearly vertical or dip very steeply northeast. For the most part, they strike northwest; in lower Fern Creek they strike about N. 60° W., but near the head of the creek they turn sharply and, for some distance, strike nearly north. Farther north- west tiiey appear again to strike northwest. A generalized section measured from the contact with the granodiorite on the ridge to the west of the head of Fern Creek, along this ridge, around the head of Fern Creek, and along the ridge to the west of Cinnabar Creek, is given on page 77. The thicknesses are only approximate. The order represents simply the succession in space, and the beds given first may be either the top or the bottom of the section.

Bell, B. N., Twentieth annual report of the mining industry of Idaho, ftx- 1918, p. 92, 1919.

YELLOW PINE CnTKABAB-MINING DISTRICT, IDAHO. 77

Seetionaeron the ndmeiUmy rodba wutkwett to noftheast along the ridges west of

Fern and Cinnabar creeks.

GoozBo, porpbyritic graaodiorite, intruBive into the aedimentB. Feet.

Pebbly quartzite 300

Micaceous BchiBt 330

Hazd quartzite, very reaLstant 300

Pebbly quartzite '. 150

Marble, thin bedded and more or less altered to lime-edlicate min-

eralfl in the northern part 600

Mica and andaludte schiats 220

Quartfldte 220

Schist 80

Quartzite : 80

Micaceous schist 40

White sugary quartzite, with some pebbly beds near top 460

Dark quartzose schists, giving poor outcrops 40

Marble, with some thin layers of dark quartzite and schists 150

Nearly white sugary quartzite 200

Gray marble, well banded and leas metamorphosed than marbles

totheaoudi. Only a part seen 1,000+

4, 170

In Fern Creek the quartzite and schist member, which b in con- tact with the granodiorite where the section was made, is succeeded to the north by another layer of marble.

In general the sediments have been considerably motamorphosed, probably during the intrusion of the granodiorite. The original limestoneB are now marbles, and they carry more or less silicate minerals, partly disseminated in the marble and partly aggregated in lenses or bimches of varyiog size. Locally, considerable bodies of the marble are replaced by lime-silicate rock. These bodies do not represent the replacement of a particular bed, as in places their long direction is across the bedding. In passing from the less silici- fied marble to the lime-silicate homf els bodies, lenses, and layers of homfels parallel to the bedding and an inch or so thick first appear in the marble, and the resulting rock has a prominent ribbed ap- pearance on the outcrop due to alternating layers of marble and resistant homfels. The homfels bands may increase in size and abundance until they completely replace the marble. This homfels is made up of quartz, orthoclase, diopside, tremolite, carbonates, and more or less phlogopite, epidote, titanite, magnetite, apatite, and a scapolite near wemerite (MagoMcTo) . The marble is in part a calcite marble and in part a dolomite marble. It carries scattered crystals of phlogopite, tremolite, and diopside.

The original sandstones and quartzose conglcxnerates have been altered to hard quartzites, and the less pure sandstones to quartz schists. A specimen of the schist collected as typical of the thick schist layer on the ridge southwest of the Smith camp proved to be

CONTRIBTlnONS TO ECONOBilC QEOUMIY, 1920, PART I.

made up mostly of andalusite, with some quartz, phlogopite, sericite, magnetite, and rute.

No fossils were found in the sediments, and the lithology is not sufficiently characteristic to correlate them with near-by deposits of known age. Their general character and their relation to the granitic intrusive rock indicate that they are prohably Paleozoic.

A number of dikes or less regular bodies of a rhyoUte porphyry, some of them over 100 feet across, intrude the sediments. TMa rhyolite porphyry carries rather abundant crystals of orthoclase as much as 5 centimeters across and smaller crystals of quartz and biotite in a micrographic matrix of quartz and orthoclase, ynth some shreds of biotite and an altered prismatic mineral. A single small dike of hypersthene andesite was seen on the ridge at the hoad of

Yeuow Pine Cinkabab-Miking Bistbiot, Idaho. 79

Fern Creek. These dikes are probably related to the Tertiary lavas that overlie the sediments less than a mile to the east of the cinnabar deposits. A generalized reconnaissance geologic map of the district is shown in figure 7.

Ore Deposits.

OBNEBAIi FEATX7BB8.

The cinnabar prospects and mines lie in the upper drainage basins of Fern and Cinnabar creeks and are included in an area about a mile square. They are confined to the sedimentary rocks and are mostly in the marbles near the quartzites or schists and to a small extent in the quartzites adjoining the marbles. The Fern mine, on the upper part of Fern Creek; the Bucks Bed claims, to the east; and the White Metal group, still farther east, are near the southwest contact of one of the larger limestone layers with quartzites and conglomerates. The claims of H. T. Abstein lie stiU farther east and are probably near the northeast contact of the same limestone. The Hermes group of claims, about a mile north of the main workings of the Fern mine, are in a limestone member only about 150 feet thick that is separated from the limestone of the other prospects by over 1,000 feet of quartzites and schists. The lower workings are near and along the southwest contact of this marble; the workings farther up the small gulch to the northwest are near the northeast contact of the marble.

The cinnabar deposits appear to have been formed by replacement of the marble and to be mostly near the contacts of the marble with the quartzites or schists. No evidence was seen of continuous veins, but the deposits appear rather to be in the irregular or lenticular bodies that are common in replacement deposits in limestone. In some places the silica forms a network of anastomosing veinlets in the marble; in others it completely replaces the marble. Cinnabar is the only sulphide in most of the ore, although considerable pyrite, more or less altered, is present in some parts of the deposits, and stibnite is associated with cinnabar on the ridge just north of the Fern mine. The cinnabar is rather coarsely crystalline, and much of it is in the cherty silica, but some is in a friable sandy marble near the silica zones and some is disseminated in the hard white marble. A considerable part of the ore treated at the Fern mine came from material partly filling a cave in the marble and was made. up of blocks of hard ore embedded in a cinnabar-rich sand.

The antimony deposits in the granodiorite just south of the cinnabar deposits carry a little cinnabar and axe probably related in origin to those deposits; the antimony deposits about 15 miles to the west near Yellow Pine post oflice, axe also in granodiorite and are probably related deposits. The evidence as to the origin of the deposits is

80 OONTBIBUnOKS TO EGOKOMIC OEOLOOT, 1920, PART I.

Dot entirely clear, but the silicification of the limestone and deposition of the cinnabar probably took place at no great depth and through the agency of hot solutions, possibly hot springs. The mineraliza- tion was probably related to the general igneous activity of which the intrusion of the rhyolite porphyry and the extravasation of the Tertiary volcanic rocks of the Thunder Mountain area were mani- festations.

Ouoms Of Fekn Qx7Ick6Ilveb Minino Oo.

The Fern Quicksilver Mining Co. owns a group of claims at the head of Fern Creek, extending northward into the drainage basin of Cinnabar Creek. A claim map is shown in figure 2. This company has been most active in developing the deposits and has erected a 12-retort Johnson-McKay furnace capable of treating about 2 tons of ore a day.

The mun workings of the company are on the north side of Fern Creek and consist of three short tunnek. The best showing of ore is in the northwest tunnel, which is about 100 feet long and runs about N. 28° E. It is mostly in white marble that carries streaks of iron-stained friable marble and veinlets of hard chalcedonic silica. The silica veinlets make the best ore, but the iron-stained marble also carries cinnabar. The ore seams are irregular and are mostly less than a foot across, rarely 5 feet. About 20 feet to the east another tunnel is driven about 40 feet and exposes similar material. On the surface there is little evidence of extensive silicification in the limestone. About 30 feet northwest of the portal of the main tunnel there is a dike of rhyolite porphyry 100 feet across, and its strike is such that it should be cut by the tunnel not far from* the present face. A large limestone cave near the face of the main tunnel was partly filled with loose blocks of good ore. The good ore taken out in driving these tunnels and from the blocks in the cave was run through the furnace and yielded an average of about 2 per cent of quicksilver, in all about 14 flasks up to August 26, 1918. In addition 5 flasks were produced in 1917 from float.

A tunnel about 60 feet lower on the slopes and to the south is driven about 90 feet but shows no ore. This tunnel is driven in rhyolite porphyry near the portal, quartzite farther in, and marble near the face. The quartzite and marble are separated by a streak of white gouge, but there is no evidence of ore in this tunnel.

The course of the ore horizon seems to be across the bedding of the marble, but it is probable that the main ore horizon is along the bedding of the marble and near the contact with the quartzite. No large body of ore was shown at the time of the writers' visits, nor did there appear to be a large body of silicified, mineralized marble.

Yellow Pikb Oikkabab-Mikikq Distbiot, Idaho. 81

Oxjoxs Of Ybllow Pine Qx7Ick6Ilvek Co.

The Yellow Pine Quicksilver Co. owns the Bucks Bed claim and a claim and fraction to the east of the Fern mine. Its main showing is on an outcrop of silicified limestone on the east edge of the Bucks Bed claim, about 2,000 feet east of the Fern workings. Little work hsd been done at the time of the writers' visit, and the form and character of the deposit had to be interpreted largely from natural oQtcrops. The deposit appears in the outcrop to be an irregular to raddy lenticular body of silicified limestone 260 feet or so in length and about 60 feet across at its widest part. Its length is approxi- mately parallel to the bedding of the marble, and it appears to be near the southwest contact of a thick limestone with quartzite. The beds strike about N. 50 W. and are nearly vertical. Much of this iens is more or less porous to honeycombed iron-stained chalcedonic silica, and this material grades into marble with irregular seams of silica and finally into comparatively fresh marble. Much of the marble in the silicified zone is friable. On the surface little cinnabar is seen, but several shallow cuts show more or less cinnabar and some limonite derived from pyrites. The cinnabar is chiefly in the porous silica, but in places it is in the iron-stained marble, especially where silica streaks are present; rarely cinnabar was seen in the white marble. The lens of silicified rock appears to be irregular, and it includes bodies of little-altered marble. The widest part of the outcrop of silicified limestone appears to be near the east border of the Bucks Bed claim, and the company had started a tunnel to cross- cut this lens at about its widest part. A few himdred feet west of the main lens of silicified limestone and at about the same horizon in the limestones are one or more smaller lenslike outcrops similar to that of the main outcrop. These silicified bodies appear to be near the quartzite contact and at about the same horizon in the Umestone as the Fern ore body. Other bodies of silicified rock that carry ciimabar are present between the workings of the two companies.

OLAIHS OF IDAHO QX7I0E:SILVE& lONINO OO.

The Idaho Quicksilver Mining Co. owns seven claims just east of die Bucks Bed claim and the large silicified lens of the Bucks Bed continues eastward into the Idaho Co.'s ground, although it appears to narrow rather rapidly in that direction. Little work has been done on these claims, but a cut near the west-end line shows con- siderable silicified marble and some friable iron-stained marble with some cinnabar.

Ab8Tbin Olaims.

H. T. Abstein's claims are still farther to the east and appear to be in a limestone bed that hes more to the north. The claims have

82 CONTRIBUTIONS TO ECONOinC GEOLOGY, 1921), PABT I.

oiAy a few shallow pits, and most of the cinnabar found up to the time of visit was float, but some dnnabar was shown in place in one of the pits.

CLAIMS OF 1C0NT71CENTAL HE&CX7&Y lONBS CO.

The Monumental Mercury Mines Co. has 10 claims in the drainage basin of Cinnabar Creek, bonded and leased from Pringle Smith. At the end of August, 1918, the company had 12 screw-top retorts, each capable of holding 14 pounds of ore and of carrying three charges a day. The company planned to increase this equipment imme- diately to 52 retorts and to treat about a ton of 2 per cent ore a day. The main workings are on the Hermes claim, just west of Cinnabar Creek and about a mile north of the Fern workings; they are along the south contact of a layer of limestone that is about 150 feet thick. The upper workings are on the Pretty Maid claim and are about 1,500 feet northwest of the lower workings, near the north contact of the limestone layer. The lower or southeastern body has been most prospected. It is at the limestone-quartzite contact, and the zone of brecciation carrying some cinnabar is 20 feet or more across and can be followed for about 200 feet along the strike. Where prospected it includes brecciated quartzite and brecciated silicified limestone and carries more or lees cinnabar throughout, partly in seams and partly disseminated. Much of the material is soft and wet and requires close timbering. There are some streaks and vein- lets of very good ore, notably a small exposiire near the portal of the upper tunnel which shows a seam of fine ore that is as much as 2 feet wide but can be followed for only a short distance along the strike.

The workings about 1,500 feet to the northwest are on a body of silicified rock in the limestone that is elongated parallel to the bed- ding of the Umestone and is 60 feet across at its widest part and is exposed for about 100 feet. It is covered by talus at both ends but is probably lenticular in outcrop. It is made up of iron-stained chalcedonic silica and more or less limestone, much seamed by sihca veinlets. It shows little cinnabar on the outcrop but is reported to carry some cinnabar throughout and to have a 3-foot band of very good ore. Just north of. this is a body of rhyolite porphyry.

Other prospects to the southeast along this northeast contact of the limestone show some cinnabar.

Some have regarded the two main ore bodies on the Smith property as a single vein, but this conclusion does not seem to be justified, as both bodies appear to be irregular and lenslike or chimney-like replacement deposits, and they are on the opposite contacts of a limestone hier that is about 150 feet thick.

Yblix)W Pine Oinnabae-Mininq District, Idaho. 83

Summabt And Conclusions.

The Yellow Pine cinnabar district is in Valley County, Idaho, about 70 miles by a poor mountain road from Cascade, Idaho. The active prospects are included in an area of about a square mile.

The deposits are in a body of sedimentary rocks made up of quartz- ite, limestone, and subordinate schist only a few square miles in extent and surrounded by a great body of granodiorite. Tertiary andesite lavas overlie the sediments and granodiorite only a mile or so from the cinnabar prospects, and numerous dikes and less regular bodies of rhyolite porphyry intrude the sediments and the granodiorite.

The cinnabar deposits are in the limestones or in the sediments immediately adjoining the limestones, and for the most part they are very near the contact between the limestones and quartzites. The deposits covered by the claims of the Fern Quicksilver Mining Co., the Yellow Pine Quicksilver Co., and the Idaho Quicksilver Mines Co. are on Fern Creek, near the south contact of a thick layer of limestone. The workings of H. T. Abstein are higher up in this limestone layer. The deposits covered by the claims of the Monu- mental Mercury Mining Co. are in a limestone layer only about 150 feet thick and about a mile north of the limestone in which the other deposits are located. The lower workings on this group of claims are along the south contact of this limestone, but the upper workings are along the north contact.

The ore bodies appear to be irregular lenses or chimneys of sili- cification in the limestone, and the ore is in part the chalcedonic silica and in part the friable marble that adjoins the silica bodies. Cinnabar appears to be the chief sulphide in the ore, but some pyrite is present and more may be found at greater depth. Stibnite is present in the district and is associated with some cinnabar, but it was not observed in the cinnabar ores.

The district has not been sufficiently prospected to justify any definite prediction as to the futtu'e outlook, but some good ore is shown, and the feinnabar is distributed over a considerable area. As vet no ore bodies that can be considered large are shown, but some of the bodies of altered silidfied limestone appear to be large, and further exploration may expose ore bodies of considerable size.

/

Iron-Ore Deposits Near Stanford, Montana.

By Lewis G, Westgate.

Location.

The iron ores known as the Running Wolf hematite deposits are in Cascade and Fergus comities, in central Montana, on Rxmning Wolf and Dry Wolf creeks, 12 miles southwest of Stanford, on the Great

PiGUKE 8. — Map of a part of north-central Montana showing the location of the hematite deposits near

Stanford.

Xorthem Railway, and about 54 miles southeast of Great Falls. (See fig. 8.) They lie just within the northern border of the Little Belt Mountains, in an area where the altitudes range from 5,200 feet at stream level to 7,000 or even 8,000 feet on the adjoining summits. The outcrops of the ore cross hill and valley and show variations in height nearly equal to those of the surface.

86 Contributions To Economic Geology, 1930, Pabt I.

Acknowiedombnts.

The deposits were visited by the writer August 27 and 28, 1918. It is a pleasure to acknowledge the aid of Mr. Paris Gibson, of Great Falls, chief owner of the claims, who lent reports and plans, and of Mr. Frank C. Whittaker, of Stanford, who showed the writer over the property.

OENEBAIi OEOIX>OT.

The broader geologic features of the region have been described by Weed.' A great series of sedimentary rocks, ranging in age from Algonkian to Cretaceous, here rests lunconformably upon Archean

FIotiHi S.— Oeologlo map of the vktnjty ottbe bemMlW deposits near BUnlird, Hon

granite and gneiss. The belt series, comprising the Algonkian rocks of the region, thus belongs above the great unconformity near the base of the section. Folding and some faulting took place at the end of Cretaceous time. Intrusions of igneous rocks accompanied or followed the mountain making. Subsequent erosion has laid bare the Paleozoic and older rocks and the igneous intrusions in the Little Belt Mountains.

The deposits, which are essentially hematite, occur in the Madison limestone (Carboniferous), at the contact with intrusive porphyry. Two bodies of porphyry are shown on the map (fig. 9) — the larger one on Woodhurst Mountain, the other 4 miles west, on Dry Wolf Creek.

Weed, W. H., U. S. Oeol. Survey Oeol. AUu, Fort Benton lollo (No. 55), 18W; Unit Belt UountabiB

Ibon Ore Near Stanfobd, Mont. 87

It is likely that they are nearly if not quite connected by dikelike masses. The rock of the western body is described by Weed as a diorite porphyry, and that of the eastern body as a syenite porphyry. Xear the hematite the larger body is nonporphyritic except toward the border, where there are local porphyritic facies. It is a medium- grained rock; probably equivalent to monzonite in composition, and shows orthoclase and a little plagioclase feldspar and crystals of biotite and hornblende. On some of the eastern claims the border facies is a white nonporphyritic aplitic rock. Both bodies will be referred to as porphyry.

The Madison limestone is a blue-gray, well-bedded, and in places rather thinly banded limestone with gentle dips, mainly to the east in the small area imder consideration. Here and there, especially about the Woodhurst stock, the limestone is a fine-grained yellow marbleized rock.

Mode Of Occurrence Of The Hematite.

Figure 10 shows the location of the claims. Beginning on the southeast, they follow the south and then the west side of the Wood- hurst Mountain porphyry intrusion. Then crossing Eunning Wolf Creek they follow the dike connection over the moimtain to the western body and continue along the northern and eastern contacts of this body down to Dry Wolf Creek. The following notes on the claims give an idea of the character of the ore body and the degree of developnient. The numbers and names of the claims can be identified on figure 10.

The ore body does not show on the Willow Creek claim (1).

Stripping has shown steel-gray solid hematite in a body as much as 8 feet in width on the Geroux claim (2). Ore shows in a pit to a depth of 20 feet. It is fractured and broken at the top but becomes solid and massive within a few feet. No limonite occurs. Yellow limestone is found south of the ore body. (See analysis 17, p. 91.)

The width of the ore on the Iron Crown claim (3) is 35 feet. Yellow fractured limestone occiirs on the south. (See analysis 18, p. 91.)

Over 40 feet of ore is shown in a cross trench on the Iron Cross claim (4). The ore is a fine-grained gray hematite; with minute specks of cleavable hematite. (See analysis 19, p. 91.)

Xo ore shows at the surface on the Iron Moimtain claim (5). A shaft sunk on the contact reached a wedge of ore at a depth of 18 feet, and this had widened to 5 feet at the bottom of the shaft, 3 feet* farther down. The ore is fine-grained specular hematite, some- what rusty.

The highest point of the ore body on Woodhurst Mountain is on the Lookout claim (7). A 37-foot shaft disclosed ore at a depth of 33 feet and followed the top of the ore 12 feet across the ore body

coNTBiBnnoirs to economig geology, im), pabt l

from the porphyry. The ore is red granular hematite; stained with limonite. The adjoining limestone is cream-white and finely crystalline.

A cut at the southwest end of the Le Roi claim (8) shows no ore. To the east ore is reported at a depth of 25 feet.

'Nsi'X

'Mw±

From the Iron Moimtain (5) to the Iron King (9) through the Lookout (7) and Le Roi (8) claims little ore shows. On the Iron King claim the contact between porphyry on the north and lime- stone on the south trends N. W. The limestone shows a strike of N. 60° E. and a dip of NW. and so is cut across by the por- phyry and likewise by the hematite body, which is here 50 feet ide. At one prospect the contact of ore and limestone is fairly

Iron Orb Near Stanford, Mont. 89

sharp, rather even, and nearly vertical. The ore, where in contact nth limestone, shows a banding parallel to the bedding of the Imestone, indicating clearly that the ore is a replacement deposit in tiie limestone. A very little ore runs out beyond the gener&i con- tact betweea limestone and ore along bedding planes into the limestone. A second project 50 feet lower shows at the surface some interbedded lean ore or "rock," which is reported to disappear i& depth, giving place to soUd ore. The ore at these openings is in part fine-grained hematite, in part medium-coarse crystalline hema He. (See analysis 20, p. 91.)

At the east end of the Albright No. 1 claim (23) the top of the ore body is 18 feet below the surface and is 12 feet wide. About 300 feet farther west 26 feet of ore is reported next to the porphyry, which at the surface is soft and weathered. The ore is a fine-grained gray and red hematite, with considerable disseminated calcite.

A trench on the Albright No. 2 claim (24) shows a width of 50 to 60 feet of ore with cream-white limestone on the south and porphyry CQ the north. The contacts of the ore and the adjacent rock do not now. The ravines down the slope to the north are reported to on tain boulders of fine-grained black hematite.

The work done on the east-west line of claims west of the point I'here the vein crosses Running Wolf Creek has been sufficient to iow the continuity of the porphyry westward to the end of this series of claims, but ore appears only at intervals. On the Bonanza lairn (17) ore occurs 350 feet north of the main body, probably m a second parallel porphyry dike. Ore is shown also in a shaft Q the Dewey claim (19).

Xear the west end of the claims they form a double series. Claims *S, 31, 36, 37, and 38 follow the main ore body. Claims 32, 33, 34, i id 35 follow a body at the contact with a second porphyry dike to tue south, which joins the main ore body in the Dorothy claim (38).

Ore 4 feet wide is shown on the Snowstorm No. 2 claim (36). The contact between the porphyry and the ore and limestone is sharp and not imeven, but there is a more gradual transition and an interfingering between the ore and the limestone, and hematite 'Xcurs irregularly in the limestone.

The ore body is 27 feet wide on the Dorothy claim (38).

On the Copper King claim (35) the ore is banded with rock at the ace but is reported to pass into solid hematite at a depth of 15 ieet. This is a parallel ore body and dike to that on Snowstorm Xo. 2. Boulders of ore are found uphill to the south, so that still another body exists in that direction.

Two shafts, 50 and 30 feet deep, are in ore to the bottom on the Snowbird claim (39). The main ore body is shown in figure 11.

1278**— 21 7

90 Contributions To Economic Geology, 19M, Pabt I.

The ore body at the surface is 26 feet wide; at a depth of 50 feet it is 32 feet wide. At a second locality 130 feet lower, to the northwest, a shaft went down 37 feet in ore.

A tunnel at the lower end of the Snowbird clEum cuts the main ore body at a distance of 125 feet below the surface. It was inaccessible at the time of visit, but the ore is reported to have a width at this depth of 16 feet. Hie ore on the dump, which probably came from the main vein, is a dense, fine-grained gray hematite, with small irregular cavities due to the removal of materials by solution. The hematite contains enough disseminated magnetite to be attracted by the magnet, and some specimens show small crystals of mag- netite. Other specimens show small irregular masses of pyrite in the hematite, and blocks stuned by malachite can be found.

FiouKi 11.— Sctioaatthargbody<

There is no ore at the surface in the Kepublican claim (40), but ore is reached at a depth of about 25 feet.

Features Op The Ore Body.

The main facts of the occurrence and character of the ore and the associated rocka are as follows:

1. The iron ore occurs in tabular bodies at the contact of the porphyry and the Madison limestone. The ore bodies range in width from 5 to 60 feet and average about 20 feet.

2. The ore is the result of the replacement of the limestone, as shown by its much more uneven contact surface against the limestone and by the retention here and there in the ore body of the banding of the limestone and of parts of the limestone itself.

3. Where the contact is inclined the hematite is more commonly foimd where the limestone is the footwall.

4. The ore is a compact gray or reddish-gray hematite. It con- ' ' ' laces enou magnetite to make it react to the magnet. It

Ibon Ors Neab Stanfobd, Mont.

is not to any large degree limonitic at the surface. At the one point There any considerable depth has been reached (125 feet, on the Snowbird claim) the ore contains a little pyrite and chalcopyrite. The limestone at the contact with the porphyry is usually altered 10 a yellowish, finely crystalline marble. No contact silicates were except a small amoimt of wollastonite in the rock taken from ihe tunnd on the Snowbird claim.

Analyses of hematite ores from deposits near Stanford, Mont.

ioalysis No.

Is

Claim and map No.

'Iron Crown (3) and Iran Cross (4)

Snowbird (39)

do

do

Iron Mountain (5)

Iron King (9)

CrysUl Spring (20)

Snowbird (39) and Dewey (19). . .

Snowbird (39)

do

Geroqx(2).

Iron Crown (3)

Iron Cross (4)

Iron King (9)

CaiTioM. (10)

Dewey (19)

Iron King (9)

Snowstorm No. 1 (37)

Snowbird (39)

do

Iron.

Phos- phorus.

.00?8

Trace.

Trace.

Trace.

Trace.

SiUrs.

Sulphur.

None. None.

Lime.

High,

1-7. 14-16 by Colorado Fuel & Iron Co. ; 8-13 by Anaconda Copper B£ining Co.; 17-26 by Dwight E. Wood- ge. Duhith/liinn.

Analyses 1 to 16 seem to have been made on selected specimens of Wtter ore. Nos. 17 to 26 were made on samples taken by Mr. Wood- bridge and are probably more nearly average analyses of the ore. Xos. 19 and 24 were made on samples taken near the limestone and show a large amount of lime and less iron. The phosphorus content is small, in many samples unusually small, and in nearly all of them Tell below the phosphorus limit for Bessemer ores. No sulphides were seen in the ores, and, except in Nos. 15 and 16, no tests for sul- phur were made. Idlneralogically the ores are entirely satisfactory for steel manufacture.

Quantity Of Ore.

Development work has not gone far enough to make possible any estimate of the quantity of ore that can be mined. At the surface the ore body is of varying width, reaching a maximum of 50 feet. As it is a contact deposit in limestone, it will vary in dimensions from place to place according to the character and course of the solutions

92 Contributions To Economic Geology, Im), Part I.

at work. It is more likely to show a series of lenses than a single continuous vein. The depth to which the ore extends below the sur- face is unknown. The greatest depth shown in any opening is 125 feet, on the Snowbird claim. Here a little pyrite is present. Whether the hematite is succeeded in depth by sulphides, and if so, at what depth, is unknown. Exploration has been made almost wholly by shallow surface trenches and pits and by shafts put down only far enough to prove the presence of ore. Further development, possibly by diamond drilling, is necessary in order to show how much ore is present.

The best showing for thickness and apparent continuity is at the east end of the property, on claims 2 to 5. Here for a length of 3,000 feet a good body of ore occurs. The average thickness at the surface is 25 feet. With an assumed depth of 100 feet, there would be approx- imately 1,000,000 gross tons of ore on claims 2 to 5.

Ore is exposed at points along the middle of the belt, but no esti- mate of tonnage can be attempted here.

At the west end showings are better. Ore appears at intervals through a distance of nearly a mile, and the average of the thickness of the ore body in the different openings is 20 feet. On the assump- tions of a continuous body (which may not be present), a depth of 100 feet, and a distance of 5,000 feet, there would be approximately 1,340,000 gross tons of ore in the western group of claims.

These estimates are suggestive only. Development may well reveal ore in much larger amounts.

The present availability of this ore depends on several factors which can not be considered in this paper, such as the cost of trans- portation to central and eastern manufacturing points and the possi- bility of economic production of iron in the near-by Rocky Moimtain region.

PRELIMINARY REPORT ON THE DEPOSITS OP MANGA- NESE ORE IN THE BATESVILLE DISTRICT, ARKANSAS.

By Hugh D. Miser.

Location.

The Batesville manganese district is in the southern part of the Ozark region, a short distance west of the Mississippi embayment of

FiouKB 12. — Index map of Arkansas showinir the location of the BatesTlUe manganese-ore

district.

the Oiilf Coastal Plain, mostly in Independence County but partly a Sharp, Izard, and Stone counties, in north-central Arkansas. (See %. 12.) It is an east- west belt, 4 to 8 miles wide, and extends from

94 Contributions To Economic Geology, 1920, Part I.

the Ball mine, 2 miles eadt of Hickory Valley, westward to Guion, distance of 24 miles, (See PI. VI.) The town of Bates ville, froi which it receives its name, is 2 miles south of the southern border c the manganese-bearing area.

Present Investigation And Acknowlbdgmenw

The field work on which this report is based was done by the write during March, April, May, and June, 1918, in connection with th plan of the United States Geological Survey to obtain informatio: regarding the location, character, and extent of the manganese-oi deposits in the United States, and to encourage the production o domestic manganese ores, so that as much shipping as possibl could be freed from use in the importation of foreign ores in ord to carry troops and supplies to Europe during the war.

A brief preliminary report entitled " Manganese in the Batesvil region, Arkansas," was published in September, 1918, as a pr bu letin of the United States Geological Survey. An abstract of a papi on the manganese deposits of the Batesville district that was pt sented April 23, 1919, before the Geological Society of Washingtq was published July 19, 1919. A paper on hausmannite in the BatI ville district, by J. G. Fairchild and the writer, was published Jal uary 4, 1920.* The present preliminary report is abstracted from d final detailed report, which the author has completed but which nu not be printed for at least a year.

The writer desires to acknowledge his indebtedness to the foUowil members of the United States Geological Survey : D. F. Hewett, ft advice in planning the field work and for many suggestions duri] the office work;E. F. Burchard, for advice during both the field al office work; E. O. Ulrich, for the examination of fossil coUectio) and for much information regarding the age and relations of the ro( formations of the Ordovician, Silurian, and Devonian systems ; G. 1 Girty, for the study pf fossil collections from the rock formations i Carboniferous age ; W. T. Schaller and E. S. Larsen, for mineralog determinations ; and R. C. Wells, J. G. Fairchild, and Chase Palim for chemical analyses of rock and mineral specimens. Acknowlec ment is also due to the residents in the Batesville district for thi uniformly courteous treatment and to the mine operators and othi interested persons for information.

The following reports on the district under discussion have bei

consulted :

Owen, D. D., First report of a geological reconnaissance of the northern con ties of Arkansas, pp. 37-41, 136, 138, 1858.

Washington Acad. Sci. Jour., toL 9, No. 13, 1919. Idem, TOl. 10, No. 1, 1920.

Manga17Ese Qbe In The Batesyiixe District, Abk. 96

Elderhorst, William, Ghonlcal report of the ores, rocks, and mineral waters of Arkansas, in Owen, D. D., First report of a geological reconnaissance of the northern counties of Arkansas, pp 161-169, 1858.

Cox, El T., Report of a geological reconnaissance of a part of the State of Arkansas, in Owen, D. D., First report of a geological reconnaissance of the northern counties of Arkansas, pp. 216-222, 1858.

Penrose, R. A. F., Jr., Manganese — its uses, ores, and dKxsits : Arkansas Qeol. Survey Ann. Rept for 1890, vol. 1, 1891.

Branner, J. C, The phosi)hate deposits of Arkansas: Am. Inst Min. Eng. Trans., vol. 26, pp. 580-598 1896.

Branner, J. C, and Newsom, J.- F., The phosphate rocks of Arkansas : Arkansas Agr. Exper. Sta. Bull. 74, pp. 61-123, 1902.

Hopkins, T. C, Marhles and other limestones: Arkansas Oeol. Survey Ann. Rept. for 1890, voL 4, 1893.

Williams, H. S., On the age of the manganese beds of the Batesville region of Arkansas : Am. Jour. Sci., 3d ser., vol. 48, pp. 325-1, 1894.

Williams, H. S., The Paleozoic faunas of northern Arkansas : Arkansas Oeol. Survey Ann. Rept for 1892, voL 5, pp. 268-362, 1900.

Van Ingen, Gilbert, The Siluric fauna near Batesville, Ark., I : School of Mines Quart, vol. 22, pp. 318-329, 1901 ; CJolumbia Univ. Geol. Dept Contr., vol. 9, No. 76, pp. 318-829, 1901.

Van Ingen, Gilbert, The Siluric fauna near Batesville, Ark., II: School of Mines Quart, vol. 28, pp. 33-74, 1901 ; CJolumbia Univ. Geol. Dept Contr., vol. 9, No. 76, pt. 2, 1901.

Purdue, A. H., Developed phosphate deposits of northern Arkansas: U. S. Geol. Survey Bull. 316, pp. 463-473, 1907.

Ulrlch, E. O., Determination and correlation of formations [of northern Arkansas] : U. S. Geol. Survey Prof. Paper 24, pp. 90-113, 1904.

Harder, E. G., Manganese deposits of the United States, with sections on foreign deposits, chemistry, and uses : U. S. GeoL Survey Bull. 427, pp. 102-118, 127, 269-270. 1910.

Harder, E. C., Our mineral supplies — Manganiferous iron ores: U. S. GeoL Survey BuU. 666-EE, 19ia

Harder, E. G., and Hewett, D. F., Recent studies of domestic manganese de- posits (abstract) : Am. Inst Min. and Met. Eng. Bull. 149, pp. 895-901, 1919.

Hewett, D. F., Manganese output in Arkansas district affected by labor short- age: Eng. and Min. Jour., voL 104, No. 21, p. 931, Nov. 24, 1917.

Girty, G. H., The fauna of the Moorefield shale of Arkansas: U. S. GeoL Survey BulL 439, 148 pp., 15 pis., 1911.

Glrty, G. H., Fauna of the so-called Boone chert near Batesville, Ark. : U. S. GeoL Survey Bull. 595, 45 pp., 2 pis., 1915.

Girty, G. H., Fauna of the Batesville sandstone of northern Arkansas : U. S. GeoL Survey Bull. 603, 170 pp., 11 pis., 1915.

Woodbridge, D. E., The Arkansas manganese field : Eng. and Min. Jour., vol. 106, No. 16, pp. 669-670, Oct 12, 19ia

Shiras, Tom, Manganese mining in Arkansas : Eng. and Min. Jour., vol. 104, No. 26, pp. 107&-1080, Dec. 22, 1917.

Special mention should be made of the monographic report by Penrose on the uses, ores, and deposits of manganese. Both the text of this report and the accompanying geologic map were constantly used by the writer in his field and office work. It is referred to at many places in the present report, and parts of it are quoted.

Contributions To Economic Geology, 190), Part I.

History And Production.

The manganese deposits of the Batesville district have been worked at times since 1849 and have yielded both manganese and ferruginous manganese ores. Most of the work on the deposits of manganese ore has been done during two periods of activity, one beginning in 1885 and ending in 1898, and the other beginning in 1916 and ending in November, 1918, when the demand for domestic manganese ores practically ceased, except for the filling of war-time contracts. Most of the work on the deposits of ferruginous manganese ore has been done since 1904. By far the greater part of the manganese ore pro- duced during the first period of activity was mined at the Southern mine, and most of the ferruginous manganese ore was produced by the Cason mine.

The production of these two classes of ore in the Batesville district from 1849 to 1918, inclusive, is given in the accompanying table, which is compiled mainly from Mineral Resources, published by the United States Geological Survey, but partly from other sources.

Manganese and ferruginous manganese ores produced in the Batesville district,

Ark., 1849-1918, in long tons.

Year.

184-1867.

188fi

1895.. ..

liazunnese

ore (35 per

cent or

more of

manffa-

nese).

Ferrugi- nous man- ganese ore

(10 to 35

per cent of

manganese).

1,483

3,316

5,651

4,312

2,528

6,339

1,650

6,708

2,020

1,934

2,901

3,421

3,240

2,662

Year.

Mansanese ore (35 per center more of manea- neseT.a

Ferrugi- nous man- ganese ore

(10 to 35

per cent of

manganese)

1,288

6,250

10, 140

7,731

3,321 8,900 4,133 4,066 5,030 2,177 1,333 9,650 1,970 2,655 3,645 9,100 9,173

75,985

69,237

The figures for production of manganese ore for 1910 and previous years perhaps In- clude a small amount of ore carrying less than 85 per cent of manganese.

Geography.

The Batesville district is on the southern edge of the Ozark Plateau, south of which lie the Boston Mountains. Both the Boston Mountains and the Ozark Plateau are subdivisions of the Ozark region.

Manganese Ore In The Batesville District, Ark. 97

The district here described is rough, but the relief is not great. Many narrow valleys trench all parts of its plateau surface, so that very little level land remains in the interstream areas, which consist of hills and ridges. The lowest elevation, which is less than 250 feet above sea level, is on White Biver near Batesville, and the highest, 950 feet, is on Pine Mountain, 2 miles north of Anderson. The streams flow in channels that are generally 100 to 400 feet below the crests of the hills and ridges. The hill slopes are steep, and there are many bluffs adjacent to the streams, especially on the outer sides of the stream bends. Of the bluffs along White River the largest and most picturesque is Penters Bluff, which is about 1 mile long and about 400 feet high. The comparatively small number of level tracts and the more gentle slopes are mantled with residual soil or with wash from higher ground. Rock outcrops are conmion in most parts of the district but are especially abundant on the steeper slopes.

The drainage of the Batesville district empties into White River, the largest stream. Cura and Dota creeks enter Black River, which in turn enters White River outside the district. The streams north and northeast of Cave City enter Strawberry River, which joins Black River. White River is navigable above Guion, though a series of three dams and locks have been built by the United States Govern- ment to aid navigation. One of these is just below Batesville, the second is at Earnharts, and the third is at Walls Ferry station. The largest streams of the area besides White River are West Laf- ferty, East Lafferty, Spring, and Sullivan creeks, and Polk Bayou. Many of the creeks are perennial and are supplied with water from numerous springs in all parts of the area.

The Batesville district is not densely populated, though all parts of it are inhabited. The largest town is Batesville, the county seat of Independence County.

A branch of the Missouri Pacific Railroad passes through Sulphur Bock, Moorefield, and Batesville and thence runs near the left bank of White River beyond the limits of the area here described. Short branches of this railroad extend to Pfeiffer and Cushman. A spur formerly ran from the mouth of Lafferty Creek to the village of Phosphate, but both the spur and the village have long been aban- doned.

Public and secondary roads reach all parts of the district, but only a few of them are maintained in good condition, although lime- stone, broken chert, and gravel suitable for road building are at hand in many places.

98 Contributions To Economic Qkologt, 1020, Part I.

Geology.

Bock Fobmatiokb.

OEVEBAL FZATTniXB.

The rocks of the Batesville district are all of sedimentary origin and consist mainly of sandstone, shale, limestone, and chert, with beds of gravel and sand. They are of Ordovician, Silurian, De- vonian, Carboniferous, Cretaceous (?), and Quaternary age. The Femvale limestone and Cason shale, of Ordovician age, and their residual clays contain the manganese ores and are the only forma- tions that need be described in detail in this report.

The succession and thickness of the Ordovician, Silurian, Devo- nian, and Carboniferous rock formations are shown on Plate VII, and their distribution is shown on Plate VT. The principal lithologic features of these formations are set forth below.

Batesville sandstone : Brown or buff fine-gained sandstone with lenticular beds of shale. Exposed south of manganese-bearing area.

Moorefleld shale: Black and greenish shale, limestone concretions, and a lime- stone phase at base, which has been called Spring Creek limestone.*' Exposed south of manganese-bearing area.

Boone chert : Composed mainly of chert but partly of Umestone, sandstone, and shale. Lower part caps most of hills in manganese-bearing area.

Chattanooga shale: Platy black shale. Exposed only near village of PfelflPer. Was described by Penrose* as a part of the Boone chert. A few fossils which have been procured from the shale are stated by E. O. Ulrlch to show that it Is of the same age as the Genesee shale of the northern Ap- palachian region.

Penters chert: Gray and bluish chert; upper part Is dark colored at places. Exposed near Pfelffer and Penters Bluff station, and receives its name ttom the latter place. No fossils have been discovered in the chert, but its llthology and stratigraphic relations indicate that it Is of the same age as the Camden chert of west-central Tennessee and the lower part of the Arkansas novaculite of west-central Arkansas and southeastern Okla- homa. The Camden chert has yielded fossils and has been regarded by most geologists as being equivalent in age to a part of the Orlskany group of the northern Appalachian region. The Penters chert was described by Penrose as a part of the Boone chert.

Lafferty limestone: Thin-bedded compact earthy limestone. Upper part gray, lower part mostly red but partly gray. Only known exposure at the Tate Spring, li miles north of Penters Bluff station. Name of limestone taken from West Lafferty Creek, which Is half a mile east of exposure. The stratigraphic relations and llthology suggest that it is of the same age as the Dixon limestone of west-central .Tennessee, and the evidence of a few fragmentary fossils from the Lafferty limestone is stated by Ulrtch not to militate against this correlation.

Penrose, B. A. F., Jr., op. cit, pp. 182-188. Idem, pp. 181-188.

U. 8. Osoxooical 8Ubtkt

Bullettn 716 Plate Vii

Composite section of rocks exposed in most of the principal manga - nese- bearing areas of the Bates- ville district.

Composite section of all rocks exposed in the Batesville district

System

Formation

Formation

Boone chert

t

Caaoo shale.

Fcrnvalc limestone iimmswick limestone

PlatUn linnestone

'4MCW/XfRltfrY

Joachim limestone

St Peter sandstone

Batesvilie sandstone

Columnar Seqion

tii.V.'if-HH

Tmckness In Feet

Moorefield shale

Boone chert

I00(?)- 250+

WtCOf/rORMfTr-

Chattanooga shale "" WfconnuMtry

Renters chert

UftCOffFORM/TY

Lafferty limestone

St.Clair limestone

BrassfieixJ limestone

Cason shale.

u/iicoffORMnr

1 ' /'I ' /"L

Fernvale limestone

UMCOftFOfw/ry

Kimmswick limestone

Plattin limestone

1 . I . 1

iTTr.i 1

i.'i ! I

OMcmfOR/ry

5 Joachim limestone

TTyr-,

Ttt

StPcter sandstone

OMCOfFO/iM/rr

Magnesian limestone and a small amount of sandstone

2W

TTT.-n

1 I r

J — U— L

210+

(;kne!;baxized sections of the paleozoic rocks of the batesville district, ark

Mangai7Ese Ore In Ths Batesville District, Ark. 99

St Clair limestone : Massive coarse-grained pinkish light-gray fossiliterous lime- stone. Exposed in several small areas but absent over most of manganese- bearing area. The typical St Glair limestone is stated, by Ulrich, who has recently studied its fossils, to be of approximately the same age as the Rochester shale of New York or the Laurel limestone of Tennessee, Ken- tucky, and Indiana.

Brassfield limestone: No exposures are known in the BatesviUe district, but fossils derived from it through weathering occur in residual clay at the Montgomery mine. The limestone is exposed farther west in Arkansas. There its lithology, fossils, and stratigraphic relations show that it is equivalent to the Brassfield limestone of southwest-central Tennessee. In previous reports on northern Arkansas this limestone has been included in the St Glair limestone, but it is not present at the St. Clair type locality and Is regarded by Mr. Ulrich as of Albion (upper Medina) age.

Cason shale : Greiish-gray calcareous shale and smaller amounts of sandstone and phosphate rock; contains manganese and iron minerals. For a de- tailed description of the Cason shale see pages 101-104.

Femvale limestone: Coarse-grained massive cross-bedded dark-gray and pink- ish-gray limestone; contains manganese minerals. For a detailed descrip- tion of the Femvale limestone see below.

Kimmswick limestone: Even-bedded massive light-gray fine-grained limestone. Exposed in much of manganese-bearing area. This limestone, according to Ulrich, is the same as the Kimmswick limestone of southeastern Missouri. It comprised the lower part of the Polk Bayou " limestone of some of the earlier rx>rts on the BatesviUe district, whereas the Femvale limestone, which overlies the Kimmswick, comprised the upper part of the "Polk Bayou " limestone.

Plattin limestone : Even-bedded dove-colored or grayish-blue compact limestone ; breaks with conchoidal fracture. Ixposed over a large part of manganese- bearing area. This limestone, according to Ulrich, is the same as the Plattin limestone of southeastern Missouri. In earlier geologic reports on this part of Arkansas the Plattin has been described as the Izard limestone," but the " Izard " as it was defined Included not only the Plattin but also the Joachim limestone.

Joadiim limestone : Drab fine-grained magnesian limestone ; thin beds of sand- stone in lower part. Exposed over much of manganese-bearing area.

St. Peter sandstone : Massive white or cream-colored sandstone. Exposed over large and small areas in northern part of BatesviUe district.

Hocks below St Peter: These rocks crop out at places along West Lafferty, East Lafferty, and Sullivan creeks and Polk Bayou and are probably the equivalents of rock formations to which names have been assigned in other parts of the Osark region.

Tebnyals Liicebtoke.

The Femvale limestone is the surface rock on the hill slopes in much of the manganese-bearing area. It ranges in thickness from a feather edge to 125 feet ; the maximum thickness occurs at Penters Bluff. It is about 100 feet thick at most places, but it thins westward so that it is only 28 feet thick three-fourths of a mile northwest of Goion, and it thins out to the east less than 1 mile southwest of Hickory VaUey.

100 Contributions To Economic Geology, 1920, Part I.

The Femvale consists almost wholly of limestone. The o4 constituents are manganese ore and a small quantity of chert. 1 limestone is coarse grained, massive, and cross-bedded. Its ex] ledges are friable and have rough surfaces, and on some steep sh thin slabs break off parallel with the exposed surfaces that ai high angles to the bedding. The color is dark gray, but the weathered parts of the limestone, as well as some of the weathe parts, have a pinkish cast. Parts of the limestone, especially uppermost beds, are very dark gray or brown, owing to the occ rence of iron and manganese oxides that are more or less unifori disseminated through the rock. A few fossils occur in all parts the limestone, but they are most numerous in beds near the top a near the base.

At some places the limestone contains nodules and thin lenses gray and brown chert and many irregular masses of brown chert much as several feet in their longest dimensions. The irregu masses were formed in the limestone near the surface, but many them have been freed from the limestone, so that they are now mr numerous in the residual clays than in the limestone. Such mi are found in the manganese-bearing clays at many of the mines prospects, one of the most noteworthy occurrences being at the Soi em mine. There, as well as at other places, the chert contains mi drusy quartz and numerous doubly terminated quartz crystals, an inch or less in their longest dimension, which are now found the waste dumps. Many of the crystals are transparent, but most them are brown from the presence of minute inclusions of mangan( oxide. Most of the chert is porous, and much of it contains casts fossils. The presence of this chert in residual clays a few mil away from any known occurrence of the unaltered limestone indicat that the limestone once existed at such localities, though it has sii been completely removed except for its insoluble constituents, whi were chert and clay.

Although exposures of the Femvale limestone are numerous, el pecially in bluffs and on steep slopes, it is concealed over much d the Batesville district by its own residual clay and by clays anr'Hi chert fragments derived from younger rocks. The clay that residual from the limestone is usually sticky, and the prevailinj colors are red and chocolate-brown, but at some places parts of th clay are yellow. These clays and the other surficial materials overU the irregular surface of the unweathered limestone, in which unde< ground hollows and channels 50 feet or more deep have been formal by solution. (See figs. 14 and 15 and PI. VIII.) Such channels an| hollows, as well as the limestone pinnacles and horses that sepa rate them, are well displayed in open cuts at the Cummins Hollol and Club House mines. Some of the channels are straight and

Sp

T-

St. Pel sandsl

NG THE Oi

Manganese Ore In The Bxb&Vuxe District, Ark. 101

resent widened fissures along joints. A. fe: cves and sink holes have also been formed in the limestone. /'

The Fern vale limestone rests uncx>nformably up(j£cthe.Kimmswick limestone and is unconformably overlain by the Qabn i>hale or where the Cason is absent, by younger formations. The uppr.-sur- face of the Fern vale is irregular, containing in places channel.: jrid fissures as much as 2 feet deep that are filled with the materials of the succeeding deposit, which is usually a conglomeratic or earthy material, but in a few of the fissures is a gray oolitic limestone.

The Femvale is the oldest formation of Eichmond age in the Batesville district. The Bichmond deposits, according to the ac- cepted usage of the United States Geological Survey, are placed in the Ordovician system, but they are placed by E. O. Ulrich in the Silurian system. The Femvale was included in the St. Clair lime- stone of Penrose," in the St. Clair marble of Hopkins,* Branner, and Newsom, and in the upper part of the Polk Bayou limestone of Williams and other geologists.* This limestone was first identified by Ulrich as being the same as the Fernvale limestone of middle Tennessee.

Gabon 8Hale.

'ITie Cason shale receives its name from its occurrence at the Cason mine, 8 miles north-northeast of Batesville. It is generally present in the vicinity of Cushman, Penters Bluff station, and Williamson, and along East and West Lafferty creeks and their tributaries but is absent at most places along Polk Bayou and farther east. It appears to be absent also in the vicinity of Guion, although the rocks in that part of the district were not studied in as great detail as those farther east.

The shale is thin, at no place exceeding 12| feet in thickness, but its residual clay at the Montgomery mine is 20 feet or more thick, suggesting that the shale at that locality was probably more than 12i feet thick.

Penrose, R. A. F., Jr., Manganese — Its UKes, ores, and deposits : Arkansas Geo]. Survey Ann. Rept. for 1890 vol. 1, 1891.

Hopkins* T. C, Marbles and other limestones : Arkansas Geol. Survey Ann. Rept. for 1890, TOL 4, 1893.

7 Branner, J. C. The phosphate deposits of Arkansas : Am. Inst. Mln. Bng. Trans., vol. 26. pp. 580-598, 1896. Branner, J. C, and Newscm, J. F., The phosphate rocks of Ar- kansas: Arkansas Agr. Exper. Sta. Bull. 74. pp. 61-123, 1902.

Williams, H. S., The Paleozoic faunas of northern Arkansas : Arkansas Geol. Survey Ann. Rept. for 1892, vol. 5, pp. 268-362, 1900.

Ulrich, E. O.. Determination and correlation of formations [of northern Arkansas] : IT. 8. Geol. Survey Prof. Paper 24, pp. 90-113, 1904. Purdue, A. H., Developed phosphate deposits of northern Arkansas : V, S. Geol. Survey Bull. 315, pp. 463-473, 1907. Harder, E. C., Manganese deposits of the United States, with sections on foreign deposits, chem- istry, and uses: U. S. Geol. Survey Bull. 427, pp. 102-118, 1910.

Ulrich, B. 0., Revision of the P&leosoic systems : Geol. Soc. America Bull., vol, 22, p. 421, pis. 27, 28, 1911.

102 CONTRIBUTIONS TO EiSoloklC GEOLOGT, IWO, PABT I.

The Cason is coinpio9| inainly of shale but partly of sandstone and phosphate rokJin tiddition to manganese and iron minerals. Not only does the* qaiatfty of these constituents vary from place to place, but their clracter also varies considerably, so that sections of the f oriiittioQ. even at places near together would generally differ. - T]i6' fehale is greenish-gray, platy, and calcareous, and contains ': ;more or less quartz sand and phosphatic material. Several pieces of ' the shale were tested for phosphate, and it was found in all of them, indicating that at least a small quantity of it is probably present in all parts of the shale. At a few places the phosphatic material occurs as fine pebbles, some of which are almost 1 inch in their longest diameter. The shale in most of its exposures has been affected considerably by weathering and is yellow or brown, but at the Cason mine most of it as shown in the workings at the time of examination was red. Only a small part of the shale there retains its greenish- gray color.

A bed of greenish-gray, brown, or yeUow sandstone attaining in places a thickness of several feet is generally present west of Polk Bayou. This sandstone contains quartz grains and more or less phosphatic material, which occurs in the form of fragments of shells or of well-rounded and angular grains and pebbles 1 inch or less in their longest dimension, and it is known as 'phosphate rock" on account of its high content of phosphorus. It is exposed as ledges on the hill slopes, and blocks of it lie on the slopes below the ledges. These ledges are a great aid to prospectors for manganese ore, be- cause the ore is always found below them.

Although phosphate is widely distributed in the Cason shale, it has been mined in commercial quantity at only a few places in the vicinity of the abandoned village of Phosphate. The mines have not been worked for several years. The developed deposits were de- scribed by Purdue, and deposits in all parts of the Batesville district were described by Branner and Newsom.

The Cason shale rests upon the Fernvale limestone everywhere in the Batesville district except at the Ball mine, where it apparently overlies the Kimmswick limestone, though both the Kimmswick and the Cason at that locality have completely disintegrated to clay. The contact between the Fernvale and the Cason is irregular. This fact, together with the thinning out of the Fernvale in the vicinity of Hickory Valley, indicates that an unconformity separates the Cason shale from the underlying rocks — in other words, that a period of emergence and erosion preceded the deposition of the materials that now constitute the Cason shale. The fossils, according to Ulrich, indicate that this shale was deposited in shallow marine waters. That it was deposited in shallow water is also indicated by the con- glomeratic character of parts of the formation.

Uaitqanese Obe In The Batisville District. Abe. 103

The Cason is overlain &t some places by the St. Clair limestone, but the occurrence of fossik-of the Brassfield limestone in residual clays above the altered Cason shale at the Montgomery mine shows that the Brassfield once overlay the Cason shale at that locality. The Brass- field, according to its fossils, is older than the typical St. Clair. This fact and the apparent absence of the Brassfield at other localities in the region seem to furnish sufficient proof that an unconformity sepa- rates the Cason from the St. Clair, but the contact between the Cason and St. Clair, wherever it is revealed, is even and does not suggest an unconformity, because there is no abrupt change in the character of the rocks at the contact. In much of the Batesville district all the

Fiocu 13. — Beetlon nmr th central part ol tbe Caw>D mine. BatesTtlle district. Ark., bi>wliig the relBtlons oI tbe red and Kien shales Id tb Cason sbale and the telatlonB of lb* red, bisck, and partly blackened " bottons." The beaTjr ruIloB represents ted ibilc, and the light sreen shale.

Silurian and Devonian rocks, including the St. Clair limestone, are absent, and the Boone-chert, of Carboniferous age, rests unconform- ably upon the Cason shale.

Except for the " buttons," which are numerous at a few localities, fosdls are comparatively rare in the Cason shale. The " buttons " are flattened concretion-like masses half an inch to 1 inch in their longer diameter and from a quarter to half an inch thick and are stated by E. 0. Ulrich " to be fossils belonging to the genus Girvanella, which is a form of algal growth. They were once spherical, or nearly so, and were composed mainly of calcium carbonate and partly of man- ganese carbonate, but they have been flattened by pressure. (See fig. 18.) As they are revealed in the rock outcrops and in the "Personal commDnlcatlon.

104 CONTKIBUnONS TO ECONOMIC GBOLOGT, 1920, PART I.

residual clays most of them have been replaced by manganese and iron oxides. The unaltered buttons'' are greenish gray, the partly oxidized buttons " red, the buttons '' of manganese oxides black, and those of iron oxide red. Many of them show concentric band- ing, and many contain centers of chert and earthy material. They lie parallel with the bedding of the shale and are more or less uni- formly disseminated through the shale and its residual clay. Their most noteworthy occurrence is at the Cason mine, which has been the largest producer of low-grade ferruginous manganese ore in the district. There buttons'' composed of manganese oxides are so numerous that the residual clay itself has been mined and shipped without treatment, and much of the shale has been quarried as ore. Only a part of the shale at this mine, however, contains " buttons " of manganese oxides ; the rest of it contains '' buttons " whose princi- pal constituents are manganese and calcium carbonates. This is in fact the only locality in the district where the carbonate buttons' have been discovered.

These fossils, according to Ulrich, are similar to (Hrvanella rich' mondensis a species which is found in beds of the Eichmond group in Indiana. These and the other fossils, together with the relation of the Cason shale to the underlying and overlying rocks, indicate that the Cason is the next to the oldest formation of Richmond age, the Fernvale limestone being the oldest. The Richmond group, as previously stated, is placed in the Ordovician system by the United States Geological Survey and in the Silurian system by Ulrich.

The Cason shale was included in the St. Clair limestone by Pen- rose." Williams,** the first geologist to define the Cason as a separate formation, placed it in the Silurian system.

STBTJCTUBE. GEKEBAL FEATimES.

The strata in the Batesville district, which must have been de- posited in a nearly horizontal position, have undergone little defor- mation. The general doming of the beds in the Ozark region has given those of this area a slight dip to the south, which is disguised at several places by minor folds and a few normal faults. Most of the minor anticlinal flexures form small domes, and the synclinal flexures form basins, but they are referred to simply as anticlines and synclines in this report.

" Penrose, R. A. P., Jr., op. clt., p. 125.

Williams, H. S., On the age of the manganrao beds of the BatesvUle region of Ar* kanaas: Am. Jour. Sci., 3d aer., vol. 48, pp. 325-831, 1894.

Masqanje Ore In The Batesyillb Distbict, Abk. 105

lt>£Df.

Many small folds were observed during the present investigation, and many others can doubtless be discovered in future field work, especially with the aid of a better topographic map than the one at present available. Although a few folds are so small or so poorly defined as to make their description impracticable, a few are suffi- ciently pronounced to warrant special mention. Folds that are inti- mately associated with valuable manganese deposits are also de- scribed.

An anticline whose axis lies along the crest of the ridge north of the Cason mine extends in a northeasterly direction for at least li miles from the mine. A small area of outcrop of the Plattin lime- stone half a mile northeast of this mine is on the crest of the anticline.

The rocks at the Cason mine lie in a shallow syncline on the south- east side of the anticline just mentioned. The axis of the syncline trends northwest. In the West cut, which is on the west side of the syncline, the St. Clair limestone and Cason shale dip 15°-20® NNE., and in the North cut, which is on the east side of the syncline, they dip at about the same angle to the southwest.

A broad eastward-trending syncline lies about miles north- northeast of Cushman, and in it are the Blue Ridge, Southern, Grubb Cit, Sogers, Wren, Polk Southard, and Turner mines. The Blue Ridge, an east- west ridge which is capped by the Boone chert, is on or near the axis of the syncline. (See PI. VIII.) On the south side of the syncline the St. Peter sandstone and Joachim limestone are revealed in an anticline in the southern part of sec. 3, T. 14 N., R. T W., and on the north side of the syncline these two formations are revealed in two anticlines just north of Turner Creek, in sees. 33 and 34, T. 16 N., R. 7 W.

The axis of a shallow east- west syncline half a' mile wide passes through Anderson. The oldest exposed formation in this syncline is the St. Peter sandstone, and the youngest that is present in the part of the syncline east of Anderson is the Femvale limestone. The Earl Collie, Sand Field, Manganese Field, Ruminer Rough, and Barksdale mines and the Caraway prospect are in this syncline.

rAlTLTS.

Faults are rare in the Batesville district, only seven being known, and all are normal faults. They are shown on the accompanying map (PI. VI) . The longest fault is 7 or 8 miles long, and the amount of downthrow along the faults is 400 feet or less.

1278**— 21 8

106 Contributions To Economic Geology, 192D, Pabt I

Ore Deposits. Minebals Of The Obes.

General features, — The manganese ores of the Batesville district consist of oxides, six of which, psilomelane, hausmannite, braunite, manganite, pyrolusite, and wad, have been identified. Although these minerals may be found separately, two or more are generally mixed in a single deposit, and at a few places they are associated with ferru- ginous manganese ores and with small quantities of brown and red oxides of iron. At some places the ferruginous manganese ores pre- dominate. Psilomelane is the most abundant manganese mineral, but hausmannite, braunite, and wad constitute a considerable part of the ores.

PsUomelcme. — Psilomelane is black or steel-blue, is amorphous, breaks with a conchoidal fracture, and at a few places shows botry- oidal surfaces. It has a specific gravity of 3.7 to 4.7 and commonly has a hardness of 5 to 6.5, which means that a knife blade scratches it with difficulty if at all. Although the chemical composition may be represented by the formulas Mn02.(Mn,K,Ba)0.nH20 and HMnOg, the composition is not definite, as the percentage of manganese varies from 50 to 57 and as the amounts of minor accessory ingredients, such as iron, barium, potassium, and water, show a wide range.

Hausmannite, — Hausmannite is a brittle steel-gray mineral with a chestnut-brown or reddish-brown streak and submetallic luster. It is finely to coarsely granular but partly crystalline, is weakly magnetic, is translucent on thin edges, and has an uneven fracture, a perfect basal cleavage, and a hardness of about 5.5. The crystals, which resemble small octahedra, line cavities in the massive mineral. The chemical composition is expressed by the formulas MngO and MnO-MngOg. This mineral, next to psilomelane, is the most abun- dant in the Batesville district. It has heretofore been classed as braunite. It differs from braunite in having a lighter-colored streak, in containing very little or no silica, and in having a higher per- centage of manganese protoxide (MnO) and a smaller percentage of oxygen. Chemically pure hausmannite contains 72 per cent of manganese. The following anal>-ses, which were made in the chemical laboratory of the United States Geological Survey by J. G. Fairchild, show the composition of samples from the W. T. Gray and Club House mines. The sam])les were carefully separated as much as possible from the psilomelane, with which the hausmann- ite was rather intimately mixed.

Manganese Orb In The Batesville District, Ark. 107

Analyses of hausmaamUe from the BatesvUle district. Ark,

[3. Q. Fairchild, analyst.]

W. T. Gray mine.

Club House mine.

W. T. Gray mine.

Club House mine.

Mancuese protoxide

(jEo)

None. None. None. Trace.

ft. 48

Trace.

Maimesia (UttO)

Trace.

Trace.

Baryta (BaO)

None.

OzTnn(O)

Total water (H|0)

Manganese (Mn)

Speclac gravity at 15.5*> C.

Los

InmfFei

Silica (810,)!]]!'*-'.!.!.!.! AlandnA(AltOz)

ioao4

ioa88

a Included with alumina.

ft Plus a trace of iron.

Braunite, — Braunite is a brittle steel-gray mineral that has a brownish-black streak and submetallic luster and a hardness of 5.5 to 6. It is weakly magnetic, and is either granular or crystalline but generally crystalline. Its crystals are small and numerous and are octahedral in form. The composition is usually expressed by the formula 3MnaOg.MnSi03. Sbme silica — 7 to 10 per cent — that is, chemically combined, is always present, as is indicated by its occur- rence in all the specimens that have been tested. It appears as a gelatinous residue when hydrochloric acid containing braunite in so- lution is evaporated. The percentage of manganese in chemically pure braunite ranges from about 63 to 66.

Manganite, — Manganite ('MnjOa.HjO) is a brittle steel-gray gran- ular or crystalline mineral with a dark-brown or nearly black streak. It has a hardness of 4 and therefore can be scratched with a knife but not with a brass pin. Manganite crystallizes in the ortho- rhombic system, and the crystals are generally bladed, wedge-shaped, or needle-like. It contains 62.4 per cent of manganese and 10.3 per cent of water. The specific gravity ranges from 4.2 to 4.4. Although it is present at a number of localities in the Batesville district it forms a very minor part of the manganese ores. Nodules from some of the deposits are made up of alternate layers of psilomelane and radiating crystals of manganite.

PyrolusUe. — Pyrolusite (MnOj, generally with a little HjO) is a grayish-black to black mineral with a crystalline or granular struc- ture and a black or bluish-black streak. It has a hardness of 2 to 2.5 and can therefore be scratched with a brass pin. Much of it crumbles between the fingers, which it blackens. The specific gravity is about 4.8. It contains 63.2 per cent of manganese. It has been generally regarded as having been derived from manganite by the loss of water. Pyrolusite is present in small quantity at a few locali- ties in the Batesville district.

108 Contributions To Economic Geology, 1920, Art I.

Wad. — Wad is a dark-brown to black, very soft earthy mineral which is commonly considered an impure hydrous oxide of manga- nese. It is associated with more or less iron, silica, alumina, and water. It is present at many localities in the Batesville district, and at some of them is more abundant than the higher-grade manganese minerals. During the last few years, when there was a demand for low-grade ores, considerable wad was shipped from the district. Most of the wad that has been shipped contained from 20 to 30 per cent of manganese. Dendrites, branching mosslike growths of wad, are common along joints in the parts of the Boone chert that are associated with the manganese deposits and along cracks and on fossils in the St. Clair limestone.

Iron oxides. — Iron oxides that probably comprise several hydrous sesquioxides of iron are associated with the manganese ores at many localities. Of these limonite (2Fe20s.3H20) and hematite (FejOa) are the most abundant.

Ferruginous manganese ore, — The ferruginous manganese ores are generally mixtures of poorly defined oxides of manganese with oxides of iron in various proportions. The iron oxides are usually limonite and hematite. The manganese is generally in the form of psilomelane, though at some places braunite, manganite, and wad are common. The iron and manganese oxides occur as a mixture of two minerals that are readily distinguishable in the hand specimen or so intimately mixed that it is impossible to determine the propor- tions of each. The amount of manganese in the ferruginous ores ranges from 10 to 35 per cent or more and the amount of iron from a few per cent to 31 per cent. The higher-grade ores are used in the manufacture of spiegeleisen and ferromanganese, and the lower- grade ores are used in the manufacture of high-manganese pig iron.

Other minerals. — Minerals that are foimd in small quantities asso- ciated with the ores besides phosphate rock are barite, quartz, calcite, arsenopyrite, chalcopyrite, pyrite, galena, pyromorphite, manga- niferous calcite, and a mineral that is composed of manganese, iron, and calcium carbonates.

Types Of Deposits.

The workable manganese and ferruginous manganese deposits may be grouped into five types, partly according to the different rock formations and clays in which they occur and partly according to their origin :

1. Replacement deposits in the Cason shale and its residual clay.

2. Replacement deposits in the Fernvale limestone.

3. Residual deposits derived from the Fernvale limestone.

4. Replacement deposits in clays.

5. Transported deposits in stream, gravels.

Manganese Ore In The Batesville District, Ark. 109

The residual deposits derived from the Fernvale limestone are rep- resented at more mines than those of any other type and have 3nielded more high-grade ore than any others. At most mines and prospects only one type is represented, but at some two types and at a few three types are present and have yielded ore in commercial quan- tities.

The principal features of these different types of deposits are described below in the order in which they have just been named.

Bjspulcemsnt Deposits In Thb Cason Shaxjb And Its

Besidtjal Clay.

Manganese and ferruginous manganese ores are widely distributed in the Cason shale. They have been worked at a number of places and have furnished most of the ferruginous manganese ores and a considerable part of the manganese ores that have been produced in the Batesville district. This formation is generally present in the vicinity of Cushman and farther west and occurs at a few places east of Cushman, where its ore deposits are larger and contain a higher manganese content and a lower iron content than the de- posits farther west.

The ores consist of iron and manganese oxides, which are in places more or less intimately mixed. The manganese oxides are mainly psilomelane and braunite, and the iron oxides include both red and brown oxides. These minerals occur as irregular masses, as thin horizontal seams and beds, and as buttons" or flattened concre- tion-like masses about an inch in longest diameter.

The most noteworthy occurrence of the manganese "buttons" is at the Cason mine, which has produced more low-grade man- ganese ore than any other mine in the district. (See fig. 13.) Here they are so numerous that the " button "-bearing residual clay of the Cason shale has itself been shipped without any treatment, and in recent years much of the " button "-bearing shale has been quarried and shipped as ore. The average manganese content of the ore thus shipped has been about 20 per cent and the iron con- tent has ranged from 6 to 10 per cent. Only a part of the shale at the Cason mine contains "buttons" of manganese oxide; the rest contains red and gray " buttons " composed largely of manganese- bearing calcite. Various stages in the transition of the gray car- bonate " buttons " to the red carbonate and the replacement of the red " buttons " by manganese oxide are well displayed in the cuts.

Other noteworthy occurrences of " buttons " of manganese oxide are at the Montgomery mine and Button prospect, and compara- tively small numbers of them were observed at the Adler mine, O'Flinn prospect, Johnson Hill mine, and Ball mine. At the

110 CONTRIBUTIONS ife ECONOMIC GEOLOGY, 1920, PART I.

O'Flinn prospect, Button prospect, and Johnson Hill mine some of the buttons" are in shale; at the other places they occur in clays.

" Buttons " of red iron oxide were observed in the residual clay of the Cason shale at two of the Pittman mines, at the mine of the United Phosphate &, Chemical Co., at the Breeden prospect, and at the W. T. Gray mine.

The irregular masses of ore are generally porous and usually have rough surfaces, but some of them have botryoidal surfaces. Such masses constitute most of the ore at the Ball mine and much of it at the Montgomery mine. The lenses and beds are shaly and porous at most places and are parallel with the bedding of the shale. Three of the localities at which they occur are the Meeker and Blue Ridge mines and the F. M. Barnes prospect. (See PL VIII.) Although they occur in different parts of the shale, they are most common in the base. At some places it is difficult or even impossible to distin- guish the ore bed in the base of the Cason shale from a nearly hori- zontal deposit of ore that occurs in the top part of the Femvale limestone, which the ore has replaced.

The masses, lenses, and beds just described occur partly in sand- stone but mostly in shale and clay, and the manganese oxides have replaced parts of these rocks, as is shown by the occurrence of sand grains, of pebbles of phosphate rock, and of irregular areas of shale, clay, and sandstone in the ore. Buttons " of manganese oxide were also observed in lenses and masses of ore at the Ball, Cason, and Montgomery mines, showing that manganese oxides have replaced some of the clay and shale through which the manganese buttons " were originally scattered.

The occurrence at the Cason mine of manganese-bearing calcite disseminated through parts of the Can shale that have been least affected by weathering suggests that all the manganese oxides in the deposits described above have been formed by the oxidation of the carbonate. This supposition is corroborated by the occurrence in the Femvale limestone of manganiferous calcite that has yielded at least some of the manganese oxides in that limestone and its residual clays. If this supposition is correct, the oxidation of the manganese- bearing carbonates is perhaps superficial, and the oxides may not extend below the water level of the district.

Beplacembnt Deposits In The Febnvale Limestone.

The occurrence of manganese minerals in the Femvale limestone

is discussed as follows by Penrose :

The manganese, as seen In the St. Clair [Femvale] limestone, exists In the same or almost the same chemical and physical condition as in the clay that now Incloses it in the various nuinjranese localitios — that is, it occurs as

" Penrose. R. A. F., Jr., op. clt., pp. 167-168.

MANGANESE ORE IN THE BATESVnXE DISTRICT, ARK. Ill

ozidee in bodies of different sizes. It Is very probable that the manganese origiDally existed in the limestone In the form of a carbonate and was subse- quently oxidized into Its present condition. Possibly this oxidation may be only superficial, and below the water level of the country the ore may still retain its carbonate form. Small quantities of the carbonate sometimes exist in a finely disseminated state in the limestone, even on the surface, but prac- tically all the manganese In the limestone, as now seen in surface exposures, is in the oxide state, and the disseminated carbonate is insignificant in com- parison with the larger masses of oxides.

The shape of the ore bodies in the limestone varies considerably in different places, but always conforms in a general way to the bedding of the rock. The ore occurs as irregular lumps and masses, often connected by thin layers of the same material ; as lenticular bodies, a few feet to several yards in length ; as flat masses or small concretions lying in the planes of bedding of the ock ; as small disseminated particles and nodules, the size of small shot; and, ia some places, in so fine a state of division as to form a dark chocolate-brown coloring matter. This last form sometimes occurs in thin layers in the rock and sometimes as a finely disseminated material, giving the dark-brown color often seen in the limestone. When considerable quantities of it are present, the rock often loses part of its highly developed crystalline structure and pre- a dark, earthy appearance. The larger masses of ore occur both in this dark-colored and in the light-colored rock. In the latter case they are usually associated with more or less red clay, either in the form of a thin coating anmnd the masses of ore or as films between layers of ore.

Since the above paragraphs were written by Penrose several open- ings have been made in the Batesville district that reveal the pres- ence of manganese-bearing calcite. The discovery of such calcite, together with evidence that much if not all of the manganese oxide in the Femvale limestone and its residual clay is derived from it, supports the statement by Penrose given above, namely, that the oxidation of the manganese-bearing calcite is possibly only super- ficial and that the manganese may still retain its carbonate form below the water level of the country. The most noteworthy occur- rences of manganese-bearing calcite are in the uppermost beds of this limestone at the Harvey mine and the recently opened Manganese Cave mine, just west of the Harvey. This calcite is a fine to coarse grained mineral which has entirely replaced parts of the limestone and which has been partly oxidized and replaced by manganese and ferruginous manganese oxides. Some of the oxide-bearing carbonate has been quarried at these mines and shipped as a low-grade ore. A. few boulders of ore that were nained near the surface appeared to consist entirely of manganese and ferruginous manganese oxides, but when they were broken open they were found to contain cores of the unoxidized carbonate.

The manganese oxides and also the manganese-bearing carbonate generally occur in the upper part of the Fernvale limestone, but they are by no means uniformly distributed through this part. The oxides have been found in sufficient quantity to warrant quarrying

112 COKTRIBUnONS TO EGOKOIOC QEOLOOYy 1900, PABT L

shipping of the limestone only at one of the Pittman mines, the Club House mine, the Henley mine, the Adler mine, the Manganese Cave mine, the W. A. Chinn cut, and one of the Walter Chinn pros- pects. None of the deposits at these localities have so far yielded more than a few hundrod tons of manganese-bearing limestone that was found profitable to work.

Besidtjal Deposits Bebived 7B0X The Febnvale Uxestozte.

esviRAL ncATirmxB.

The manganese deposits that have been derived from the Femvale limestone are more numerous than those of any other type and have yielded not only the greater part of the output of high-grade man- ganese ore from the Batesville district but also a considerable part of the output of low-grade ore. Furthermore, they contain the largest reserves of available ore in the district. The largest known deposit of this type is that at the Southern mine, whidi has produced 36,500 tons of ore. Other deposits of this type which have yielded about 400 tons or more each are at the W. T. Gray, Searcy, G. A. Wilson, Roberts, Denison, Sis Clark, Brooks Hill, Grubb Cut, Rogers, Polk Southard, Turner, Lassiter, Club House, Shaft Hill, Hankins Hol- low, Cummins Hollow, Ruminer Rough, and Manganese Field mines.

The manganese ores consist entirely of masses of oxides and occur in residual clays that overlie not only the Fernvale limestone but also the Joachim, Plattin, and Kimmswick limestones. These masses in their shape and in the character of their component minerals are like the masses of manganese oxides in the Fernvale limestone that have been described above. In fact, they were once embedded in this limestone, and after they were set free from it by the removal of the calcium carbonate they settled by gravity to their present position in the residual clays of the Femvale and lower limestones (see figs. 14 and 15 and PL VTII), or were washed to their present position by streams. Although the ores that have been thus transported by streams are of minor commercial importance they represent a class of deposits of scientific interest, and are described under the heading " Transported deposits in stream gravels."

]CAHOAyS8E.BEA&XNO 0LAT8.

The manganese-bearing clays are a residue from the decomposition of the Fernvale, Joachim, Plattin, and Kimmswick limestones. Most of the clays, however, were derived from the Fernvale limestone, although at many localities this limestone has been almost if not entirely decomposed, so that such clays rest upon the lower limestones or upon their residual clays. The decomposition of the Fernvale

MAlTGANBSe ORE IN THE BATESVHXB DISTRICT, ARK. 113

limestone has formed subsurface hollows and channels as much as 75 feet deep, and some of these have been widened so much that only narrow pinnacles or horses of the unaltered limestones separate them. (See figs. 14 and 15 and PL VIII.) Such channels and pinnacles are well displayed in open cuts at the Cummins Hollow and Club House mines. Some of the channels are straight and represent widened fissures along joints. A few caves and sinkholes have also been formed in the limestone. Manganese ore has been discovered and mined in the caves at the Manganese Cave and Club House mines. The manganese-bearing clays vary greatly in thickness, even in a single locality, owing partly to the irregularity of the surface of the unaltered limestones upon which they rest and partly to the extensive decomposition of the limestofies. They are usually thin where the chert capping has been entirely removed. At most places they are only a few feet thick, but at some places they attain an exceptional

Flaru 14. — Sketch secHoD at tbe Club House mine, BaleBvllle district. Ark., ihowlDi the Cason sha1p. la ttiu Fernrale llmcBloDe. aad In n tbc llmestDDeB, Cli, Boooe chert; Oc, CaaoD DiDSwIck llmesloue ; Op. Plattin llmeBtone. Black dubet and beivy Itnea repieBoxt mansanege ore.

thickness of 80 feet. Abundant outcrops of limestone in an ore- bearing area indicate that the ore-bearing clays occur in relatively snail quantities. At such places the clays are confined almost entirely to subsurface channels and pockets in the limestone. The absence of rock outcrops, on the other hand, suggests that the clays may be relatively thick.

The clays are generally red and chocolate-colored but in places re yellow. They are usually sticky when wet and they become fri- able when dry, so that most of the clay that adheres to the masses of manganese ore crumbles and falls off of the ore before it is shipped. Slickensides in the clays are numerous. Besides man- ganese ore the clays contain loose masses of undecomposed limestone and fragments of chert which is residual from the Kimmswick and Pemvale limestones, and its surfioial portions contain chert frag- nents that have been derived from the Boone chert and chert pebbles

114 Contributions To Economic Geology, Imo, Pabt I.

jt that have been derived from the gravel

1 1 of Upper Cretaceous or later age, which

'° once occurred over much of the district

I U but which has since been almost com-

I pletely eroded. At the Southern mine M - and a few other localities the chert is

I I drusy, and small, doubly tenninatcd S I quartz crystals are associated with it.

° i. lUHOAHZSl OBBS.

£-3

t % The manganese ores are, as previously

I stated, a residue from the weathering of

1 ° the Femvale limestone, having been

- a set free by the removal of the inclosing

B calcium carbonate through solution.

I s This source is shown by the similarity

in shape of the masses of ore in the clay

and those of the manganese oxides in

m the limestone, by the occurrence of the

z same manganese oxides in the same rela-

- tions in both the clay and the limestone,

"; and by the presence of casts of fossils in

r B £ some of the ore that is in the clay. Some

I I ° of the masses of fossiliferous chert that

S have been derived from the weathering

s a of the Femvale limestone have been

S partly replaced by manganese oxides,

S I and the casts of the fossils they contained

a re preserved in the ore, but the purity

of much of the ore that shows casts of

f I fossils, together with the absence of fos-

£ I siliferous chert at most places, indicates

p ° a that at least much of the fossil-bearing

1 1 " ore has not replaced fossiliferous chert

„ £ a but fossiliferous limestone. The chert

S I may have been replaced before it was set

3 free from the limestone or afterward.

Is No evidence bearing mi this point was

a I observed. Penrose " says :

o a The distribution of mongnnese ore In the

i' 1 .. Plii.v, lis would tie expected from Its unequal

n 2 I clistrlbutlim in tlie llmesloue, is trresular ami

B S f 's the principal cause of the uncertainty in

g J J mining It In some places, thouph rarelf, it Is

/

Manganese Ore In The Batesville District, Ark. 115

evenly distributed througliout a large body of clay, but in most places it is in Dumerous poclcets surrounded by clay containing no ore. These pockets vary grpatly in character; sometimes they are comparatively solid bodies, separated only by thin films or seams of clay and containing from 50 to 500 tons or more of ore; sometimes they consist of large and small masses of ore embedded together in greater or less quantities in certain places in the clay ; at other times they are (X)mpoBed of small nodules or grains (called " wash dirt " or " shot ore " by the mioers) disseminated throughout the clay. The mass of these pockets of wash dirt contain from 5 to 25 per cent of manganese ore. Sometimes large areas of clay contain little or no ore, Just as large areas of the original limestone often hold enough insoluble material to form a clay bed yet contain no manganese.

As the bodies of ore' in the original limestone tended, in a general way to follow the almost horizontal bedding of the rock and often had an oblong, flat shape, it would be exi)ected that they would retain something of that shape in the residual clay. In most cases, however, the horizontal position has been con- siderably disturbed by the unequal decay of the limestone, and the flat bodies of ore have been broken into angular fragments or crushed together in a shape- less, shattered mass. Sometimes the fragments of ore have been separated in the unequal sinking of the clay and have been carried to different depths. Where the ore originally existed in the limestone as separate nodules, the same agencies have tended to scatter them, thus still further dividing the d)osits &8 they orginally existed in the limestone. This action has undoubtedly, in many places, caused a more general distribution of manganese in the clay than was the case in the St Clair [Fernvale] limestone. Of course the aggregate amount of ore has not been increased, but the original pockets have been broken Qp and SQ[Nirated.

In some places, however, where the decaying limestone has retained a com- paratively even surface, the pockets of ore preserve their general horizontal position. Such is the case at the Southern mine, near Cushman, where, though the ore bodies sometimes pitch at high angles, a characteristic mode of occur- rence is as almost horizontal pockets, gently undulating and of variable thick- ness.

It is also a noteworthy fact that where the surface of the St Clair [Fernvale] limestone has been worn into the domes and peaks [pinnacles] already described the day and its accompanying ore have a distinct dip, pitching away from such pi*otuberance8 on all sides. This feature is a natural consequence of the sinking of a soft plastic clay on an uneven surface, and a knowledge of it will prove of value in the practical mining of the ore. When a body of ore is found in the clay at or near the surface of one of these limestone peaks, its dip will be found to conform more or less closely to the angle of slope of the surface of the limestone.

The manganese ores consist mainly of the hard oxides, psilomelane, hausmannite, and braunite, with brannite in the least quantity, and of the soft oxide wad. The hard oxides occur partly as slabs and nodules but mostly as irregular masses ranging in size from fine par- ticles to boulders that weigh as much as 22 tons, though boulders so large are rare. The wad occurs as irregular bodies of large and small size and as lenses and beds, and there are masses of hard oxides distributed through many of these bodies. Some deposits contain two or even three different grades of ore. The larger masses gener- ally contain a higher percentage of manganese and a lower per-

116 Contributions To Economic Geology, 1920, Part I.

centage of iron than the finer particles. This means that the " lump ore " is, as a rule, higher in grade than the " wash ore." The first- grade ore at some of the mines is hard and compact and contains 50 per cent or more of manganese; the second grade is porous, light, and soft, though firm, and contains 30 to 35 per cent of manganese, and the lowest or third grade is light, earthy, and soft and contains 20 to 25 per cent of manganese. At some places there is as much of the second grade as of the first grade and twice as much of the third grade alfe of the other two grades combined. The character and rela- tive proportions of the several grades of ore,- however, differ in different deposits.

Much of the highest-grade ore produced in the district — that con- taining 55 per cent or more of manganese — has been obtained from areas (called " roughs ") over which outcropping boulders and ledges of the Joachim and Plattin limestones abound, but in such areas the manganese-bearing clays occur in comparatively small quantity. Such ore is farther from its source than most of the other ore in the region, and the chert covering has been entirely removed from above the ore-bearing clays. As a consequence this ore has been more easily attacked by weathering than most of the other ores, and it has lost its more porous soft parts by erosion or solution or both processes, so that only the hardest and most compact parts remain. Some of the occurrences of these high-grade ores are at the Denison, Hankins Hollow, Cummins Hollow, Johnson Hill, Ruminer Rough, Manga- nese Field, Barksdale, Sand Field, and Earl Collie mines. Analyses of ore of this grade are given on page 121.

Capping Of The Deposits.

The clays containing residual deposits derived from the Femvale limestone are capped at many places by the Cason shale, by the Boone chert, and by gravels and sand.

AAliere the Cason shale is present, its shaly parts and the phosphatic sandstone that it contains in much of the western part of the district have been broken up during the decomposition of the Fernvale lime- stone, and, as stated by Penrose, they have in places " been disinte- grated into a more or less sandy clay and mixed with the other residue from the limestone; in other places they have not as yet been entirely decomposed and are associated with the clay as soft, earthy, honeycombed, and partly disintegrated masses commonly known as ' ocher.' " Although in places this weathered shale overlies the man- ganese-bearing clays and is in turn generally overlain by the Boone chert, in most of the eastern pait of the Bates ville district this chert rests directly upon the manganese-bearing clays, the Cason shale being ai)sent except in small areas.

'" IVnrosc, K. A. l\. jr., op. <il., p. 170.

Makganese Ore In The Batesviixe District, Ark. 117

The Boone chert and the weathered Cason shale overlie the man- ganese-bearing clays at many places, not only where the Femvale limestone has been .partly or entirely decomposed but where the Kimmswick limestone has been completely decayed and even where a part or all of the Plattin limestone has been decayed. The chert and shale have therefore at many places settled far below their original position. (See figs. 14 and 15 and PI. VIII.) The amount of the settling of the chert is equal to the thickness of the limestones that have been removed less the thickness of the residual clays that separate the chert from the undecomposed limestones. The beds of the chert have settled 75 feet or more at the Club House mine, at least 150 feet at the Polk Southard and Turner mines, and at least 250 feet at the Lassiter mine, but probably at no place have they settled more than 300 feet. During the settling of the beds they have been shattered, faulted, and bent so as to conform with the irregular surface of the underlying limestones, and at such places they now dip at angles that range from a few degrees to 60°. ' In general they dip away from the limestone pinnacles or horses, toward the subsurface hollows or channels in the underlying limestones. These displaced masses of chert are known by the miners as flint bars. The thickness of the chert capping ranges from less than 10 to more than 60 feet.

Surficial beds composed of well-rounded chert pebbles and quartz sand not only overlie some of the ore-bearing clays, but at a few places, as at the W. T. Gray mine, they occur as lenses and irregular masses in the clays. These lenses and masses are known as sand and gravel bars and were probably formed in underground channels in limtones that have since decomposed, leaving their residual clays, in which the gravel and sand are now found. The sand and gravel have been derived from beds of Upper Cretaceous or later age which once covered much if not all of the Batesville district, and which have since been almost completely eroded. Much if not all of the sand and gravel has settled below its original level or has been carried below that level by streams.

Beplacemsnt Deposits Tn Clats.

Manganese deposits that have been formed by the replacement of the clays by manganese minerals that have been introduced by ground waters from outside sources are not numerous in this district and their aggregate tonnage is not great, though some deposits probably contain 10,000 tons or more of this ore. The original source of the manganese in such deposits was probably the Cason shale or Fernvale limestone, but at all localities where deposits of this type occur these

118 Contkibutions To Economic Geology, 1920, Part I,

formations have been completely decomposed and if any of their constituents remain it is clay.

The clays in which these deposits occur contain more or less sand and pebbles and fragments of chert, and as 'some of the clay has been replaced by manganese ore these materials are present in much of the ore. Furthermore, the replacement of much of the clay has not been complete, and irregular areas of clay are included in parts of the ore. The ore is a low-grade ferruginous manganese ore, the manganese content usually being 35 per cent or less and the iron, silica, and alumina contents high. It occurs in large irregular masses and as veins several feet in their longest dimension and also in small masses many of which are nodular and have botryoidal sur- faces. Most of the larger masses are composed mainly of a soft, earthy compact black wad but partly of psilomelane, manganite, and iron oxide and are cut by many joints whose faces are black and show deeply striated slickensides. The smaller masses contain a larger proportion of psilomelane and manganite.

Most of the deposits of this type examined by the writer are at the McGee, Hawkins, Chapel Hill, Montgomery Hill, and Beach mines and at the Cochran, Eliza Patterson, E. W. Roach, Jeff Weaver, and Pool prospects.

TBANSPOBTED DEPOSITS JN STBEAH GBAVlLa

Some of the hard, compact masses of manganese oxides that have been set free by the decomposition of the Femvale limestone and Cason shale have been transported by streams and laid down in gravel beds. Some deposits that have been formed in this way occur in the beds of wet-weather streams that drain hollows on whose hill slopes the manganese-bearing clays and loams are ex- posed at the surface ; others occur in alluvial cones at the mouths of some of such hollows. The deposit at the Sand Field prospect is on a terrace standing about 100 feet above East LaiBferty Creek, but this terrace is perhaps the remnant of an old alluvial cone. The deposits of this class that have been worked have been formed by small streams only, and the masses of ore in them have not been trans- ported far from their source, but much ore has doubtless found its way into the larger streams and has been carried by them out of the district.

The best example of a manganese-bearing alluvial cone is at the Pittman mine, at the mouth of Cummins Hollow, though another fairly good example is at the mouth of Hankins Hollow. Manganese ores have been mined from the beds of small streams in hollows at the Hankins Hollow, Cummins Hollow, Johnson Hill, Puph. Adler Hollow, Earl Collie, and McConnell mines, and the O'Gilsby and Rudolph prospects.

MANiSANESE ORE IN THE BATESVILLE DISTRICT, ABK. 119

The manganese ore of these deposits consists of hard, compact masses which have been partly rounded by abrasion and which range in size from fine pebbles to cobbles weighing 30 pounds, though at the Sand Field prospect the occurrence of boulders weighing 1,000 pounds is reported. The Pittman mine, at the mouth of Cummins Hollow, has produced 200 tons of ore, which is the largest output from a deposit of this type. The ore marketed there as well as at the other places named consisted of high-grade lump ore. The wash ore, which includes the finer pebbles, is usually a ferruginous manganese ore. The high percentage of iron is due to the occurrence of small pebbles of iron oxides mixed with those of manganese oxides.

Outcbops 07 The Deposits.

The outcrops of the deposits are especially important to the prospector, for they generally present certain features that have served as guides in the discovery of the many deposits of the district.

The manganese ore itself, regardless of the type of deposit to which it may belong, is exposed at most places. The exposures gen- erally consist of fine particles and large masses lying loose on the hill slopes and in the beds of small streams, and such ore is usually of the same quality as that below the surface. At places where the ore is not exposed its possible presence may be indicated by expo- sures of reddish-brown or chocolate-colored clays and by the occur- rence of manganese and iron stains in afid on chert that overlies the ore-bearing clay. At a few places the iron oxides with which the mangane ores are associated are revealed on the surface.

The brown loamy soil that overlies the manganese-bearing clays is usually very fertile where it does not contain too many chert fragments, and it supports a good growth of white oak, hickory, walnut, and other hardwoods.

BEULTION OP THE DEPOSITS TO BOCK STKUCTUBrE.

Although most of the manganese deposits bear no definite relation to the structure of the rock formations, several of them, including a few of the largest deposits in the district, occur in synclines. The Southern, Grubb Cut, Rogers, Wren, Polk Southard, Turner, and Blue Hidge mines are in a single syncline ; the Barksdale, Ruminer Rough, Manganese Field, Sand Field, and Earl Collie mines are in a single syncline; the W. T. Gray mine is in a syncline; and the Cason mine is in a syncline. Most of these synclines are described on page 105. The above-named mines are only a few of those in the district, but their aggregate production of both high-grade and low- grade ores is more than twice the combined production of all the other mines and prospects. The writer is therefore led to believe that the occorrenoe of large dejKisits in synclines is not accidental,

120 Contributions To Economic Ge0Ux3Y, 1920, Pabt I.

that' the synclines have been favorable places for the accumulatioii of the ores. This subject will be discussed more fully in the final report.

Beultion 07 The Deposits To Sttbface Peatxtbes.

The manganese ores occur at all elevations from the bases of the hills to their crests, or from about 300 to about 800 feet above sea level, but most of the ores are found on and near the summits of even-crested hills, many of which mark the approximate elevation of a peneplain of Upper Cretaceous or Tertiary age, now dissected A fuller discussion of the relation of the deposits to the surface fea- tures is given in the final report

Chemical Composition' Ot The Obs&

The manganese ores may be grouped according to composition into two general classes — high-grade ores and low-grade or ferruginous manganese ores.

Most of the high-grade ores contain 45 to 62 per cent of manganese, though some of the ore that has been shipped contained as much as 60.80 per cent in carload lots. They generally contain from 3 to 8 per cent of iron, 0.15 to 0.30 per cent of phosphorus, and 2 to 8 per cent of silica. Some of the ore that has been marketed contained more than 0.30 per cent of phosphorus, and a very little contained 0.50 per cent or more. As the usual requirements of ores that are used for metallurgic purposes specify that their phosphorus content should not be in excess of 0.25 per cent, it is evident that some of the ores are too high in phosphorus. Phosphorus is, in fact, the most harmful ingredient in the ores of the district, but as it is not uni- formly disseminated through the ores it can generally be avoided in mining. Also the high phosphorus content is in places due to the large amount of phosphorus in the material associated with the ore, and in such places it can be largely reduced by properly preparing the ore for the market. At some places the silica content is high, exceeding 8 per cent, which is the maximum amoimt that is usually accepted by buyers without deducting penalties, but at some such places the silica content can be materially reduced by properly treating the ore. During the last few years, when the demand for domestic manganese ores was especially great, much ore was shipped from the Batesville district that contained very high percentages of both silica and phosphorus.

The two analyses given below represent the approximate average composition of the greater part of the high-grade manganese ore that was shipped during 1917 and 1918. They were computed from the available analyses, supplied by W. H. Denison, of carload shipments that contained 35 per cent or more of manganese. The computation

Makqanesb Ore In The Batesville District, Ark. 121

consisted in adding together the percentages of each constituent in the analyses of the carload shipments and dividing the sums by the number of carload shipments in which each constituent was de- termined. The analyses used in the computation do not include any shipments from the Montgomery mine in 1917, but all the shipments from this mine in 1918 were included. This accounts in part for the high percentage of phosphorus in the ore that was shipped in 1918. for the ore from that mine has averaged approximately 0.40 per cent of phosphorus.

Approximate average composition of the high-grade ores that were shipped from

the Batesville district. Ark,, in 1917 and 1918.

Manpiiwrw(Mn). Iroii(P6)...; PbosphonisCP).

(231 car- loads).

8ilic&(8i0,)

Ahmiliia(AltOa).

as. 77

''.24

(165 car- loads).

it.36

/8.6S

a Iron WB8 determined in 194 ears. h Iron was determined in 125 cars. c Phosphorus was determbied in 198 cars. Phosphorus was determined in 91 cars.

Silica was determined in 135 cars. / Silica was determined in 130 cars. g Alumina was determined in 125 cars.

The highest-grade ores of the district consist of compact or nearly compact, very hard masses of psilomelane, hausmannite, and braun- ite ranging in weight from about a pound to several hundred pounds. The first analysis given below represents the approximate average composition of 39 carloads of lump manganese ore from the Kuminer Kough, Manganese Field, Sand Field, Johnson Hill, Earl Collie, Barksdale, Cummins Hollow, Hankins Hollow, and Denison mines, and the second represents the composition of 250 tons that was shipped from the Cummins Hollow mine in 1918. All of this ore was hand picked. " Wash ore," consisting of pieces that weigh less than a pound, is also present at these mines, but it generally con- tains a higher percentage of iron than the Mump ore," because there are so many small particles of iron oxide which can not be profitably separated from the manganese minerals.

Arcrage cont'position of the highest grade of manganese ore produced in the

Batesville district. Ark,

UansaneseCMn).

Iran(Pe)

nu))honis(P).. SilicaSlO,)

AlOTina(AliO,). Hoistace

a 2. 80

d2.41

'i.'i6

Iron was determined in 34 cars.

b Fhosphoms was determined in 28 cars.

1278"— 21 9

e Silica was determined in 32 cars, d Altunina was determined in 11 cars.

122 Contributions To Economic Geology, 1920, Part I.

The most common type of high-grade ore is represented by the bulk of the ore at the Southern, Grubb Cut, Rogers, Turner, Polk South- ard, Wren, Lassiter, Club House, Searcy, Ozark, Brooks Hill, and other mines. The ore at these mines occurs as loose masses varying greatly in size, from the " wash ore " to masses of " lump ore," some of which weigh several tons. The masses are generally compact, irregular in shape, and black on weathered surfaces but have a bright luster on fresh surfaces. They are composed mainly of black and steel-blue psilomelane and fine to coarse grained hausmannite, which may or may not occur in equal proportions. Tests at some places show about equal quantities of wash ore and liunp ore. Analy- ses of ore of this type follow :

Analyses of the most common type of high-grade manganese ore.

Mazigaxies6(Hn).

Iroii(Fe)

Phosphorus (P).,

SUica(Si0,) ,

Alumina (A1,0|). Moisture

1. Analysis by A. S. McCreath of 5 cars of wash ore from the Southern mine.

2. Analysis by A. 8. McCreath of 3 cars of wash ore from the Southern mine.

3. Analysis by A. 8. McCreath of 15 cars of lump ore from the Southern mine.

4. Approximate average composition of 56 care of lump ore from the Rogers, Polk Southard, South- ern, Oxark, Searcy, and Brooks Hill mines. The percentage of iron is the average of 55 cars; that of phosphorus is the average of 53 cars; that of silica is the average of 28 cars; and that of alumina is the average of 23 cars. These constituents were not determined for the other cars.

The wash ore at any particular mine generally contains at least a few per cent less of manganese than the lump ore, and some of it con- tains more iron, phosphorus, and silica than the lump ore.

Most of the low-grade or ferruginous manganese ores contain 20 to 35 per cent of manganese, 8 to 20 per cent of iron, and 5 to 26 per cent of silica. The phosphorus content is about the same as that of the higher-grade ores.

Uses Of Obes.

The ore from the Batesville district has been used for making ferromanganese, spiegeleisen, and high -manganese pig iron. Very little if any of it has been found suitable for chemical uses, because the amount of manganese dioxide is as a rule less than 80 per cent — the minimum usually required of such ores — and it is not likely that commercial quantities of chemical ore will be discovered. Penrose states that the dark-brown manganiferous clay at the Brooks Hill mine has been successfully used in St. Louis in the manufacture of artificial brownstone and colored bricks. Similar clays occur at other localities. They could be used to produce the spots of some varieties

Penrose, R, A. F., Jr., op. cit., p. 251.

Mangaitse Ore Ik The Batesville District, Ark. 128

of speckled bricks and could be mixed with red-burning clay for brown bricks and with buff-buming clay for gray bricks.

Ecoitomic Possibilities.

Yery little manganese ore has been mined in the Batesville dis- trict since November, 1918, except to fill a war-time contract of 2,000 tons. As stated under the heading " History and production " the output of manganese ore was 75,985 tons from 1849 to 1918, inclusive, and that of ferruginous manganese ore for the same period was 697 tons. Mining in the district was especially active during the World War, when the restriction of imports of foreign ores caused a great demand for domestic ores, for which very high prices were paid.

The manganese deposits of the Batesville district were examined by the writer in the spring and summer of 1918, during the period of increased activity, and as a result of his examination the follow- ing statement concerning available ore reserves was issued in Septem- ber of that year :

Ao estimate of the quantity of available manganese ore of aU grades in this region, where mining is not preceded by systematic prospecting, is difficult to make. Of the 180 deposits examined about half contain an estimated available reserve of 200 tons or less. Only about one-third contain about- 1,000 tons or more, and only a few contain more than 5,000 tons, though certain of these contain many thousand tons. A small number of prospects and mines, however, were not visited, and these and the unexplored deposits may con- siderably increase the reserve. The deposits of the region perhaps Include at least 250,000 tons of available ore containing 40 per cent or more of manganese and 170,000 tons of available ore containing less than 40 per cent of manganese.

It is impossible to make any estimate of the available ore that can be mined and marketed at a profit under normal or nearly normal conditions, when the ores command much lower prices than they did (luring the war, because there are a number of factors that affect the domestic production of manganese ores in normal times. The comparatively high cost of producing the ores and the high percent- ages of phosphorus and silica in some of them are a few of the factors that will retard the manganese-mining industry in this dis- trict, though the district can doubtless produce some ore under normal conditions in the future just as it has at times in the past. The quantity, however, will probably be considerably less than the above estimates of total available ore.

Whenever conditions in the future again cause an abnormal de- mand for domestic manganese ores, mining in the Batesville district will doubtless be stimulated and the result will be an increased production.

8. Oeol. Surrey Presfl Bulletin, September, 1918.

124 Contributions To Economic Geology, 1920, Part I.

UMITS OF THE OBE-BEABINa ABBA.

The manganese deposits that have been developed nd have pro- duced ore in commercial quantity occur in an eastward-trending though irregular belt 4 to 8 miles wide extending from Lafferty Hollow, near Williamson, eastward to the Ball mine, 2 miles east of Hickory Valley, a distance of 20 miles. (See PL VI.) Cave City and Mount Pleasant are near the irregular north border of the belt, and Hickory Valley, Pfeiffer, the Cason mine, Cushman, and Walls Ferry are on or near the south border. Manganese minerals have, however, been found in small quantity as far west as Guion. It is in this belt that the Femvale limestone, one of the ore-bearing for- mations, is apparently thicker than it is elsewhere in the southern part of the Ozark region, and that the Cason shale, the other ore- bearing formation, is present in larger areas than it is elsewhere in the southern Ozark region. Although manganese ore is not present in these formations or in their residual clays everywhere in this belt, it occurs in commercial quantity only in the areas that contain outcrops of one or both of these formations or their residual clays. At many places, as in the vicinity of Cave City, Sandtown, and Mount Pleasant, the ore-bearing residual clays have escaped erosion, although the Fernvale limestone and Cason shale have been entirely decomposed, but such clays occur only in areas where either one or both of the Joachim and Plattin limestones have not been eroded. It is therefore useless to look for large quantities of manganese ore in areas where the St. Peter sandstone and lower formations are exposed.

The Femvale limestone and Cason shale have a general though low southward dip, and in this direction, they pass beneath rock formations of Silurian, Devonian, and Carboniferous age. None of these younger rocks contain manganese ores, and probably no work- able deposits will be discovered by deep drilling in the Femvale and Cason where they are overlain by younger rocks, because the manganese has been concentrated into minable deposits only at and near the surface.

Potash Resources Of Nebraska,

By W. B. Hicks.

Introduction.

The alkali lakes of Nebraska attracted attention many years ago, and about 1900 A. M. McCarty shipped a carload of alkali crust to ' Omaha from the shores of the lake which now bears his name. After this meager attempt at exploitation interest in these lakes lagged until students of the University of Nebraska became interested in their alkali content, probably as a result of classroom discussion with Profs. Barbour and Condra and of packing-house experience in Omaha. Among these students were J. H. Show and Carl Mode- sitt, who began exploring the region about 1910 and for several years collected and analyzed the waters of many lakes. Their in- vestigations led them to believe that Jesse Lake offered the best possibilities of commercial exploitation because it contained larger quantities of richer brine and was more favorably located than the other lakes.

Explorations for potash in the region proceeded slowly at first but became more rapid as the value of the deposits began to be recog- nized. Gradually many data were accumulated, particularly by the potash-producing companies and by Dr. G. E. Condra, of the Ne- braska Conservation and Soil Survey. Reports were prepared by Dole, Hance, Ziegler, Barbour, Condra, and others, as indicated in the bibliography on page 139. These authors presented data on the potash content of certain lakes, with other valuable information, but, except for a rather indefinite estimate by Condra, no attempt was made to estimate the quantity of commercial potash brines in Nebraska.

With the primary purpose in view of getting a more precise esti- mate of the quantity of brine available for potash production in the Nebraska region, the writer spent three months in the fall of 1918 in the region, visited all the potash plants and nearly all the produc- tive lakes, did a considerable amount of exploration, collected many samples of brine, water, sand, and mud for analysis, copied a large amount of unpublished data from the records of producing com-

126 CONTRIBUTIONS TO ECONOMIC GEOLOGY, i960, PART 1.

panies, and obtained much information from Dr. Condra and others in regard to the region. The data thus procured have formed the basis for this report

Acknowledgments are due to Dr. G. E. Condra, director of the Nebraska Conservation and Soil Survey, who contributed much information concerning the potash region ; Mr. W. E. Sharp, presi- dent of the American Potash Corporation, who gave free access to his records, which contain a vast amount of data relating to the productive potash lakes; Mr. W. E. Eichardson, vice president of the Hord Potash Co., who furnished data regarding the potash lakes on the Hord ranch ; Prof. E. H. Barbour, of the University of Nebraska ; Messrs. T. E. Stevens, J. H. Show, Carl Modesitt, and Charles Runey, of the Potash Reduction Co. ; Mr. W. G. Haldane, of the Western Potash Works; Mr. John O'Brien, of the National Potash Co.; Mr. D. C. Atkins, of the Nebraska Potash Works Co. ; Messrs. Frank Abegg and C. L. Emerson, of the AUijnce Potash Co. ; Mr. R. D. Kirkpatrick, of the Standard Potash Co. ; Mr. A. L. Kreiss, of the William Berg Co. ; Mr. D. E. W. Jones, and many others.

Potash Lakes.

Shallow lakes are abundant in depressions scattered all over the sand-hill region of Nebraska. They are reservoirs for rain and spring water, and they range in size from mere ponds to lakes covering about 600 acres and in depth from practically nothing to about 5 feet. Some are fresh ; others are nearly saturated with salts ; and still others show all degrees of saturation between these two extremes. Some persist throughout the year with little diminution in volume ; many of them go completely dry during the summer.

Fresh-water lakes are common in Brown, Cherry, Grant, Arthur, Keith, Box Butte, and Morrill counties, the southern part of Garden County, and the northern part of Sheridan County. They are also scattered through the potash-producing section. Most of them, show a heavy growth of grass around the edge and in the shallow water, also muskrat houses in the fall. However, some of the fresh- water lakes are practically free from grass. The bottoms of many of these lakes are pervious or semipervious, affording underground drainage, which explains the freshness of the water. However, a lake that is practically fresh on the surface may rest on a practically imper- vious layer below which is a subsurface body of strong brine.

Potash lakes as here represented contain alkaline water carrying 1 per cent or more of salts and are often characterized by swarms of flies and a putrefying odor. They occur principally in Sheridan and Garden counties. Many of them dry up in summer. Each one rests on a bottom of impervious mud, below which is usually a sub- surface body of salts, which rests on a second impervious bottom.

POTASH KESOtTBCES 07 NEBRASKA.

In some lakes there is a third body of salts and impervious layer. Below the potash deposits beds containing fresh water usually occur. In most lakes only a small portion of the subsurface material con- tains commercial brines, and in some lakes none of it does.

There are more than 100 known productive lakes in Nebraska, scattered over an area of some 800 square miles and covering an aggigate area of more than 6,097 acres. Many of them are indi- cated on the accompanying map (fig. 26) , and most of them are listed in the following table :

Location and area of productive potash lakes in Nebraska.

Sheridan Coontj.

Name.

Acme

AsbNo9.1-4

Ashborsher

Bauer

D. BriggsNo.l

D.BrtMNo.2

Briggs school sections Nos. l-5 . T. Brijigs.

T- %i£g8 school section No. 1

T. Briggs school section No. 2

Cat.

Cook

DtBovanNo. 1 ,

FaiDerNo8-l-2.,

goyd

Haooock

HcrmnPond

&t Herrian ,

Jaw

Annie Jesse

Frank Jesse Nob. 1-2

Joy Nos. 4, 7, 13

KnuseNo.l.

KnaseNo.3

KntueNo.4

KiBU9eNo.6

UvlessNos. 1-7

Lifly ,

Lflog ,

Peter Lone

JlcPall

Marks

MnHiAll

Momper.JII!!!!

Uurray

Patmore Nos. 1-4

N.C. Peterson Nos. 1-2.

Plant

PotmesU

Rogers-Smith

Schoolsection

Sessler

Shriner

Snow

Stooijitan

Wilkersoo No. 1

WUker80oNo.2

WflkBrsonNo.3 ,

Wilkerson No. 4

Windmill

(Unnamed) ,

Do

Location.

8eo.20,T.25NR. 44W

T.24N.,R.44W

Sees. 13-24. T. 24 N., R. 45 W

T.25N.,R.46W..:

Sec.28,T.26N.,R.46W

T.26N.,R.46W

Sees. 28, 29. 32, 33, T. 25 N., R. 45 W.

Sec. 10, T. 25 N.,R. 45 W..

8ec.35JP.26N.,R.45W

Sec.l,T.25N.,R.46W

Sec. 36, T. 26 N., R. 45 W

do

Area (acres).

Sec. 7, T. 24 N., R. 45 W

8ec.8,T.24N..R.45W

Sec. 28, T. 25 N., R. 46 W

Seo.30.T.25N.,R.46W

Sees. 32-33, T. 24 N.,R. 44 W

8ec.l7,T.24N.,R.45W

6ec.25,T.26N.,R.45W

Seo.29,T.25N.,R.45W

Sec.33.T.26N..R.45W

Sees. 25-26, T. 25 N., R. 46 W

T.26N.,R.45W

Secs.l9&nd29,T.25N.,R. 45W

T,26N..R.44W

S€C.29,T.26N.,R.45W

Sec8.2ior22,T.26N.,R.45W

do

Sec.21,T.25N.,R.46W

6ec.34,T.26N.,R.44W

Sec. 33, T. 26 N., R. 45 W

Sees. 7, 8, and 9. T. 26 N., R. 46 W

Sees. 20, 21, and 29, T. 26 1., R. 44 W Sees. 22, 26, and 27, T. 24 N., R. 45 W. . . ,

Sec. 18, T. 26 N., R. 45 W

Seo.32,T.25N.,R.44W

Sec.34,T.24N..R.44W

Sec8.25and26,T.24N.,R. 45W

Sec. 22, T. 28 R. 45 W

Secs.3andlO,T.25N.,R.45W

Sees. 15, 16, and SO, T. 25 N., R. 46 W

Sec.22,T.24N.,R.44W

8ec.27,T.26N.,R.44W

Sec.29,T.24N.,R.46W

Sees. iS, 16, 21, and 22, T. 26 N., R. 45 W.

Secs.8and9,T.26N.,R.44W

Sees. 14, 23, and 24, T. 26 N., R. 45 W

Sec.21,T.25N.,R.44W

Sec.l8,T.26N.,R.44W

Secs.22and27,T.26N.,R.45W

Secs.27and34.T.26N..R.45W

Sec. 27, T. 26 N., R. 45 W

Sees. iS and 14, T. 26 N., R. 45 W

T.24N.,R.44W

Sec.36,T.26N.,R.45W

Sees. 26, 27, and 34, T. 26 N., R. 45 W . . . .

37

3,107

Total mimher of lakes, 56.

Contributions To Econouic Geoloot, 1900, Fabt I.

Bbowlng poUsb-lakc in weBtera Nebraska. (Arter the Nebraska

Potash Besources Of Nebraska.

Location and area of productive potash lakes in Nebraska — Continued.

County*

Name.

AlkaH

AsbtHJIjbflT. . . ,

Barbwtra

Bristol

EldredNos.1-2. HensanNo.1.. HerznaiiNo.2..

Do

ClTde Johnson.

Mifcs

Ridurdson

Robbing

Storeoon

Little Sturgeon.

Total number of lakes, 16.

Location.

Sec. 1. T. 21 N., R. 46 W

8ecs.32and33,T.a2N..R.44W

Sec.6,T.23N.,R.44W

Soc.31,T.22N.,R.44W

Secs.8,18,T.21N.Jl.45W

Seo.8,T.23N.,R.44W

ao

do

8ec.8,T.22N..R.46W

Sec. 27, T. 23 N., R. 46 W

Sec.5,T.22N..R.46W

Sec. 21, T. 23 N.. R. 45 W

8eca.4and9.T.23N.,R.46W

8ec.3,T.23N.,R.46W

Sees. 23, 25, and 26, T. 23 N., R. 44 W

Area

(acres).

To

loa

Morrill Coantj.

Arcocf .

Clark

Clooirh

Kan Valley..

MaRUne

WcCartv

Rock Nos. 1-3

Sec.25,T.22N.,R.47W

Sec. 30, T. 22 N., R. 46 W

8ec.2,T.23N.,R.47W

Sees, is and 19. T. 22 N., R. 46 W

Sec. 19, T. 22 N.. R. 46 W

T.23N.,R.47W

8ec.l9,T.23N.,R.46W

T.23N.,R.47W

a20

Total number of lakes, 8.

0 Small neck in'southeast corner of ICcCarty Lake. The main body of water covers an area of about 300 IOCS and is practically fresh.

Box Butte and Cherry coantlee.

Bones... Phelan... Hathome

Sec.9,T.24N.,R.47W

Sec.36,T.24,NR.47W

Sees. 21 and 28, T. 34 N., R. 39 W

Total number of lakes, 3.

Lakes whoae location is in doubt.

Bloestsm

Buldi

CodyNo.1

Cody No. 2

Cowlin

Gammon.

Kent

KickenNal

RickenNa2

KickenNo.3

Kraose school section .

MitcheD

RiGeNos.1-4

UttteSesskr

Thompson No. 1

Thompson No. 2

WUson

(?)

T.23N.,R.46W

(7)

T.26N.,R.45W

do

T. 26 N.Vr. 45 W.

do

T.22or23N.,R.45W.

do

do

T.26N.,R.46W

do

T.23N.,R.47W

(?)

T.24N.,R.45W

do...

(?)

1,191

Total number of lakes, 18.

10 Contributions To Economic Geology, 1920, Part I.

In addition to the lakes listed in the table there are a number of reported productive lakes about which very few data are at hand. These are listed on page 132.

Potash Reserves.

Early in 1918 Condra made an estimate of the supply of high- testing productive brines and stated that it would be greatly reduced in four years if the rate of production at that time continued. This estimate corresponded to more than 100,000 tons of potash (KgO) and was moderate considering the data available. Since Condra's estimate was made the potash-producing companies have continued their explorations to such an extent that they now have more or less reliable data on most of the lakes that show any indication of potash. However, this does not signify that the region has been explored thoroughly, as it is known that a considerable number of productive lakes have been very incompletely explored, that nearly fresh lakes which show no indication of potash on the surface may contain pro- ductive brines in the subsurface sands, and that some wells sunk in valleys at a considerable distance from lake beds have encountered low-grade potash brines.

Through the courtesy of the potash-producing companies and Dr. Condra, information concerning most of the potash-yielding lakes has been made available for use in the preparation of this report. The data on individual lakes are of a confidential nature and can not be disclosed. They are approximately complete for some lakes and very incomplete for others. Largely with such informa- tion as a basis, an attempt has been made to calculate the quantity of potash in the known producing lakes. In the calculation an acre-foot of brine containing 10 per cent of solids was considered to weigh 1,450 tons and an acre-foot of 5 per cent brine 1,400 tons. For convenience in estimating subsurface volumes the voids were placed at 33 per cent, which is somewhere near the truth. The result should be considered simply as a rough estimate. It is in all probability a minimum, (1) because there are probably a good many unexplored productive lakes, (2) because the reported pro- ductive subsurface area of most of the lakes is small compared with the surface area, and undoubtedly other parts of the subsurface ma- terial contain at least low-grade brines, and (3) because small quan- tities of potash leached from the surrounding hills are continually being carried to the lakes.

All the productive lakes about which sufficient data were at hand to form a basis for an estimate were included in the calculations, and

1 Condra, G. E.. I*reliminary report on the potash industry of Nebraska : Nebraska Con- servation and Soil Survey BuU. 8, p. 86, 1918.

Potash Resources Of Kebraska.

these lakes are listed on pages 127-129. A summary of their esti- mated potash content is shown in the following table :

Estimated potash content of productive lakes in Nebraska,

Area (acres).

Brine (short tons).

Solids (short tons).

Potash

(Short tons).

County.

Surface.

Sub- surface.

Surface.

Sub- surface.

Total.

3,107

1,147

15,872,000

4,655,000

2,607,700

266,000

9,363,000

146,690 103,150

40,880

76,260

329,216 83,440 42,020 13,720

105,190

475,806

186,500

82,900

14,470

181,450

116,360

40,910

17,670

2,440

38,730

GMden

MorrilL

Box, Batt6, and Oierry . . . . In doubt

6,097

1,324

33,763,700

367,656

573,585

941,215

215, Uo

The data on productive lakes in Sheridan County are further classified according to townships in the following table :

Estimated potash content of productive lakes in Sheridan County Nebr,

Area (acres).

Brine (short tons).

Solids (short tons).

Potash (K,0) (short tons).

Township.

Surface.

Sub- siurface.

Surface.

Sub- surface.

Total.

T.2Sn.,R.46W

1,050

1,429,000 554,000 1,527,000 9,180,000 1,307,000 326,000 1,549,000

26,440 2,200 21,345 41,020 20,715 5,550 28,420

128,170 37,360 41,690 67,280 35,286 19,750 9,680

154,610 39,560 63,035 99,200 56,000 25,300 38,100

42,920

T.a4N..R.45W

T.25N.'R.46W

12,500

T.28N..R.45W

20,550

16,580

5,060

9,970

T.24N.,R.44W

T.25N.,R.44W

T.N..R.44W

3,107

15,872,000

146,690

329,215

475,805

115,360

About one-third of the potash in the productive lakes is repre- sented by brines containing 10 per cent or more of solids, nearly half by brines containing from 5 to 10 per cent of solids, and less than one- fourth by brines containing from 1 to 5 per cent of solids. These data are shown in the following table :

Estimated potash content of productive lakes in Nebraska classified according

to strength of brines.

[Short tons.]

County.

'Sheridan

Qvden

Morrill

Box Butte and Cherry hidoubt ,

10-t- per cent brine.

Solids.

180,710

3,140

28,440

54,600 275,800

K,0.

49,665

6,230

11,600 68,435

6 to 10 per cent brme.

Solids.

KjO.

169,495

131,860

21,530

13,720

107,070

443,675

36,540

29,950

4,840

2,310

22,930

96,570

1 to 5 per cent brine.

Solids.

116,600

51,590

32,930

19,780

221,650

KtO.

29,155 10,020

6,600

4,200

50,105

Total.

Solids.

475,805

186,590

82,900

14,470

181,450

941,215

KaO.

115,360

40,910

17,670

2,440

38,730

215,110

132 Contributions To Economic Geology, 120, Part I.

In addition to the productive lakes whose estimated potash content is indicated in the foregoing pages, there are a good many reported productive lakes, particularly in Sheridan and Garden counties, about which very few data are at hand. Among these lakes are Backus, Beck, Boyer, Butcher, Camp, Cary, Curb, Gaunt, Gillis, Hog Valley, Krause No. 2, Howard Miller, Josh Miller, Murphy, Old Lady, Patton, Peterson, Sand, Sand Hill, Schoonover, Sam Smith, Taylor, Tin Barn, and Wild Horse. They cover an area of about 2,000 acres and probably contain about 250,000 tons of solids, includ- ing 50,000 tons of potash (Kfi). If these figures are approxi- mately correct, they more than balance the 48,000 tons of potash (KgO) which had been produced from the Nebraska mines by the end of 1918.

Immense quantities of water which contain less than 1 per cent of solids but which carry relatively high percentages of potash in the solids occur throughout the potash-producing region and also far to the east in Cherry, Grant, and other counties. Some idea of the volume of such dilute surface waters in the region may be gained by considering reports on certain groups of lakes in Sheridan, Garden, and Cherry counties. Data on 27 lakes in Sheridan County, including Collins, Donnahue, Goose, Johnson, Krause, Ranch House, Reed, Ross, Twin, and some 19 lakes on the Spring ranch scattered over the productive region, indicate that these lakes cover an aggregate area of about 3,000 acres and contain 12,000,000 tons of surface water, 40,000 tons of solids, and about 10,000 tons of potash (KgO). Data on 54 weakly alkaline lakes in Garden County indicate a surface area of 2,200 acres, 11,000,000 tons of water, 25,000 tons of solids, and 5,000 tons of potash. Data on 16 selected lakes in the vicinity of Merriman, in Cherry (ounty, including all that have shown the best indications of potash, namely, Club House, Eli, Hale, Ilathorne, Jessen, Mud, Xelson, Preacher, Round, S. B., Snyder, Snyder's Goose, Steel, Steer, Twin, and Walker lakes, indicate an aggregate area of about 2,000 acres, 10,000,000 tons of surface water, 50,000 tons of solids, and 10,000 tons of potash. There are many other lakes containing a very low percentage of solids scattered throughout the productive region or bordering on it, so that the actual quantity of potash in such surface waters is probably several times as great as that indicated by the data cited. Moreover, it is probable that the quantity of such dilute waters in the subsurface sands exceeds that at the surface.

Composition Of Brines.

Commercial potash brines vary much in salinity and in the composi- tion of the dissolved salts. The salts are composed of carbonates, bicarbonates, sulphates, and chlorides of sodium and potassium in

Potash Resources Of Nebraska.

varying proportions. Carbonates usually predominate, bicarbonates are high, and sulphates are variable but often high. The following analyses of selected brines from lakes in widely separated parts of the productive region are probably representative :

Composition of productive potash brines in Nebraska.

[E. T. Erickson, analyst.]

K

2H.56

Xa

a

4.15 3.99

so

Co,

HCOl

11.20 19.52

BiO,

Stghiitj

K}0 equivalaat

'21.32

SpecificgraTityat25*C. aSioNVK...

iio"

1. Alkali Lake.

1 Ashbwher Lake (Garden County).

S. Floyd Lake.

4. Hauiome Lake.

5. Jesse Lake.

6. Mitchel Lake.

7. PhelanLake.

8. Plant Lake.

0. Stoughton Lake.

10. Sturgeon Lake.

11. Average.

Jesse Lake has yielded far more potash than any other lake of the sand-hill region and consequently is relatively of greater interest. Three analyses of brine from this lake are tabulated below.

Composition of potash brines from Jesse Lake.

K

Na

n

So,

Co,

HCOl :

Salinity

KO equivalent

Ratio Na/K

1. Jesse Lake water. Colorado School of Mines Quart., vol. 10, No. 3. p. 21, 1015; J. H. Show, analyst.

2. Brines from subsurface .sand 300 feet from shore, collected in 1912: J. F. Breaxeale, analyst.

3. Brine from subsurface sand from east side of lake, collected in 1918; £. T. Erickson, analyst.

4. Arerage.

NoTB. — Analyses 1 and 2 have been recalculated to Ionic form and to 100 per cent by B. Hicks.

The foregoing analyses are believed to represent fairly well the composition of the productive brines of the potash region. They indicate that the average composition of the brines of the region is very similar to that of the brine of Jesse Lake, although the latter

134 Contbibutions To Economic Geology, Iwd, Part I.

is richer in potash. It should be noted in this connection that the brine of Eichardson Lake is said to be composed ahnost exclusively of carbonates, and the brine of one of the Wilkerson Lakes is so rich in sulphate that large quantities of sodium sulphate crystallize out of it in cold weather. There may be other abnormalities, but most of the brines conform to the type indicated in the tables.

Origin Of Nebraska Potash.

The geologic history of Nebraska as generally interpreted* pre- cludes any deep-seated origin of the potash brines in the sand hills. The Dakota sandstone, which contains fresh water, lies 2,500 feet or more below the surface and is covered by several hundred feet of Benton and Niobrara strata, overlain by the Pierre shale, an im- pervious formation, in places more than 2,000 feet thick. Above the Pierre shale are a number of formations which were deposited in shallow lakes and which carry fresh water where they are water bearing. The deposits forming the sand hills are probably about 100 feet thick Sn the valleys of the potash region. Nearly all the waters from depths greater than 30 feet in this region that have been analyzed are practically fresh, and the composition of the dissolved salts, so far as known, is distinctly different from that of the pro- ductive brines. Underground waters tributary to the sand-hill re- gion from the west and northwest are also fresh and differ in com- position from the waters of the potash section. These facts seem to show conclusively that potash brines in the sand-hill region are con- fined to a relatively thin layer near the surface.

Petrographic examination by E. S. Larsen of 13 samples of sand collected by the writer from the potash region, including potash- bearing sands of Jesse Lake and other localities, shows that they are composed largely of quartz, feldspar, and volcanic ash and are prac- tically free from clay, calcareous matter, and other cementing ma- terials. Quartz makes up more than half of the material; plagio- clase ranging from albite to labradorite and mostly andesine is next in abundance; potash feldspar usually makes up several per cent of the samples. Volcanic-glass fragments of the kind that make up rhyolitic ash beds are present in all the samples and range in amount from about 1 to 6 per cent. Fragments of chert or related material are rather abundant. Hornblende, augite, tremolite, bio- tite, epidote, garnet, zircon, titanite, magnetite, apatite, calcite, and hypersthene are present in very small amounts, and minute needles of an unidentified mineral are rather abundant in some of the quartz

'See bibliography (p. 139), particularly the report by Darton.

POTASH BESOUBCES OF ISffiRASKA. 135

and feldspar grains. For the most part the mineral grains and volcanic glass are but slightly decomposed or altered. These sands differ from ordinary sands in the abundance of feldspar, especially plagioclase, in the freshness of all the minerals, and in the presence of Tolcanic glass. They are sands such as might be formed under conditions of aridity from andesitic and latitic tuffs with some ad- mixture of ordinary quartz-rich sands, such as are conmionly de- rived from the weathering of granites and similar rocks.

Samples of fine sandy material known as Box Butte clay, from the table-land northwest of the potash region, contain probably from 10 to 20 per cent of volcanic glass, 6 per cent of potash feldspar, and a considerable amount of fine material composed of calcite, clay, etc. The glass is more or less altered.

Potash is contained in the sands principally as a constituent of potash feldspar and of volcanic glass, and the percentage is not exceptional. Such potash is present in insoluble combinations and is rendered soluble in nature only after prolonged weathering. The freshness of the mineral grains of the sands and the comparatively %ht indications of alteration as shown by petrographic analysis lead to the belief that no large quantity of the potash in these sands has bee rendered soluble by weathering processes and that the sands can not be considered the direct source of the potash in the productive lakes of Nebraska. The potash content of a number of samples of sands from the potash region and vicinity is shown in the following table :

Percentage of potash (KO) in Nebraska sands.

[B, T. Erickson, ftnalyst.]

No.

S-6 S-4 S-18 S-24 S-62

Description.

Wind-blown sand along Niobrara River

Sand from 4-foot hole at Hay Springs

Sand from 7-foot hole on southwest oank of Broncho Lake.

Sand from blow hole 4 miles north of Antioch

Sand from 4-foot hole on north bank of Boness Lake

Sand bom. depth of 34 feet at south end of Jesse Lake

Sand from depth of 15 feet at south end of Jesse Lake

Sand fh>m depth of 13 feet in Jesse Lake

Sand from potash horizon in Mclntirre Lake

Sand from depth of lOfeet in Stoughton Lake

Sand from depth of 1 0 feet In E 11 Lake

Sand clay 4 miles west of Oordon

Percentage

ofnotash

(K.O).

Dilate waters from the table-land immediately northwest of the potash region are low in potash and rich in sodium and calcium and have little relation to the potash brines of the sand hills. The fol- lowing four analyses probably represent typical waters of this region :

136 CONTBIBUTIONS TO ECONOMIC GEOLOGY, 192a, PART I.

Composition of dilute icaterg northwest of and adjacent to the Nebraska potash

region,

(Samples collected Nov. 17, 1918. E. T. Ericlcsan, analyst.]

K

Na

Ca.

Mg

n

8O4

COi.

9.Sd 2.M

HCOi.

SiO,

56,37

61. $4 13.(6

Salinity

Ratio Na/K...

1. Niobrara Riyer water at bridge on road from Alliance to Hay Springs.

2. Water from well 54 feet deep on Watson's farm, 26 miles nortn of Aliutnoe.

3. Water from well 90 feet deep at Hay Springs.

4. Water from wells 200 feet deep at Goroon (city water supply)

5. Average.

The ratio of sodium to potassium in these dilute waters is about 11.1 to 1, whereas the ratio of sodium to potassium in the brine of Jesse Lake is 0.85 to 1 and the average ratio in the brines of the potash region is 1.4 to 1. (See table below.) These figures show conclusively that the dilute waters represented in the preceding tables of analyses are not the main source of potash in Nebraska.

Dilute waters from beds underlying Jesse Lake and vicinity are somewhat similar in composition to the dilute waters northwest of the region, but one conspicuous difference is that they are much richer in potash. Their potash content and their general composition can be explained by considering them as mixtures of dilute waters such as are represented in the preceding table and of dilute waters having a saline content similar in composition to that of the waters of Jesse Lake. The second group of dilute waters would represent leaching of the sand hills. The composition of such a mixture would depend on the relative proportion of the two types of waters and also on the exact composition of the two waters making up the mixture. Analytical data on three samples of water from beds underlying Jesse' Lake and vicinity are given in the following table:

Composition of waters from beds underlying Jesse Laks and vicinity.

[E. T. Erickson, analyst.]

K

Na

Ca . . .

Mi!

SOi

COi

HCOl

51.S8

Salinity

Ratio Na/K

1. Water from well half a mile north of Jesse Lake.

2. Water from 98-foot well on edge of hill 150 yards southwest of Jesse Lake. 8. Water from artesian well in Jesse Lake.

4. Avoage.

Potash Resources Of Nebraska.

As is indicated in the following table, dilute waters east and north- east of the potash region are richer in potash than the dilute waters from the northwest represented on page 136.

Composition of dilute toatera ectst and northecMt of the Nebraska potash region,

[E. T. Eiickaoiii analyst.]

K

Na

Xe

So*

t

COi

HCOi

aoj

t

BaltnitT nerts iter million , .

RattoNa/K

I. Water from Niobrara River near Valentine.

1 Wato* from 96-foot cased well at Merrlman (city water supply).

3. Water from lSO>foot railroad well at Hyannis.

4. Average.

The ratio of sodium to potassium in the dilute waters east and northeast of the potash region as represented in the foregoing table is 2.67 to 1. Relatively this means a much larger percentage of potassium than is contained in the dilute waters northwest of the potash region. The increased percentage of potash is no doubt due, at least in part, to admixture of leachings rich in potash from the sand hills, which means simply that potash is gradually leaving the sand-hill region through surface and underground drainage.

There appears to be a subsurface drainage in the potash region from the northwest toward the southeast, and it is presumed that considerable quantities of potash are leaving the potash region through this means. Unfortimately no analytical data are available to show the potash content of dilute waters southeast of the potash region.

The alkali content of the lakes of the potash region is such as might result from various mixtures of the leaching of plant ashes and of sediments. As has been pointed out by Hance, Ziegler, and others, the quantity of alkali would not require any excessive growth of vegetation in the region or to the northwest to account for the potash. It is therefore concluded that the alkali content of these lakes was derived primarily from the leaching of vegetable ashes resulting from many destructive fires, and to a lesser extent from the leaching of underlying rocks. On the assumption that this view of the origin of potash in Nebraska is correct, the following suggestions are offered with the hope that they may throw some light

1278*—21 10

188 CONTR3XJnONS TO ECX)NOMIC GEOLOGY, 1920, PART

on existing conditions in the potash region and on the potash reserves.

Such leachings of ashes and underlying rocks from the table-land to the west and northwest and also from the sand hills themselves were partly absorbed by the sand and partly concentrated in valleys. In the valleys the leachings finally reached the lowest areas, where they were absorbed by the sand and concentrated by evaporation, forming intermittent lakes. At the same time there was present a body of ground water such as now underlies the region to the north- west and probably the sand hills, which was being forced to the sur- face by capillarity or otherwise and which was being concentrated by evaporation. The intermingling of the leachings and of the ground water at the proper concentration caused the precipitation of carbonates and silicates of calcium and magnesium and the deposition of sediments, which finally formed an impervious layer between the ground-water horizon and that of the leachings. In Jesse Lake such an impervious layer was laid down at a depth of about 15 feet from the surface. The leachings coming into the lake were continu- ally concentrated by evaporation, until in Jesse Lake the brines contained more than 10 per cent of solids. At the same time the leachings carried into the basins small quantities of clay and other fine-grained materials, which were deposited in large part on the floors of the lakes and which finally formed a more or less impervious layer of mud between the present surface lakes and the subsurface potash beds.

Some of the leachings did not reach the low valleys but were absorbed by the sands on the hills and slopes. In dry weather the leachings thus absorbed were forced toward the surface by capillarity and were gradually concentrated by evaporation. Finally the sand hills as well as the valleys contained potash-bearing waters, but as most of the leachings reached the valleys and only a comparatively small portion was absorbed on the hills and slopes the great bulk of the potash of the region was concentrated in the lakes of the valleys. After the last destructive fire and the final leaching of the ashes rain water falling on the sand hills was absorbed by the sands and mixed with the potash- bearing waters already there, and this mixture gradually made its way to the potash lakes. Such a process of leaching out the potash in the sand hills is believed to be in prog- ress to-day. The leachings are probably very dilute, such as are represented by the fresh waters in the beds underlying Jesse Lake, as shown on page 136, but the composition of the dissolved salts is more probably similar to that of the productive potash lakes.

This view implies that only small quantities of potash are being leached from the sand hills and reaching the potash lakes and that

Potash Resources Of Nebraska. 139

no large potash reserves are likely to be found in regions not occu- pied by lakes. It is assumed, however, that some potash lakes may have been covered over by sand when the hills were shifting as sand dunes and that much of the potash thus covered may not have yet been leached out. Such conditions are believed to be exceptional.

Bibliography,

1903. Darton, N. H., PreUnunury report on the geology and water resources of Nebraska west of the one hundred and third meridian : U. S. Geol. Survey Prof. PaiH:r 17.

1903. Barbour, E. H., Nebraska Geol. Survey First Ann. Rept.

1912. Dole, R. B., Potash in Nebraska : U. S. Oeol. Survey Press Bull. 82.

1912. Hance, J. H., Potash in western saline deposits: U. S. Geol. Survey Bull.

540, pp. 465-467.

1913. Bates, C. G., and Pierce, R. G., U. S. Forest Service Bull. 121.

1915. Lee, W. T., Stone, R. W., Gale, H. S., and others, Guidebook of the western United States, Part B, The Overland Route: U. S. Geol. Survey Bull. 612.

1915. ZiEQLER, Victor, The potash deposits of the sand-hills region of north-

western Nebraska : Colorado School of Mines Quart., vol. 10, No. 3, pp.

1916. Babbour, E. H., a preliminary report on the alkali resources of Nebraska :

Nebraska Geol. Survey, vol. 4, pt. 28.

1917. Crawford, R. P., Potash from sand-MU lakes : Sci. Am., vol. 116, pp. 167-

1917. Crawford, R. P., Pumping potash from Nebraska lakes: Bug. and Min. Jour., vol. 103, pp. 777-781.

1917. Thum, E. E., The Nebraska potash industry: Met. and Chem. Bng., vol.

17, pp. 693-698.

1918. Condra, G. E., Preliminary report on the potash industry of Nebraska:

Nebraska Conservation and Soil Survey Bull. 8, 39 pp., Lincoln. 1918, Letteras, J. M., Potash in Nebraska : Chem. and Met. Png., vol. 19, pp.

633-634 ; Chem. Abstracts, vol. 12, p. 61. 1918. NoRRis, W. A., Origin of Nebraska potash lakes : Met. and Chem. Eng.,

vol. 18, p. 281 ; Chem. Abstracts, vol. 12, p. 1035. 1918. Lo>TXAND, G. A., Summary of the climatological data for the United

States, section 35, U. S. Weather Bureau.

Phosphate Rock Near Maxville, Granite County,

Montana.

By J. T. Pardee.

Introduction.

Some of the most extensive and easily accessible of the phosphate deposits of Montana occur in the vicinity of Maxville (formerly Flint), a small settlement on the Philipsburg branch of the Northern Pacific Railway. (See fig. 27.) The quantity of minable material in these deposits is at least as great as that in the known deposits near

too>aiM

Fiouu 27.— Index map showing location of PhiUpsburg phospbate field, Mont.

Metose/ Garrison,* and Elliston,' and they are less than 6 miles from the railway. The Maxville area is in the northern part of the Philips- burg phosphate field, a general description of which has been pub- lished.* Part of it lies also within the Philipsburg quadrangle, the surface features of which have been mapped and the geologic f ea-

H. 8., Rock phosphate near Melrose, Mont.; U. 8. Oeol. Survey Bull. 470, pp. 44(M51, 1911. 'Pardee, J. T., The Oarriaon and PhiUpsburg phosphate fields, Mont.: U. 8. Oeol. Survey BuU. 640, #

'Btooe, R. w., and Bonlne, C. A., The Elliston phosphate field, Mont.: U. 8. Oeol. Survey Bull. 680L pp. 373-383, 1915.

*V. 8. Oeol. Survey topographic map or the Phihpsburg quadrangle, Mont.: 1906; reprinted 1912.

142 Contributions To Economic Geology, 1920 — Pakt I,

tires described.* The field work on which this paper is based done in the summer of 1916 by the writer, with the assistanot T. Hi Rosenkranz.

Structural Features.

In the northern part of the Philipsburg field (PI. XIII) the p|( phate bed, together with the inclosing rocks, is bent into several allel tightly squeezed folds that trend northward. The westemial of these folds is a large, greatly faulted downfold or syncline tl lies just east of Maxville and may be traced a short distance nd and 7 or 8 miles south of that place. Throughout most of its are| is overridden by a huge mass of rocks brought by thrust faulting fi the west, but part of its western limb, with its included phosph bed, is now uncovered. Along this limb the dip, which should mally be east, is west, and the strata that compose it appear to hi been overturned by a force acting from the west. This fold is exposed along the upper course of Wyman Gulch and may be coni niently called the Wyman Gulch syncline. ,

In the area east of the Wyman Gulch syncline the folds are ft

from overthrust matter and in general their features are well expos4

All the anticlines lean to the west, as if they had been pushed of

by a force acting from the east, in the opposite direction from til

indicated by the results of the force which later on thrust a mass o1

the Wyman Gulch syncline. The dips along their west sides are cd

sequently very steep and in places even overturned, whereas on thi

east sides they are only moderately steep. The structure is furthj

complicated by faults, some of which are parallel to the folds aij

locally cause the outcrop of the phosphate bed to be repeated. Aloi

Boulder Creek and in the mountains around the Royal mine the fold

end in areas of faulted and intrusive rocks. They show througho

a pitch to the north, which several miles beyond Douglass Cre

finally carries them beneath a cover of later rocks. The southed

parts of the folds have been so deeply eroded that the phosphate

remains mostly in the troughs or synclines. Owing to their deed

northward, however, the folds are less deeply cut away in that dire<

tion, and the outcrop of the phosphate bed rises higher and higher

the sides of the anticlines and at length passes entirely over them. -4

a result of the folding and the erosion combined, the surface trace 0

outcrop of the phosphate bod winds back and forth, forming loDj

loops that close alternately at the north and south around the and

clines and synclines, respectively. Although the bulk of the phd

phate that has escaped erosion remains in the synclines, the ou<

cropping edges of the phosphate-bearing beds are at most places rell

I tively high enough to be regarded as on the sides of the anticlintf

I ft U. S. Qeol. Stirvey Qeol. Atlas, PbiUpsburg folio (No. 196), 1915.

Phosphate Rock Near Maxville, Mont. 143

The three largest anticlines are about 2, 4, and 7 miles east of Maxville. The axis of the first passes through Princeton, the second through Douglass Mountain, and the third through Dunkleberg Ridge. Between the southern parts of the Douglass Mountain and Dunkleberg Ridge anticlines there is a narrow arch, which is here called the Royal anticline, from a well-known gold mine a short distance east of it.

Phosphate Rock.

Occttbbence And Compositiok.

Wyman Gulch syndine. — Along the west limb of the Wyman Gulch syncline the presence of the phosphate bed is indicated generally by loose fragments of phosphate rock in the surface mantle and the bed has been exposed by the workings at the Fields mine. Here an adit 100 feet below the working mentioned in the previous report* cuts 4 feet of soft, earthy black phosphate. A representative sample of this material, according to a determination made by R. M. E!anmi in the laboratory of the United States Geological Survey, contains 13.62 per cent of phosphorus pentoxide (P2O6), equivalent to 29.5 per cent of tricalcium phosphate (Ca8(P04)j). This is practically the same quantity that is contained in the material exposed by the upper working. The comparative poverty of the bed in phosphate, as shown by these samples, is presumably the result of faulting.

Princeton anticline. — Around the Princeton anticline, from Gird Creek to a point half a mile north of Douglass Creek and back along the east limb nearly to Princeton, a total distance of 7 or 8 miles, the phosphate bed is in general thinly mantled and its presence is com- monly indicated by float. South of Gird Creek, along the west limb, the bed is rather deeply covered, but it is definitely located at a point 2 miles east of MaxviUe by the shaft of Axel Miller, in which 2 feet of phosphate is reported. A mile and a half north of Gird Creek, along the east limb, in sec. 1, T. 8 N., R. 13 W., the phosphate bed is exposed by a shallow trench. Here it is divided by 3 feet of clay mto two layers, 4 feet 7 inches and 3 feet 8 inches thick. No analyses are available, but by comparison with material from the deposit on Douglass Mountain, described below, the thinner layer is estimated to carry at least 60 per cent of tricalcium phosphate and the thicker layer somewhat less.

Douglass Mountain anticline. — Along the Douglass Mountain anti- cline, from a point about a mile north of Princeton northward to the end of the loop nearly 2 miles beyond Douglass Creek and back on the east limb to Granite Creek, just below Finley Basin, a total distance of about 14 miles, the phosphate bed is not deeply covered and its presence is generally indicated by float. For a considerable

Pardee, J. T., op. cit., p. 224

144 Contributions To Economic Geology, 1920 — Part I.

distance along the west limb of the anticline the bed is cut by a strike fault that causes the outcrop to form two parallel bands. Trenches made across the bed near the top of the slope west of Princeton Gulch and on the south slope of Douglass Mountain expose the following sections:

SectionB ofphoBphaU bed in Dcuglau Mountain ttntidintj near MaxvilUf Mont,

Locality.

Slope north of Prfnoeton Otdch, 8eo.l8,T.8N.,R.12W. Inner outcrop on weet limb of Doug- lass Mountain anticline.

South slope of Douglass Moun- tain, sec. 81, T. 0 iy.,R. 12 W. Inner outcrop on west limb of Douglass Mountain anticline.

Character.

Quartette.

Hard phosphate ,

White cherty quartslte, gray to black

near bottom

Hard blue-black phosphate

Yellow shale

Phosphate

Yellow shale

Phosphate

Sandstone, phosphatio

Quartsite.

Sandstone and quartsite.

Black phosphate, indadiiig two very

thin beds of shale

Shale

Black phosphate

Shale and sandstone

Black phosphate

Conglomerate with nodules of ibos-

phate

limestone.

Thick-

(phos- phorus pent- oxide).

Ca,(P04),

(trical-

dum

ph09-

pbato).

Percent,

PereetU.

a&36

a Omitted from sample.

In the exposure in Princeton Gulch the highest layer of phosphate, 1 foot 3 inches thick, is probably one of the lower thin layers repeated by faulting parallel to the strike. Otherwise the section is unmodified. No evidence of faulting was observed in the exposure at Douglass Mountain.

Dunkleherg Ridge and Royal anticlines. — No exposures of the phosphate bed in place are known along the Dunkleberg Bidge and Royal anticlines. Its presence in both, however, is mdicated by float, which was observed along the west limb of the Dunkleberg Ridge anticline about a mile south of the Wasa mine and along both of the Royal anticline on the slope north of Granite Creek, below Finley Basin.

Besebvbs.

Along the west limb of the Wyman Gulch syncline the strata have been greatly squeezed, and the phosphate bed is, therefore, probably at most places crushed and mixed with foreign matter, just as it is at the Fields mine. Parts of the bed have no doubt escaped the destructive forces and are workable, but it is not possible to estimate the quantity of phosphate they contain.

Phosphate Rock Near Maxville, Mont. 145

The lack of exposiires and the probable modification of the deposit by the deformation produced by the intrusion of a large igneous mass near by also make very uncertain any estimate of the quantity of phosphate in the Dunkleberg Ridge and Royal anticlines, though these anticlines doubtless contain much minable phosphate.

On the Princeton and Douglass Mountain anticlines, however, the phosphate bed appears to have been changed but little or not at all by the rather severe deformation that the strata have undergone. In the several exposures that were examined the deposit is made up of two or more layers that have an aggrate thickness of 6 or 7 feet and an average content of more than 60 per cent of tricalcium phos phate. At some places the layers are so near together that aU can be worked advantageously through one opening, but comjnonly they are so far apart that they must be mined separately. Therefore the principal layer, which is 4 feet or more thick, is persistent, and con- tains 64 per cent or more tricalcium phosphate, is the only one con- sidered in estimating the quantity of phosphate available. The float and the artificial exposures show that the phosphate outcrop extends from a point at Gird Creek, on the west limb of the Princeton anticline aroimd that fold and the Douglass Mountain anticline for a total distance of about 21 miles. The structure of the inclosing strata shows that the bed is nearly everywhere carried down on a steep slope to a depth of several thousand feet before it reaches the bottoms of the synclines. The upper part of the bed, particularly the part that stands above the natural drainage channels, is the most vahiable, because it can be mined most easily. The part that stands above Douglass, Gird, and Boulder creeks is roughly estimated as equivalent to a body 400 feet deep, 4 feet thick, and 21 miles long. Estimated at 180 pounds to the cubic foot this part of the bed con- tains about 14,000,000 long tons. If a depth of 3,000 feet is assumed as the limit of profitable mining the minimum total quantity of min- able phosphate in this vicinity is more than 100,000,000 tons.

The Divide Silver District, Nevada.

BjAdolph Knopf.

Summary.

The Divide district, one of Nevadas newest silver camps, centers at Gold Mountain, 5 miles south of Tonopah. The discovery of silver ore that started the great activity at this camp was made late in 1917, wholly by chauce. A crosscut was heing driven to cut a small gold vein that had been worked higher on the slope of Gold Mountain in- termittently since 1902, and before it had been driven far enough to cut the gold vein it quite unexpectedly intersected a rich sUver-

UNCONRDWHrnr

I wfute tuflT

Oddie riiyclita

;-pBtned>i9fattB biflP

FlOTJBE 28.— Generalised oolumnar section of the rocks of the Divide district, Nev.

bearing lode. Further exploration indicated that a large and valu- able ore body had thus accidentally been discovered. In February, 1919, Tonopah awoke to the possibilities of the new field and the boom began in earnest, and soon an area of 50 square miles surrounding Gold Mountain was staked. By midsummer between 80 and 100 hoists were in operation and a large amoimt of exploratory work was being done.

The prevailing rock in the Divide district is the Fraction rhyohte breccia. This is intruded by several stocks of the Oddie rhyolite and by a large mass of andesite. Later than all of these is a series of latite lava flows, which cap the highest peaks of the district. The distribution of the rocks of the Divide district is shown in Plate XIV, and a generalized columnar section of the rocks is shown in figm'e 28.

The ore bodies are zones of fracturing and shearing in the Fraction rhyolite breccia; strictly speaking they are lodes, not veins. The

148 Goktributions To Ecokomig Gsoloot 1920 Part

chief silver-bearing mineral is cerargyrite (horn silver), which is com- monly concentrated in rich masses along irregular seams of sericite that traverse the lodes. The primary metalliferous material is leanly mineralized rhyolite breccia carrying a small amount' of finely disseminated pyrite and threaded by thin veinlets of exceedingly fine grained quartz. What the prixoary silver-bearing mineral is has not been determined. The scarcity of quartz or of silicificatum is a noteworthy feature of the ores of the Divide district, especially in contrast with the high silica content of the ores in the adjoining dis- trict of Tonopah. The silver in the lean primajy material of the lodes was concentrated by downward enrichment as soft ''sooty" aigentite, and subsequently most of this supeigene argentite was cod> verted to horn silver.

The chief producing mine is the Tonopah Divide, which yields oie averaging 25 ounces of silver and S2.S0 in gold to the ton.

Intboduction.

The Divide district lies just south of Tonopah, Nov., and is traversed by the main road that joins Tonopah and €k>ldfield. It can be said to center at the Tonopah Divide mine, tlie site of the first and chief discovery of silver ore, on the east slope of Gold Mountain a few hundred yards from the highest point on the Tonopah-Goldfield road. From the fact that this locality is near the divide the name Divide was given to the district in 1917. The area of the district is 60 square miles.

The district has a general altitude of 6,000 feet. Its prevailing aspect is that of a broad expanse of lowland, above which rise abruptly isolated hills or mountains, of which Gold Mountain is the best known. Southeast of the Tonopah Divide mine there is a fairly large mountainous area, the highest summit of which, said to be called Donovan Peak, attains an altitude of 7,000 feet.

The field work on which this report is based occupied two weeks during July and August, 1919. At that time the district was at its highest activity, although the crest of the boom had just been passed. To Mr. Jay A. Carpenter, who was able from his knowledge of the district to facilitate this work, I am especially indebted for many courtesies during this investigation.

Discovery And Development.

The recent activity in the Divide district is the result of the acci- dental discovery of a rich silver lode on Gold Moimtain in 1917. But the history of the district goes back farther than this, for gold was foimd on Gold Mountain in 1901, about the time of the beginning of Tonopah. Even some of the silver-bearing lodes in the Fraction rhyolite breccia attracted attention in those early days. At what is now the Crown Divide considerable work was done in 1905 and 1906

Divide Silver District, Nbv. 149

by Gavin Johnston, who shipped some ore, supposed to ran 100 ounces in silver and 1 ounce in gold to the ton. The low ridge ex- tending from the Belcher shaft to the Belcher Extension shaft was also the scene of prospecting in early times; some work was done here by the Lucky Baldwin Mining Co. in 1903, and small streaks carrying $110 to the ton, mainly in silver, were found. A shaft 300 feet was sunk, but further prospecting was abandoned during the Ooldfield rush.

The gold veins on Gold Mountain continued to be worked in a small way by lessees during the intervening years, and the district became kaown as the Gold Moimtain district. The most work was done on the Grold Mountain vein. In 1916 H. C. Brougher, one of the chief owners, decided to prospect this vein by means of a shaft sunk lower on the flank of the mountain. Sinking was started in April, 1917, and at a depth of 165 feet a crosscut was driven southwestward to cut the gold vein. At 145 feet from the shaft the crosscut reached a wide silver-bearing lode averaging $53.80 to the ton. Further ex- ploration work was naturally concentrated upon this find, and by the spring of 1919 it began to appear that a largo and valuable silver iode had been discovered. A great boom set in, and an area of 50 square miles was staked. The discovery was named the Tonopah Divide mine. The value of the find, its nearness to Tonopah, a great silver-producing center, and the psychologic setting all combined to cause an intense boom: the time was soon after the signing of the armistice, the find was the most promising strike that had been made in Nevada in years, and the price of silver was soaring. Some 350 companies were organized, nearly all with Divide'' as part of their designations. A period of intense activity set in, and between 80 and 100 shafts, each with its own hoisting plant, were being sunk in the summer of 1919. Much money was spent in exploratory work, some wisely, much unwisely. The favorite method of prospecting was to sink a shaft to a considerable depth, commonly from 200 to 500 feet, and crosscut back to the lode, or to a supposed lode, or to a contact. Surface prospecting was little employed, although the country is admirably suited to this method, and bedrock is nearly everywhere exposed at the surface. The almost imiversal adoption of deep shafts and crosscuts from them as a method of prospecting was of course a reflex of the way in which the discovery had happened to be made. This remarkable reflex is one of the outstanding f eatiu*e8 of Divide as a mining camp. Generally a shaft was sunk first and surface prospecting and trenching were done afterward. Late in the summer of 1919, however, surface exploration began to become more common.

1 Vahmble aooounts of the history and development of the district are given by J. A. Carpenter (The Dhide district: Eng. and Min. Jour., voL 107, pp. 869-861, 1919) and by O. J. Young (Divide silver-gold district of Nevada: Eng. and ICin. Jour., vol. 109, pp. 6-M, 1930).

150 Contributions To Economic Geology, 1920, Part I.

Electric power was brought to the Tonopah Divide jiune in Sep- tember, 1918, and subsequently was extended to most of the pros- pects that began operations in 1919. There is no water in the dis- trict, nor has water level been reached in any of the shafts, and all water must be hauled from Tonopah.

As a result of the exploratory work undertaken up to the time of my visit one ore body had been partly blocked out, the possibility of another one was indicated, and indications of silver were found at a large number of places. Subsequent work has not greatly altered this state of affairs; indeed, there has been a drastic downward re- vision of the amount of ore indicated in the Tonopah Divide mine, from 330,000 tons of ore containing 9,000,000 ounces of silver, to 52,000 tons, containing 1,000,000 ounces, and the boom in the Divide district has very materially subsided.

General Geology. Fbagtiox Bhtoltte Breccia Of The Siebebt Formation.

General Features.

Rhyolite breccia predominates throughout the Divide district. Be- cause it incloses practically all the silver-bearing lodes that give the district its prominence it is the rock of chief economic interest. It underlies the low country that surrounds the isolated hills or moun- tains of the district, such as Gold Mountain and Hasbrouck Moun- tain. It forms characteristic smooth, gently rQunded surfaces of light-yellowish color and conmionly barren of vegetation.

The breccia on fresh fracture is an ash-gray rock carrying numer- ous broken crystals of quartz and glassy feldspar, sporadic flakes of biotite, and angular fragments of darkish andesite and pumiceous rhyolite. In general it is fine or moderately coarse in texture, but locally it contains fairly large angular fragments of various rocks. Unusually good outcrops of the breccia north of the Dividend shaft show fragments of coarse granite 6 inches in diameter and of andesite, resembling the Midway andesite, 12 inches long. The coarsest bed of breccia noted in the district is 800 feet north of the Northwest Divide shaft; it is 6 feet thick and contains angular blocks of andesite as much as 3 feet in diameter. Thick massive beds of breccia dipping westward are prominent features of the landscape near the Toggery Divide claims.

Beds of soft white tuff arc interstratified with the breccia at many places in the district. They are not only common in surface exposures but have been cut underground in some of the mines, as the Tonopah Divide and Gold Zone. They serve to indicate the strike and dip of the formation, which would otherwise generally not bo ascertainable as the breccia that prevails throughout the district forms thick homo-

r,8. OSOLOOICAL 8UKVKT

dtTLLfirxN 1U tLAtt trf

CXPLANATidN

La-bite

D ivide andesrbe (/ntruatVeJ

5 Miles

Gbologig Map Of The Divide District. Nev.

Oddierhyolite

Ul

Fraction rhyol ite breccia of Siebert formation (inc/uding someinitr- bedded white tuff)

Divide Silver District, Nbv. 151

geneous masses in which bedding is rarely recognizable. The intor- calat64 beds of tuff range in thickness from a few inches to an observed raaximmn of 200 feet. Some thin beds of gritty tuff occur with the soft fine-grained tufFs; under the microscope tuff of this kind is found to consist largely of fragments of quartz and glassy feldspar (sanidine) crystals and volcanic rocks in a cement made up of minute sherds of Tolcanic glass. Locally the prevailing coarse breccia of the district is interbedded both with this gritty tuff and with the soft chalklike tuff.

The fine-grained white tuffs intercalated with the coarser breccias correspond in composition to Spurr's Siebert tuff of the Tonopah dis- trict, which beyond doubt represents a somewhat thicker accumida- tion of volcanic ash deposited during the same general period of eruptive activity.

Although the rhyolite breccia and especially the associated bedded white tuffs are soft, not highly indurated rocks, nevertheless locally there are exceedingly hard, tough, resistant rocks that are scarcely Incognizable as part of the same series of beds. The induration of these rocks has resulted from silicification of various forms, chiefly through the growth of fine-grained quartz, or of chalcedony, or even of opal. The bulk of Hasbrouck Mountain consists of such silicified breccias and tuff. Locally, as near the Tonopah Hasbrouck mine, the breccia of this mountaia has been opalized in such a way as closely to resemble a massive rhyolite. In places the induration of the tuff is clearly connected with the wide zones of shattering, which evidently were pathways of the silicifying solutions, as is well shown near the Grimes Divide prospect.

Associated Igneous Bocks.

Some flows of rhyolite occur with the breccias. They contain so many fragments of various rocks which they have picked up during flowage that they are veritable flow breccias and are extraordinarily like the Fraction rhyolite breccia in appearance. A flow of this kind on the north flank of ths moimtain northwest of the Mizpah- Divide prospect was particularly examined. It is a light-gray rock containing crystals of feldspar, quartz, and biotite and fragments of various volcanic rocks. Sanidine (a clear glassy potassium feldspar) is seen under the microscope to occur in numerous large crystals, being in fact the predominant porphyritic constituent. Quartz, oligoclase, and biotite are the other porphyritic minerals. They are embedded in a porous matrix of spherulitic glass. Inclosures of various rock fragments are common, as already noted. If it were not for the sphermitic nature of the glass it would harcQy be possible to distinguish this flow rock from an ejection breccia.

152 Contributions To Economic Qbology, 1920, Pabt L

Dikes of rhyolite and andesite cut the Fraction rhyolite breccia. The rhyolite is of two kinds — a white rhyolite carrying phenocrysts of quartz and sanidine and a darker variety crowded with inclusions so that it resembles a breccia. The white rhyolite is identical in appearance and composition with the rhyolite that forms the main mass of Gold Mountain, and the dikes obviously were injected at the time when that mass was intruded. Dikes of this rhyolite cut the Fraction rhyolite breccia near the Tonopah Divide mine and in the workings of the Oold Zone mine, and doubtless others occur in the district. A rhyolite differing markedly from these, at least in appearance, forms a dike extending along the low ridge between the Bcdcher and Belcher Extension shafts. This rhyolite incloses innu- merable fragments of white rhyolite resembling the Oddie rhyolite, and these inclusions are held in an aphanitic matrix of a color consid- erably darker than their own. Such a rock, were its field relations not known, would be difficultly distinguishable from a breccia made up of rock and crystal particles blown from volcanic vents.

In addition to the large mass of Divide andesite intrusive into the Fraction rhyolite breccia, isolated dikes of andesite occur at various places in the district. They differ somewhat from the Divide andes- ite, and some of them may have been injected at a different time from that of the Divide andesite. The narrow dike of gray andesite carrying numerous porphyritic crystals of plagioclase and biotite that cuts the Fraction breccia west of the Brougher shaft is probably of the same age as the Divide andesite, but the dikes of andesite near the Mizpah Divide prospect appear to represent a different period of igneous injection. The andesite near the Mizpah Divide is highly por- phyritic, the phenocrysts, which consist of plagioclase, biotite, and hornblende, equaling the groimdmass in volume.

Correlation.

The Fraction rhyolite breccia extends continuously from the adjoin- ing Tonopah district southward into the Divide district, where it is areally the predominant rock. In the Tonopah district, where it is of subordinate interest, it was called by Spurr' the Fraction dacite breccia, but the recent study of the Divide district, where it is the the rock of chief economic interest, indicates that it is more accurately termed a rhyolite breccia. The prevailing feldspar in the breccia, as found under the microscope in numerous specimens from widely separated localities throughout the district, is sanidine (a glassy potassium feldspar), which occurs commonly in broken crystals. Plagioclase is comparatively rare and proves to be albite and oligo- clase. The abundance of broken quartz crystals in the breccia has

s Spurr, J. E., Geology of the Tonopah mining district, Nev.: U. S. Geol. Survey ProL Paper 42,

Divide Silveb Distbict, Nbv. 153

already oeen mentioned. In conformity with these petrographic features the rock is here renamed the Fraction rhyolite breccia.

The southern part of the Divide district was studied in a reconnais- sance way in 1905 by Ball, who mapped the rhyolite breccia occurring there as ''Siebert lake beds'' and stated that these beds comprise tuffaceous sandstone, conglomerate, and clays.' He correlated them ''with the Siebert lake beds of Miocene age at Tonopah described by Spuir."* As a matter of fact Spurr did not describe explicitly a series called the ''Siebert lake beds," but he did describe a formation of white tuff at Tonopah which he named the "Siebert tuff (lake beds)." Ball tacitly assumed that what in the present report is called the Fraction rhyolite breccia and the tuff are members of a larger strati- graphic unit, which he named the Siebert lake beds. That in this assumption he was undoubtedly correct is believed to be proved by the occurrence of white tuffs at various horizons in the Fraction rhyolite breccia identical with those on Siebert Moimtain. This larger unit was called by Bansome the Siebert formation in his report on the Goldfield district, where it consists of bedded tuffs, tuffaceous sands, pumiceous ash, conglomerates, and some thin beds of diato- mite. It is likely that the Siebert formation, according to Ransome, 'Vas laid down with at least a part of the Esmeralda formation in a common basin."* The age of the Esmeralda formation has recently been determined by the careful work of Merriam and shown to be approximately upper Miocene. From the foregoing discussion the conclusion is reached that the Siebert formation is very probably of upper Miocene age.

Stbxtotube And Thiokness.

The general dip of the Fraction rhyolite breccia is at a low westward aogle, 20 being the average. Locally, however, the beds have been considerably disturbed, as around the intrusive necks of rhyolite, such as Gold Mountain. Here the rocks have been tilted up to angles as high as 70 and in places the dip is even reversed. These features are exactly like those prevailing aroimd the volcanic necks at Tono- pah, notably aroimd Butler Moimtain, which have been so well described by Spurr.'

Ball, S. H., A geologic reconnaiaaance in southwestern Nevada and eastern CaUfocnia: U. 8. Qeol. Sorrey Boll. 306, pU 1, 1907.

Idem, p. 33.

Raoaome, F. L., Geology and ore depositii of the Ooldfleld distrlot, Nev.: U. S. Qeol. Survey Prof. Paper 6A, pp. eCMSigoO.

Idem, p. 98.

' Meirlam, J. C, Tertiary vertebrate Cauna from the Cedar Mountain region of weatem Nevada: Gali- fomia Univ. Dept. Geology BuU., vol. 9, pp. 171-172, 1910.

" , J. E.. Geology of the Tonopah mining distrirt, Nov.: U. S. Oeol. Survey Prof. Paper 42, p. 47, 19Q&.

1278*— 21 11

154 Contributions To Economic Geology, 192D, Paet I.

The breccia is broken by numerous faults, showing the southward extension of the conditions prevailing at Tonopah. As Spurr* says in discussing the faulting at Tonopah, ' ' the phenomena within this small, carefully studied area are typical of the unstudied similar vol- canic region beyond the limits of the map.'' Adequate delineation of the faults in the Divide district would accordingly require mapping on the scale employed at Tonopah, namely, a scale of 4 inches to the mile. The complex nature of the faulting that will be found by such detailed mapping of the Divide district is apparent on inspection of Plate VII of Spurr's Tonopah report.

The rocks that underlie the Fraction rhyolite breccia are nowhere exposed in the Divide district, but in the Tonopah district the breccia is known to rest on the later andesite (now called the Midway andesite) and the Heller dacite.® Because the base of the breccia is nowhere shown in the Divide district and because of the complex faulting, the thickness of the Fraction rhyolite breccia can not bo estimated. At the Tonopah Divide shaft the breccia is at least 600 feet thick, but the total thickness will probably be foimd to be many times that figure.

Oddxe Bsyoltfb.

RhyoUte in intrusive masses occurs throughout the district, forming the bulk of many of the hills and moimtains that stand above the lowland. Gold Moimtain is the chief of these. The rhyolite has many of the earmarks of lavas erupted upon the earth's surface, such as conspicuous streakiness, banding, and flowage lamination, but the contacts show that most of the rhyolite, if not all, is intrusive into the breccias and tuffs of the Siebert formation. The extreme illus- tration of an intrusive rhyoUte that resembles an extrusive rock is afforded by a remarkable outcrop in the hill northwest of the Royal Divide prospect. The rhyolite of this extensive outcrop, because of its pronounced flowage lamination, closely resembles a series of thin- bedded, steeply dipping, folded sedimentary strata resting uncon- formably on an imderlying more steeply tilted series ; but the rhyo- lite breaks through the imderlying rocks, which are bedded tuffs dipping 60 N., and the contact is marked by a selvage of glass several feet thick. Such glassy contacts are well exposed on Gold Mountain, also, and at other places in the district. They are likewise notable features of the volcanic necks at Tonopah, especially of Butler Mountain. Flow layering also is conspicuously developed in the intrusive rhyolite of Siebert Moimtain. These features of the rhyolites of Divide and Tonopah indicate that they were intruded at shallow depths, with consequent rapid cooling, and the speed of

SpuzT, J. £., Geology of the Tonopah mining district, Nev.: U. 8. Oeol. Survey Prof. Paper 43, ppi 82-83,1905. 10 Idem, p. 40.

Divide Silver District, Nev. 155

cooling was doubtless hastened by the water content of the porous breccias and tuffs in which they were intruded.

The rhyolite is a white or pale cream-colored rock studded with abundant small phenocrysts of quartz and glassy feldspar and con- taining a few tablets of biotite. Under the microscope the feldspar phenocrysts in the rhyolite of Gold Moimtain prove all to be sanidine, and in this respect, as also in appearance, the rhyolite resembles exactly the Oddie rhyolite of Mount Oddie at Tonopah. The rhyoUte from the summit of the 6,600-foot peak east of the Knox Divide prospect carries, in addition to the quartz, sanidine, and biotite pheno- cTysts, some plagioclase, thus approaching in composition the rhyoUte (or quartz latite) of Brougher Mountain and Butler Mountain of Tonopah. In the arher report on the Tonopah district the rock of these two last-mentioned volcanic vents was termed the Brougher dacite by Spurr," although their essentially rhyohtic natiure was recognized. In his later report " Spurr refers to the Brougher dacite as dacitic rhyohte or rhyolite-dacite, buu it can more simply and with gain in precision be termed a quartz latite. SpiUT has pointed out ibat although the rhyoUte of Moimt Oddie differs perceptibly from tliat of Brougher Mountain, transition phases that bridge the gap between the end members occur in neighboring vents. Ih the Divide district the rhyolite of Gold Mountain is clearly the equivalent of the Oddie rhyohte, and the other masses in the district shown on the geologic map (PL XIV) are nearer to the Oddie rhyoUte in compo- sition than they are to the quartz latite of Brougher Moimtain. The rock of the rhyolitic vents in the Divide district has therefore been shown on the map under the name Oddie rhyoUte.

DrVIDB AITOBSITE.

A large mass of andesite that lies southeast of the Tonopah Divide mine forms the main bulk of the largest and highest mountainous area in the district. The andesite is excellently shown at the highest point on the Tonopah-Goldfield road — the divide from which the district received its name — and accordingly it is here named the Divide andesite.

The andesite is a gray porphyritic rock carrying numerous crystals of glassy striated feldspar and biotite. Its weathered exposures tint the landscape a characteristic lilac-gray. East of the Goldfield road, south of the divide, it weathers exactly like a horizontally bedded formation, but at the divide it weathers like a bedded formation standing on edge. Despite this appearance it is found to be intrusive into the Fraction rhyoUte breccia. A long, sinuous offshoot extends

" SpuiT, J. E., U. 8. Geol. Survey Prof. Paper 42, pp. 67-60, 1905.

, f . B., Geology and ore deposition at Tonopah, Nev.: Econ. Geology,*Tol. 10, p. 746, 1915.

156 Contributions To £Cx)Nomic Geology 1920, Pari I.

from the main mass more than 200 feet into the breccia near the Argonne Divide prospect. The contact is well exposed south of the Gold Zone prospect and shows the chilling of the andesite against the white tuffs which it intrudes. Locally the intruded rocks are dis- turbed near the contact and tilted from their normal dip of 20 W. up to 70. In places also the andesite adjoining the contact is intensely autobrecciated, as near the Operator Divide prospect, where the newly congealed andesite along the contact was evidently shatr tered and brecciated by flowage of the unconsolidated portion.

Under the microscope the feldspar phenocrysts of the Divide andes- ite prove to be a sodic labradorite (AbaoAnco). In a specimen from the prominent knob south of the Gold Zone shaft the plagioclase is largely altered to calcite. The biotite, too, is generally altered. The groundmass is cryptocrystalline and in the autobrecciated f acies is hyalopilitic. The accessory minerals are magnetite; apatite, and zircon. The light color of the andesite suggests that the rock may havelatitic affinities, but the specimens collected, although apparently fresh, proved on examination under the microscope to be too much altered to put this supposition to chemical test.

The Divide andesite appears to have no equivalent in the Tonopah district. As the Oddie rhyolite and the Divide andesite have not been found in contact, it is not known whether the andesite is older or younger than the rhyolite. It is provisionally held, however, that the andesite is the younger of the two.

Latite Lava&

The youngest rocks of the district are a series of latite lavas that cap the high peaks in the area southeast of the Tonopah Divide mine. The base of the lavas consists of a black glass. The bottom of the glass flow is well shown in a prospect tunnel at an altitude of 6,400 feet south of the Allied Divide prospect. The glass, here 20 feet thick, with horizontal layering, has flowed over the Divide andesite and is crowded with fragments from that rock. Manifestly it flowed over a stony soil derived from the disintegration of the underlying Divide andesite, and as it moved along it incorporated fragments of the andesite in great numbers and permeated the interstices of the stony rubble, so that the contact between the flow and the Divide andesite is somewhat suggestive of intrusion.

The black glass is overlain by an exceedingly streaky, highly vesicular pitchstone. Above this are lithoidal lavas, some of which have a characteristic irregularly corrugated, thinly platy structure. These lavas are very sparsely porphyritic, and their general appear- ance suggests that they belong to the more siliceous varieties of andesite. Lava from the highest summit is markedly poijphyritie

Divide Silver District, Nev. 157

and resembles the Divide andesite rather closely, except that it is more or less pitted with gas cavities.

The latite flows attain a maximum thickness of 300 feet. They weather to a much darker color than the characteristic lilac-gray of the Divide andesite, which is the chief rock on which they rest. Where the black glass predominates because the superposed lavas have been stripped off by erosion the capping, as viewed from a distance, resembles the basalt cappings so common in Nevada.

The latitic character of these lavas, the youngest rocks in the district, is suggested by their flow streakiness, a feature rarely seen in true andesites. To verify this conjecture the following partial analysis was obtained. It fully confirms the inference as to the latitic character of the rock, but it shows an unexpectedly high percentage of silica.

Partial analysis of latite from, the Divide district , Nev.

(R. C. Wells, analyst.]

SiO, 69.97

CaO 1.77

KaO 5.02

Na,0 4.20

The rock selected for analysis is a faintly banded dark-gray lava carryiog small sparse phenocrysts of plagioclase, biotite, and horn- blende. Under the microscope the plagioclase crystals are found to be a sodic andesine (AbasAuss) near oligoclase in composition. The biotite and hornblende show no unusual features. The groundmass is a glass crowded with obscure microlites of feldspar and dusted with minute grains aggregated as globulites and margarites, most of them suggestive of incipient forms of biotite. Magnetite and apatite are the accessory minerals. It is noteworthy that in spite of the high silica content of the rock as disclosed by the chemical analysis no quartz has crystallized out, either as porphyritic crystals or in the groundmass.

The series of latite lavas of the Divide district is not represented in the Tonopah district. They have been traced, however, to a point within less than a mile south of the Belmont mine of Tonopah, where the occurrence of a great mass of coarse agglomerate and cinders associated with the lavas indicates one of the volcanic centers from which the latites were erupted.

East of the Divide district the latites overlie rhyolite vitrophyres canying numerous phenocrysts of quartz and sanidine and sporadic tablets of biotite. The rhyolites have a marked flow structure and contain steam cavities which are filled with opal or chalcedony or both. The spherulitic obsidian occurring north of the Ben Hur prospect probably belongs with these rhyolites. These rhyolite

158 CONTRIBUTIONS TO ECONOMIC GEOLOGYj 1920, PART I.

lavas extend northward into the Tonopah district in the area south of the Beknont mine, where they have been mapped by Spurr as Brougher dacite. On account of the prevalence of gas cavities in these rockS; their marked flow layering and the occurrence of glassy and spheruliti6 layers at various horizons, they are regarded as the extrusive equivalents of the magmas that solidified in the volcanic necks forming Brougher Mountain and Butler Mountain.

SILVER-BEARING LODES. OCCX7BBBNCB AITO OHABAOTEBr.

The ore deposits are silver-bearing fracture zones in the Fraction rhyolite breccia. The filling between the walls of these zones — the ore, in short — is not greatly sheared but consists of fractured rhyolite breccia, in general inconspicuously mineralized; and the ore bodies, as they are not tabular fillings of preexisting open spaces, are strictly not veins but lodes. The walls of the lodes as a rule are excellently defined, and at least some of them can be demonstrated to mark zones of faulting. Evidence of notable displacement is most clearly shown in the Gold Zone workings, where well-stratified tuffs inter- calated in the rhyolite breccia are cut off by the Tonopah Divide lode.

The Tonopah Divide lode strikes northwest and stands vertical. Other mineralized fracture zones subsequently found have this same general trend, but still others strike at various azimuths — for example, the Divide Extension, which strikes N. 10° E., so that most azimuths are now Represented. No systematic arrangement of the fracturing is yet discernible, and that none exists seems probable in view of the complexly faulted condition of the Fraction rhyolite breccia demon- strated by the detailed mapping of the Tonopah area.

The outcrops of the lodes are rather lightly iron stained by dis- seminated limonite, and this staining is the only evidence likely to suggest that the fracture zones are mineralized.

In depth pyrite appears in the lodes and in the adjacent wall rock. In places the lode matter is netted with a few thin veinlets of fine- grained quartz resembling chalcedony in appearance, but chalcedony does not occur. These veinlets, which are short and discontinuous and do not exceed a small fraction of an inch in thickness, are more abundant in some lodes than in others, though they can not be said to be really abundant in any, but they in no way influence the tenor of the ore. They are not common, for example, in the ore of the Tonopah Divide or the Divide Extension lodes. The almost com- plete absence of vein quartz and of silicification, contrasting with the siliceousness of the ores at Tonopah, caused the Divide ores in the early history of the camp to be viewed with skepticism by engineers familiar with the ore deposits of Tonopah.

Divide Silveb Distbict, Nbv. 159

A characteristic featiixe of the Tonopah Divide lode is that it is traversed by white gouges. The gouged range from a fibn up to masses several inches thick and consist of the so-called talc, a soft white fine-grained unctuous material, in many places visibly con* taining brown horn silver. Assays running up to hundreds of ounces of silver to the ton are commonly obtained from such gouges. Under the microscope the material was found to be of great purity, to be brilliantly birefringent, and to resemble sericite in every respect. The refractive indices were then determined and found to be 7 1.575 and a s 1 .55. They differ somewhat from those recorded for sericite (7=1.597 and, a 1.560), but chemical analysis establishes conclu- sively that the mineral has the composition of sericite, to which it is therefore referred. Like minerals of the leverrierite group (micaceous hydrous silicates of aluminum), it slacks in water and becomes plastic and sticky.**

The chemical composition of the sericite from one of the so-called talc gouges in Tonopah Divide lode is as follows:

Arkofyns of seridU from the Divide district Nev.

[J. Q. Falrcbild, analyst.]

SiOj 48.16

AljO, 34.00

FeO (reported from total iron) 2. 07

KaO 9.62

H,0+(total vater) 5.84

TiOa (approximately) 20

The silver in the lodes of the Divide district is chiefly in the form of cerargyrite. Except in the sericite gouges, where in places the cerargyrite occurs in particles large enough to be recognizable, the cerargyrite is indistinguishably disseminated throughout the ore. In consequence the appearance of the ore gives no clue tO' its tenor, and the determination of what is ore must depend wholly on assays. Although cerargyrite is the main silver-bearing mineral in the ore, some soft black pulverulent argentite, the so-called sooty argentite, has been foimd. The most notable find of this kind was in some ore cut on the 100-foot level of the Divide Extension mine, where argen- tite occurs together with pyrite, which it has partly replaced.

Some rare molybdenum minerals occur in the Tonopah Divide lode at the point where it was cut by the discovery crosscut, but so far they have not been found elsewhere in the lode or elsewhere in

B4)CBr9, A. F., Striate, a low-tempentun hydrothennal mineral: Eoon. Geology, voL 11. p. 120, 1910. Tfaia deteimiDation of the refract. ve indices of oerlclte by Rogers appears to be one of the few on record; Msondly the Indioes of other seridtea should be measured.

Larsen, E. S., and Wherry, £. T., Leverrierite from Colorado: Washington Acad. Sd. Jour., vol. 7, pp. B-U7, 1917.

160 Contributions To Economic Geology, 1920, Part I.

the district. At the discovery point the lode contains a considerable amount of the brilliant yellow mineral molybdite (hydrous ferric molybdate), crystallized in aggregates of minute needles. The molyb- dite diminishes in depth, and at the corresponding position on the next lower level powellite (calcium molybdate) occurs abundantly.

The lean primary silver-bearing material found in depth is a light- gray rock that is not conspicuously mineralized. It contains numer- ous crystal fragments of quartz and sanidine and fragments of rhyo- lite and andesite, is sparsely impregnated with pyrite, and is traversed by a few thin veinlets of fine-grained quartz nearly resembling chal- cedony. Under the microscope much of the sanidine, is seen to be more or less thoroughly replaced by quartz ; where it has been com- pletely replaced the resultant aggregate resembles a quartzite frag*- ment, but the outlines of some of the sanidine crystals axe perfectly retained. Some of the feldspar is chloritized and some is sericitized. The wall rocks contain disseminated pyrite, and under the micro- scope they show that the sanidine has been partly replaced by cal- cite, instead of by quaxtz, as in the lodes.

The outcrops of the lodes are either barren of silver or are of low grade. The pyrite in the upper part of the lodes has been oxidized and is represented by limonite, but at depths of 100 feet or so it begins to appear. The barrenness of the tops of the lodes in silver has led to the general policy in exploring new lodes to sink shafts to considerable depths — as much as 500 feet — before crosscutting from the shafts to the lode. Experience has now amply demonstrated that this is not good practice, and that crosscutting to the lode should be commenced at the 100-foot level, or at most the 200-foot level. To ignore the plain lesson of the district may cause unnecessary and wasteful expenditure in useless prospecting.

The only considerable body of ore that had been developed in the district at the time of my examination is that in the Tonopah Divide mine. It forms a shoot pitching steeply southward in a vertical lode; it is 450 feet long, 500 feet high, and 21 i feet wide. The silver is irregularly distributed within this shoot, which contains, according to the estimate of Mr. E. A. Julian, 52,000 tons of first-class ore averaging 20 ounces of silver and 0.08 ounce of gold to the ton. Because a knowledge of this shoot is of paramount importance to an understanding of the ore deposits of the district it is described in some detail on pages 165-167. In August, 1919, the downward limit of the shoot had not been determined, nor had the water level been reached at the greatest depth then attained (581 feet). It then appeared probable that water level would be reached at a depth between 800 and 1,000 feet.

DIVIDE SILVER DIS1?BlCT, OTSV. 161

Some rich ore has been found at the Divide Extension mine, as described on pages 167-168, and high assays have been obtained at scores of places in the district, sufficient to justify well-considered prospecting. It is undeniable, however, that a number of lodes having all the obvious features of the famous Tonopah Divide lode have failed to disclose ore in depth, even after extensive prospecting. Nevertheless the possibility that other ore bodies comparable in value to the lode may yet be discovered is not exhausted.

Obioix Of The Obb.

Although by far the most of the silveibearing lodes under develop- ment are in the Fraction rhyolite breccia, some are in the Divide andesite, and the gold lodes are in the Oddie rhyolite. Therefore possibly more than one period of minerahzation has occurred, but the most recent must have been later than the intrusion of both the Oddie rhyoUte and the Divide andesite. The results of the minerali- zation were to produce in the fracture zones in the Fraction rhyolite breccia a low-grade silver-bearing material — the "protore" — car- rying disseminated pyrite. What the primary (hypogene) silver- bearing mineral in the protore is has not yet been determined.

The silver in the outcrops of the lodes was oxidized, taken into solution, and carried downward, where it was precipitated as soft black argentite by reaction with the pyrite of the protore. Thus the outcrops were leached of their silver, and a zone of rich supergene silver sulphide was formed lower down. Subsequently, evidently in response to a climatic change, the composition of the descending oxidizing surface waters changed; they became charged with chlo- rides. As a result the supergene argentite was oxidized and converted to chloride (cerargyrite), and the ore thus formed is the ore now being mined or developed by exploration.

The barrenness of the outcrops in silver, although the chief metallif- erous mineral in the lodes in depth is silver chloride, is one of the outstanding features of the geology of the Divide district. At first thought it would seem that on account of the insolubility of silver chloride the otltcrops of the lodes should contain as much silver as the ore beneath them, but the reason for this apparent anomaly, as previously explained, is that a period of downward enrichment pre- ceded the formation of the cerargyritic ore. During this earUer period the surface waters were evidently not charged with chlorides and the silver was consequently dissolved and largely or completely removed from the outcrops; subsequently, owing to the increasing aridity of the region in late Quaternary time, the surface waters became charged with chlorides and, sinking through the lodes, altered the earlier-formed supergene argentite to cerargyrite.

162 Contributions To Economic Geology, 1920, Pabt L

Gold Veins.

A few narrow gold veins occur in the Oddie rhyolite of Oold Moun- tain. The best known of these is the Gold Mountain vein, on the property of the Tonopah Divide Mining Co., as it was this vein that led to the discovery of the silver lode. The vein filling consists of angular fragments of rhyolite cemented by an exceedingly dense bluish quartz. It contains considerable disseminated pyrite, which is the only visible metalliferous mineral. Under the microscope the ore shows in addition to the quartz and pyrite a little adularia and considerable of a thinly tabular hexagonal mineral closely resembling apatite (but tabular instead of prismatie), which has not been identified.

The ore that was extracted is reported to have carried from S18 to $40 in gold to the ton, but the ore occurred in quantities so small that the lessees who worJed the vein intermittently after 1902 made barely more than wages.

Another vein of this same character — that is, consisting of angular fragments of rhyolite in a matrix of bluish chalcedony-like quartz — occurs near the northwest end of Gold Mountain. Under the micro- scope the ore also shows adularia, locally abimdant, and hexagonal tablets of the apatite-like mineral that has not been identified.

The Kernick vein, which traverses sihcified tuflfs on the west flank of Hasbrouck Mountain, resembles closely the gold veins. The vein filling consists of angular fragments of silicified tuff inclosed in a cement of dense bluish, extremely fine grained quartz. Although in appearance so similar to the fiUing of the gold veins, it is never- theless a silver ore, recent shipments of sorted ore having averaged 20 ounces of silver to the ton. The resemblance of this silvex- bearing vein to the gold veins suggests that this vein, the silver- bearing lodes upon which the activity of the district is centered, and the gold veins are all of the same age. On the other hand, the complete absence of sericitization in connection with the gold veins and its prevalence in the main silver-bearing lodes would indicate that the gold veins were deposited during one epoch of mineraUza- tion and the silver-bearing lodes during another, and this interpreta- tion has at present the balance of evidence in its favor.

COMPARISON OF THE GEOLOGY OF THE DIVIDE DIS- TRICT WITH THAT OF TONOPAH.

The dominant rock at Divide is the Fraction rhyolite breccia. It is an extension southward of the same breccia as it occurs at Tonopah, where, however, the rock does not inclose any ore bodies. The chief productive veins at Tonopah are in the Mizpah trachyte, a formation that does not occur in the Divide district. Another

Divide Silver District, Nbv. 163

and younger but far less productive group of veins is genetically related to the later intrusive West End rhyolite, also not known to occur at Divide. Younger than both the Mizpah trachyte and the West End rhyolite and later than the veins associated with them is the Midway andesite, which flowed over and covered the veins. This rock also is not represented in the Divide district.

Subsequent . to the formation of all these older rocks and the mineral veins associated with them the Fraction rhyolite breccia was ejected and the interbedded white tuff was deposited. These stratified rocks were later intruded by rhyolitic magmas, part of which consoUdated as a highly autobrecciated glass, termed the Tonopah rhyolite by Spurr, and as massive rock, such as that form- ing Mount Oddie and known as the Oddie rhyolite." According to Spurr the Tonopah rhyolite-Oddie rhyolite intrusions were followed by the third period of vein formation, which produces usually small but occasionally very large quartz veins, with small amounts of the metals, and, so far as known, commercially valueless."

It is obvious from the foregoing sketch that if the mineralization at Divide corresponds to any period of vein formation at Tonopah it can only correspond to the last period — that subsequent to the intrusion of the Tonopah and Oddie rhyolites. However, it probably represents a stUl younger period of mineralization and is genetically related to the intrusion of the Divide andesite, a rock not known to occur at Tonopah. Spurr " was inclined to correlate the gold veins on Grold Moimtain with those of the then newly discovered gold veins at Groldfield, but since that suggestion was made Ransome has shown that the Groldfield veins are of a very specialized type, distin- guished by their abimdance of alunite and probably related genetically to an intrusion of dacite. The most reasonable conclusion, in view of what scant evidence is available, is that the Divide mineralization is not to be correlated with any of the recognized periods of vein for- mation at Tonopah or at Gk)ldfield, but that, as already stated, it is probably linked with the intrusion of the Divide andesite.

The results of the primary mineralization at Divide were to produce in the Fraction rhyolite breccia wide bodies of low-grade silver-bearing material. By the concentrating action of downward-moving surface water this primary material was enriched to form the high-grade silver ore now being developed by mining. The chief silver mineral is cerargyrite, though some sooty'* argentite has been foimd.

At Tonopah cerargyrite occurred in considerable abundance in those veins that outcropped at the surface. According to Burgess,

Spurr, J. E., Geology and deposition at Tonopah, Nov.: Boon. Geology, toI. 10, p. 760, 1916. V Spurr, J. £., U. 8. Oeol. Survey Prof. Paper 42, p. 99, 1906. ° Banaame, P. L., U. 8. OeoL Survey Prof. Paper 66, 1909.

Burgeas, J. A , The halogen salts of silver and associated minerals at Tonopah, Nev.: Eoon. Geology, VOL 6. pp. 13-31, 1911.

164 CdimtlBtmONS to EGOKOMIC OEOLOOTy 1990y PABT I.

who made a (Careful study of its occurrence, the silver chloride and related halides persist downward as far as the oxidized ore extends — that is, to the TOQ-foot level. Below the zone of ceraigyrite occurs an ill-defined zone of silver bromide, and below this sUver iodide. This succession of zones is the reverse order of at at first thought would be expected to occur as the result of deposition from descending waters, as the iodide is by far the most insoluble of the silver halides, but this order is determined by the reversible reaction between iodide and ferrous and ferric iron,* as is practically proved at Tonopah, where one of the prominent minerals associated with the silver iodide (iodyrite) is the hydrous basic sulphate of ferric iron, jarosite. In few places at Tonopah, however, was the larger part of the silver present as cerargyrite, but most of it was in the unaltered sulphides. In this respect the mode of occurrence differs from that at Divide, where most of the silver occurs as ceraigyrite. Burgess found that the silver was nowhere carried far from the original sulphide ore, and the silver halides were deposited almost immediately after the oxidar tion of the sulphide from which the silver was derived.

As part of the silver in the imoxidized sulphides represents an enrichment by downward-moving waters of surface origin, its conver- sion into ceraigyrite was therefore subsequent to the supeigene enrichment. Evidently the alteration to ceraigyrite was not as com- plete at Tonopah as at Divide, but the fact that during this conver- sion of the silver-bearing sulphides to cerargyrite no noteworthy redis- tribution of the silver in the ore bodies was effected is important as corroborative evidence in confirming the deductions drawn as to the distribution and genesis of the silver in the lodes at Divide, namely, that it was concentrated in the form of supergene aigentite, and this argentite was subsequently changed to cerargyrite.

Mines And Prospects.

In August, 1919, ore was being shipped steadily from the Tonopah Divide mine for treatment at Tonopah, and small shipments were being made occasionally from two other properties. These three mines, which are described in the following paragraphs, illustrate the salient features of the geology of the ore deposits of the district. In addition to these there were several scores of prospects under active development, at some of which much exploratory work had been done. Shafts from 200 to 500 feet deep are common. To describe each property separately, however, woiild not add much to the knowledge of the district gained from those in which ore had been developed, so the description of these prospects is omitted.

w Knopf, Adolph, OocuRenoe of the attver taaUdoB In tho oildUed noo of on deporits: Boon. Qeoloij, ▼OL 19 pp. 623-634. 1918.

BoriMi, J. A., op. Glt. p. 10.

DIVIDE SILViSR DISTRICT, NBV. 165

Tonopah Divibb Hine.

The Tonopah Divide mine is on the east flank of Gold Mountain, a few hundred yards west of the divide on the main road between Tonopah and Goldfield. In the rhyolite, well up' on the side of the mountain, is a narrow, erratic gold vein, which was worked by lessees more or less continuously after its discovery in 1901. The gold occurred in this vein in short, irregular shoots of ore, carrying from S18 to $40 a ton, and the lessees mined this ore in a small way, making little more than wages. In 1916 H. C. Brougher, one of the principal owners, decided to sink a shaft lower on the flank of the mountain, crosscut southwestward from it, and prospect the gold vein in depth. Sinking was started in April, 1917, and at a depth of 165 feet a cross- cut was driven southwestward to cut the gold vein. In November the crosscut, then out 145 feet from the shaft, to the great surprise of the owners intersected a wide silver-bearing lode. This find natu- raUy altered the company's plans, and its main energy was thence- forth devoted to exploring and developing the new discovery. The company increased its capital stock to 1,250,000 shares (par value SI) and acquired additional ground on the northwest. The property now consists of nine patented claims of 112 acres and four claims of 38 acres in process of being patented, a total of 150 acres.

The mine in July, 1919, was developed by a vertical two-compart- ment shaft 581 feet deep, from which crosscuts have been driven to the lode at depths of 165, 265, 365, 470, and 580 feet. Drifts have been run along the lode northwest and southeast from these main crosscuts. Electricpower equipment was installed in September, 1918, and in October the mine began to ship ore. Up to July 1, 1919, 7,304 tons of ore, carrying $24.88 a ton, had been shipped, most of it to the mill of the Tonopah MacNamara Mining Co. in Tonopah. This ore was obtained chiefly as the result of development work. During the first six months of 1919 the ore treated amounted to 6,464 tons, averaging $28.24 a ton, from which a total net profit of $57,757, or $8.96 a ton, was realized.

The silver lode of the Tonopah Divide mine crops out promi- nently 150 feet southwest of the shaft, but on account of the feeble iron staining and the absence of silicification, sericitization, or other pronounced evidence of the action of mineralizing solutions, the outcrop wotdd not be suspected as the top of a large and valuable ore body. In fact, its significance was unappreciated by the present owners until after ore had been struck underground, when it imme- diately became of very lively interest. It was then seen that at one place in the outcrop a prospector had simk a shaft 10 feet deep; this work, according to report, had been done in 1902 by Dick Rochelle,

B TonoiMb Divide Mining Co., report of July 1, 1910.

166 Contributions To Economic Geology, 1920, Part I.

one of the original locators in the district. Careful sampling of the outcrop showed it to be barren, except for a narrow streak against the wall of the old prospect shaft, which yielded, according to Super- intendent William Watters, 100 ounces of silver to the ton.

The lode is inclosed in the Fraction rhyolite breccia and is a few hundred feet northeast of the intrusive mass of Oddie rhyolite of Gold Moimtain. The contact between the Oddie rhyolite and the Fraction rhyolite breccia is exposed in the crosscut on the 265-foot level at a point 250 feet southwest of the footwall of the lode. It is marked by a fault gouge from 6 inches to 1 foot thick dipping 75° X., the contact, originally that of an intrusion, having been a locus of movement subsequent to the intrusion of the rhyolite. A rhyolite dike in the Fraction breccia is well shown in an open cut at the end of the dump at the main shaft, and a rhyolite dike has been cut on the 365 and 470 foot levels.

The lode trends northwest and stands practically vertical. The walls are generally well defined and mark a zone of faulting, as is well shown in the Gold Zone prospect, where conspicuously bedded tuffs abut against and are cut off by the lode. In the upper levels of the mine the material between the walk of the lode — the ore — is iron-stained rhyolite breccia. In depth the lode filling becomes lighter in color, being nearly ash gray, like that of the normal rhyo- lite breccia of the district, and carries dissemiuated pyrite, and the few thin veinlets of fine-grained quartz that traverse it become apparent. In places, especially on the higher levels, the lode is irregularly traversed by seams of extremely fine grained sericite, the so-called talc, the largest several inches in thickness. These seams commonly contain visible amoimts of horn silver and yield assays running up to several thousand dollars a ton. In the leaner ore there is less oxidation, fewer sericite streaks, and more pyrite.

The ore at the place where the lode was first cut, on the 165-foot level, differs notably in one respect from any other since f oimd in the mine. It contains a considerable quantity of the brilliant yellow mineral molybdite. The molybdite disappears in depth, and at the corresponding position in the next lower level powellite (calcium molybdate) occurs abundantly. Molybdenum minerals have not been noted elsewhere in the mine. At the discovery point the lode is 20 feet wide and averages $53.80 a ton across this width. Although pyrite is more abundant in depth, owing to decreasing oxidation, some occurs even in the ore at the discovery point. In places through- out the mine the ore has a blackish cast, suggestive of the occurrence of sooty argentite through it, but this mineral has not been definitely identified as occurring in the mine, although known to occur in the district.

Divide Silver District, Nev. 167

The exploration so far accomplished shows that the ore occurs in a shoot approximately 400 feet long that pitches southward at a steep angle. The Assuring continues in full strength both northwest and southeast of the known ore, and the lode has been explored on the 500-foot level of the Gold Zone property, adjoining the Tonopah Divide on the southeast, where it averages $6 a ton across the width of 40 feet on the Tonopah Divide side of the end line. Between this point and the face of the drift on the 580-foot level, 200 feet southeast of the main crosscut, there remained in August, 1919, a length of 800 feet on the course of the lode to be explored.

The lode averages 21 i feet in width, and the ore averages $27.60 a ton, according to the report of the Tonopah Divide Mining Co. In computing the value of the ore the gold was figured at 820 an ounce and the silver at $1 an ounce. The ratio of gold to silver as shown by the assay returns of all samples is 1 ounce of gold to 200 oimces of silver.

According to the report of A. I. D'Arcy, formerly consulting engi- neer to the company, under date of July 1, 1919, mine has not been sufficiently developed to measure the ore reserves, but as a matter of speculation the openings now existing in the mine if taken to represent the true average over a width of 21 feet, a length of 400 feet, and a depth of 500 feet would produce 330,000 tons of ore, and if the value as indicated by sampling is taken as $27.60 per ton the mine could be expected to produce $9,108,000 gross from the present workings.*' Further development failed to substantiate this estimate, however, and E. A. Julian, who succeeded Mr. D'Arcy as consulting engineer, estimates in the second annual report of the company a probable reserve of 62,000 tons of first-class ore averaging 20 oxmces of silver and 0.08 ounce of gold to the ton.

The main crosscut on the 265-foot level after cutting through the silver lode was continued southwestward, penetrating the rhyolite stock of Gold Mountain, and at 450 feet from the silver lode it cut a narrow gold vein, probably the downward extension of the gold vein fonnerly worked higher on the mountain. The vein strikes N. 40 W. and dips 80® W.; it was followed a short distance southeastward to a point where it is cut off by a fault. The vein is 6 inches thick and is reported to carry in places $40 a ton in gold. It has also been cut on the 370-foot level, but there it was found to contain no ore.

Divide Extension Mine.

The claims of the Divide Extension Mining Co. adjoin those of the Tonopah Divide Co. on the north. Early in the history of the dis- trict a shaft, known as the Kendall shaft, was sunk near the southwest comer of the property in order to prospect the northwest extension of the Tonopah Divide lode. At a depth of 150 feet a

168 Contributions To Economic Geology, 1920, Part I.

crosscut was driven southwest, but it reached the side line of the claim without cutting the extension of the Tonopah Divide lode. By great good fortune, however, it was found at this time, when the Tonopah Divide lode had thus been shown not to traverse the ground of the Divide Extension Mining Co., disproving the supposition under which the company had been organized and named, that a wide ore zone, unknown when the company had been formed, crops out several hundred feet north of the Kendall shaft. This mineralized zone or lode trends N. 10 E., making therefore an angle of 60 with the course of the Tonopah Divide lode.

The country rock is typical Fraction rhyolite breccia, and the out- crop of the newly discovered lode, consisting of somewhat altered and iron-stained rhyolite breccia, resembles in all respects the similarly unpromising-looking material of the Tonopah Divide lode. A shaft, called the Caldwell shaft, was sunk in the middle of the outcrop of this lode; in July, 1919, it had reached a depth of 100 feet and was being deepened. A crosscut, at a depth of 45 feet, was driven west and at 20 feet from the shaft reached 7 to 9 feet of ore lying against a well-defined wall, supposedly the footwall of the lode. A crosscut was also run eastward to the hanging wall, where 7 feet of ore carrying 40 to 60 oimces of silver to the ton was cut. The intervening rock between these two belts of ore on the footwall and hanging wall averages 2 ounces in silver to the ton. The total width of the lode, as shown by the crosscuts, is 50 feet, indicating a thickness of 40 feet; but as crosscuts had not been extended into either wall it is not certain that the full thickness of the mineralized zone has been determined.

On the 100-foot level a crosscut was run east, intersecting a body of ore that is reported to assay $200 a ton across 12 feet. This body of ore is probably the downward extension of the hanging-wall belt of ore foimd on the 45-foot level; if this supposition is proved true by further development work, then the ore body dips E. A winze was sunk here, 6 feet deep at the time of my visit, and ore rich in sooty argentite was found. The lode was developed for 30 feet along the strike, the width being 16 feet and the dip 60° E. Although argentite, which is associated with pyrite, was found in the winze, as already mentioned, the prevailing ore is highly oxidized, and the silver occurs as cerargyrite. The lode is traversed by many well-defined slips that strike and dip in various directions, evidently having been formed by irregular movements of adjustment within the mineralized zone.

A crosscut was being driven from the bottom of the Kendall shaft — the 426-foot level — to cut this lode on its projected strike and dij), N. 10° E. and 57° E.

Dividb Silvbb District, Nbv. 169

TONOPAH HASBBOnCK MINE.

The Tonopaii Hasbrouck mine is ia the western part of the district, on the west slope of Hasbrouck Mountain. It is one of the oldest properties in the district, having been located about 1902, and has been worked intermittently ever since. The ore shipped to date is reported to aggregate 1,000 tons, whose value was chiefly in silver and to a minor extent in gold, the average being 1 ounce of gold to every 100 oimces of silver. Recent shipments to Tonopah averaged about 20 oimces of silver to the ton.

Most of the workings are on the vein known as the Kemick, which is cut at a moderate depth by an adit at 500 feet from the portal. The adit was continued for 700 feet beyond the vein and in the last 100 feet penetrated a silicifled rhyolite tuff, which is in the condition of an iron-stained rubble and was said to carry $4 in gold to the ton.

Northwest of the portal of the adit a shaft has been sunk to a depth of 230 feet. From the 200-foot level the former operators ran a crosscut, which cut a vein that they thought was the extension of the Kemick; because of its low tenor interest in the mine lan- guished thereafter. It is now believed that this vein is a separate vein, and it has been renamed the McKane. From the bottom level the present operators are running crosscuts south and also northeast. The country rock in these workings is all Fraction rhyolite breccia in unshattered condition, in marked contrast to the liighly broken state of the rocks on the 200-foot level.* In the face of the south crosscut at the time of visit was a thin intercalated layer of banded fine gray tuff, whose attitude proves that the formation dips 20° W. here, in conformity with the general dip throughout the district.

The Kemick vein, as seen in the upper workings (above the main adit), trends nearly due west, dips 70° N., and averages between 3 and 4 feet in width. It consists of angular fragments of the country rock, highly silicified, inclosed in a cement of exceedingly fine grained bluish quartz. It is an extremely hard, tough ore. The walls are fairly well defined in places but as rule are rather rough, as if not much movement had taken place on them. The country rock inclosing the vein is a silicified well-bedded tuff, locally showTQg cross-bedding.

The main adit affords an instructive section across the stratified tuffs, showing their change from comparatively soft strata to ex- tremdy hard silicified rocks near the vein. At the intersection of the vein by the adit a fair shoot of ore 50 feet long was stoped out above the level. The vein is a few feet wide, but only a few inches of postminerally crushed and oxidized gouge pays to extract. In places 10 inches of such material on the footwall will, it is claimed,

1278*— 21 12

170 CONTRIBUTIONS TO ECONOMIC GEOLOOTy 1920, PART I.

yield $50 a ton. The fonner operators broke out 3 to 4 feet across the vein and sorted out the material of the footwall streak; this rejected material is said to carry, according to recent sampling, 12 ounces in sUver to the ton and a little gold. Under present conditions ore is material carrying at least $15 a ton in precious metals. According to the manager if a mill were at the mine considerable ore of average Tonopah grade — that is, about $14 a ton — would be available.

The Mogollon District, New Mexico.

By Henry G.. Ferguson.

Introduction.

The MogoUon (mo-go-yohn') or Cooney district is in the south- western part of Socorro County, N. Mex., about 14 miles from the Arizona line. (See fig. 29.) Silver City, the nearest available rail- road point, is about 85 miles to the southeast. The district lies near the western border of the Mogollon Range, which here presents a

PiouBB 29.: — Map of Boutliwestern New Mexico showing the location of the Mogollon

district.

steep front facing the valley of San Francisco River, to the west. The crest of the range, marked by a line of high peaks, is a few miles the east. To the south the change from mountain to valley topog- raphy is less abrupt, and the steep rock cliffs facing the valley are aot so prominent a feature of the landscape as they are near the Mogollon district.

TMs paper was transmitted for publication prior to the appearance of an excellent article on the ore deposits of the MogoUon district by David B. Scott in Mining and Metallnrgy, No. 158, section 33, February, 1920. The writer has, however, added a few notes drawn from Mr. 8cott*8 paper.

172 Contributions To Economic Geology, 1920, Part I.

The plains to the west and south of the mountains show the char- acteristic vegetation of semiarid regions. In the MogoUon district, however, there is considerable rainfall and heavy showers are fre- quent, particularly during the summer. A rather scrubby vegeta- tion, including several varieties of small oaks, mountain mahogany, and small juniper and pinon, characterizes the district itself. The higher hills east of the Mogollon district are heavily wooded and furnish an abundant supply of mine timber.

The district was visited by L. C. Oraton in 1905, and his report was published in 1910.* In 1915 a survey for a detailed topographic map of the district on a scale of 1 : 24,000 was made by R. W. Berry. The writer spent three months during the autumn of 1916 in a study of the geology. The war prevented the completion of even a pre- liminary report, and the district was therefore revisited in Septem- ber, 1919, when about two weeks was spent in the field. The follow- ing report is presented as preliminary to a more detailed study, which it is hoped to complete in the near future.

The writer desires to thank his friends in the Mogollon district,

particularly Messrs. S. J. Kidder, C. A. Botsford, W. Johns, C. E.

Wheelock, R. P. Wheelock, and G. C. Baer, for their assistance and

helpful suggestions. Detailed reports on the geology of the Last

Chance and Maud S. mines, by Wilbur H. Grant, of San Francisco,

made available by the courtesy of Mr. S. J. Kidder, and geologic

maps of a portion of the district, by Mr. G. C. Baer, were studied

with much profit.

History.

In August, 1875, James Cooney discovered rich silver-copper ores in the canyon of Silver Creek. The first settlement, now abandoned, was made in this valley and bore the name of Cooney. The region was infested by Apaches, and development work was slow. The first shipment was not made until 1879. In 1880 Cooney was killed by Apaches while assisting in the defense of the settlements in the San Francisco Valley. It was not until 1885 that the Indians ceased to be dangerous. The silver sulphide ores of the Mineral Creek region were discovered about this time, and the present village of Mogollon was established. Mining now proceeded actively, and Graton esti- mates that up to 1905 the total production had been about $5,000,000 in silver, copper, and gold. The following table shows the annual production of the district since 1904:

'Llndgren, Waldemar, Graton, L. C, and Gordon, C. H., The ore deposits of New Mexico : U. S. Geol. Survey Prof. Paper 68, pp. 191-201, 1910. Graton, L. C, op. clt, p. 192. U. 8. Geol. Survey Mineral Resources, 1917, pt. 1, p. 719, 1918.

Mooollok District, K. Mex.

Mine production in Mogollon or Cooney district, Socorro County, N. Mew.,

190Jhl917,

Year.

Ore.

Short tont.

11,276

15,534

16,076

20,608.

19,546

23,945

60,514

101,361

115,730

136,124

119,710

118,257

111,934

962,933

Gold.

$61,880 97,158 127,907 105, 413 116, 418 111,464 304,210 631,358 524,858 619,886 629, 102 509,165 373,068 258,620

4,370,307

Silver.

Fine ounces.

79,014

240,943

268,567

418,338

278,939

249,413

505,669

1,067,038

1,093, 158

1,306,766

1,410,327

1,301,059

1,008,483

722,642

10,040,356

Copper.

Pounds, 422,308 295,175

160,000 46"

1,873

4,418

875,276

Lead.

Pounds.

1,862 1,217 2,426 3,232 1,593

11,355

Total value.

S162.484

288,735

307,847

411,516

264,256

241,167

625,871

1,097,206

1,197,197

1,409,912

1,409,035

1,168,916

1,037,064

854,327

10,475,553

Topography.

The Mogollon district is on the western flank of the Mogollon Bange, which rises abruptly from the valley of San Francisco River. Between the flat river bed, which at Alma is about 4,900 feet above sea level, and the mountains are flat-topped mesas of partly consoli- dated gravels, with altitudes ranging from 5J400 feet on Whitewater Mesa to more than 6,000 feet at the top of the mesa north of Copper Creek. Above these flat mesas are the steep, forbidding cliils of .the Mogollon Range. This frontal wall is trenched by deep stream can- yons. Mineral Creek and Silver Creek cross the area covered by the accompanying detailed map (PI. XV) from east to west, and Houston Canyon drains a small tract in the southeastern part. The magnifi- cent canyon of Whitewater Creek is just south of the area, and to the north is Copper Creek, both about parallel with Silver and Mineral creeks. The stream canyons are extremely youthful, and their walls, particularly near the scarp that marks the front of the range, are precipitous. In the western part of Mineral Creek canyon, locally called Cooney Box, the altitude at stream level is 5,450 feet ; at the edge of the plateau, 600 feet to the north, it is 6,300 feet. The topog- raphy of Silver Creek canyon is similar, but for the most part the cliffs are not so steep. Along Whitewater Creek the canyon walls are as steep as in Cooney Box. Farther up the stream courses the valleys, although still bordered by sharp cliffs, are not of the box-canyon type which characterizes them at their exit from the range.

Above the cliffs the topography changes abruptly and the inter- stream areas are comparatively flat between altitudes of 6,300 feet in the western part of the area shown on the map, and 7,500 feet in the eastern part. The boundary between this upland bench and the stream canyons is nearly everywhere sharply defined. This plateau is less well developed in the interstream area south of the Mogollon district and better developed in those to the north, particularly be- tween Copper and Deep creeks.

174 Q0KTBIBXrnOK8 TO BOOKOiaO GBOLOGY, 1900, PABT L

Eastward from the area mapped this bench disappears and ground rises steeply to the line of peaks which forms the crest of range. Ciooney Creek heads on the south slopes of Bearwall Mountain, which has an altitude of 9,820 feet. Willow Mountf with an altitude of 10,800 feet, stands opposite the head of Sil Creek. CNJier peaks of the range south of Willow Mountain Whitewater Baldy, 10,892 feet; Center Baldy, 10/2 feet; and 1 gollon Peak, 10,778 feet

West of the crest the aspect of the mountains changes complefa The slopes are smooth and gradual and the streams, all tributary Gila River, have cut only shallow canyons. A short distance east the crest the interstream areas are nearly flat and contain numer small lakes.

GBOIiOOY.

The rocks of the MogoUon district (see PL XV) are dominao lavas, of Tertiaiy age, separated by sandstones that represent peri* of quiet between volcanic outbursts. After extensive faulting m eral-bearing solutions found access to the fault fissures. In Q ternary time the rocks were considerably eroded and a thick co ing of gravel was laid down. Then followed renewed faulting, which the principal fault plane was along the present front of range, with downthrow on the west. Renewed erosion stripped gravel covering from the 7,000-foot bench already described and lowed the irtxeams to cut sharp canyons across the area.

Boca

The following table shows the sequence of rocks as observed in district, the oldest at the bottom of the column :

Maximum observed thickness of rocks in the MogoUon distrust.

Quaternary : Feet.

Gravels 700

Basalt dlkea Tertiary :

Mineral-bearing veins. Intrusive andeslte porphyry.

Red sandstone and conglomerate 400

Andesite with dadte flows 600

RhyoUte tuff 400

Dike of tuffaceous rhyoUte.

Andesite 600

RhyoUte, coarsely spheruUtlc 1,200

Andesite and basalt 800

Sandstone 100

RhyoUte with quartz phenocrysts 700

Sandstone with andesite flow In lower part 400

RhyoUte and rhyoUte tuffs 1,400

RhyoUte, minutely spheruUtlc 700+

l06C*7'

Mogollon District, N. Mex. 175

The sum of the maximum observed thicknesses amounts to 8,000 feet, of which 6,400 feet represents lava flows and pyroclastic rocks, and the remainder sedimentary deposits laid down by streams. This total is of course not a measure of the original thickness of the formations, as these rocks are not all present throughout the area. The rhyolites in particular are very imeven in thickness, and a flow may be lacking in one section and show a thickness of several hundred, feet a short distance away. Moreover, there was considerable erosion at different stages in the upbuilding of the mass, and parts of the different flows have been removed. In many places exposed con- tacts show erosional unconformities, indicating that an extremely rugged topography was developed between periods of volcanic ac- tivity. Graton considers that the lavas were probably extruded in the early part of the Tertiary period.

No petrographic examination of specimens collected in the field has vet been made, and the following descriptions are based principally on the writer's field notes. It is probable that some modifications, particularly in nomenclature, will be required when the rocks are studied with the aid of the microscope.

The oldest rock exposed in the district is a rhyolite of light purple color that breaks with a platy fracture. It is commonly flow-banded and in places shows numerous small spherules. More rarely it is sUghtly porphyritic and carries smaU crystals of milky feldspar and biotite in a glassy base. A characteristic feature of the rock is the presence of ellipsoidal cavities as much as 3 inches in length lined with small quartz crystals. These cavities are parallel to the lines of flow. In places inclusions of andesite are found, but these are much rarer than in the younger rhyolites. Several flows are present, and beds of white tuff mark periods of explosive activity. The maxi* mum thickness as exposed in Cooney Box is about 700 feet. This rhyolite is also well exposed in Whitewater Canyon, south of the area mapped, but does not crop out on Silver Creek.

The formation above this rhyolite consists of alternate thin flows of rhyolite and beds of rhyolite tuff with a few lenses of red and purple or, more rarely, green sandstone. The flows, which are best exhibited along the power-plant road, in the southwestern part of the area, consist of a red, very porphyritic rock with numerous and prominent crystals of biotite and feldspar. As a rule the volume of the phenocrysts equals or exceeds that of the groundmass. The feldspar crystals are in part milky white and in part glassy, with minute striations characteristic of plagioclase. Large poikilitic feldspar crystals were observed in places. According to Graton,* the feldspar consists o£ about equal amounts of orthoclase> and of plagio- clase that ranges from andesine to labradorite. Quartz is usually

Gnton, L. C, op. clt, p. 194. Graton, L. C„ op, clt., p. 192.

176 Contributions To Ecx)Nobcig Geologt 1920, Part I.

inconspicuous or not visible to the eye, but in a few of the flows quartz phenocrysts are prominent and the rock resembles the next younger of the rhyolites. Quartz intergrown with feldspar is a common feature. The groundmass is generally glassy in appear- ance; only rarely was a spherulitic texture observed. A partial analysis of the rhyolite from the canyon wall directly above Cooney, made by W. T. Schaller, shows the rock to be richer in soda than is normal, and it is therefore designated soda rhyolite by Graton.

Partial analysis of soda rhyolite from canyon above Cooney, N. Mex.

Sio. 67.83

CaO 2. 10

KaO 5. 46

Na,0 3.30

From Gratons description and the analysis it would appear that quartz latite is the name most applicable to this rock. This name, however, is not used in this preliminary paper, because it is not yet known whether this is the only quartz latite of the series or whether the high soda content and the presence of abundant plagioclase characterize all the silicic rocks of the district.

This rhyolite appears to have been more fluid than the others and has spread out in thinner sheets. Probably none of the individual flows in this formation exceed 100 feet in thickness, and the average thickness appears to be much less. The tuffs resemble the lavas in mineral composition but show rather more weathering and are white and pink instead of reddish. Many of them contain pebbles of andesite. The tuff beds are of about the same thickness as the flows.

The maximum thickness of the formation within the area mapped is 1,200 feet, in the southwest comer of the area. Neither the base nor the top is here exposed. On the north wall of Whitewater Canyon, a short distance to the south, there is a thickness of 1,400 feet above the lower rhyolite, and an unknown amount has been removed by erosion. To the north the thickness is much less, and on the north wall of Cooney Canyon, between the lower rhyolite and the sandstone above, there is a thickness of only about 700 feet.

After the deposition of these rhyolite flows and the accompanying tuffs, there was a period of erosion during which deep canyons were cut. Remnants of these canyons can be seen in the steep contacts of rhyolite tuff and sandstone on the sides of Gold Dust Gulch and Houston Canyon. As shown in the walls of Houston Canyon, a steep-sided canyon over 300 feet in depth was cut out before being filled with sandstone A change in the character of the streams caused the filling of this canyon and the covering of a wide belt in

'Graton, L. C, op. cit, p. 192.

mogoujon district, n. mex. 177

the western part of the area with sandstone containing lenses of con- glomerate. The deposition of sandstone was interrupted once by a flow of andesite, 40 feet thick, with phenocrysts of biotite and pyroxene, and later by the deposition of white rhyolitic tuff, about feet thick. The sandstone is commonly red to deep purple and nearly everywhere shows cross-bedding. Except for the rather rare conglomeratic phases it is fine grained and made up largely of small fragments of feldspar. The irregular dips that characterize the formation are, in part at least, the residt of deposition on a sloping surface, as in the north wall of Mineral Creek canyon, opposite the Cooney mine, where sandstone dipping 15°-30° to the east and north- east overlies rhyolitic tuffs that dip 10°-15° to the northwest, and is itself overlain by andesite tuffs with sandstone beds which show easterly dips of 6-8°.

The thickness of the sandstone exposed exceeds 400 feet in Hous- ton Canyon. At the edge of the old canyon referred to above the thickness changes from 200 feet to about 20 in a distance of less than 300 feet, and 200 feet farther east the sandstone disappears altogether. 5ear the mouth of Silver Creek over 500 feet is exposed. The thick- decreases northward to about 100 feet on Silver Peak. It also decreases eastward, and within a short distance the sandstone dis- appears, although the change is not as abrupt as in Gold Dust Gulch. The next flow of rhyolite apparently occupied part of the valley in which the sandstone was being deposited, its maximum thickness lieing nearly coincident with the thickest portion of the sandstone. The distinguishing field characteristic of this lava is the presence of vifjble quartz. Commonly the rock shows prominent quartz and feldjspar, apparently both orthoclase and plagioclase, and subordi- niice biotite, in a groundmass which is glassy in appearance, and in a few localities shows spherulitic texture. Tuffs having about the same mineral composition are of common occurrence. At the base of the series, quartz is less prominent and the rock closely resembles the older rhyolite below the sandstone. The steep contacts exposed on the northern wall of Gold Dust Gulch show that this lava in part occupied a valley eroded in the earlier tuff and rhyolite.

This quartz-rich rhyolite forms the prominent cliffs near the mouth of Silver Creek and the summit of Silver Peak, in the northwest comer of the area. It is also present in considerable thickness on the ridge between the power-plant road and Houston Canyon, south of the Confidence mine. Here, however, the formation appears to be predominantly tuffaceous. In the cliffs of Silver Creek canyon the quartz-rich rhyolite in thick flows, showing rough columnar struc- ture and separated by thin beds of tuff, has a total thickness of 600 feet. On Silver Peak there is about 500 feet remaining, and east

178 CONTRIBUTIONS TO ECONOMIC GffiOLOGY, 192D, PAET I.

of Houston Canyon the alternate tuffs and flows are about 700 feet thick. The thickness is very irregular. Between the sections in Sil- ver Creek and east of Houston Canyon the formation is lacking en- tirely, and half a mile east of the thickest part of the Silver Creek section only about 100 feet is present A similar thinning out is observable east of Silver Peak, in the northern part of the area.

Deposition of the sandstone continued after the eruption of the quartz-rich rhyolite. In this upper portion, however, there is much coarse conglomerate with large pebbles of quartz rhyolite and of the older biotitic rhyolite. In the north branch of Houston Canyon, just under the Silver City road, the quartz-bearing rhyolite is lack- ing and the conglomerate with pebbles of this rhyolite rests, without apparent break, on fine-grained cross-bedded sandstone. In Cooney Canyon a thin flow of andesite occurs in the conglomerate.

The conglomerate is overlain by the first of the series of andesite lavas that are so prominent in this region. The following petro- graphic description is quoted from Graton

Plagioclase feldspar Is the principal constitiient. It Is of the composition of either andeslne or, less commonly, ollgoclase. Phenocrysts of pyroxene were present but are now much decomposed, the usual products being quartz, chlorite, and Iron ore (magnetite?). Some of this material may originally have been hornblende or even olivine. The groundmass consists principally of minute plagioclase laths with profuse grains of magnetite, now much altered to limonlte. Glass Is much less common than in the soda rhyolite. Alteration, while of the same character as that which has affected the soda rhyolite, has had a much more pronounced effect on the andesite. It many places the rock has been greatly bleached to a greenish-gray color; quartz has formed plenti- fully in the groundmass and has replaced the calcite of many of the amygdules. Calclte is abundantly developed in places, however. Where the most alteration has taken place pyrlte, chalcopyrlte, and bomite are present in scattered grains and in tiny velnlets. The general composition of the rock is expressed by the following partial analysis of a specimen from the Cooney mine, made by W. T. Schaller :

Partial analysis of latite from the Mogollon district,

Sio, 48. 00

CaO 7.72

K,0 3. 28

NaiO 1.95

It is difficult to account for the amount of potash shown by the analysis, as by far the greater part of the feldspar appears certainly to be plagioclase. The analysis was repeated and found correct. Probably most of the so-called andesltes of this region are In reality latite, and the x>otasslum is probably contained in the groundmass.

The complete alteration of the ferromagnesian phenocrysts makes field determination of the andesites very uncertain. The lower series appear to be more nearly basaltic in character than those above the rhyolite flow. In the lower series augite occurs nearly everywhere in

Graton, U C, op. cit., pp. 192-193.

Mogoij/)N District, N. Mbx. 179

prominent phenocrysts, and a few of the flows appear to have con- tained phenocrysts of olivine. Rarely small altered crystals of biotite may be observed. The only good exposure of the lower andes- ite is in the south wall of Mineral Creek canyon above the Cooney mine. Here a series of thin flows with beds of breccia and agglomer- ate and a few thin beds of reddish-purple feldspathic sandstone occupy the lower 700 feet of the canyon wall. In the Last Chance mine the rock forms the footwall of the vein for a vertical distance of over 800 feet. Less than a mile to the northeast, however, the andesite is missing and the overlying spherulitic rhyolite rests directly upon quartz-bearing rhyolite. In many places there is a few feet of reddish-purple sandstone above the andesite, indicating a short period of quiescence before the outflow of the spherulitic rhyolite, next to be described.

The next in the series, a rhyolite with well-marked spherulitic texture, seems to have flowed out in a very viscous condition and solidified in the form of a rather flat mound. The maximum thickness observed was at a point south of the area studied in detail, near the junction of Whitewater Creek and South Fork, where at least 1,200 feet is exposed. On the south edge of the area mapped the thickness does not exceed 1,000 feet. A mile to the north, in the Last Chance workings, the flow is 800 feet thick. The Little Fanney workings, on the south side of Fanney Hill, show a thickness of 600 feet. On the north side of the same hill the thickness decreases sharply until at a point 1,000 feet west of the Cooney mine a few feet of rhyolitic tuff is all that remains. Farther west only a thin bed of sandstone with rhyolite fragments separates the upper and lower andesites. On the north side of Mineral Creek there is a thin bed of rhyolitic tuff which is believed to mark the same horizon. To all appearances this mass of rhyolite represents a single flow. The only evidence to the contrary is the presence of rhyolite breccia on the point above the Eberle mine, about 150 feet lower than the upper contact. It is possible, however, that this is merely a flow breccia due to pre- mature solidification of part of the flow.

The distinguishing characteristic of this rhyolite is its spherulitic texture, and it is the only member of the rhyolite series in which spherulitesare at all prominent. Most commonly the rock shows closely crowded light-pink to white spherulites in linear arrange- ment in a rather glassy groundmass of a delicate light-purple shade. The spherulites are usually from a quarter of an inch to more than half an inch in diameter and show a radial structure. In places they are so closely packed as to form over half of the rock mass; elsewhere layers composed largely of spherulites alternate with flow-banded rhyolite in which spherulitic texture is subordinate. The viscous nature of the flow resulted in the formation of cavemo"''

180 Contributions To Economic Geology, 192D, Pabt I.

open spaces before complete solidification. The larger of these spaces show clusters of spherulite-like bodies from a fraction of an inch to 2 inches in diameter. Some of these look almost like clusters of grapes; others have a reniform appearance. They consist of a thin shell of lithoidal matter lined with crystals of bluish quartz. Quartz crystals also line small cavities in the rock mass itself.

Obsidian is not common but was observed in places. A very strik- ing variety of the rock was observed on the ridge northeast of the limekiln, where a dark-brown glass of resinous appearance is thickly studded with pink spherulites.

Porphyritic crystals are found here and there in the flow-banded portions of the rock. Feldspar is the most common, and two kinds were observed — stout milk-white crystals and thinner glassy crystals, many of which are striated. The milk-white variety is by far the commoner. Biotite is also present in small amount, but quartz phenocrysts were rarely observed.

In many places the upper part of the rhyolite to a depth of a few inches is dark purple, in contrast to the light brown or pink of the main rock mass. This difference appears to be due to inclusions of minutely divided foreign matter, a sort of scum carried on the sur- face of the molten rock. Small inclusions of andesite are also numerous near the upper surface of the flow.

Although a few feet of sandstone containing rhyolite fragments was observed in places above the rhyolite, there does not appear to have been any considerable erosion prior to the next period of andes- ite flows, and, except as modified by faulting and recent erosion, the lenticular shape of the rhyolite body represents the ojriginal form of the flow.

After the rhyolite extrxision the country was covered by successive thin flows of andesite. The eruptions were accompanied by consider- able explosive action, and in certain places breccias and agglomerates exceed the lavas in volume. Some of the breccias have been re- worked by water and consist of subanguJar andesite blocks in a sandy matrix. Thin beds of sandstone also occur.

Owing to the' complete decomposition of the f erromagnesian min- erals, the andesites of this series are difficult to distinguish from those above and below. On the whole, however, they appear to be less basaltic than the lower series. Augite is the most prominent phenocryst, but many of the flows also contain small crystals of biotite. Olivine appears to be lacking. In other respects the rock closely resembles the andesites below the spherulitic rhyolite.

The series is thickest in the northern part of the area, where the rhyolite is represented only by a few feet of tuff. Here it is about 600 feet thick. In the southern part, where the rhyolite is much thicker, not over 300 feet of andesite is present. Overlapping of the

MOGOLIiON DISTRICT, N. MEX. 181

andesite flows on the mound of rhyolite is shown in the south wall of Mineral Creek canyon, where thin beds of sandstone containing broken spherules derived from the rhyolite occur between the andesite flows.

A small rhyolite dike crosses the central part of the area, extending northward from the Last Chance fault to a point a short distance west of the Trilby mine, a distance of a little over a mile. This dike ranges from 6 to 20 feet in width. Secondary silicification makes field determination difficult, but the material of which it is composed appears to be a rather siliceous flow-banded rhyolite, intensely brec- ciated. The dike cuts both the spherulitic rhyolite and the overlying andesite and is similar in composition to the tuff above. It may occupy a channel through which the tuff was erupted.

Above these andesites is a bed of white rhyolitic tuff. This bed appears to be persistent throughout the area, although it varies greatly in thickness, from a minimum of less than 10 feet to a maxi- mum of about 400 feet. Its glaring white color makes its conspicu- ous on steep bare slopes, as in the eastern part of Mineral Creek canyon. Generally, however, where not protected by overlying harder rocks or rendered more resistant by later silicification, it forms gentle slopes. This tuff consists of small fragments of a glassy flow-banded rhyolite, similar in appearance to the less spheru- litic parts of the rhyolite next below, in a white fine-grained, some- what kaolinized matrix. In places, particularly near the veins, later silicification of the matrix has given the tuff the appearance of a very siliceous rhyolite flow. In most places, however, a faint bedding is observable. The tuff is nearly everywhere capped by a few feet of red sandstone containing small rhyolite pebbles.

The youngest effusive rocks of the area iire andesites, a series of. flows from 250 to 600 feet thick. As with the lower flows, field de- termination is difficult, owing to the alteration of the dark silicates. So far as could be observed, however, this series is more silicic than the older andesites. As in the lower andesites, pyroxene is the most common phenocryst, but amphibole is prominent in several flows. Otherwise the rock for the most part closely resembles the andesite above the spherulitic rhyolite. A characteristic feature of the upper andesites is the presence of a flow of dacite near the top of the series. This rock is dense and dark reddish brown and shows comparatively few amygdules. It contains small corroded crystals of quartz, which appear almost black against the dark background of the rock, and small crystals of biotite and glassy feldspar. Within this series of flows, about 50 feet above the top of the rhyolite tuff, there is in many places a thin bed of red sandstone containing small fragments of rhyolite, indicating that a rhyolitic eruption, not otherwise repre-

ites, the ferromagnesian minerals are much altered. The intrusive cuts both the andesite series and the rhyolite tuff. Its age relation to the conglomerate is not certain. Possibly the eastward dip of the base of the conglomerate to the southeast of MogoUon, as shown .in section C-C, Plate XVI, may be due to doming caused by the intrusion. Both the intrusive andesite and the conglomerate are older than the faulting and subsequent mineralization. Andesite with a pronounced diabasic texture was found on the dump of the Cooney mine and was encountered in the new workings of the 1,10ft- foot level of the Fanney mine, which were not accessible at the times of visit. The relations of the rock to the other formations are unknown, but its texture and its small areal extent suggest that it is intrusive.*

A few dikes of basalt cut the older formations of the area. At one place a small basalt dike crosses a fault, and it is probable that all the basalt dikes in this district were intruded subsequent to the faulting and mineralization.

Gravel deposits of considerable thickness occur west of the scarp that forms the front of the Mogollon Range. In the area mapped

Sow older than the lower

mogoij:x)n district, n. mex. 188

these deposits appear only in a small strip in the northwestern por- tion, where they are faulted against the rhyolite tuffs. They consist of roughly consolidated, rather coarse gravels with lenses of sandy material. The bedding is coarse and in general obscure. In most places a gentle westward dip is observable. Flows of basalt occur in a few places between the beds of gravel. The thickness of the gravel, as measured from Mineral Creek to the top of the mesa to the north, is about 700 feet. The pebbles include lavas of various types, but basalt and basaltic andesite appear to predominate.

Stbucttjbe.

The present attitude and to some extent the relative positions of the rock formations are due' to complex normal faulting, which has brought blocks of the younger rocks of the series into juxtaposition with the older. Two periods of faulting are discernible — one of unknown date but subsequent to the deposition of the conglomerate and the intrusion of the andesite porphyry and prior to the intru- sion of the later basalt dikes and deposition of the gravels, and the other comparatively recent, for it has determined the present topog- raphy and has brought the recent gravels into contact with the older rocks.

The faulting of the first period was much the more widespread and complex. The area was broken up into a great number of irregular blocks, bounded by faults that follow two main direc- tions—one between north and north-northeast and the other between west and northwest. Nearly all the fault fissures in the area are occupied by veins, consequently they are more easy to trace than is usual in an extensively faulted district of this nature. As will be seen from the geologic map and Plate XVII the most persistent fault in the area is the one that crosses the eastern portion from north to south, known as the Queen vein. The fissuring along the Queen vein is not simple, and in many places the total throw is distributed among several nearly parallel faults. This fault is very persistent, however, and has been traced not only across the area mapped but for a dis- tance of 3 miles to the north and 2 miles to the south, a total distance of nearly 7 miles. The fault plane dips steeply to the east. The amount of displacement varies from place to place, as the territory on each side is likewise broken up into blocks by faults at angles to the strike of the Queen fault, with varying amounts of throw. As shown by sections A-A', B-B', C-C', and D-D', Plate XVI, the verti- cal displacement along the Queen fault is from 500 to more than 1,000 feet. Other north-south faults of considerable magnitude lie to the east of the area, between MogoUon and the crest of the range. Near the western border of the area is another zone of northerly faulting.

184 Contributions To Economic Gbology, 1920, Part I.

less well defined than the Queen fault. In the southern part, from the southern border of the area to the Confidence vein, this appears as a single fault of considerable throw, which brings the spherulitic rhyolite against the much earlier biotite-bearing tuffaceous rhyolita In this portion it is chiefly remarkable as being one of the few f rao tures in the areas along which there was no important mineralizatioit Between the Confidence vein and Silver Creek there is a complex f ra(j ture zone about half a mile in width, which consists of blocks bounded by minor northerly faults, and has been depressed relatively to til blocks on either side. The surface rocks are not well enough exposei in the flat interstream area north of Silver Creek to permit tracii]| with any certainty the faults that compose this complex series, but number of similar small faults appear on the northern edge of th plateau. Thence northward the system appears to be represented bj a single fault, known as the Great Western, which has a northeasterly strike and dips to the southeast. The maximum vertical displace- ment along this portion of the fault exceeds 600 feet. The faults with dominantly westerly and northwesterly strikes are for the most part best defined close to the Queen fault and tend to disappear toward the west. The most persistent of these, the Last Chance- Confidence fault, is, however, traceable for nearly 2 miles. The structure produced by block faulting in this part of the area may be likened to two flights of steps, one leading down from the north and the other from the south, the lowest step, which is common to both flights, being represented by the block north of the Maud S. fault, which has a total vertical displacement of about 1,000 feet below the highest block on the north and 1,200 feet below the highest on the south. The same structure is repeated east of the Queen fault, though here the faulting appears to be less complex, and the lowest block includes the conglomerate-covered ridge between the town of MogoUon and South Fork.

A peculiar feature of the faults with westerly strike is the marked change in strike which they exhibit close to the Queen fault. On nearly every fault that could be followed at the surface there is a marked tendency toward parallelism close to the Queen and increas- ing divergence in strike a short distance away.

The general appearance of the entire fault system of the district, as shown in Plate XVII, indicates that the northerly and westerly faults were formed at the same time. The Queen fault appears to be the site of the principal fissuring, and the faults branching out from it on either side represent subsidiary fissuring. It is thought prob- able that this branching is due to faulting under light load, and that if the cover had been heavier the change in strike of the minor faults close to the Queen fault would have been less pronounced and the junctions would not be complicated with minor cross faulting.

7,000

-CiOOO

Dn Map, Plate Xv

V f K 4 fc A

Gnvrii lutsriiyolito

Bhyolite and rfayditetnff

LowrfayoliU!

Mogolx.On District, N. Mex. 186

East of the Queen vein the change in strike of the fault planes close to the Queen is less distinct, probably in part because these faults are less mineralized and consequently less easy to follow. So far as observable these fault planes turn sharply to the north as they ap- proach the Queen, whereas those west of the Queen bend to the south.

The relative vertical displacement of the different blocks is shown in the accompanying sections. The horizontal displacement or heave is, however, difficult to determine. It is evident that in a fault block which is bounded by inclined planes and in which the vertical dis- placement decreases away from the inajor fault some horizontal move- ment must have taken place. The grooves and slickensides on the walls of the faults indicate that the horizontal component was less than the vertical, for these grooves stand at angles of 60 or greater in the plane of the fault. A rough guide to the amount of horizontal displacement is found in the -offsets of the small rhyolite dike that crosses the central part of the area. This dike shows offset between 100 and 700 feet in the group of faults between the Maud S. and Trilby mines. These offsets, however, would afford a true measure of the horizontal displacement only if the dike were vertical, and as it is notably irregular along its strike its probable irregularities in dip lessen its value as a means of measuring horizontal displacement.

Later faulting seems to have been confined almost exclusively to the great fault that bounds the front of the range. The outcrop of this fault is everywhere concealed by talus, but the section revealed on Mineral Creek canyon just west of the mouth of Cooney Box shows partly consolidated gravels abutting the steep rhyolite cliffs, with only 200 or 300 feet of talus-covered ground intervening. The physiographic evidence of the fault is unmistakable. The moun- tains end in a sharp and well-defined cliff which, except where broken by the stream canyons, extends in a nearly straight line for 10 miles from Deep Creek on the north to Little Whitewater Creek on the south. The difference in topography on the two sides of the range is additional evidence of faulting. The streams flowing west- ward from the crest have cut deep canyons throughout the greater part of their courses. These canyons are broadly V-shaped near their heads but become narrower to the west and finally close to the narrow clefts or " boxes " through which the streams issue from the range. The eastward-flowing streams, on the other hand, have lower grades, and the interstream areas are flat or gently sloping.

A rough estimate of the vertical displacement along this frontal fault can be made on the assumption that the nearly flat inter- stream areas in the MogoUon district represent approximately the surface from which the gravels east of the fault have been eroded, those on the west owing their preservation to downthrow by f ault- 12780— 21 — 13

186 Conteibutioks To Economic Geology, 192D, Pabt I.

ing. As stated previously, these flat interstream areas are a promi- nent feature of the topography in the immediate vicinity of the MogoUon district. The change from the steep walls of the trans- verse canyons to the nearly flat upland is everywhere sharp, and even the minor tributary canyons show very little gradation. This upland was cut on rocks of greatly different resistance, and so must represent a surface at one time reduced nearly to base-level. As the faulting and consequent relative elevation of this region took place after the deposition of the gravel that now abuts against the fault on the west, it is evident that the gravels must have had a much greater extent toward the east, and therefore that this bench represents very closely the old valley surface upon which the gravels were laid down. East of the region covered by the map the rising ground of the interstream areas marks the limit of this old valley. The benches range in altitude from 6,700 to 7,600 feet* The base of the gravel beds West of the fault is not exposed, but on Mineral Creek, close to the fault, they occur at an altitude of 6,400 feet. The minimum ver- tical displacement must therefore exceed 1,300 feet by whatever thickness of gravel may lie below the valley of Mineral Creek.

Before this later faulting took place the fault fissures of the older series had been healed by the introduction of the veins. Consequently, rejuvenation of the older faults does not appear to have been of much importance. Nevertheless, there is evidence of renewed motion on many of them.

Along a portion of the Pacific vein there is heavy gouge of ap- parently postmineral age, and in the western part of the Last Chance workings a transverse fault accompanied by postmineral gouge cuts but does not visibly offset the vein. Apparently the only effect of the later faulting has been to cause a slight readjustment of a few of the older fault blocks close to the frontal fault. This renewed motion, small as it was, elsewhere than along the main fault, was of considerable economic importance in that it appears to have provided channels through which the oxidizing solutions had better access to the ores than elsewhere along the veins.

Tilting has to some extent accompanied all the faulting. The amount has probably not been great, although the irregular contacts between the flows and the sediments and the extensive cross-bedding of the sandstones make the determination of the amount of tilting a difficult matter. On the whole, the older members of the series seem to show higher and more irregular dips than the younger, a differ- ence which indicates some movement prior to the principal period of faulting. The andesite intrusion at the mouth of Dog Gulch seems to have caused a gentle doming of the overlying formations. Close to the major faults, particularly the Queen, the dips of the flows and beds are in places steeper than elsewhere, owing to drag along the

MOGOLIiON DISTRICT, K. MEX. 187

faults. In the western part of the area the upper contact of the oldest rhyolite dips to the west. This may be due to erosional uncon- formity, to earlier tilting, or to the drag of the recent fault bounding the range. West of this fault the gravels show a gentle westerly dip.

It is probable that a more detailed physiographic study of the whole range would show that the effect of the recent faulting was not simply the relative depression of a block on the west of the fault, bat involved a tilting of the whole mass now forming the Mogollon Mountains, with relative elevation on the west and depression on the east.

The faulting of both periods probably took place under light load. The later faulting affected the unconsolidated gravels and its topo- graphic expression has been only slightly obscured by later erosion. In the older series the feathering of the faults near their junctions and the dying out of many of the transverse series at short distances from the main north-south fault is evidence of movement under light load. Although the geology of the range must be studied in detail before a definite statemit can be made, it is probable that the surface at the time of the earlier faulting was not over a few hun- dred feet above the youngest formation now exposed in the Mogollon district.

The cause of the faulting may be assigned to local overloading of the crust due to the transfer of great masses of igneous rock material from the interior to the surface of the earth.

BECENT QEOIiOOIC HI8T0BY.

The surface prior to the first period of faulting was probably a- fairly flat lava plain. Faulting broke this plain into irregular seg- ments and gave opportunity for renewed erosion which continued un- til the irregular mountain mass was reduced to a mature topography. On the western flank of the range was a broad valley which later be- came filled with gravel to a depth of several hundred feet. The next geologic event was the formation of the great fault which de- fines the present front of the range. This faulting gave another impetus to erosion on the west side of the range and began the cycle in which the present topography has been carved out. As the re- juvenated streams flowing westward began cutting their canyons the easily eroded gravel remnant was removed, leaving the nearly flat bench which to-day gives the interstream areas of the Mogollon district so striking a contrast to the steep- walled canyons below. On reaching the harder rock the streams cut more slowly, and as yet they have only had time to cut narrow canyons near their points of emergence from the range. The courses of the main streams that crossed the rock bench were determined by the preexisting topogra-

188 GONTRIBUTIOKS TO ECOKOMIG GEOLOGY, IfiOQ, PABT I.

phy, and oonsequently their canyons now cut rocks of all degrees of hardness without adjustment to structure. Their tributaries, how- ever, which have heen developed for the most part since the erosion of the gravels on the bench, show some slight accord with the rock structure. Houston Canyon, in the southwestern part of the area, owes its development to erosion in the soft sandstones, and the same is true of Bluebird Gulch. In the south-central to northeastern part of the area there is a line of tributary gulches roughly parallel to the Queen fault and generally a short distance to the east. These, from south to north, are Deadwood Gulch, Graveyard Gulch, two gulches entering Mineral Creek from the south and north near the old Queen mine, and a gulch draining northeastward in the north- east comer of the area. All these gulches probably owe their origin to easy erosion in the fractured zone bordering the Queen fault. This zone of easy erosion, however, seems to have been of shallow depth, and these gulches, which are now cutting resistant quartz veins and the silicified areas near the vein walls, show a canyon topography comparable to the main streams. Pauses in the process of canyon cutting are marked by secondary benches in the canyon walls. The largest and oldest of these is preserved only in rem- nants along the edges of the present canyons. On the south side of Silver Creek canyon this bench, cut in the resistant spherulitic rhyo- lite and the overlying andesite, occurs at an altitude of 6,700 to 6,800 feet and has a maximum preserved width of about a quarter of a mile. On the north side of the canyon the bench does not app)ear, but the possible remnant of a still older one at an altitude of 7,100 feet is found on the point south of Fanney Hill. The only bench of similar nature in Mineral Creek canyon is found on the north wall, just south of Silver Peak, at an altitude of 6,350 feet. The well- defined bench on the south side of Silver Creek canyon is at about the same altitude as the two rhyolite hills that guard the mouth of the canyon. Probably the imcovering of the dome of resistant rhyo- lite retarded erosion to some extent. Other less well-defined benches occur in places along the canyon walls but are not sufficiently ex- tensive to show on the topographic map. Here and there along Mineral and Whitewater creeks there is a little water-worn gravel at about 50 feet above the present streams.

Ore Deposits.

The ore deposits of the region are all in veins that are closely connected with the faults. Although veins along the faults are a feature of the country for a considerable distance from the mining district, the deposits which have so far proved productive occupy only a small area bounded by the Last Chance-Confidence and Pacific

Mogoixok District, K. Mex. 189

veins on the south and west, the Queen vein on the east, and the Cooney mine in Mineral Creek canyon on the north, an area of less than 2 square miles. The most productive veins have been those following the lateral series of faults, which branch out from the Queen toward the northwest, iparticularly the Last Chance-Confi- dence, the Maud S., and the Little Fanney. With the exception of the Pacific vein and its northward extension into the South Alpine claim, the group of mineralized faults in the west has not been pro- ductive. Small ore bodies have been developed in places along the Queen vein, but over the greater part of its course this vein appears to be barren. The veins east of the Queen vein have ais yet shown no ore.

The veins are for the most part well defined and form prominent outcrops. In places the resistant quartz veins form walls standing out above the surrounding surface. In a few places along the strike of the veins mineralization is lacking, and only the fault lines mark the direction which must be followed. Nearly everywhere along the fissures, however there is some slight mineralization. The veins Tary greatly in width from place to place and are not constant in dip or strike. Near the Queen vein all the branch veins show a sharp change in strike, indicating that the fissures were contempo- raneously formed. Although the association of veins with major fault planes is nearly universal, there are a few places where a vein leaves a major fault fissure for short distances and follows minor fissures in the foot or hanging wall. This indicates that the min- eralization was not contemporaneous with the principal faulting, although it probably followed the faulting closely. Mineralization was contemporaneous throughout the veins. Where intersections of veins have been exposed, as those of the Pacific and Confidence in the main level of the Confidence mine and the Last Chance and Queen in the 700- foot level of the Last Chance mine, the two veins show a blending of their filling and structure. Near the intersec- tions are commonly also numerous small veins linking the two larger ones. This shows particularly well on the surface at the inter- section of the Independence and Fanney veins with the Queen.

The veins exhibit a considerable uniformity of mineral content. Quartz and calcite are the principal gangue minerals, and a little adularia is also present. Fluorite is plentiful in many places. In most veins the principal valuable mineral is argentite, although pyrite, chalcopyrite, bomite, a little galena, and probably small amounts of sphalerite also occur. In a few veins copper sulphides, principally bomite, chalcopyrite, chalcocite, and tetrahedrite, pre- dominate. Oxidation is shallow and irregular in extent, and where found at any considerable depth below the surface appears to be

190 CONTBIBUTIOKS TO BCONOmC 0B0L067, IMO, PART

dependent on recent movement along older fissures. Sulphide en- richment has probably occurred to considerable extent, but to what proportion the rich sulphide ores are dependent on such enrichment is not yet clear.. Cerargyrite and probably other silver haloids, native silver, rare free gold, malachite, azurite, limonite, copper pitch ore," cuprite, and manganese oxides are present in the oxidized ore. The chalcocite and covellite and part of the argentite, pyrite, and native silver appear to be due to sulphide enrichment, but a part of the argentite, most of the pyrite, and all of the bomite, chaloo- pyrite, tetrahedrite, and galena are apparently primary

The earliest of the gangue minerals is in most of the veins a minutely crystalline quartz, which in places shows a delicate banding and is similar to chalcedony in appearance and elsewhere is massive and porcelain-like, resembling hornstone. In some of the veins this quartz appears to have been brecciated before the introduction of the later quartz and calcite. Sulphides are rarely found in this fine- grained .quartz. The deposition of the chalcedonic quartz was fol- lowed by the main period of mineralization, in which quartz and calcite were deposited alternately and together. There appears to have been much overlapping, and intimate intergrowths of the two minerals are common. The quartz pseudomorphs after tabular cal- cite apparently belong to this phase. Elsewhere a rough banding is observable. In most places quartz appears to have been the earlier of the two, and the deposition of the greater part of the sulphides accompanied the beginning of this stage of quartz deposition. The sulphides, particularly in the argentite veins, were commonly de> posited in a band of crystalline quartz surrounding silicified frag- ments of the wall rock or fragments of the earlier chalcedonic quartz. Sulphides are only rarely found in association with calcite. The lamellar calcite and intergrown quartz and the quartz pseudomorphic after calcite appear to represent some of the later stages of deposi- tion. Fluorite was likewise one of the later minerals to be de- posited. The fluorite is light green to colorless or, very rarely, purple. In a few crystals there are well-defined zones marked by narrow brown bands. Sulphide minerals were deposited to some extent throughout this period. In ore from the Cooney mine chalcopyrite crystals were found in association with delicate blades of calcite rest- ing on fluorite. Apparently the last stage of vein filling was marked by the deposition of coarsely crystalline calcite, largely manganif er- ous and barren of sulphides. This calcite occurs in places in the productive veins and is the principal mineral found in the barren veins east of the Queen.

Besides the ore minerals mentioned above Scott (op. dt., p. 10) mentions bromyrlte and Btromeyerlte.

Mogollon District N. Mbx. 191

Mineralization of the wall rock is not a prominent feature. Frag- ments included in the veins are largely silicified and have served as nuclei for the deposition of the sulphides. Where andesite forms the wall it is in places penetrated by pyrite for a short distance from the vein, and, particularly in the veins rich in copper minerals, the rock is cut by minute veinlets carrying quartz and calcite with bomite and chalcopyrite. The rhyolites are practically free from pyritiza- tion, except for the rare replacement of biotite plates by pyrite. The extent of rock alteration dependent upon the vein-forming proc- ess must be determined by future microscopic investigation. So far as can be judged from hand specimens, the rhyolite is only slightly affected, but the andesite appears to have suffered widespread altera- tion. The dark silicates of the andesite are almost completely altered, knd the amygdules contain calcite and quartz. There ap- pears to be in places considerable calcitization in the rock itself. The alteration of the f erromagnesian minerals is probably due chiefly to hydrothermal action rather than weathering, for the basalt dikes of postmineral age are comparatively fresh, and the andesites on the interstream plateau, which have been much longer exposed to weathering, are not noticeably more altered than those that crop out in the more recent canyons.

The rhyolites near the veins show more or less secondary silicifica- tion. This is most strikingly evident in the rhyolite tuff, in which the matrix is in places almost completely silicified. The feldspars of the massive rhyolite show, near the veins, a pecidiar cavernous alteration, apparently the result of replacement by quartz with decrease in volmne.

The zone of oxidation is shallow and irregular, although patches of oxidized ore have yielded considerable high-grade ore. In most of the veins sulphide ores have been stoped close to the surface. In a few places, however, oxidation has proceeded to a considerable depth, notably in the western ore body of the Last Chance mine, where quartz with well-crystallized cerargyrite or other silver haloids and rare platy native silver, together with small amounts of azurite, malachite, and chrysocoUa, occur on the 500 and 700 foot levels, while in the next ore shoot to the east sulphate ore was mined nearly to the surface. Apparently this anomalous condition is due to the presence of a later fissure on the hanging-wall side which crosses but does not perceptibly fault the vein.

It is not yet certain how large a part sulphide enrichment has played in the formation of the ore bodies. Argentite appears in places as a filling of minute cracks, apparently later than the vein, and pyrite clearly of later origin is seen in places in fissures in the quartz. A kaolin-like mineral, probably kaolinite or halloysite, is

192 OONTRISnTIOKS TO EOOKOMIC GEOLOGY, 199, FABT I.

found in places in the sulphide ore bodies, usually associated with vuggy quartz, 'fhis mineral has been obserred in specimens from as great a depth as the 1,100-foot level of the Fanney mine. The minerals commonly indicative of sulphide enrichments in silver ores, such as proustite, pyrargyrite, polybasite, and stephanite, are not present in sufficient amounts to be visible to the eye, although there appears to be a little pyrargyrite in concentrates from the Last Chance ore. In the ores in whidi copper minerals predominate, however, chalcocite and a minor amount of covellite are present, commonly in close association with primary bomite, or tetrahedrite.

With the exception of the Deadwood, which receives the surface drainage of Deadwood Gulch, the mines are dry, and no pumping is required, even at depths bdow the present level of Silver Creek. This is probably due to the fact that the Queen vein and its branches tend to divert the ground water in the region east of the district. Although the Queen vein carried no water where it was cut in the 700-foot level of the Last Chance mine, a copious flow was en- countered where the vein was tapped in the 500-foot level of the Fanney. The only ground water in the district, therefore, aside from what may seep through the Queen vein, is that derived from the small area west of the Queen.

The outcrops of the productive veins were subject to stseam erosion prior to the later faulting and were, later buried under a thick cap- ping of gravel. Faulting and renewed erosion have caused a very rapid lowering of the water level. Consequently it is possible that sulphide enrichment has played an important part in the ore forma- tion only where favorable conditions, such as later fracturing and minor post-mineral faulting, were present.

A feature of the ore bodies indicative of some enrichment is the tendency of the ore shoots to show flat bottoms or poorly defined prongs projecting downward from the main ore body. This is par- ticularly well shown in the Last Chance mine (PI. XX). The vein material below the ore shoots is similar in nature to the ore but is below the limit of economic exploitation.

The ore shoots are large, commonly from 300 to 600 feet in drift length and about the same along the dip. The old upper stopes of the Fanney mine, however, indicate an ore body measuring about 1.500 feet along the strike and about 500 feet along the dip. The width of the ore in places exceeds 20 feet, but the usual width is from 6 to 15 feet. Here and there the best ore is found close to one or both walls. Many of the ore shoots show a nearly straight boundary on one side. In nearly every place where this was observed it could be correlated with a minor vein branching off from the main vein. As a rule widening of the vein is an indication of ore. In some

MOGOIXOK DISTRICT, 2T. MfiX. 193

places, however, swells in the veins were found to be in whole or in part filled with barren calcite.

A peculiar feature of the district is the extreme localization of the productive area. The only mines that have furnished any notable production — the Deadwood, Last Chance, Confidence, Picific, Maud S., Fanney (including the Johnson and Little Charley) , and Cooney — are all included in an area a little over 1 square mile in extent. Of the north-south veins in the western part of the area only the Pacific has been a producer. The Queen vein carries ore in places, but over the greater part of its course it is barren, though it is the largest and best-defined vein of the district. The veins west of the Queen have been the largest producers, but only those between and including the Silver Bar and the Last Chance-Confidence have been profitable. The veins east of the Queen consist at their outcrops almost entirely of barren manganiferous calcite, but a few assays showing a low tenor have been obtained in places.

This extreme localization may be due in part to differences in origi- nal distance from the surface. It is surmised that in veins such as these, formed at comparatively shallow depths, the limiting condi- tions of temperature and pressure causing ore deposition were largely dependent upon the distance from the surface and consequently that the zone of original ore deposition in the different veins occurred at different levels but in each at approximately the same distance below the surface as it existed at the time the ore-bearing solutions entered the fissures. As the faulting that controlled the position of the veins probably preceded vein formation by a short time only, and as this faulting was effected under a comparatively light load, it follows that the original outcrops of the veins were at considerably different altitudes, their position depending on the relative position of the fault blocks bordered by the veins. If the zone of original deposition was a comparatively narrow one and not far below the original surface, then the veins whose original outcrops stood the highest would have their original ore bodies in large part eroded away, those in which the surface was much lower would hold whatever ore was originally deposited in them at a depth not yet reached by either erosion or ex- ploration, and only those in which the original surface was at an intermediate altitude would contain ore at a level now reached by erosion, which has imcovered the outcrop but not cut deep enough to carry away the greater part of the ore. Such veins, owing to their topographic position, are likewise those most favorably situated with regard to enrichment.

A more detailed study of the whole range will be necessary before the surface as it existed at the time of ore deposition can be recon- structed with any approach to accuracy. It is believed, however.

Id4 C017TBIBUTI0NS TO EOONOIOO GSOLOGY, 191M>, PABT L

that the original surface at the time of faulting was not greatly above the present upper sandstone and conglomerate. On the as- sumption that this surface was 600 feet above the base of this con- glomerate, an attempt has been made to reconstruct sections of the surface as it existed at the time of vein formation. The accompany- ing sections (PI. XVIII), drawn along the lines E-E', Gr-G', and H-H' of Plate XV, show this reconstructed surface. Owing to the irregularity of the formations as deposited and the greater erosion in the western part of the area, the probable error is greatest in section E-E' and least in section H-H'. Section GK-G' is taken through the productive part of the district, in the portion showing greatest devel- opment. The known productive portions of the veins as shown by development work lie in a zone over 1,000 feet thick, the upper sur- face of which is from 1,000 to 1,800 feet below the assumed original surface and the base from 1,900 to 2,500 feet below this surface. The outcrops of the veins west of the Queen are for the most part above this zone, and in the western part of the area, along the line of sec- tion E-E, erosion has reached to greater depths.

The mineralogic evidence is also in accord with the hypothesis outlined above. The barren veins east of the Queen vein are com- posed chiefly of coarse manganiferous calcite, which is believed to be the youngest of the gangue minerals and presumably was de- posited under conditions of less pressure and lower temperature than were required for the sulphide-bearing quartz.

The westernmost deposits, such as the Pacific and South Alpine, have not proved productive in depth ; the ore bodies are small, and the ore is widely oxidized. Copper minerals are likewise more prev- alent than in the upper levels of the eastern group. The Cooney mine, which is the only mine yielding predominantly copper ore, lies at an altitude corresponding to the lowest portion of this hypothet- ical zone of original deposition.

It is realized that other conditions whose importance can not be evaluated, such as original width of the fissure and consequent free- dom of migration of the solutions or distance from the original source, to a great extent controlled the original deposition of the ore, and this fact tends to weaken the foregoing hypothesis. It is believed, however, that this hypothesis affords the best explanation of the extreme localization of the productive veins of the district.

Mines And Prospects.

In this paper only short notes on the more important mines of the region are given, the detailed descriptions being reserved for the complete report.

U. a. GSOLOQICAI.

-poo feet 9deme sea Jeyk

looofeef iftn

"I

Mogollon District, K. Mbx. 195

Cooney Kine.

The Cooney mine is in Mineral Creek canyon near the deserted town of Cooney. It has not been worked for several years, and the following description is quoted from Graton's report

The Ck>oney mine, sometimes called the SUver Bar, Is owned by .the Mogollon Gold & Copper Ck). It Is situated In the canyon of Mineral Creek Just above Cooney Camp. The claim was among the earliest locations, having been stalled by the discoverer of the district In the early days the precious metals only were sought, the copper not being recovered by the extraction processes then employed. In recent years copper has been the chief product of value. The total output up to 1905 was stated to have been over $1,000,000. At that time the mine was Idle, but production has since been resumed. The workings con- sist of an adit at the level of Mineral Creek which follows the vein to connect at a depth of 100 feet with an inclined shaft on the vein. Below the adit level there were In 1905 six levels, the lowest being 600 feet below the surface at the shaft The shaft has since been extended to a depth of 700 feet The mill equipment consisted of rolls, Huntington mills, WUfley tables, and Frue vanners, with a capacity of 100 tons dally.

The predominating rock Is andeslte, much of It brecdated ; soda rhyoUte is present also, though the two rocks can not be distinguished underground. Both rocks show the alteration common in the district The mine Is located on the Cooney vein, which strikes about northwest and has an average dip of about 72' NE. It is a quartz-caldte-fluorite vein, ♦ ♦ ♦ The principal ore body extends downward from the surface a little southeast of the shaft. It has been stoped through most of Its extent. On the first leyel, 115 feet below the adit, the stope was 100 feet long and 12 to 15 feet wide ; and on the second, 50 feet lower, the stope was of similar dimensions. On the third level, 50 feet below the second, the stope was 00 feet long and 25 to 30 feet wide, but not all the ore was mined out It was at this point, especially in a stringer 8 to 8 Inches wide lying In the hanging wall a foot or two from the main vein, that were found the finely crystalline sipeclmens described on page 197, and consisting of calcite, fluorite, and quartz, with bomite, clialcoclte, and chalcopyrite. This streak was very rich In copper. The stope on the third level was said to be at the junction of the Twig vein, which lies Just northeast of the Cooney vein, bat writer was unable to observe any Junction. A crosscut to the northeast revealed, about 35 feet from the Cooney vein, a narrow streak carrying calcite and bomite, but this appears to be simply a stringer running east and west. Little pay ore had been encountered In a long drift on the fourth level. The two lowest levels were not visited. It Is reported that in the new workings at the bottom of the mine bomite and chalcoclte have practically disappeared and pyrite carrying some gold Is more abundant than It Is above. Such a statement at once suggests secondary enrichment, but the writer believes that If this con- dition is general through the mine it is due to difference in original deposition resulting from unlike temperatures and pressures at different depths from the surface.

At the time of the writer's visit only the adit level was accessible. Here the average strike of the vein is about N. 42° W. and the dip 75°-80° NE. The tunnel follows a definite vein for about 500 feet ; beyond this point the vein splits and becomes indefinite. The only

"Ormton, L. C, op. clt, pp. 200-201.

Id6 CONTRIBUnoKS TO ECOKOMlC GEOLOGY IMO, PART I.

slopes are within 400 feet of the portal and indicate three small ore bodies, each about 50 feet in drift length. Above the adit level there are old stopes, particularly near the junction of the Silver Bar and Twig veins, where both veins appear to have yielded ore. On the north side of the stream the Silver Bar vein has been developed to a considerable extent and exposed on at least two lervels. The mine is now owned Dy the Socorro Mining & Milling Ca The production is said to have been about $1,700,000.*

Ai.Bebta Xinxl

The Alberta mine lies near the crest of the ridge between Mineral and Silver creeks, about half a mile northwest of the Little Fanney. In this mine the Independence vein has been developed on the adit level for about 300 feet northwestward from its junction with the Ida May vein. The average strike is about N. 40° W. and the dip 60°-65° SW. The vein is well defined and over most of the distance developed exceeds 5 feet in width.

For 200 feet northwestward from the junction with the Ida May the drift is in good ore, said to have in places a tenor exceeding 70 ounces of silver to the ton. There has ben no postmineral faulting and, although the depth below the surface is less than 300 feet, prac- tically no oxidation. The ore consists of alternate bands of quartz with finely disseminated sulphides, chiefly argentite and calcite. In the low-grade material northwest of the ore shoot calcite predomi- nates. .

At the northwest end of the drift a 30- foot winze has been sunk and a short crosscut runs southwest from it. This cuts a 4-inch vein of chalcopyrite, partly oxidized to malachite and azurite.

JOHirSON ICIKE.

The Johnson mine has opened a small vein that crosses the head of Johnson Gulch with a westerly strike, dipping about 70® N. The mine was being prospected by the Socorro Mining & Milling Co. in 1916 but was idle in 1919. It has been developed by two inclined shafts on the vein, about 100 feet apart, connected by drifts on the first and third levels. Thf lowest level is about 300 feet below the collar of the eastern shaft. During a previous period of exploitation considerable stoping was done above an adit level east of the eastern shaft, and recent work has exposed small bodies of good ore in the lower levels. The vein is narrower than the more prominent veins, such as the Fanney, Maud S., and Last Chance, and in few places ex- ceeds 3 feet in width. The cupriferous type of mineralization has occurred in places. The ore is almost completely oxidized.

Scott, D. B., op. clt., p. 20.

M060Lix)K District, N. Mex.

Uttle Fanney Mike;

The Little Fanney mine is north of Silver Creek and has been one of the largest producers of the district. The production date has been $4,869,000.** The mine was in operation at the time of the writer's visit in 1916 but was idle in 1919. The workings, which include those formerly known as the Little Charley mine, cover a vertical range of 1,500 feet and a length of 4,000 feet on the strike of the vein. (See PL XIX.) Ore has been exposed through a verti- cal distance of 1,200 feet, to the 1,100-foot level, and for about 2,700

Feet

-moo

N.

rtET

MkJdle andesite

Spherulitic rtyolite LoMer sndetrte

A.

Quartz rhyofite

-1,000

Section On Unc A-B. Plate Xix Section On Une C).Plate Xix

FicrEE 30. — TrtLngverne sections across Fanney vdn, Mogollon district, N. Mex., alon

lines A-B and C-D, Plate XIX.

feet along the strike. The strike over the greater part of the deposit is X. 74° W. and the dip about 70° S. In the eastern part, near £he Queen vein, the strike is about northwest, and on the surface close to the Queen a north-northwesterly strike is observable. In the west- em part of the workings the vein appears to split into several branches. Minor splits in the vein are numerous and appear to exer- cise some degree of control over the position of the ore bodies. (See fig. 30.)

u

Scott, D. op. cit., p. 16.

198 Contributions To Economic Geoloqy, 1920, Part I.

The ore is of the silver-rich type common to the district, copp minerals occurring only sparingly. The average ratio of gold t silver is 1 to 70.4 by weight. The usual grade of ore mined has tenor of $10 to $12 a ton.

Two large and rather irregular ore bodies have been mined. Tb eastern of these appears to consist of two shoots — an upper flat shoo that bottoms at about the 300-foot level, which was inaccessible the time of visit, and a lower irregular body between the 400-foa| and 900-foot levels, embracing a maximum drift length of about 901 feet. The ore in this lower body consists entirely of sulphides, al* though traces of oxidation were observable in places down to thi 1,100-foot level. Subsequent to the writer's visit a body of ore wai found in the eastern part of the mine on the 1,100- foot level, sup- posedly at the junction of the Fanhey and Ida May veins. The west- p em ore body is divisible into two parallel eastward-pitching shoots, j the eastern of which has been opened to the 1,000- foot level and the I western to the 1,100-foot level. These shoots appear to be formed at the junction of the Fanney vein with intersecting fault veins (fig. 30) . i: The ore in the western workings is for the most part completely oxidized and in places shows specks of free gold. The proportion of gold to silver is higher than in the unoxidized ore.

Dsep Do Wk . Mine.

The Deep Down mine, southeast of the Maud S. mine, on the same vein but on the south side of Silver Creek, has not been in operation for many years. So far as known, all the ore produced (estimated by Graton as worth $75,000) capie .from stopes near the surface. Exploration in depth was apparently not profitable. The vein is / similar in character to the others in the same region, but the width stoped does not appear to have anywhere exceeded 4 f eet

Mattd S. Kine.

The Maud S. mine is on the north side of Silver Creek about 2,000 feet west of the town of Mogollon and is owned by the Mogollon Mines Co. The mine is the oldest in this part of the district, but no work has been done for several years. The total production is said to be $800,000."

The adit level is about 1,000 feet in length and shows a strike of N. 32° W. in the southeastern part and of N. 86° W. near tiie north- west end. The dip is about 65° NW. The principal ore body was in the southeastern part of the mine, where narrow stopes have been carried up to the surface, a distance of about 100 feet.

Scott, D. B., op. cit., p. 18.

MOGOUiON DISTRICT, K. MBX. 199

Two shafts hare been sunk on the vein. The old shaft, at the southeast end of the adit, reaches permanent watei* level at a vertical depth of about 200 feet, and the new shaft, at the northwest end, at a depth of 600 feet vertically, or 700 feet on the vein. Little work was done from the old shaft, although a small body of cupriferous ore was encountered above the 150-foot level. From the new shaft the vein was explored by drifts at the 4<K), 600, and 700 foot levels, but with the exception of a small body near the shaft the 400-foot level no ore was found.

Extbeka Pbospect.

The Eureka prospect lies just west of the area included in the geologic map, at the base of the cliff that forms the western edge of the range, between Silver and Mineral Creeks. The prospect was visited in 1916 but not in 1919.

As might be expected from the nearness of this prospect to the great fault on the edge of the range, postmineral faulting is here of considerable extent. The lower of the three tunnels starts in uncon- solidated gravel and passes through the fault zone, which brings the gravel against the rhyolite.

From the work done at the time of the visit it could not be de- termined whether there wetid several veins present or whether a single vein had suffered complex postmineral faulting. The princi- pal vein seems to strike about north and has an unusually flat dip-- 35° W. Intense postmineral movement is evident in the heavy gouge carrying particles of ore and in the crushed condition of tiie vein itself.

At the time of visit 96 tons of ore had been taken out. Of this 50 tons of high-grade ore assaying $98 in gold and silver to the ton was shipped direct to the smelter, and 45 tons assaying $22 to the ton was milled at the Deadwood and Socorro mills.

The ore is partly oxidized and carries a larger proportion of gold than is usual in the district. The gold-silver ratio is about 1 to 25, and free gold can be panned from samples of the best ore.

Clipton Pbospect.

The Clifton prospect is on the Queen vein just north of Silver Creek. The vein, which is here from 20 to 30 feet wide and consists principally of white calcite, had in 1916 been developed by an adit for a distance of 600 feet For about 100 feet there is along the hanging wall a shoot of ore containing sulphides, for the most part associated with amethystine quartz.

Ebesle Mine.

The Eberle mine, owned by Weatherhead & Cleaveland, has been developed by two tunnels. The mine was visited in 1916 but not in

200 CONTRIBUTIONS TO ECONOKIG GEOLOGY, 192Dj PABT I.

1919. In the northern tunnel the Maud vein and a branch of the Queen vein have been prospected near their intersection* The southern tunnel follows the Queen vein to a point close to its inter- section with the Maud S. Postmineral faulting has occurred along the footwall. The vein filling is largely calcite, but a small rich ore shoot consists chiefly of quartz carrying horn silver and a little native silver. A shaft near the portal of the southern tunnel has developed ore at a depth of 50 feet. Here argentite occurs in quartz closely associated with calcite and apparently also in the calcite as well.

Dbadwood Hinb.

The Deadwood mine was idle and inaccessible during both the writers visits to the district. The workings lie beneath Deadwood Creek and receive the surface seepage, so that it is the only mine in the district that requires pumping. The vein, which is probably the southward extension of the Last Chance, has been explored for 500 feet below the collar of the shaft. The vein strikes nearly due north and is only a short distance from the Queen vein, which has been cut in the lower workings but not explored. Two ore bodies were encountered. The width of the vein is said to be 20 feet at its maximum and the width of the stopes- from 8 to 13 feet. The ore is similar in character to the sulphide ore of the Last Chance. Between 1911 and 1914, 38,480 tons were mined, yielding 6,653 ounces of gold and 323,510 ounces of silver, or 0.173 ounce of gold and 8.40 ounces of silver to the ton. Up to the time of suspension of opera- tions in 1915 the total production was 44,000 tons of ore, valued at $325,000."

*The mine has recently been taken under option by the Mogollon Mines Co., and the 300-foot level of the Last Chance has been ex- tended to a point below the center of the north ore body.

Last Chance Mine.

The Last Chance mine of the Mogollon Mines Co. is south of Silver Creek and just west of Deadwood Creek, about half a mile southwest of the town of Mogollon. The mine is the largest in the district, as the vein has been opened through a horizontal distance of nearly 4,000 feet and to a vertical depth of more than 1,400 feet below the highest point of the outcrop. The ore, as revealed up to the present time, shows a horizontal range equal to the total development and a vertical extent of 1,100 feet The lowest level, 900 feet below the adit, showed no ore, although the new ore body encountered on the 500 and 700 foot levels in the west end of the mine gives promise

"Scott, P, B., op. cUm p. 15.

Moooij/>K District, K. Mbz. 201

of greater extension in depth. The recorded production for the last 25 years has been about $7,500,000.

The vein over the greater part of its length has an average strike of N. 69° W. and dips 60*-70° N. For the most part it follows a well-defined fault plane, but at one place it leaves the fault contact for a short distance. The fault contact itself shows several minor irregularities in the east end. Near the Queen vein the fissuring is more complex. The principal vein makes a sharp turn pud for a short distance follows a course about N. 24/° E. into the Deadwood mine. At this point a parallel vein about 30 feet to the west has yielded good ore over a short distance on the 300-foot level. On other levels branch veins connect the Last Chance and Queen veins.

The vein ranges from a mere fault contact, with slight mineraliza- tion, to 20 'feet or more in width. The average width of stope is about 12 feet in the western part and 8 to 10 feet in the eastern part.

The ore bodies are large and irregular in outline. No definite pitch is observable, but there are numerous downward-projecting points. The lower boundaries of the ore shoots are as a rule indefi- nite, the ore passing gradually into material of similar nature below the limit of profitable exploitation. In their lateral extension there is usually one sharply defined border which can be correlated with a minor split in the vein. On the other end of such a body the boundary may be indefinite, the width of the vein remaining the same but the ore grading off into barren calcite. In the large ore body in the western part of the mine the vertical intersection of two veins forms the boundary of the ore body from the 150-foot sublevel to a point below the 500- foot level.

As can be seen from the projection (PI. XX), the outcrop of the vein was ore bearing at only one point. Here the ore was largely oxidized, but the oxidation extended only to shallow depth. The ore bodies throughout the remainder of the mine, with one excep- tion, contain sulphide ore almost exclusively. The principal sul- phides are argentite and pyrite; copper minerals are of rare oc- currence, although a mass of bomite was found at the east end of the 300-foot level. The new ore body in the extreme western part of the mine on the 500 and 700 foot levels is, however, almost com- pletely oxidized and contains horn silver and native silver, and the large ore body just to the east, extending from the 150- foot to and below the 500- foot level, contains only sulphide ore. This peculiar condition appears to be due to postmineral faulting transverse to the vein, which is shown by a heavy streak of gouge that cuts the vein but does not penetrate the footwall. The oxidized ore contains a higher ratio of gold to silver than the average of the mine, which

"Scott, D. B., op. clt. p. 13.

202 C0Ntribt7Ti01Ts To Egonomig Geology, 1900, Pabt I.

is about 1 to 50, and several assays of material from the broken ground along the postmineral fracture showed a ccmtent of gold exceeding that of silver.

The Confidence mine, on the west, and the Deadwood, on the south, have recently been taken under option by the company. The workings of the three mines together on this vein aggregate about a mile and a half.

Gonptdekce Mute.

*The Confidence mine, west of the Last Chance and on the same vein, has been idle for many years. According to Graton" the workings extend to a depth of 1,030 feet. No ore, however, appears to have been mined below the 450- foot level. The largest ore body extended from the surface near the intersection -of the Pacific vein to the 200- foot level, a vertical distance of about 500 feet. On the main level this body had a length of 800 feet. Smaller bodies that did not crop out were mined farther east. The ore was similar to that of the Last Chance but is reported to have been more largely oxidized. The production is said to have been about $1,200,000.

The 500 and 700 foot levels of the Last Chance mine are now being extended under the old eastern stopes of this mine, and the new body of oxidized ore discovered in these workings extends into the Confidence ground. (See PL XX.)

Oxidized ore has recently been mined on the surface at the inter- section of the Pacific and Confidence veins.

Pacific Hike.

The Pacific mine, which is on a northerly vein between the Con- fidence mine and Silver Creek, is one of the oldest mines of the dis- trict, but its production has been comparatively small. The mine was idle in 1919, but in 1916 it was being developed by the Socorro Mining & Milling Co., and the ore was carried to its mill at the Fanney mine by a cable tramway across Silver Creek. According to Scott*' the production has amounted to about $200,000.

The vein strikes N. 6° W. and dips 70° E. It is well defined and can be followed from the Confidence vein to Silver Creek. Its width ranges from 1 to 15 feet. Its intersection with the Confidence vein is well exposed in the Confidence workings and shows contem- poraneity of the vein filling.

The stopes are irregular, and no ore has been found below the third level, which is about 400 feet below the highest point of the outcrop. In contrast to the ore of other mines of the district the Pacific ore is oxidized and very irregular in tenor. The good ore is

Graton. L. C, op. dt., p. 199. " Scott, D. B., op. clt,, p. 10.

Buu.Btin T1& Plate Xz

Mogollon District, H. Me;C. 203

spotty in occurrence and the ore bodies are irregular. The highest- grade ore contains horn silver, a little native silver, and rare specks of native gold.

Postmineral movement has been more prominent here than in other mines of the district, and a streak of gouge in places a foot wide fol- lows the hanging wall. The gouge consists of a sticky red mud con- taining fragments of quartz and wall rock.

South Alpine Pbosfegt.

The South Alpine claim, on the northward extension of the Pacific vein, has produced ore from surface stopes near the top of the south wall of Silver Creek canyon. Recently a new ore body has been discovered farther north, about 100 feet above Silver Creek. The prominent post-mineral faulting of the Pacific vein is lacking here, and a well-defined vein with tight walls follows the earlier fault contact.

The ore shows a large proportion of copper minerals, principally malachite and cuprite. In places pyritous ore with a high silver content is found. In this ore small plates of native silver occur close to the pyrite crystals or in threadlike veinlets associated with iron oxide. Horn silver is found in vugs and fractures in the quartz. Free gold occurs in small amount.

Ibok Cboss Pbosfegt.

The Iron Cross prospect lies just south of the area included in the detailed map (PL XV) near the top of the north wall of White- wood Canyon. The ground is developed by two small tunnels, about 100 feet vertically apart, and a shaft from the upper tunnel reaching nearly to the lower. The vein appears to be the southern extension of the Queen vein.

Faulting is complex and, at least in part, is postmineral. The vein is accompanied by a thick seam of gouge containing crushed fragments of vein matter.

The best ore is said to have come from the shaft, and 32 tons with an assay value of $15 to $20 a ton has been mined. The ore shows a much brecciated chalcedonic to fine-grained quartz, with the frag- ments cemented by red iron oxide. The fragments of chalcedonic quartz are in places cut by veinlets of drusy quartz. Bare specks of pyrite are visible, usually close to small fragments of altered wall rock, included in the vein. Another vein, as yet undeveloped, strikes about west along the base of a steep rhyolite cliff. Along the out- crop of this vein are masses of psilomelane together with brecciated rhyolite cemented by quartz.

204 CONTRIBtTTIOlfS TO EGOITOBnG GEOLOGY, 1920, PABT I.

Summary.

The rocks of the MogoUon district are nearly all lavas or sedimen- tary rocks composed of materials derived from lavas. Flows of rhyolite and andesite, together with sedimentary and pyroclastic rocks, had reached a total thickness of several thousand feet when faulting of considerable magnitude took place and the region was broken up into irregular blocks bounded by normal faults.

The faulting was closely followed by the introduction of mineral- bearing solutions which followed channels determined by the pre- vious faulting, so that practically all the faults are the sites of veins.

The faulting and the introduction of the mineral veins marked the end of the period of volcanism, and except for a few basalt dikes no postmineral igneous rocks are found in the area. The faulted region suffered extensive erosion, and later a considerable thickness of gravel was deposited over part of it.

In comparatively recent geologic time renewed faulting took place along what is now the front of the range. The disturbance was con- fined principally to the great fault that bounds the range, but some minor movements took place along the faults that had been formed in the earlier period.

The ores of the district are valuable mainly for silver. Argentite, pyrite, bomite, chalcopyrite, and tetrahedrite, together with small amounts of horn silver and native silver, are the principal ore min- erals. The gangue consists chiefly of quartz, calcite, and a little fluo- rite. The veins are large and well defined.

The ores are principally sulphides and give evidence of being in part due to enrichment, although the relative importance of second- ary processes has not yet been fully determined.

The productive portion of the district covers only a comparatively small area. Elsewhere the veins, though well defined, are mostly barren. The cause of this extreme localization is believed to lie in differences in the distance from the original surface at the time of deposition. In those areas which have suffered the least relative de- pression through faulting the ores have been largely removed by erosion. On the other hand, in those areas of greatest relative depres- sion erosion has not yet reached the zone of ore deposition.

Permian Salt Deposits Op The South-Central

United States.

By N. H. Dabton.

Introduction.

During the last few years extensive drilling for oil, gas, and water has revealed a vast deposit of salt constituting part of the Permian succession in eastern New Mexico and northwestern Texas and Okla- homa. The northern extension of the deposit in the Hutchinson- Lyons area, central Kansas, has been known for many years. The limits of this deposit, especially to the northwest and south, have not been ascertained, but in general the area of thick salt extends fully 650 miles from north to south and 150 to 250 miles from east to west. The thickness and succession of beds are variable, but 700 feet is re- ported in one hole, and in many places the aggregate is more than 300 feet. These facts indicate that it is the largest known salt deposit in the world. (See PL XXI.)

In this report will be given a brief statement of the principal data so far obtained, especially with the purpose of stimulating the col- lection of further information regarding the succession of salt beds, the nature of the associated strata, and the limits of the several de- posits. To this end it is important that those who are drilling in the general region should keep careful records of the strata and collect samples of salts and brines for testing. The United States Geological Survey, in cooperation with the Texas Bureau of Economic Geology and Technology, maintains a field laboratory near Amarillo, where D. D. Christmer, chemist in charge, provides for the collection and general testing of samples without charge.

In most processes of deep drilling there is considerable difRculty in recognizing salt because of its solubility in water, and for that reason many records fail to give reliable information regarding the presence and thickness of salt beds. Some records of borings pass- ing through salt beds either fail to refer to them at all or group them with the insoluble sediments as '' shale, salty," sand and salt,'' brine and red sand." Owing to these reasons many of the data given in the following pages are not as reliable as might be wished.

206 Contributions To Economic Geology, 192D, Part I.

Some borings in whose logs no salt is recorded are in areas that are known almost certainly to be underlain by salt.

In connection with the endeavor to find potassium salts in the United States it is believed that the place in which such deposits are most likely to occur is in this great basin of saline accumulation, where the mother Uquors of the sodium chloride might at some time have become so desiccated that their potash content was laid down in small local basins. Many tests have been made of salt and brines from borings in the area treated in this report, and inva-* riably the potassium content has been far too low to have any com- mercial significance. However, the districts not yet explored by borings are very extensive, and there is a possibility that commercial deposits of potassium salts will yet be found. Such a discovery ii not likely to be made, however, unless there is careful collection and testing of samples of salts and brines.

Age.

The great salt succession occurs undoubtedly in the Penniafl series, in beds which belong to the Manzano group in New Mexici and the Marion formation in Kansas. The classification of the in Kansas is made by the geologists of that State. The section ce the rocks of central Kansas (PI. XXII) shows the stratigrapfaii relations. From the evidence in New Mexico it is certain that thi salt is in the underground extension of the Manzano deposits, whic) imderlie the Triassic in the eastern part of the State. The crosi section in figure 38 (p. 220) shows the broader relations to th6 structure and stratigraphy.

Stratigraphic Relations.

The salt beds occur in a succession of red shales and sandstones and are associated with more or less gypsum, anhydrite, dolomite, and limestone. The salt is in bodies that vary in thickness and are doubts less lenticular. The records are not comparable in detail, althougl no doubt part of the diversity is due to the imperfections in th< records themselves. In some areas apparently there is an upper and a lower series of salt measures, and some of the holes probably did not reach the lower series.

The records given in this report illustrate the principal features of the stratigraphic relations of the salt measures, especially the two de- tailed sections of shafts at Lyons and Little Biver, Kans. (p. — Unfortunately many of the records do not state the true nature of the beds, failing particularly to recognize anhydrite, which in many records is reported as limestone or other rock. In Kansas there

Permiak Salt Deposits Of South-Cektkal States. 207

appears to be but little anhydrite or gypsum interbedded in the salt measures or closely associated with them, although thick deposits of gypsum are reported from both higher and lower horizons. In Okla- homa, Texas, and New Mexico gypsum and anhydrite occur abun- dantly in close association with the salt, notably at Carlsbad, where the main body of salt is overlain by 185 feet of anhydrite and under- lain by 1,325 feet of it With the present lack of knowledge as to the true nature of the materials penetrated in most of the borings it is not possible to recognize any definite order of the strata in tiie salt succession.

Structure.

In general, the great Permian salt deposit lies in a wide, flat, shallow syncline, and the thickest salt beds occupy approximately the bottom of the basin. There are also local structural features of various kinds, most of which have not been determined, especially in the wide area of the Staked Plains, where the strata are deeply buried beneath sands of Tertiary age. It may be that the basin structure has persisted from Permian time and influenced the location of the sea from which the salt was deposited. This question, as affecting the western Texas area, has been discussed by Udden.

Kansas.

Many published data show that a continuous body of thick salt beds underlies an area of at least 7,000 square miles in central Kansas. The salt is worked as a commercial product at several localities, notably near Hutchinson and Lyons, which are the centers of the industry. The sections in Plate XXII show the principal relations of the deposit as determined by borings. The salt measures, which are from 200 to 400 feet thick in the major deposits, are regarded as an upper member of the Marion formation, of Permian age. They are overlain by 200 to 400 feet of the Wellington shale, which separates them from the Permian 'Bed Beds" (Cimarron group). The salt thins out toward the east and presumably also toward the north, but it may extend to the Nebraska line. Its relations to the northwest and west are not known, for beyond Great Bend the deepest wells have not reached it.

The principal features of the Kansas salt measures are shown in Plates XXII and XXIII and figures 31 to 33. Some of the details are taken from the report by Kirk and Haworth, and others have been obtained from the drillers.

Udden, J. A., Potash in the Texas Permian : Texas Unlr. Boll. 17, p. 61, 1916. 'Kirk, M. Z., and Haworth, SraemnB Salt: Kansas UnJy. Qeol. Survej Bftlneral Re- Kmrces, 1898.

208 CONTRIBtTTIONS TO ECONOttlC GEOLOGY. 1930, PAKT L

At Anthony the salt beds are 415 feet thick (depth, 946 to 11 and 1,360 to 1,490 feet) ; at Kingman, S68 feet thick (depth, 665 to 1,028 feet) ; at Hutchinson, 380 feet thick (depth, 430 to 810 feet); at Lyons, 275 feet thick {depth, 793 to 1,068 feet); at Kanopolis, 250 feet thick (depth, 630 to 880 feet) ; and at Wellington, 60 feet thick (depth, 239 to 289 feet). Wells at Arlington, 650 to 1,000 feet deep, were in salt at the bottom, and the record of the 1,365- foot hole at Great Bend reported 125 feet of salt and shale at the bottom. Holes at Bago and Xickerson pene- trated the beds for some distance. The thinning of the salt to the east is I ndi shown by thei records of the Welling- ton and McPherson wes. Appar- ently it does not quite reach the sur- face in central Kansas, although probably the salt springs at Grenda are at or near the outcrop of the salt beds. A record of the McPherson boring is given In figure 31. The following table gives the principal data available as to wells in the south-central part of the State :

Borinffs in tough-central Kangaii Khich penetrated salt 1>edg,

208 cowTEiBtmoNs TO :

At Anthony the eali hed and 150 to 1,490 feet) ; M

Fievu 81.— acord of boring a1 HcPbenon, Kani.

N.

salt beds. A record of th

The following table give the south-centrat part of t

Boringi in louth-oen

h in

AhInd,io.l7,T.3ia.,R.I3W

lOmuaU. SE. inc. 10,T. 30 B., B.igl

CrUflolil,c.lS,T.a8.,E.W

Authonf

Kingmui

Pebmiak Salt Deposits Of South-Centbal States. 209.

m m m mi

s

ao

g

I

Co Co

cS

s

mr

% 2 g

J i

.J

S '5

kiilMj

210 CONTBIBUnOKS TO ECOKOMIG GEOLOGY, 192Q, PABT I.

In the two following records are given the details of the succession of salt and overlying and interbedded strata in the central Kansas region. They are much more accurate than well records.

Record of shaft of Lyons Book 8aU Co., Lyons, Bioe County, Kans.*

Thick- nes8.

Depth.

Boil and 8nd7 loam

Sandy loam

Sandstone

Variflcated days

Blue clay

Black shale

Gray sandstone

Bedsandstone

Red sandy shale

Red day

Softlimestone

Gypsum andlimestone

Blue shale

Red and blue shale, mixed with gypsum

Dark-gray shale

Reddish-gray shale.

Dark-gray shale

Dark-gray salt and rock

Light-gray salt rock

Dark-gray saltroek

Light-fray salt rock

Reddish-gray salt rock

Gray shale t

Dark-gray salt rock

Gray shale and salt, mixed.

Gray shale

Lit-gray salt rocks

Rock salt and shale

Light-gray saltroek

Gray shale

Light-gray saltroek

Shale

Light-gray salt rock

Shale andsalt rock, mixed

Dark salt and shale

Crystalsalt

Shale and salt.

Dark salt and shale

Dark-red shale

Dark salt and rock

Dark salt, with crystals

Rock and salt and shale.

Dark salt and shale

Crystalsalt

Shale

Light-gray salt

Shale

Light-gray salt and a little shale

a £i7k, If. Z., and Hawortfa, Erasnms, op.dt., p. 88.

U. 8. Geological Survj

Sec. 17, T. 31 S.,

R. 23 W., 12 miles

north of Ashland,

Clark County, Kans.

fv..

BULLETIN 715 PLATE XXni

Sec. 1. T. 19 N.,

R.25W.,nearAmett,

Ellis County. Okla.

Feet

,

iSfiO

Red beds

Salt, 226 feet Redahale

&lt. 5 feet jKed shale Salt. 5 feet

Shales, red and

Limestone and It, 16 feet

: Shales, red and

um, some red ahals

?, blue and brown

stone, heavy brine

;edsfaa)e, some andgypsam

40 feet and red shale

[Shales, blue and

Salt red. 7 feet )Shale and Innestoi

'Salt. 130 feet, sol shale and limest

ed shale, some tone and gypsum

66 feet fe, green to brown

rt- — TTT.-t—--

Salt, 45 feet, etc. Limestone and shi Salt. 15 feet j

' Limestone and sh

Limestone and Sandstone

Limestone and sai

Limestone and 8ha|

Shale, brown to red. some sandstone

Iioo±

Gypsum

'Shale, brown,some salt

<Salt. 10 feet

. Sandstone and shale

VSalt, 100 feet

Salt and shale

J: ) Shale. red.and conglomerate

FEBUIA2I iUI DEPOSITS OF SODTH-CBNTBAL STATES. 211

I hii

212 CONTRIBUTIONS TO ECONOMIC GB0L007, 1920, PAST I. Becortl of haft of Btandard Bait Co., Little Biver, Rice County, Kantfi

TMok-

IXpth.

JtM.

r

!

h

la 6

Kirk, If. Z., and Baworth, ErrMouw, op. dt., p. DS.

A boring in progress in sec. 35, T. 21 S., R. 30 W., 25 miles north- east of Garden City, reached & depth of 2,200 feet late in 1919. It passed out of the base of the Dakota sandstone at about 810 feet and finally penetrated several hundred feet of red shale. Strong brines were found at intervals from 1,135 to 1,224 feet, but do beds of salt were reported. Salt beds may exist in this locality, but it is probable that the main salt horizon of the central part of the State was not reached.

0, B. Obolooical Survey

Sec. T. 28 N.,

R. 17 W., 28 miles

northwest of Aiva,

Woods County, Okla.

€0 S50

Red rodo compact

Nw,

R.

nort]

Woo

Fecf &o

37a

Sandstond

'

lOM)

S'tQ

SBSBHiS

Red rocks with limestone 6i5

I Limestones and shales, I some red

Red shale

iKedciay and salt Tlt.40feet

Shale, blue and red

J

20ti

299f 3Zii

39K RECOl

Pebmiai7 Salt Deposits Of South-Central States. 218

A 3,055-foot boring in sec. 11, T. 85 S., E. 2 E., in the southeast comer of Sumner C!ounty, apparently was sunk beyond the eastern edge of the salt deposit, but no salt is mentioned in the record.' Red materials extend from the surface to 773 feet, and gypsum from 773 to 993 feet, with shale and limestone below.

OKIiAHOMA.

The great Permian salt deposit has been penetrated by numerous borings in western Oklahoma, but useful data regarding the salt beds have been given in only a few of the records. R. K. Bailey, of the tJnited States Geological Survey, visited several of the wells in 1917 and 1918 and obtained records and samples for testing. The greatest thicknesses of salt reported were 580 feet at Gate and 540 feet in the Cosden well, northwest of Alva. Smaller amounts were reported in the records of other holes in Harper, Woods, Alfalfa, Woodward, and Ellis coimties. Several deep holes, such as those near Enid and Fairview, Okla., and Quanah, Tex., report little or no salt, but this may be due to imperfect observations. For the same reason the reported thickness at Woodward, Amett, Alva, and Laveme may be too low. The following are the principal data available :

Deep hol€9 in western Oklahoma in the records of which thick heda of aU

were reported.

Locality.

Depth (feet).

Msterialii.

Liivne.

AirayXiear

Ahra, 20 miles north of west of, NW. c. R, T. 27 N., R. 10 W.

Alvs28 mile northwest of, NW. aeo.

.2.T.28N., R. 17W.

AlWfti County, sec. 27, T. 29 N., R. 9 W..

Gate, three-fourths mile east of, sec. 8, T.5N.,R.28E.

Woodward, 8 miles southwest of, sec. 8,

T. 21 N., R. 21 E. Antt.aec.l,T.19N.,R.25E ,

Cimarron County, sec. 22, T. 4 N,, R. 1 E.

MacnoliaCoimty, 8 miles north of Sayie, Beckham Coanty.

i,oao

8,681 8,915

1,830 3,725

2,840

fll,n5 1,740 2,090

o 1,780

Red beds to 700 feet, with salt at 420-70 feet, eyusam at 480-490 feet, and salt at 490-500 feet; shale (some of it red) at 700-1,820 feet.

Red beds to 1,100 feet; salt at 1560-140 and 1,680- 1,700 feet; shale and salt at 1,780-1,800 toet.

SiJt at 1,020-1,030, 1,035-1,045, 1,050-1,170. 1,900- 2,040, 2,m2-2,100, 2,115-2,230. and 2.256-2,800 feet; ''sand and salt" at 1,860-1.900 feet; brines at 2,010, VSa 8,175, 3,250, 3,333, 8,835, and 3,915 feet. (See

Salt 'at 1,0>-1,080 feet: clay and salt at Mi-irTO and 1.010-1,ORO feet. (See lop, PI. XXIV.)

Red beds to 780 feet; shales and limestones below. Salt at 880-920, 1,100-1,120, 1,230-1,250, 1,260-1,280, UOl-1,830, and 1,340-1,427 feet. (See log, PI.

Salt at 4(-567, 572-585, 620-630. 670-720, 1,045-1,048,

1,160-1,166, 1,252-1,288, 1,290-1,895, 1,405-1,430,

1,990-1,997, 2.010-2,020, 2.035-2,040, 2,060-2,063,

2,072-2,087, and 2,107-2.190 feet: anhydrite at 2,370-

. 2!395feet. (See log, PI. XXIIT.)

Salt at 1,500-1,645 feet, under red beds.

Salt at 1.430-1.440, 1,496-1.596. and 1,685-1,660 feet.

(SceloK, PI. XXITI.) No salt mentioned in record, but outside reports refer

to salt. Salt samples at 1,345-1,850, 1,395-1,416, and 1,500-1,510

foet.

a In profress.

*Kanaaa Univ. Qeol. Surrey BuU. 8, p. 845, 1917,

214 C0Ntbibx7Ti0Ns To Economic Geology, 1990, Part I.

Deep borings in ioestem Oklahoma in the records of ioMeh Utile or no eaU

was reported.

LocaUty.

Depth (fct).

Materials.

Enid

8,365

8,396

1,588 2,030 1,758

2,010

2,507 3,475 2,015 2,135

3,315

Red beds at 48-1.000 feet, alternating Umertooe and

Cannte, near, sec. 18, T. 11 N., R. 10 W. . AUalfa County, 8W. see. IS, T. 28 N.,

R. 11 W. Cimarron Ccxmty, see. 22, T. 5 N., R. 5 B . Cimarron County, aec. 22. T. 4 N.R. 1 E. South Painriew, sec. SsTt. 20 N.. R. 12 E .

Leedy . 4 miles northwest oL BE. sec. 27,

T. 17 N., R. 21 W. Cilnt<. Ciuter CoontY

shale at 1.000-8,365 feet, with few red sandstones

at intervals between 2,165 and 2,660 feet. Shale and sandstone, red and nay. Red and brown rocks to 830 teei; UmestoiM, sandnone,

and shale below. Red beds, with gypeom. Red beds to 1,940 feet; Umestone below. Red shale to l,flOO feet; smaU bed of saHat about 1,800

feet. Poor record.

Red beds, with seme blue shale.

Ellis County, sec. 1. T. 19 N., R. 25 W.. .

Oace, sec. 2, T. 21 N., R. 24 W

Ma)orCoonly,8ec.33,T.20N.,R.12W.. Cititer, CiiiitAr Coimty- .,.,,- r . - , .

Red beds!

Do. Red beds to 1,600 fltset; limestone and shale below. Red beds.

Greer County, 8W. sec. 24, T. 7 N., R.

21 W. Kl Rftno, Canadian County

Red and brown beds. Do. .

Texas.

Data from borings. — The presence of salt under the greater part of western Texas is known from many deep borings, most of which have been described by TJdden.* The record of the hole bored by the United States Geological Survey south of Amarillo and data from other holes since bored add to the evidence. However, in this area, as elsewhere, doubtless the salt has been penetrated by some holes whose drillers have failed to report salt or have not noted the thickness of the several beds. The greatest thickness reported is at Adrian, where the aggregate is 700 feet; other notable records are 680 feet in the Miller hole, 645 feet in the Boden well, and 460 feet or more in the United States Geological Survey well. The following are the principal data available regarding salt deposits in wells in western Texas (see also fig. 34) :

Deep borings in western Texas in the records of tchich salt beds were reported.

Locality.

Adrian, Oldham County, 2 miles south- west of. Boden field , Potter County

MUIer randi, Palo Duro Canyon, 7 miles above Canyon, Randall County.

United States Oeoiofical Survey boring. Cliff side, 6 miles northwestof Amarillo, Potter County.

McLean, Gray County, half a milesouth of.

2,675

1,703

1,670

Principal materials.

Salt at 1,185-10 and 2,240-2,440 feet; salt and gyp- vam at 750-1,185 and 1,370-1,517 feet. (See loff!)

Salt at 640-645j050-65, 701-710, 720-730, Jb-wSi 030- 950, 1,006-1,230, 1,290-1,460, and 1,090-1,720 feet; salt and silt at 730-745 feet, a few thin layers at 1,720-2,010 feet. '

Saltand red shale at 940-1,170 feet; salt at 1,300-1,430, 1,435-1,600, 1,508-1,530. 1,570-1,610, 1,635-1,680, 1,710-1,720, 1,830-1,950, 2,025-2,206, 2,212-2315, and

Salt and shale at*66&-860 feet; salt at 972-1,058, 1,116- 1,322, and 1,392-1,440 feet; salt and sandstone at 1,475-1 ,538feet; anhydrite, shale, and salt at 1,581- 1,703 feet.

Red beds to 1,650 feet at least; considerable salt to 1,670 feet.

Udden, J. A., Potash in the Texas Permian : Texaa Unir, BulL 17, 69 pp., 1015.

FEBMIAIT SALT DBFOSIIS OF SOTrTH-CBNTRAl, SIATBS. 215

A 1

1 . iHll 1

216 OONTBIBUnONS TO ECONOMIC GEOIiOGY, 1920, PAST I.

Deep hoHngg toestem Texa9 in the records of which salt beds were reported —

Contlnned.

LocaUty.

Childress, Childress County.

JustioelmiK. Oam County. Spur, Dickens County

Poet. Oam County

Snyder, Scurry County.

Upland , Upton County

Buena viste, Peoos County .

Scoggln, Kent County-

Shamrock, Wheeler County.

Hangood well, 28 miles north of Ama-

rillo, Potter County. ICasterson well No. 2, 28 miles north of

Amarillo, Potter County, liasterson well No. 3, 28 miles north of

Amarillo. Potter Countv. well, 28 miles north of Amarillo,

Potter County. Ranch well No. 1, 28 miles north of Ama-

rlllo, Potter County.

Pullman, Potter County

Memphis, Hall County, 5 miles south of.

Hollowfleld No. 1 welL Hall County

Oil Issues No. 1 well, Oldham County. . .

Hdbrook No. 1 well, Potter County

W. & P. Masterson well. Potter County . .

TuGk- wellotter County. , Palo Duro well, Randall County ,

1,283

4,489

1,074 2,500

1,300

1,114

2,027

2,125

2,195

3,010

1,900

1,276 1,908

2,395

1,185

(2,020

a 2, 980

3,920 2,635

Pnncipal mateilali.

Salt at 84ft-l,098, 1,118-1,138, 1,17-1,203, and 1,31-

l,238feet. (SeelqK,flE.35.) Sal t at 585-600 and 770-785 feet and below. Salt at 570-80, 633-638/ and 732-741 feet; modi sUt

withshales at0OO-l,2S0feet. Saltatl,6S6-l,674feet. Salt rock at 655-705, 720-765, 770-775, 785-800, m-

1,020, 1,570-1 .600. and 1.660-1,806 feet. Probably In salt at 1,300 feet. Some rock sal t at 962 and 975 feet. Salt at intervals from 880 to 961 feet. Shale and salt rock " at 9S&-l,090feet and near 1,380

feet. (See log, fig. 36.) Salt in shale at 840-1,300 feet. (See log, fig. 37.)

No salt reported.

Salt at l,32S-l,415feet; "lime salt" at 1,415-1,585 fest.

Salt 200 feet or more at Intervals from 700 to 2;

feet. Red bMls at 2,835 to 8,010 foet. Salt at 88&-020, 1,370-1,382, 1,505-1,560, and 1,S-

l,670feet. Rocksaltat 1,143-1, 160 feet. Salt rock, etc., at 560-770 and 1,UO-1,290 feet: hard

red and blue shale and salt at l,39O-l,580feet. Salt at 730-735. l,08O>l,320, and M7D-1,580 feet. Salt 80 feet at hitervals from 660 to 1,140 feet. Salt 160 feet at Intervals from 956 to 1,630 feet. Salt at 1,480-1,610, 1/570-1,700, 2,510-2,515, and 2,855-

2 755 feet. Salt 200 feet at Intervals from 666 to 2,460 feet. Salt 140 feet at Intervals from 310 to 2,630 feet.

a In 1920 still dziUing in soft red rocks, but granite is reported in borings near by.

Deep borings in tvestem Texas in the records of which little or no salt uoas

reported.

Locality.

Glenrio, Deaf Smith (bounty

San Angelo, Tom Oreen County, 4 miles

west of. littlefleld, Hockley Cotmty, midway on

north line of league 730.

Toyah. Reeves (bounty

Quanan, Hardeman Cxxinty

Materials.

Red beds, sandstone, dolomite, and anhydrite. No red beds below 183 feet; gray limestone and swe.

Red beds; some lime and sand.

Red beds, gypsum, limestone, sandstone, and sbale- Red beds to 1,105 feet, possibly lower; no salt.

Spur, — According to Udden,® the 4,489-foot hole bored at Spur in 1909 to 1913 revealed three beds of salt at 570 to 580, 633 to 638, and 732 to 741 feet. The lower sands of the red beds, from 900 to 1,250 feet, contained from 15 to 67 per cent of salt, the average being 36 per cent, equivalent to about 105 feet of solid salt. All the salt is in red beds consisting of layers of red sandy shale containing 18 beds of anhydrite and gypsum. A bed of anhydrite extends from 330 to 403 feet, and other thick beds occur at 540 to 570, 603 to 628, and 1,175 to 1,200 feet. Gypsum beds 1 to 15 feet thick occur in the upper 285 feet of the boring. The combined thickness of gypsum and anhydrite is stated by Udden to be at least 250 feet. Below 1,250 feet the hole is in

6 Uddn, J. A., The deep boring at Spur : Txaa Univ. Bull. 363, ad. ser. 28, 1011

Febmiait Salt Deposits 0? South-Okktbai< States. 217

dolomite interrupted by minor amounts of sandstone, shale, and anhydrite.

McLean. — Udden gives a detailed driller's record of the 1,870-foot boring of the Panhandle Oil & Oaa Co. half a mile south of McLean, but it contains meager data as to salt. Gypsum and salt are recorded at 15 to feet; salt and whit* lime rock

at to feet; hard and soft wdJST"

lime, red shale, and salt at 1,800 to 1,360 feet; and red-brown shale and salt at

l,589to 1,593 feet It is sUted that beds

of salt of " considerable thickness were

penetrated" ending at 1,260 feet and m

somewhat above 1,670 feet. Large

amounts of gypsum and anhydrite ud rrfam

were found.

Kenty Scurn/, and Garza cowitiee. — Udden' gives some data regarding the records of borings at Post, Scoggin, Justiceburg, and Snyder which indicate that the salt bed is present but apparently thinner tlian in other regions to the north. However, most of the records are not very specific as to the amount of salt penetrated.

The Double U boring, near Post,

ended in salt at 1,672 to 1,674 feet, and

dudUiM salt appears to have occurred in small

bodies down to 1,344 feet, most of it

mixed with sand, clay, and anhydrite.

The 2,600-foot hole at Snyder pene- la ud tdt rfc trated several beds o5 " ealt rock " below Mtiind. 665 feet, possibly aggregating 100 feet.

' Alternating thick beds of salt and red

™ rocks occurred from 690 to 800 feet, clay

mixed with salt from 870 to 1,020 feet,

feet. The salt rock at 2,130 to 2,160 feet

was the lowest salt bed,

Piaou se.— Becord of borinK near The Scoggin boring afforded meager

8h,nirk.Tex. jata, but it was reported that salt beds

were penetrated at intervals from 880 to 961 feet.

The 600.foot well of the Atchison, Topeka & Santa Fe Railway at Justiceburg was in Permian red shale with "sheets of rock salt" from 311 to 685 feet and pure rock salt " from 586 to 600 feet.

Uddoi, J. A., PotBbln Um Texas PemiUn : Txu . BuIL IT, pp. l-23, leiB. 'Idem, pp. 2B-ST, 1278°— 21 16

218 Contributions To Economic Geology, 19, Pakt I.

Big Spring. — It is reported that the well sunk in the courthouse 7ard at Big Spring in 1892 found salt water at 500 feet and salt from about 900 feet to about 1,340 feet.

WeU north of Arruirillo. — The record of the well bored by the United States Geological Surrey 6 miles northwest of AmariUo is given in figure 34. It penetrated 160 feet or more of salt in several beds between 680 and 1,600 feet One bed of nearly pure salt was 150 feet thick.

The Hapgood well, bored to a depth of 2,396 feet in section 65,

block 018, 28 miles north of Amarillo, had the record shown in

figure 37. The record shows red shale with some salt from 840 to

1,300 feet, but the total amount is not given. The hole was later

deepened to 2,395 feet, but although no more salt was reported the

record is too general to be useful. Several other holes were sunk in

the same vicinity. Masterton well No. 3

I of the Amarillo Oil & Gas Co., in sec. 102,

1, block 018, was completed at 2,195 feet;

the only salt reported was at 1,325 to

1,415 feet followed by "lime salt" at

1,415 to 1,585 feet. Masterson well No. 2,

<fa)M in sec. 70 of the same block, was 2,125

JJjJlJ feet deep, and its record shows no salt.

The record of Bivins well No. 1 of the

same company, in sec. 106, block 46, 1,535

feet deep, reports salt and red rock at 692

to 940 feet, salt at 1,145 to 1,188 feet, and

boring In see. 80. block ois. Salt, gypsum, and slate at 1,200 to 1,330

28 miiM nocth of Amartiio. feet. The record of Ranch Creek well No.

, 1, 1,900 feet deep, reports salt at 885 to

920, 1,370 to 1,382, 1505 to 1,550, and 1,590 to 1,670 feetl72 feet in

all. The drillers of the Miller well at Pullman, Potter County, which

had reached a depth of 1,276 feet November 8, 1919, reported salt at

1,143 to 1,160 feet.

Memphis. — The 1,908-foot boring 5 miles south of Memphis passed through an extensive series of salt-bearing strata, but the record is so general that the thickness of salt can not be ascertained. The amount was probably considerable.

Qfionah. — The absence of salt in the record of the 1,160-foot hole at Quanah, in Hardeman County, may indicate either that the salt measures do not extend that far east or that they have been over- looked by the drillers.

San Angelo.—The 3,967-foot hole at San Angelo, in Tom Green

County, is apparently in the same category with the Quanah boring.

Buena Vista. — The 1,414- foot hole at Buena Vista, in Pecos County,

according to a report given to Udden, penetrated rock salt at 962 and

Permian Salt Deposits Of South-Central States. 219

975 feet, and he states regarding the Permian red beds from 588 feet down : It is probable that these contain more salt than would appear from the two isolated mentions of rock salt by the driller, who stated that cuttings from some parts of the borings were difficult to obtain and seemed to disappear before coming to the surface.' "

Upland. — boring at Upland, Upton County, reached a depth of 1,300 feet in 1913. According to Udden, the drillers reported salt and brine at 1,100 to 1,120 feet, and at 1,300 feet the cuttings were so scanty that probably a bed of salt or salt-bearing shale was pene- trated.

Reeves Covmiy. — Apparently no salt has been noted in the holes sunk for oil in Beeves County, although the upper strata penetrated are the red-bed succession of the Pecos Valley region. The 4,100- foot hole northwest of Toyah, described in detail by Udden,® began in the Comanche series and apparently penetrated beds of about the same age as those in the 2,820-foot hole at Carlsbad, N. Mex., 80 miles farther north, in which 633 feet of salt was found.

New Mexico.

General features, — Several bore holes indicate that an area of about 20,000 square miles in eastern New Mexico is underlain by the south- western extension of the great salt bed. Possibly the salt may extend northward under parts of Union, San Miguel, and Mora counties. In the 2,820- foot hole at Carlsbad the salt beds were found to be 633 feet thick, and the record of the hole north of Eoswell reported 526 feet of salt. Probably there is not a continuous sheet more than 500 feet thick under all of the eastern or southeastern part of the State, but it seems probable that a large area is underlain by the thick deposit. The limits can only be conjectured within the area under- lain by Permian rocks. No outcrops appear, although the salt de- posits near Estancia appear to be on the zone in which the horizon of the salt-bearing beds is near the surface. The great salt flat north of Van Horn, Tex., may also mark the proximity of this horizon to the surface. A section across the southeastern part of the State is given in figure 38.

Carlsbad. — In 1913 a large body of salt and anhydrite was found in a 2,820-foot test boring for oil in the NE. sec. 4, T. 22 S., R. 28 E., near Carlsbad. Samples from this well were tested chemi- cally by E. E. Lyder and W. A. Whitaker, at the University of Kansas. The record in figure 39 and other data were kindly fur-

"Udden, J. A.p opu dt., p. 30.

220 Contributions To Economic Geology, 1020, Part I.

Svx3X

ODDCaKMaK

PwptWD

ijb/

w,

§

o

a

nished by the late William H. Andrews. This record is remarkable in showing not only a very thick body of salt but a large amount

of anhydrite, features which do not appear in many records of wells in dif- ferent parts of the lower Pecos Valley in New Mexico.

In 1916-17 a boring 787 feet deep was made in the NW. sec. 21, T. 22 S., B. 27 E., about 6 miles southwest of the deep hole above described, by the Longyear Co., in a search for pot- ash, some traces of which had been found in the older boring. Samples were carefully collected and tested by R K. Bailey in the field laboratory of the United States Glogical Sur- vey at Amarillo, Tex. Red shales and gypsum extended to 165 feet, gypsum with a few red clay partings from 165 to 428 feet, solid anhydrite from 428 to 629 feet, and alternations of salt and anhydrite from 629 to 787 feet. The thickest body of salt extended from 743 to 775 feet. This record, so far as it goes, confirms the record of the up- per part of the 2,820-foot hole as given in figure 39.

Roswell region. — The 3,120- foot hole bored by the Toltec Oil Co. 13 miles north-northeast of Roswell penetrated 526 feet of salt in numerous thick beds interstratified in dolomite and anhy- drite, with small amounts of red and gray sandstone. The record in figure 40 is based on the driller's log, with data from a complete set of samples kindly furnished by the company and tested in the laboratory of the United States Geological Survey. 5 1 I § I § The record of the 2,943-foot hole in

east of Roswell, does not report any

salt, except 2 feet at a depth of 850 feet,

but presents the usual reiteration of such terms as "pink and red

rock," "limestone," "lime shells," which give scant information.

a

§

s

o

Ob

n

Ob

o

Os

a o

?

p

Permian Salt Deposits Of Soxtth-Centkal States. 221

Feet

Gypsum

Sandstone, red ihAle* and limestone

Anhydrite, 186 feet

Undoubtedly the hole passed through the salt and anhydrite succes- sion reported in other holes to the west and east* Much salt water was found, notably at 2,165 and 2,240 feet.

Arteaia region, — In a 601-foot hole on one of the Turkey Track ranches, 26 miles east of Artesia, near the northwest comer of T. 16 S., K. 30 E., salt was entered at 231 feet and continued to the bottom. In a well a few miles northeast of another of the Turkey Track ranches, 15 miles east of Artesia, the salt bed was entered at 281 feet, and 5 miles east of that ranch the salt was entered at 200 feet.

Lesbia. — 1,414-foot boring at Les- bia is reported to have penetrated salt at 700 feet and from 1500 to 1,300 feet"

TiuiUfncari. — The McGee test well for oil, being drilled in the SE. J sec. 27, T. 10 N., R. 31 E., 8i miles southeast of Tucumcari, penetrated rock salt at 1,100 to 1,135, 1,430 to 1,455, 2,372 to 2,377, and 3,220 to 3,225 feet. The strata below 1,455 feet as reported are 170 feet of red shale, 375 feet of gray limestone, 200 feet of brown shale, 280 feet of dark limestone, 650 feet of brown shale, 620 feet of red shale and limestone, and 194 feet of limestone, mostly dark, to the bottom of the hole at 4,014 feet (September, 1920).

Salt, 633 feet with some anhyurite

Ljmits.

a-=l

Ii Ii

Anhydrite, 1326 feet

Limestone and anhydrite

lameetone and aandstone

FioDBB 39. — Record of borinfr In the NE. i Bec.4, T. 22 S.,R.28 E., 8 miles east of Carlsbad, N. Mex.

The southern limit of the salt deposit in Texas has been discussed in connec- tion with the records at Spur, Buena Vista, Post, etc. (p. 21 6). The eastern limit is probably about 50 miles west of the outcrop zone of the basal beds of the Permian in western Texas, Oklahoma, and Kansas, and in places it is marked by salt marshes and springs. Apparently the salt thins rapidly toward the outcrop zone, for the records of wells at its eastern margin report small thicknesses. To the north in Kansas the limit is unknown, and the beds may extend to Nebraska. The rate of thinning is gradual, for the salt is more than 200 feet thick at Wilson and Kanopolis. At McPherson it has thinned to 125 feet. Some holes in Kansas north of latitude 39° have failed to report salt, but that is not conclusive evidence of its absence. The

TtauM UniT. BiilL 17, p. 8, 1915.

222 CONTBIBUnOKS TO ECONOMIC OBOLOGT, 1B, PAST I.

western extension of the depoeit in Kansas is also problematic, for the salt measures sink deeper in that direction and hare not been penetrated. The 165- foot hole at Great Bend reached the salt, but holes at La Crosse, Dodge, Jetmore, and northeast of Garden are far too shallow to penetrate it.

The failure to find salt in the two holes 1,583 and 2,030 feet deep in Cimarron County, Okla., may indicate that the salt is absent, was not recorded, or lies deeper than in the region to the east. It is stated by a local observer that some salt was penetrated in the 2,030- r foot hole in the western part of the

county.

In New Mexico the salt is so thick at Carlsbad and north of Roswell that its western margin must be some dis- tance west of Pecos River. Appar- ently no salt exists in the Sacramento Mountains; therefore the western mar- gin may be near longitude 106°, in Otero, Lincoln, and Chaves countiee.

Abba And Tonnage.

The area known to be underlain by ' the great Permian salt deposit is not far from 100,000 square miles. If it extends to the southeast comer of Colo- rado and northward to Nebraska its area is considerably greater.

On the assumption of an average thickness of 200 feet of salt, the gross quantity in the area of 100,000 square miles is about 30,000 billion tons.

Origin.

FloDUi 40, — Becord of boiins io iec

. 24 E., 13 miiea The Salt beds of this great deposit

nrHiwBBtl N Mm

doubtless originated m the evapora- tion of ocean water occupying a basin or series of basins for a considerable part of Permian time. The irregular distribution oi the gypsum and anhydrite in relation to the salt indicates remark- able oscillations in shorelines and complexity of local conditions, and the presence of limestone beds at intervals shows that deepei marine submergences occurred from time to time. It is certain thai a considerable supply of sea water was necessary for the accumula- tion of deposits of salt several hundred feet thick over a vast area.

norUi-DottheaBt of Boswetl, N. Uex.

Permian $Alt Deposits Of South-Central States. 223

A figure of interest in this connection is the fact that a body of sea water 100 feet deep evaporating to dryness deposits the greater part of its calcium sulphate, amounting to about 2 inches under ordinary conditions, and then deposits about 3 eet of sodium chloride. That the waters were shallow much of the time is shown by the large amount of shale and sandstone present, in part mixed with the salt. Most of these sedimentary materials are red, but some are of gray and other tints.

The studies by J. Usiglio on the deposition of salts from sea water are of interest in this connection. He concentrated water from the Mediterranean Sea, containing 3.77 per cent of total solids, to about one-SLxtieth of its volume and obtained the following results:

Salts laid dorcn in concentration of sea water,

[Parts per thousand.]

Spedflo grsTity.

Volume.

FeiOj.

CaCOi.

GaS04.

NaCl.

MgCl,.

NaBr.

KCl.

Trace.

Trace.

1,1087

i.ieo4

1.1732 .-

1 0778. . ..

1.3060 - .-

Total deposit . . Saltsrfimainingin so- lution ... .

Sum.

AnnaleB . et physi, 3d ser., voL 27, pp. 92-172, 1849.

Index-

A.

Page. Abegg, Frank, acknowledgment to — 126 Abfltetn, H. T., dnnabar claims of. In the Yellow Pine dis- trict, Idaho 81-82

Acknowledgments for aid 49, 73,

86, 04, 126, 172 Alberta mine, Mogollon district, N.

Mez., description of 196

Alex and Rudolf potash mine, Al- sace, history and de- scription of 41-42

Aliace, potash deposits in, access to. 18 potash deposits in, area under- lain by 19

bibliography of 49-6

discovery of 19-20

geology of 21-24

importance of - — 17

location of 18

mining of 28-44

nature and quality of 25-26

origin of 28-24,46-48

output from 20-21

ownership of 20,29-30,

88, 3S. 36, 38, 89, 41, 42-48

reserves of 26-28

shipping facilities for 18, 21

specimens from 26

treatment of 44-45

potash from, analyses of 32, 34, 85

cost of producing 45-6

AnuriUo, Tex., depths to salt beds

near 214, 216, 218

Aae potash mine, Alsace, equip- ment of 29,30,33

history and situation of.- 28-29, 80-81

ownership of 29-30

potash beds In 81-38

shaft house and head frame at,

plate showing 30

storage and refinery buildings

of, plate showing 80

Andrews, William H., acknowledg- ment to 219-220

Anna potash mine, Alsace, history

and description of 35-36

Antimony, occurrence of, in the Yellow Pine district, Idaho 83

Argentlte, occurrence of, in the

Divide district, Nev.. 159. 168

Artesla region, N. Mez., depth to

salt beds in 221

Atkins, D. C, acknowledgment to 126

B.

Baer, Q. C, acknowledgment to 172

Barbour, E. H., acknowledgment to.. 126 Barcelona province, Spain, potash

in 1-16

BatesvUle manganese district. Ark.,

earlier publications on. 94-05

field work in 94

folds and faults in 105

geologic map of 94

geology of 9&-105

location and geography

of 93-94,96-07

ore deposits in, extent of 123-124

five types of 106-119

minerals in 106-108

outcrops of 119

relation of, to rock struc ture and surface

features 119-120

section through 100

ores in, chemical composition

of 120-122

grades of 115-116

suitability of 122-128

Paleozoic rocks in, sections of 98

production' in 96

Berry, R. W., topographic work by, on the Mogollon dis- trict, N. Mex 172

Big Spring, Tex., depth to salt beds

Botsford, C. A., acknowledgment to 172

Box Butte County, Nebr., potash

lakes in 129

potash resources in 131

Boyer, Ben, manganese claims of 66

Boyer A Frankenberry, manganese

claims of 65-66

Braunite, description of 107

Brougher, H. C, silver lode in the Divide district, Nev.,

discovered by 149, 165

Buena Vista, Tex., depth to salt

beds at 216, 218-219

Buttons," manganese, nature of. 109-110

Cardona, Spain, location of . . 1-2, 4

mining of salt at 6

outcrop of rock salt at, plate

showing : 4

outcrop of tilted sandstones and gypsum at, plate show- ing 6

Index.

Cardona, Spain, potaah field near. Page.

aooess to 1-2

potaah field near, geologic

features of 5-7

owners of concessions In 9-4

salt beds at, folding of 7

folding of, plate showing 6

potassium In 7-8

salt mountain at, description of. 4-6

plate showing 4

Cardoner RWer, Spain, sources of

water in 6

rallej of, structural geology of- 9

Carlsbad, N. Mez., depth to salt beds

at 219-220

Cason shale, nature and occurrence of, In the Batesville

district. Ark 101-104

replacement deposits In 109-110

Cerargyrlte, occurrence of, in the

DlTlde district, Nev.. 169, 16&-164, 168 Chaffee County, Colo., manganese de- posits in 6a-64

manganese mines in 64-67

Cinnabar. See Mercury.

Clifton prospect, MogoUon district,

N. Mex., description of- 199

Colorado, manganese In 61-72

Colorado Manganese Mining & Smelt- 1 n g Co., manganese

claims of 68-72

Confidence mine, Mogollon district,

N. Mez.. description of. 202

▼ertlcal projection of 203

Condra, G. B., acknowledgment to 126

information on potash collected

by 126

estimate by, on potash resources

of Nebraska 126, 130

Cooney, James, discovery and devel- opment by. In ' New

Mexico 172

Cooney district. Bee Mogollon dis- trict. Cooney mine, Mogollon district, N.

Mex., description of- 195-196 Copper, occurrence of. In the Mo- gollon district, N. Mex— 189-192, 194. 196. 196

D.

Darton, N. H., Permian salt deposits of the south - central United States 206-223

Deadwood mine, Mogollon district,

N. Mex., description of- 200

Deep Down mine, Mogollon district,

N. Mox., description of- 198

Divide andesite, nature and distri- bution of, In the Divide

district, Nev 166-166

silver-bearing lodes in 161

Divide district, Nev., depth of cross

cuts in 160

discovery of silver In 147. 148-149

Divide district, Nev., eKpIoratioa Page.

and development in 149-150

geography of 148

geologic map of 150

geology of 150-15S

igneous rocks in , 151-152

mines and prospects In 164-170

ore dKMits in, comparison of, with those at Tonopah,

Nev 162-164

silver -bearing lodes in, nature

and occurrence of 168-161

origin of 161

summary of facts concerning. 147-148

water supply of 150

Divide Extension mine, Nev., de- scription of 167-168

Douglass Mountain anticline, Mont.

phosphate rock in 14

Dunkleberg Ridge anticline, Mont,

phosphate rock in 144, 145

E.

Eberle mine, Mogollon district, N.

Mex., description of.. 199-200

Bmerson, C. L., acknowledgment to 126

Erickson, ID. Theodore, analyses by— 8, 32.

133. 136. 186, 137

Eureka prospect, Mogollon district, N. Mex., description of 199

P.

Fairchlld, J. Q., analyses by 107, 159

Ferguson, Henry G., The Mogollon

district, N. Mex 171-204

Fern Quicksilver Mining Co., claims of, on Fern Creek,

Idaho 80

Fernvale limestone, nature and oc- currence of, in the Batesville district.

Ark 99-101

replacement deposits in 110-113

residual deposits derived

from 112-llT

Fraction rhyolite breccia, correla- tion of, in the Divide

district, Nev 152-153

nature and occurrence of 150-151

silver-bearing lodes In 158

structure and thickness of 153-lM

G.

Gale, noyt S., Potash deposits in

Spain 1-1

The potash deposits of Alsace.. 17-65

Galpin & Vreeland, manganese

claims of

Garza County, Tex., depth to salt

beds In 216,217

Gibson, Paris, aclmowledgment to—

Index.

Page. OoJd, occurrence of. In the Divide

diBtrlct, Nev 102

occurrence of. In the Mogollon

district. N. Mex 106, 198,

109, 200, 201. 202, 208 Gold Ifonntaln district, Ney. See

Divide district. Ney. Grant, WUbnr H., acknowledgment

to 172

Oraton, L. C, dted 178, 196

Ounnison County, Colo., manganese

claims In 67-68

Oypfun, tilted, .overlying salt beds

at Cardona, Spain,

plate showing 6

Haldane. W. G., acknowledgment to 126

Hansmannlte, description of 106-107

occurrence of. in Colorado 68,68

Haworth. Erasmus, Kirk, M. Z.. and,

cited 207, 210. 212

Hematite, deposits of, near Stanford.

Mont 86-92

ores cont&lninc;. analyses of 91

Hicks, W. B., Potash resources of

Nebraska 126-189

Higham, W., ft Sons, manganese*

claims of 64-66

Hill, Walter Hovey. acknowledgment

to 78

Horst, Dr.. analysis by 84. 86

Hutchinson, Kans.. salt Industry

near 207

Idaho Quicksilver Mining Co., claims

of 81

lola. Colo., manganese deposits

near 67

Iron Cross prospect. Mogollon dis- trict, N. Mex.. descrlp* tion of 203

Iron Mountain manganese claims, near WellbTllle. Colo., description of 65-66

J.

Jesse Lake, Nebr.. potash in 126,

127. 138. 138

Johns. W., acknowledgment to 172

Johnson mine, Mogollon district. N.

Mex.. description of 196

Johnston, Gavin, silver ore shipped from Divide district. Nev., by 148-149

Jones, D. B. W.. acknowledgment

to 126

Jones, Bdward U. Jr., A deposit of manganese ore in Wyo- ming 67-69

Some deposits of manganese

ore in Colorado 61-72

Page. Josef and Else potash mine, Alsace, history and description of 84-35

Kansas, central, sections across the

salt deposits of 208

map of salt basin partly In 206

southern, records of deep bor- ings in 210

Kansas salt field, age and extent of. 207 records of borings In 207-213

Kent County, Tex., depth of salt

beds in 216, 217

Kemlck vein. Divide district. Nev..

description of 162, 169

Kidder. S. J., acknowledgment to 172

Kirk. M. Z.. and Haworth. EJrasmus.

died 207. 210. 212

Kirkpatrlck, R. D.. acknowledgment

to 126

Knopf, Adolph. The Divide sliver dis- trict. Nev 147-170

Kreiss. A. I/., acknowledgment to — 126

Laboratory, field, location of 206

Larsen. Bsper 8., and Livingston, D. C, Geology of the YeUow Pine dnnabar- district, Idaho. 73-88

Latlte lavas, nature and distribution of. in the Divide dis- trict, Nev 166-168

Last Chance mine. Mogollon dis- trict, N. Mex.. descrip- tion of 200-202

vertical projection of 202

Lesbla. N. Mex.. depth to salt beds

at 221

Liberty Hill manganese claims, near Salida, Colo., descrip- tion of 64-65

Little Fannegr mine. Mogollon dis- trict,. N. Mex.. descrip- tion of 197-198

vertical projection of 198

Livingston, D. C, Larsen. Bsper 8., and. Geology of the Tellow Pine cinnabar- mining district 78-83

Lyons, Kans., salt Industry near 207

Lyons Rock Salt Co., record of shaft of. at Lyons, Kans. 210

M.

McCarty, A. M.. exploitation of Ne- braska potash by 125

McCreath, A. 8., analyses by 122

McLean. Tex., depth to salt beds at-

214. 217

Index.

o.

Pase.

O'Brien, John, acknowledgment to 126

Oddle rhyollte, gold velnB in, in the

Divide diatPict, Nev— 162 nature and distribution of, in the IMvide district,

Nev 1 164-15S

Oklahoma, records of deep borings

in 210, 212

Oklahoma salt field, map of 206

records of borings in 213-214

P.

Pacific mine, MogoUon district, N.

Mex., description of- 202-203 Pardee, J. T., Phosphate rock near MazTille, Granite

County, Mont 141-145

Penrose, B. A. P., Jr., cited 110-111,

Phllipsburg phosphate field, Mont., map and section of

part of 142

structural features in 142-143

Potash, deposits of, in Barcelona

province, Spain 1-16

lakes containing, in Nebraska.

possibility of finding, in Texas

and adjoining States 206

resources of, in Nebraska 180-132

Potter, J. O., manganese claims of 67-68

Poverty Mining Co., manganese de- posit developed by 67-69

Princeton anticline, Mont., phos- phate rock in 14S, 146

Prindle, L. M., acknowledgment to 49

Prinz Eugen potash mine, Alsace, history and description

of 88-39

Piilomelane, description of 106

occurrence of, in Colorado 63,

66, 66, 67, 68

Pyrolosite, description of 107

occurrence of, in Colorado 63,

66, 66, 67, 70, 71

Qnanab, Tex., no salt recorded at. 216, 218 Quicksilver. See Mercury.

Reeves County, Tex., no salt recorded

in 216,210

Reichtland potash mine, Alsace, buildings of, plate

showing 84

history and description of 86-88

RbyoUte brecca. See Fraction rhyo- llte breccia.

Richardson, W. B., acknowledgment

to 120

Rwwnkrana, T. H., work of 142

Page. Boswell region, N. Mex., depth to

salt beds in 220-221

Royal anticline, Mont, phosphate

rock in 144,145

Runey, Charles, acknowledgment to. 126 Running Wolf iron deposits, Mont.,

geology and general

features of 86-92

S.

Saguache County, Colo., manganese

prospect in 68

Ste.-Th6r6se potash mine, Alsace, history and description

of 42-48

Salida, Colo., manganese deposits

near 68, 64

Salt, beds of, overlain by sand- stones and gypsum, at Cardona, Spain, plate

showing 8

beds of, contorted, at Cardona,

Spain, plate showing 0

collection and testing of sam- ples of 205-206

deposit of, in Texas and adjoin- ing States, age of 206

in Texas and adjoining

States, extent of. 221-222

origin of 222-228

possibility of finding

potash in 206

stratigraphic relations

of 206-207

largest in the world 206

outcrop of, at Cardona, Spain,

plate showing 4'

Salt mountain at Cardona, Spain, de- description of 4-6

plate showing '4

Salts, deposition of, from sea water. 223 San Angelo, Tex., no salt recorded

at 216,218

Sandstones, tilted, overlying salt beds at Cardona,

Spain, plate showing 6

San Miguel County, Colo., manganese deposits in, general fea- tures of 68-69

manganese deposits in, geology

origin of 71-72

Scurry County, Tex., depth to salt

beds in 216, 217

Sharp, W. B., acknowledgment to 126

Sheep Creek, Wyo., manganese de

posit on 57-69

Show, J. H., acknowledgment to 126

exploration for potash by li25

Silver, mode of occurrence of, in the

Divide district, Nev 168-

161. 162, 168-164 occurrence of, in the Mogollon

district, N. Mex 189-

192, 196, 198. 199, 200, 201, 202, 2r

Ind£X.

Snowbird Iron claim, Mont, analjaeft

of ore from 91

description of 81M>1

Soath Alpipe prospect, Mogollon di0> trict, N. Mex., descrip- tion of 208

Spain, northeastern, general geology

of 11-14

potash deposits In 1-16

extent of 16

legislation concerning 16-16

Spur, Tex., depth to salt beds at 216-217

Standard Salt Co., record of shaft of, at UtUe BWer.

Kans 212

Stanford, Mont., iron deposits near,

featores and slse of — 90-02 Iron deposits near, geology of — 86-87

location of 85

mode of occurrence of 87-90

Stevens, T. E., aclcnowledgment to — 126

Snria, Spain, location of 1-2

potash deposit at, development

of 10

discovery of 8-10

shaft sunk near, record of 9-10

structure of area near 9

See aUo Cardona. Spain, potash field near.

T.

Temperature, underground, in Al- sace 88,43

Tertiary beds in Alsace, section of 22

Texas salt field, map of 206

records of borings in 214-219

Theodor potash mine, Alsace, history

and description of 88-89

Tonopah Divide lode, features of — 158-

160. 165-167

Tonopah Divide mine, Nev., descrip- tion of 165-167

Tonopah HasbrouclE mine. Nev.. de- scription of 169-170

Tucumcari, N. Mf*x.. depth to salt

beds at 221

Tuff, white, nature and occurrence of, in the Divide dis- trict, Nev 150-151

U.

Udden, J. A., cited 214,216,217

Upland, Tex., depth to salt beds at-

216, 219 Cslgllo, J., work of, on dcpoaldon of salts from sea water

Van Meter, B. H., acknowledgment

to 7S

ViUanuevt de la Agnda, Spain, pot- ash at n

w.

Wad, description of 108

occurrence of, in Colorado 68,66

Wells, B. C, analysts by 157

Wellsville, Colo., manganese depoe-

its near 68, 65, 66, 67

Westgate Lewis G., Depoalts of iron ore near Stanford,

Mont. 8&-2

Wheelock, C. B., acknowledgment

to 172

White River, Mont., features of 97

Whittaker, Frank C, acknowled|

ments to 86

Wyman Oulch syncline, Mont., de- scription of 142

phosphate rock in 148, 144

Wyoming, manganese In 67-59

Y.

Tellow Pine district, Idaho, cinnabar

deposits in 79-80

field work in 78

geology of 76-79

history of cinnabar mining in — 74-75

location and topography of 78-

74, 76-76

prospects In 80-82

summary of fSacts and conclu>

sions on 88

Yellow Pine Quicksilver Co., claims of, near Fern Creek, Idaho 81

o

Department Op The Interior

Albert B. Fall, Secretary

United States. Geological Survey

Gbobob OnB Smith, Director

in 716

Contributions To Economic Geology

(Shost Papers And Pseliminast Seposts)

f A£T n.— HI5EBAL FUELS

Dayid White And M. B. Campbell Gi0L06I8Ts In Chabgi

Washington

Ootxbitment Pbintino Offiob

Contents.

I (The letters in paientheses preceding the titles are those used to designate the papers for advance

pabUcation.)

Page.

Introduction vn

(A) Geology of Alamoea Creek valley, Socorro County, N. Mex., with special

reference to the occurrence of oil and gas, by D. E. Winchester (pub- lished May 12, 1920) 1

(B) The Upton-Thornton oil field, Wyo., by E. T. Hancock (published Apr.

29,1920) 17

(C) The Mule Creek oil field, Wyo., by E, T. Hancock (published July 27, 1920). 35

(D) Natural-gas resources available to Dallas and other cities of central north

Texas, by E. W. Shaw and P. L. Ports (published Nov. 17, 1920) 55

(E) The Lance Creek oil and gas field, Niobrara County, Wyo., by E. T. Han-

cock ( published Dec. 13 , 1920) 91

(F) Coal in eastern Idaho, by 6. R. Mansfield (published Dec. 14, 1920) 123

(G) Coal in the middle and eastern parts of San Juan County, N. Mex., by

C. M. Bauer and J. B. Reeeide, jr. (published February 11, 1921) 155

(H) Character of coal in the Thomas bed near Harrison, W. Va., by M. R.

Campbell (published February 18, 1921) 239

Index. 243

Illustrations.

Page. Platb I. A, D Cross Mountain, Socorro County, N. Mex.; B, La Cruz Peak,

Socorro County, N. Mex. 2

II. Cross-bedded sandstone of the 'Red Beds" at Ojo de los Chupaderoe,

in sec. 12, T. 2 N., R. 6 W., Socorro County, N. Mex 3

III. A, Pueblo Viejo, Socorro County, N. Mex.; 5, Bell Mountain sand- stone member of Miguel formation at foot of Bell Mountain, Socorro

County, N. Mex 8

IV. Datil formation (conglomerate and sandstone) in Alamosa Creek val- ley, N. Mex 9

V. Geologic map of Alamosa Creek valley, Socorro County, N. Mex 12

VI. Map of Upton Thornton oil field, Wyo 18

VII. Geologic map of the Mule Creek oil field, Wyo In pocket.

VIII. Index map showing location of gas pools within 200 miles of Dallas, Tex., geologic structure favorable for gas pools, and distances

from Dallas 58

IX. Map of Petrolia gas field, Tex., showing water encroachment 66

in

Iv Contents,

Page,

Platb X. Geologic map of the Lance Creek oil and gaa field, Wyo In pocket.

XI. Stratignphic aectiona in northeastern Wyoming, showing the posi- tion of the principal oil and gas sands In pocket.

XII. Sandstone including large reddish-brown concretions near the top of the Fox Hills sandstone, east side of Buck Creek valley, sec.

33,T. 37 N.,R. 63W., Wyo 104

XIII. A, B, Discharge of oil into a dammed-up gulch at the Ohio Oil Co.'s discovery well in the NW. sec. 36, T. 36 N., R. 65 W., Lance

Creek field, Wyo 120

XIV. General geologic map of eastern Idaho 124

XV. Geologic map of the Horseshoe and Hne Creek districts and Teton

Basin, Idaho 138

XVI. General map of the San Juan County coal field, N. Mex 156

XVII. The plateau surface viewed northwestward across the valley of

Chaco River, N. Mex., south of Hunter Wash 158

XVIII. A, Characteristic topography and vegetation of the highest part of the San Juan coal field, N. Mex.; J?, Exposure of Puerco and Torrejon formation making badlands miles above Ojo Alamo

Store, N. Mex 160

XIX. A, Part of the Mesaverde group in the gap cut through the Great Hogback by Chaco River, N. Mex.; B,'The Menefee formation in

the Great Hogback, 5 miles north of San Juan River, N. Mex 162

XX. A, Coal bed at location 140, on San Juan River half a mile southwest of FruiUand, N. Mex.; B, Characteristic weathering of variable

sandstone of the Fruitland formation, Meyers Creek, N. Mex 166

XXI. Fart of the Fruitland formation near Hunter's store, in T. 24 N.,

R. 13W., N. Mex 168

XXII. Columnar sections of the Fruitland formation 170

XXIII. Map of T. 30 N., R. 16 W., N. Mex., showing outcrops of coal beds

in Menefee formation 192

XXIV. Sections of coal beds of the Menefee formation in T. 30 N., R. 16

W, N.Mex 194

XXV. Map of the district near La Plata River, N.Mex 200

XXVI. Sections of coal beds of the Fruitland formation in northern San

JuanCoimty, N. Mex : 202

XXVII. Map of the district between Barker Arroyo and Youngs Reservoir,

N.Mex 204

XXVIII. Map of the district between Youngs Reservoir and San Juan River,

N.Mex 206

XXIX. Map of central part of San Juan County coal field, N. Mex 208

XXX. Sections of coal beds of the Fruitland formation in central San Juan

County , N . Mex 210

XXXI. Map of the district on Hunter Wash and Coal Creek, N. Mex 222

XXXII. Sections of coal beds of the Fruitland formation in southern San

Juan County, N. Mex 224

XXXIII. Map of the district between Black Lake Canyon and Splitlip Flat,

N.Mex 230

XXXIV. Map of the district between Meyn Creek and Alamo Anoyo, N.

Mex 232

Contents. V

Page. PiouHi 1. Log of well at Cambria, Wyo 20

2. Map ehowing cities and towns in north Texas using natural gas 61

3. Curve showing decline in rock pressure, number of wells in line,

and number on test in Petrolia gas field, Tex 65

4. Curve showing decline in open flow and total production in Petro-

lia gas field, Tex 65

5. Curve showing decline in rock pressure in the Fox gas field, Okla. . 73 6. Curve showing decline in rock pressure in the Walter gas field,

Okla 75

7. Curve showing decline in rock pressure in the Loco gas field,

Okla 77

8. Curve showing decline in rock pressure in the Duncan gas field,

Okla 78

9. Curve showing production of gas by Lone Star Gas Co 87

10. Curve showing monthly sales of gas by Lone Star Gas Co 87

11. Curve showing domestic and industrial consumption of gas at Fort

Worth, Tex 88

12. Geologic structure sections of parts of the Horseshoe, Teton Basin,

and Continental Divide districts, Idaho .' 130

13. Geologic map of part of the Continental Divide district, on Cotton-

wood Creek, in unsurveyed T. 14 N., Rs. 38 and 39 E., Idaho.. 132

14. Coal sections in the Pine Creek and Teton Basin districts and at

Cottonwood Creek in the Continental Divide district, Idaho 135

Insert.

Page. Carboniferous and later formations in eastern Idaho 128

Contributions to Economic Geology, 1920.

Part II. MINERAL FUELS.

Datid White and M. R. Campbell, OeoiogiMs in charge.

Intboduction.

The Survey's ''Contributions to economic geology" have been pub- lished annually since 1902. In 1906 the increase in the number of papers coming under this classification made it necessary to divide the contributions into two parts, one including papers on metals and nonmetals except fuels and the other including papers on mineral fuels. In 1915 the year included in the title was changed from the year in which the field work reported in these papers was done to the year of publication, and in consequence there was no volume entitled ''Contributions to economic geology, 1914." The subjoined table gives a summary of these bulletins.

United States Oeoloical Swrvey 'CorUribtUiona to economic geology.'*

Date in tiUe.

1906, Parti 1907

Partll

1907, Part I

PartU

1908, Parti

Part II

1909, Parti

PartU

1910, Parti

Part II

1911, Parti

Part II

Date of publica-

Bulletin No.

tioiLa

Date in title.

1912,

Parti

Part II

1913,

Parti

Part II

1915,

Parti

Part II

1916,

Parti

Part II

1917,

Parti

Part II

1918,

Parti

Partll

1919,

Part I

Partll

1920,

Parti

Partll

Date of

publica*

tion.a

Bulletin No.

The date given is tbat of the complete vohime: beginning with Bulletin 285, the papers have been issued as advance ohapters as soon as they were ready.

As the subtitle indicates, most of the papers in these volumes are of three classes — (1). short papers describing as thoroughly as con- ditions will permit areas or deposits on which no other report is

vn

VIII CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1920, PAJtT II.

likely to be prepared; (2) brief notes on mining districts or eco- nomic deposits whose examination has been merely incidental to other work; and (3) preliminary reports on economic investigations the results of which are to be published later in more detailed form. Although these papers set forth mainly the practical results of economic investigations they include brief theoretical discussions and summary statements of conclusions if these appear to require prompt publication.

GEOLOGY OF ALAMOSA CREEK VALLEY, SOCORRO COUNTY, NEW MEXICO, WITH SPECIAL REFERENCE TO THE OCCUR- RENCE OF OIL AND GAS.

By Dean E. Winchbster.

Introduction.

During a detailed study of the coal resources of a part of northern

Socorro County, N. Hex., made in 1913 and 1914, considerable

information relative to the stratigraphy and structure of the region

'WBS collected. Recent interest in the oil and gas possibilities of New

Mexico makes it desirable to record the observations made, so that

they may serve as a guide in the search for petroleum and natural

gas.

Fieu> Work.

In the field examination the writer was assisted by Heath M. Robinson, W. T. Thom, jr., S. D. Greene, and Delbert Williams, eadi of whom took an active part in the collection of the information.

Geographic as well as geologic features were mapped in the field on a scale of 2 inches to the mile, and the accompanying map (PI. V) is the result of the compilation of this information. The rock beds are folded and faulted and are intruded by igneous rocks, and con- siderable time was spent in the study of the structure. Much time was also given to measuring stratigraphic sections and to collecting fossils upon which to base correlations. Many large collections of invertebrate and plant fossils were made in the field and have been studied by T. W. Stanton and F. H. Kjiowlton. All surveys were tied to section comers either by stadia traverse or by direct triangu- lation. A careful study of the chemical analyses of the coals of tiiis region furnishes suggestions concerning the possibility of the presence of petroleum and natural gas in the formations of the region.

Geography.

r

LoccUion and extent. — The valley of Alamosa Creek covers an area of approximately 600 square miles, mostly in Socorro County, N. Mex. It lies north of the Bear, Gallina, and Datil mountains, between the Sierra Ladron on the east and the Continental Divide on the west, and extends northward as far as the north line of T. 4 N.

Surface fecttures. — The valley is bounded on the south and east by low nigged mountains. The Bear Moimtain range, to the souths

2 Contributions To Economic Geology, 1920, Part H.

consists of a large ntimber of peaks, the highest of which are more than 7,600 feet above sea level. The Tertiary bedded volcanic rocks, sandstones, and conglomerates of the Datil formation, which make up these moimtains, have been dissected into inniunerable conical peaks and present an entirely different landscape from that shown in the Sierra Ladron, which lies a short distance east of the area shown on Plate V.

Between the Bear Mountains and the Oallina Mountains, to the west, there is a comparatively broad area which is deeply dissected by small streams that flow into Alamosa Creek. The Gallina Moun- tains, like the Bear Mountains, consist of the Tertiary rocks, which have been dissected into innumerable conical peaks having altitudes of 9,000 to 9,500 feet above sea level.

The Datil Mountains, west of the Gallina Mountains, are the highest and most rugged mountains in the area mapped. Like the Gallina and Bear mountains, they comprise a large number of high peaks carved from rocks of the Datil formation. Several of the higher peaks rise more than 9,600 feet above sea level. The east-west series of peaks shown on the map forms only a small part of the Datil Mountains. These mountains are clothed with pine timber, a con- siderable part of which is laie enough to be of economic importance.

These three mountain ranges are separated from one another by comparatively low divides. That between the Bear and Gallina mountains is the lowest and accommodates the only wagon road by which the field may be entered from the south.

To the north of the main mountain ranges there are several high peaks which are locally designated mountains. D Cross Mountain (PL I, the highest of these peaks, is an igneous plug 2 miles north of Alamosa Creek, in the western part of T. 3 N., R. 8 W. It rises about 2,000 feet above the level of the creek, or 8,775 feet above sea level.

On the divide between Alamosa Creek and Miguel Canyon, 2 miles to the west of D Cross Mountain, is Bell Mountain, an igneous intrusive mass which rises to an altitude only a little lower than that of D Cross Mountain. Broom Mountain, 3 miles north of the area mapped, on the line between Rs. 7 and 8, is a flat-topped landmark capped by sandstones of Cretaceous age and stands about 8,400 feet above sea level.

Less conspicuous buttes in several parts of the field reach altitades 200 feet or more above the general level of the surrounding area. Three of the most noted of these are the Tres Hermanos Buttes, in sec. 28, T. 3 N., R. 7 W. These buttes are formed of igneous rock which has been forced up into the Cretaceous strata. La Cruz Peak (PL I, JB), in sec. 13, T. 2 N., R. 6 W., about 6,975 feet above sea level, and La Jara, in sec. 11, T. 2 N., R. 5 W., about 6,875 feet above sea

B. a. oBOLoou. auxvBT

A. D CROSS MOUNTAIN. SOCORRO COUNTY. N. MEX. Oilinii auidBlaaB nwiiibB mad nan of Iha uidiloDS ctf the lonr put of the Misuel ronnaliall dkowa

B. lA CRUZ PEAK, SOCORRO COUNTY, N. HEX.

Geology Of Alamosa Greek Valley, K. Mex. S

levely are particularly good examples of volcanic necks which form prominent and well-known landmarks of the region. Innumerable small buttes or points formed by the unequal erosion of sedimentary rocks, gravels, etc., may be seen within the area described. The several dteep-sided lava-capped mesas that rise abruptly above the surrounding country are in most places clothed with a good growth of grass and some scrub timber. Such mesas are conspicuous north and south of the Tres Hermanos Buttes, in Tps. 2, 3, and 4 N., R. 7 W., and north of Miguel Canyon, in T. 4 N., Rs. 8 and 9 W.

Within this area there are eiso a large number of ridges and hog- backs caused by resistant sandstones of the Miguel formation that dip at low angles. West of the little Mexican town of Puertecito suc- cessively higher beds of sandstone dipping at low angles to the west- ward give rise to several hogbacks. In the vicinity of the Chavez ranch, in T. 1 N., R. 5 W., and north of La Cruz Peak, the rocks have been faulted and tilted so that there are four or more parallel hog- backs, each capped by sandstone of the same bed.

Alamosa Creek contains running water at a great many places throughout the year, and in most places where the bed of the stream appears dry, water may be found within a foot or so of the surface. In time of rains the stream is sometimes impassable.

Springs of good water issue from the sandstones of the region and have determined to a large extent the location of the ranches. In addition to the nurnerous small springs, the following are of note:

Ojo Alamo, in sec. 13, T. 2 N.. R. 6 W.

Ojo de lo6 Barrancos, in sec. 12, T. 2 N., R. 5 W.

Ojo de loB Ghupaderos, in sec. 2, T. 2 N., R. 5 W.

Abbey Springs, in sec. 8, T. 1 N., R. 5 W.

Jaia Spring, in sec. 15, T. 2 N., R. 5 W.

Tree Hermanos Spring, in sec. 24, T. 3 N., R. 7 W.

Navajo Spring, in sec. 17, T. 3 N., R. 7 W.

I. N. M. Spring, on the south bank of Alamosa Creek in the NW. i sec. 28, T.

3 N., R. 8 W. Box Bar Springs, a small spring on the Box Bar ranch, in sec. 4, T. 2 N., R. 9 W.

The water is appropriated largely for domestic purposes. Los Terros, in sec. 1, T. 2 N., R. 10 W. Miguel Spring, in sec. 33, T. 4 N., R. 9 W. Cacho springs, near Bodenheimer's ranch, in sec. 10, T. 4 N., R. 9 W.

Culture. — Several large cattle ranches in the western part of the field are owned by Americans; but the area east and south of Puerte- cito is occupied almost entirely by smaller ranches owned by Mexicans. In the vicinity of Ojo Alamo, in T, 2 N., R. 6 W., there is a small colony of Navajo Indians, whose chief occupation is the raising of small bands of goats and sheep. The region is not suited to culti- vation and will therefore probably continue to be used largely for stock raising.

4 CONTRIBUTIONS TO ECONOMIC GEOLOGTy 190), PART H.

Puertedto, in sec. 29, T. 3 N., R. 5 W., is a small Mexican village composed of about a dozen adobe houses ranged along an east-west street. The town is the headquarters of a considerable Mexican and Indian trade and supports two small tiendas, or stores.

At present Burley is the only post office within the area. During the summer of 1913 this office was at a ranch on Felipe Gilbert Creek, in sec. 10, T. 2 N., R. 7 W., but at the end of the season it was moved to the I. N. M. ranch, on Alamosa Creek, in sec. 21, T. 3 N., R. 8 W. Since that time the post office has been again moved, so that it is now only 10 miles west of Puertecito. Mail is brought by stage from Magdalena, a distance of about 50 miles, twice a week. Magdalena, with 3,000 inhabitants, the nearest raih*oad town, is at the end of a spur of the Atchison, Topeka & Santa Fe Railway abopt 20 miles southeast of the area mapped and is the shipping point for stock from this area as well as a much larger area to the south and west.

Because of the extremely rough topography, wagon roads have been laid out along the valleys and in many places are very crooked as well as rough.

CliTnaie and vegetation. — The field is in the arid ron of the South- west, and its climate is typical of that region. Rain usually comes in torrents, and therefore the run-off is great and erosion due to run- ning water is very rapid.

GBOIiOGY.

Oenebal Featubes.

The sedimentary rocks exposed within the area here described have a maximum thickness of about 8,000 feet and range in age from Carboniferous to Recent. The red clays and sandstones of the Triassic are overlain unconformably by Cretaceous sandstones and shales, the oldest of which is correlated with the Dakota sandstone. The Dakota is overlain by a series of shales and sandstones having an aggregate thickness of about 3,700 feet. This series is subdivided into two formations, the lower of which is here named the Miguel formation and the upper of which is here named the Chamiso forma- tion. Unconformably overlying these Cretaceous sediments is a formation consisting of a series of tuffs, rhyolites, sandstones, and conglomerates, which is probably of late Tertiary age, although no fossils were foimd that lend evidence for this assumption. This formation is here named the Datil formation because it is the mountain-forming series of the Datil Moimtains, along the southern margin of the field. Quaternary unconsolidated gravels and alluviimi occur in small areas. The following table shows the character and relations of the sedimentary formations of the field:

GEOLOGY OF ALAMOSA GBEEK VALLEY, N. MEX. Oeneralized section of the rocks exposed in Alamosa Valley, N. Mex

System.

Fonnattoo.

Cbaraoter of rocks.

Thickness (feet).

Qoatarnuy.

AUnyiom.

Valley filling.

ao±

OravU.

Well-rounded and sorted pebbles.

asdb

Twtiwy.

DatilformatlGii. Unoonfomiity

Chsmiflo fannft- tion.

Well-ind'orated tuffs, rhyolites, cross-bedded sand- stones, and conglomerates. Members are extremely Tarlable.

2,000±

Soft yellow sandstones and sandy shales, with inter- calated carbonaceous beds. Contains abundant fossil leaves. Coal beds at three general horixons, but the one about 75 feet above the base is the only bed of importance.

1,860

„—

mgiMl fomiAtian.

Yellow sandstones, drab and yellow sandy shales with a few beds of clay and sevflral beds oi ooal in upper half. Abundant invertebrate fossils and a few plant remains. Thb formation contains four persistent massive yellow sandstone members, two of which are here named, the name Bell Mountain sandstone member being applied to the one at the top and Oallego sandstone member to the one near the middle.

2,060

Dakota sandstone. ITnoonformitj, era

'Red Beds."

Quartsose gray to brown sandstone which in places stones. Contains a few plant remains, nrfoni*-! angular

TiiassieandCar-

iMmtlnrans

Bed argiDaoeous shale, interbedded with thin beds of lavender sandstone; at base this conglomerate con-

800+

limestone and g3rp8om beds, base not exposed.

300+

Cabboniferous And Trla8Sig Bocks Cbed Beds").

The basal part of the section as exposed iu the Alamosa Valley is composed of sediments which are predominantly red and include a great thickness of red, vermilion, and lavender clay shales, coarse cross-bedded sandstones (see PL 11), and thin beds of conglomerate, with some limestone and gypsum in the lower part. In some places there is, about 600 feet below the top of the series, a thin bed of con- glomerate which may represent the Shinarump conglomerate of north- western New Mexico and northeastern Arizona. No fossils were found upon which to make a correlation, but from the lithology it is assumed that the beds above the conglomerate are Triassic and that those below may belong to the Manzano group, of Permian age.

CBETACEOUS BOCKS. DAKOTA SAVDSTOn.

Resting unconformably on the ''Red Beds|' just described is a sandstone ranging in thickness from 0 to 40 feet, which is correlated with the Dakota sandstone of other areas on the basis of its fossil

6 CONTRIBUTIONS TO ECONOMIC GEOLOGY, lOBO, PART n.

flora, lithology and stratigraphic position. In some places this sandstone is almost a pure quartzite; in others it is very conglomer- atic; but in most places it is simply a coarse well-cemented femi- ginons sandstone which contains a few pebbles as large as half an inch in diameter. Along the west side of the Red Lake fault the sandstone is thin and in places entirely absent.

MIOinBL FO&MATIOXr.

In this field the 3,900 feet of Cretaceous rocks that occur above the Dakota sandstone are subdivided into the Miguel and Chamiso formations, on the basis of their lithology and fossil content. The lower half of the series, here named the Miguel f ormation, from Miguel Creek, which crosses the beds in the northwestern part of the area, is composed of a succession of massive persistent sandstones, soft sand- stones, and dark shales with coal, which contains an abundant Benton (early Colorado) fauna throughout and a sparse flora that F. H. Knowl- ton regards as probably of Montana age. These beds have the strati- graphic position of a large part of the Mancos shale but are lithologi- cally quite different, being chiefly sandstone, whereas the Mancos in its type locality is almost entirely shale. According to the inverte- brates it contains the Miguel is entirely of Colorado age, but the Mancos includes beds of Montana age in addition to those represent- ing the whole Colorado group. For these reasons the local name Miguel formation is here introduced.

The upper portion of the series, here named the Chamiso forma- tion, from Chamiso Creek, in T. 2 N., R. 9 W., is composed of soft sandstones and sandy shales containing an abundant Montana (Mesaverde) flora but no invertebrates, and is wholly of nomnarine origin; the Mesaverde formation, which is in part equivalent, con- sists of alternating beds of marine and nonmarine origin.

The Miguel formation includes four thick resistant and persistent beds of sandstone. The two lower may represent the Tres Hermanos sandstone of Lee, but they are the least conspicuotis of the sand- stones of this area and were therefore not mapped. They are exposed a mile east of the Tres Hermanos Buttes. The Gallego sandstone member, named from Oallego Creek, occurs near the middle of the formation and is well exposed in Pueblo Viejo (PI. Ill, A), b, small mesa in sec. 17, T. 4 N., R. 7 W., which was once used as a stronghold by a small group of Indians. It is also exposed on the south and east sides of the Tres Hermanos Buttes, near the base of the buttes. This sandstone occurs about 900 feet above the Dakota and ranges in thickness from 50 to 90 feet. The Bell Mountain sandstone mem- ber (see PI. Ill, -B), which is well exposed near the foot of Bell Mo ' 3 N., R. 9 W., is at the top of the Miguel formation

a' feet thick.

of the Crotacooas formations to the Rocky Mountains In Colorado and New ey Prof. Paper 95, pp. 27-68, 19ia.

Geology Of Alamosa Creek Valley, N. Mex. 7

A section of the Miguel formation was measured in the gap south of D Cross Mountain as follows :

Section of Migiul formation t miU$ west of L N. M, ranch.

SandBtone, thick bedded, yellow to gray, coarse; Hcdymenites at .

the top, Inoceramus at the base (Bell Mountain sandstone mem- Feot.

'ber) 79

Shale, grtenish and drab, fissile, containing hard brown concre- tions near the top; fossil shells 10 feet below the top 175

Sandstone, brown, hard 2

Sandstone, yellow, shaly, slightly carbonaceous at the base. 34

Shale, yellow to drab, with thin beds of sandstone 35l

Sandstone, brown, hard, coarse 1

Sandstone yellow, massive 25

Shale, yellow and drab, with thin beds of sandstone 584

Sandstone, yellow, and dark to yellow shale, with 10 feet of carbon- aceous shale at the top 80

Sandstone, yellow, thin bedded, and drab shale, sandy at the top,

carbonaceous below, containing leaf fragments and 6 inches of

coal near the top 47

Sandstone, yellow, massive, containing Halymenites (Gallego sand- stone member) 93

Sandstone and shale, mostly covered 380

Sandstone, yellowish, massive, coarse, gray; fossil shells, 20 feet

above the base 78

Sandstone and shale 6

Shale, yellowish gray and drab, fissile 134

Covered 50

Sandstone, with gastropods 15

Shale, drab, with oysters and shark teeth 50

Sandstone, yellowish gray, conglomeratic and cross-bedded 23

Shale, drab, argillaceous, with oysters 10 feet below the top 82

Covered, mostly shale 109

Dakota sandstone.

2,082

Section of lower part of Miguel formation south of Puertecito, N. Mex,

Miguel formation: Feet.

Sandstone, thin bedded 5

ShJale, sandy 75

Sandstone, shaly; fossil shells.' Sandstone, yellow, massive... Sandstone, friable

Gallego sandstone member

Covered but composed of drab shale at top; fossil shells at top. 87

Sandstone 6

Shale, sandy 25

Sandstone 10

Shale 50

Sandstone 5

Shale; fossil shells 9

Sandstone, yellow, thin bedded 42

Shale and sandstone, shaly 52

Sandstone; fossil shells 10

Shale and sandstone, shaly 136

Sandstone, heavy bedded, yellow 75

8 CONTRIBUTIONS TO ECONOMIC GBOIjOGT, 199), PABT II.

Miguel fonnAtion— Continued. Feet.

Shale, light to alate-colored 90

Shale and sandatoney calcareouB 35

Sandstone, thin bedded, brown, calcareouB 10

Shale, laigely covered 40

Dakota aandBtone: "

Sandstone, maaBive, angular grains 26

Sandstone, gray, thin bedded 5

0KAMZ80 ro&icATioxr.

Above the Boll Mountain sandstone, which marks the top of the Miguel formation, is a series of yellow sandstones, sandy shales, and coal beds that contains no persistent indurated beds like the under- lying formation. This series on the basis of the fossil leaves which it contains might be correlated with the Mesaverde formation, but its lithologic character is quite different from that of the Mesaverde in its type locality: the deposits are whoUy of nonmarine origin, whereas the Mesaverde consists of alternating marine and nonmarine sediments; and as the underlying beds (Miguel formation) are all of Colorado age, while the typical Mesaverde is underlain by beds of early Montana age, it is probable that rocks older than the typical Mesaverde are included in this series. The local name Chamiso formation ia therefore introduced, from Chamiso Creek, in T. 2 N., R. 9 W.

One of the best coal beds in the field occurs about 75 feet above the base of the Chamiso and is extensively exposed west and north- west of D Cross Mountain. Other zones of carbonaceous material are present at several horizons in the formation, but none are of more than local importance. About 1,300 feet above the base there is a carbonaceous zone which contains coal in several places. The thickest coal bed is exposed in Red Canyon 3 or 4 miles south of ihe Box Bar ranch. The following detailed section was measured in the north side of Blue Mesa and shows the general character of the formation:

Section of Chamiso formation north of Blue J/esa, in T, i N,, R, 8 W.

Feet.

Sandstone, yellow to greenish, soft, and shale, sandy, yellow to green . 440

Sandstone, gray, coarse 4

Coal and carbonaceous shale IJ

Shale, and sandstone, soft 46

Goal and carbonaceous shale 2

Shale 20

Shale, yellow, and sandstone, thin bedded '. 175

Sandstone, massive, yellow, cross-bedded 30

Shale, greenish yellow and drab, argillaceous; fossils 60

Shale and sandstone 146

r. i. esoLoeioAi. btbvby bitllbtin tis piate e

A. Pueblo Vieio, Socorro County, N. Hex.

Oeology Of Alamosa Gbbek Vallbt, N. Mbx. 9

FMt

Sandstone, coarse, Qiaasive 25

Sandstone, gray, thin bedded, with thin beds of indurated brown

sandstone 205

Sandstone, yellow, massive, coane 3

Shale, yellow and drab, sandy 20

Sandstone, gray, soft, thin bedded 15

Shale, carbonaceous at the top 25

Shale and sandstone, with beds of hard brown concretions 126

Sandstone 4

Sandstone, thin bedded; fossils 5

Covered 106

Sandstone, yellow to brown, coarse 7

Sandstone, thin bedded, and shale 100

Shale, drab 60

Sandstone, thin bedded to shaly 97

Sandstone, yellowish gray, coarse 5

Sandstone, yellow, coarse, soft, thin bedded 108

Sandstone, massive (Bell Mountain member of Miguel farmation).

Section of part of CTumiiso formation in Triangulation Butte, northwest of Box Bar itmcft,

in sec. SI, T, S K, R.9W.

Sandstone, yellow, cross-bedded 27

Shale, sandy, and sandstone, soft 10

Sandstone, yellow, coarse 27

Shale 14

Sandstone, yellow 2

Shale .' 2

Coal i

Shale, light drab 10

Sandstone, yellow; fossils 20

Shale, greenish yellow, concretionary 9

Sandstone, greenish yellow 2

Shale, greenish gray to drab 55

Sandstone, yellow, coarse; fossils 5

Sandstone, friable 30

Sandstone, yellow, coarse; fossils 8

Shale.

TEBTIABY BOCKS. BATIL lOXXATXOV.

Resting imconfonnably upon the older formations and giving rise to rugged mountainous topography is a series of tuflFs, rhyolites, con- glomerates, and sandstones, which so far as known contain no fossils. Their age is regarded as probably late Tertiary, but more definite cor- iation is impossible. At most places the beds of this formation are practically horizontal, but none of the members are persistent, cross* bedding and steep depositional angles being common. (3 Fl, IV.)

IfliOl**— 21— BuU 716 2

10 Contributions To Economic Gboix)Gt| 1920, Part U.

The following section was measured at the north end of the Bear Mountains near the east boundary of the field and illustrates the general character of the fonnation:

Section of the DatU formation at the north end of the Bear Mountains.

Quartz rhyolite 120

Conglomerate and sandstone, reddish, friable, Conglomerate oon*

tainsangular fragments of igneous rock 40

Sandstone 36

Conglomerate with pebbles as laige as 1 foot in diameter 60

Sandstone and conglomerate in alternating beds 26

Sandstone, argillaceous 4

Tuff, conglomeratic, with pebbles and angular fragments as much

as 18 inches in diameter 60

Rhyolite, vitreous, light colored 4

Andesite, light purple, vesicular 8

Agglomerate wiUi igneous pebbles as much as 1 foot in diameter 17

Tuff, similar in composition to 66-foot bed below but gray and

rather porous and slightly more basic 106

Tuff, red, compact, with groimdmass of glass, iron ore, feldspar, and secondary caldte; inclusions of glassy material containing phe-

nocr>' of feldspar, biotite, and iron ore 66

Sandstone, friable, containing earthy material 127

Covered 60

Tuff, conglomeratic, dark, slate-colored; angular fragments of ig- neous rock; maximum diameterof rounded pebbles 18 inches... 420

Sandstone, red, argillaceous; contains streaks of gypsum 210

Covered but contains some yellow sand 190

Conglomerate like 4-foot bed below 6

Sandstone, thin bedded, with day

Clay, red, with sand and mica 12

Conglomerate, reddish, pebbles as much as 4 inches in diameter in

matrix of clay, feldspar, and quartz 4

Clay, red, with sand and mica specks 16

Not exposed 175

Conglomerate, reddish gray, with well-rounded fragments of ig- neous and sedimentary rock?, including limestone 8

Conglomerate, white, well-rounded pebbles, maximum diameter 6

' inches, of granite, obsidian, feldspar, and quartz 64

Quatebnaby Peposits.

The Quaternary deposits consist of unconsolidated terrace gravels, such as are present in areas many feet above the valley leveb both north and south of Alamosa Creek, and alluviimi, such as is present along several of the larger stream valleys. Little attention was paid to deposits of this character, and the distribution as shown on the accompanying map probably does not include all the areas.

Geology Of A1.Am0Sa Creek Valley, J. Mex. 11

Igneous Rocks.

Tounger than the Datil formation and younger even than at least some of the terrace gravels are the lava flows that cap several of the higb mesas of the field. From the vesicular character of the material in certain parts of these lava caps it is assumed that the vents through which the lava was extruded ore near at hand. Dikes and sills of bade material cut the Cretaceous rocks, as shown on the map (PL V).

8Tbxj0Tubb. General Features.

The field here described forms the southeastern part of San Juan Basin, a broad structural depression that occupies a very large area ia northwestern New Mexico and southwestern Colorado. The Zirni Mountain uplift, which has a general northwesterly trend in McEinley and Valencia counties, to the north of this area, almost isolates the area of Cretaceous rocks south of the Atchison, Topeka & Santa Fe Bailway, of which this field is a part, from the larger portion of the basin north of the railway.

The formations within the Alamosa Creek valley have a general dip toward the west, so that the oldest rocks are exposed at the east- em edge of the area. The attitude of the beds at numerous points within the area is indicated on the map by strike and dip symbols. Many faults and minor folds, most of which have, a trend roughly pandlel to the axis of the Zuni Mountains, interrupt the general stmcture of the area. Irregularly distributed over the field are dikes which have a trend practically parallel to the direction of the faults in the immediate vicinity and which fill fissures that apparently were (onned by forces of the same character as those which gave rise to the faults. Because of the fact that in places cross faults cut and displace dikes, it is assumed that the forces which produced the faults were effective at a somewhat later period than those which caused the fissures that were filled with igneous rock to form dikes. Both dikes <uid faults cut the rocks of the Datil formation, but neither were found catting the younger gravel deposits.

Folds.

Nearly all the antidinal folds within this area are broken by faults, so that the faults become the most conspicuous part of the structure.

Sed Lake anticline. — The Red Lake anticline is the largest fold In the area and extends northward from a point near old Burley post office, in sec. 21, T. 3 N., R. 8 W., to Broom Mountain, a distance of about 13 miles. The rocks along the west side of the fold dip at rela- tively low angles (3-8) to the west; the beds on the east side of

12 Contributions To Economic Geology, 1920, Part Ii.

the fault that marks the crest of the anticline dip as steeply as 48 E. but flatten appreciably within a mile or so. The fault, which is the most conspicuous feature of the structure, has a throw of several hundred feet, sufficient to bring beds of the upper half of the Miguel formation into contact with red clays and shales that are at least 200 feet below the Dakota sandstone. If petroleum exists in the rocks below the Dakota sandstone in this area, this fold provides what appears to be a fairly good place for its accumulation. It is probable that the beds are entirely sealed along the fault plane, and there is thus provided an effective barrier to migration of any oil and gas that may be present. Structure section D-E on the accompianying map (PL V) is drawn across the south end of the anticline.

La Oni2 arUidine, — The La Cruz anticline is a long irregular fold that extends into the field from the north, past the Tres Hermanos Buttes and La Cruz, into the northwest comer of T. 1 N., R. 5 W. This fold is cut by a large number of small faults, notably north of La Croz and near the Chaves ranch, most of which strike parallel to the axis of the fold and none of which have a throw of much over 1 00 feet. Careful study of the structure will probably make it possible to separate this fold into several domes or smaU anticlines separated by low saddles: for example, the high part of the fold at the south end, where the Dakota sandstones and underlying ''Red Beds" are ex- posed, is distinctly separated from the main portion of the antidine north of Alamosa Creek by the saddle near La Cruz, in sec. 13, T. 2 N., R. 6 W., where the Gallego sandstone (near the middle of the IkGguel formation is exposed on both sides of a narrow canyon. Dips of to 18 prevail on the southwest side of this uplift and similar or steeper dips occur on the opposite side. Structure sections A-B and D-E on the map (PI. V) illustrate the rock conditions across this anticline.

Cow Springs anMcUne. — large number of small folds were noted within the area, one of the most promising of which appeared to be the one near Cow Springs, in the southwestern part of T. 4 N., R. 9 W., where the Bell Mountain sandstone and underlying shale of the upper part of the Miguel formation are exposed in two small areas. Tins fold appears to be free from faults and should provide an excellent place for the accumulation of oil in the sandstones of the lower half of the Miguel formation. The Dakota sandstone should be less than 2,000 feet below the surface in sees. 19 and 30, T. 4 N., R. 9 W.

Pastukb Canyon Fault.

To the south, along the west side of the Pasture Canyon fault, the BeU Mountain sandstone is again exposed along Pasture Canyon and Pine Spring Canyon, while on the east side of the same fault younger beds form the siirfa:ce, so that if the beds are sealed aldng l2ie fault

wmm§mm

1 f-rr

]

Boondftiy of Dmtil National Forest

by Dean E. Winchester

I

Geology Of Alamosa Cbbbk Valley, K. Mbx. 13

plane, the area immediately west of the fault presents structural conditions favorable for the accumulation of oil. Sandstones in the lower half of the Miguel formation should be reached here by the drill at depths of less than 2,000 feet. (See section C-D, PI. V.)

OIL Ain> OAS POSSIBILTTIBS.

The accumulation of oil and gas in commercial quantities in any area is dependent on two very important factors — the presence of oil or gas in the rocks and conditions favorable for their accumulation. In imtested regions like that described in this report it may be possi- ble to say positively that oil or gas is or is not present in the sediments below the surface, but a careful study of the available information regarding the character of those rocks at their outcrop, the degree to which they have been affected by metamorphism, and their structural attitude should afford grounds for certain conclusions as to the possibilities of the area.

Two theories have been advanced to explain the origin of petro- leum, but the one that is most commonly accepted is that petroleum is a product of the alteration of certain organic materials which were laid down at the same time as the clay and sand which have since been consolidated into the shale and sandstone of the. rock formations. Evidence has been presented to show that organic materials of certain types upon alteration become coal and carbonaceous shale, whereas materials of other types are transformed into oil shale and petroleimi. White ' points out that the quantity and quality of the petroleum are determined (1) by the composition of the oianic deposit at the beginning of its dynamo-chemical alteration, and (2) by the stage of progress of the dynamo-chemical alteration of the organic sub- stances— that is, in effect, by the extent to which the initial products have been either fractioned undeiground or filtered incident to migration. He also points out that the progressive devolatilization (carbonization) of the carbonaceous (coal) beds of the region cor- responds to the progressive regional metamorphism, so that in areas where the. regional metamorphism has progressed the farthest the coal shows the highest percentage of fixed carbon and the lowest percentage of volatile matter. White shows that if the percentage of fixed carbon in a normal coal or in the organic d6bris of a richly carbonaceous shale exceeds 65 per cent (pure coal basis) the possi- bilities that the coal-bearing formation or the rocks that underlie it may contain petroleum will be exceedingly small. He calb atten- tion to the fact that wherever the regional alteration of the carbona- ceous residues has passed the point marked by 70 per cent of fixed carbon in the pure coal, only gases and soHd residues remain, and

1 6, David, Some relaUons In origin between coal and petroleum: Washington Acad. ScL Jour., ▼oL 6, pp. 18(212, 1915.

14 OONTRIBTmONS TO ECONOMIC QEOLOOY, 1020, PABT n.

no commercial deposits of petroleum may be fomid. In fact, the commercial oil line seems to fall somewhat below the 65 per ct carbon point, though the exact percentage has not yet been fully determmed. According to these conclusions oil deposits of commer- cial value wiU not be present, though gases may persist, in areas where the coals in or above the formations where the oil is hoped for are carbonized beyond the point indicated by 65 per cent of fixed carbon in the pure coal, and it is doubtful if commercial amounts of petro- leum occur where the carbonization is as high as that.

Within the Alamosa Creek valley so far as known there are no oil seeps, asphalt deposits, or gas occurrences, but the shales of the lower part of the Siliguel formation are of dark color and contain remains of organic material, both animal and vegetable, so that it is not inconceivable that there may be liquid petroleum and natural gas in the rocks. Coal occurs in both the Chamiso and the Miguel formations, and although it has not been mined and therefore unweathered material can not be obtained for fully trustworthy chemical analysis, the proximate analyses of two samples obtained from shallow prospects are available ' and give a general idea as to the character of the coal and the stage of its devolatilization. Coal from a bed near the base of the Chamiso formation, in sec. 20, T. 3 N., R. 9 W., contains 55 per cent of fixed carbon (pure coal basis), and , the coal near the middle of the Miguel formation, in sec. 8, T. 2 N., R. 6 W., shows 53 per cent on .the same basis. Therefore oil may be present in these rocks. In fact, it seems probable that if petro- leum is found in this area it will be of high grade and that it will be accompanied by natural gas.

Reservior sands of excellent quality and rather exceptional con- tinuity are present in the Miguel formation. The Bell Mountain sandstone at the top, the Grallego sandstone near the middle, and at least two imnamed but persistent sandstones in the lower part of the formation fiunish beds almost tmrivaled as sands in which oil may accumulate. These sands can be tested at points where the geologic structiu*e is favorable for the accumulation of oil by drilling comparatively shallow holes, less than 2,000 feet in depth, in Cow Spring Canyon, near the center of sec. 30 or near the south line of sec. 19, T. 4 N., R. 9 W. Unfortunately these localities are so situated topographically that some road building will be necessary in order to get rig and materials to them, but it is probable that the necessary water can be obtained in the vicinity and fuel for the boilers can be mined within sight of the rig. Careftd search wiO

1 Campbell, M. R., Analyses of coal samples from various fields in the United States: tJ. S. GeoL Sorvvy BaU. 641, p. 400, 1914. CampbeU, M. R., and Clark, F. R., Analyses of ooal samples from vsrioas ptf of the United States: U. S. aol. Smy Bull. 631, p. 833, 191tt. t

Geology Of Alamosa Creek Valley, K. Mex. 15

perhaps disclose other localities where the structure is equally favor- able and where transportation conditions are more advantageous.

The formations older than the Cretaceous contain sands that may be worthy of testing, but in the work upon which this report is based Utile attention was paid to these lower formations. The Carbonif- erous includes some sand, as does also the overlying Triassic. The general character of at least one of these older sandstone is hown on Plate II. The cross-bedded character of particular sand seems to be against it as an oil reservoir, but other sands may be much more favorable. A well 3,000 feet deep drilled near Red Lake, in sec. 2, T. 3 N., R. 8 W., should furnish satisfactory proof as to the oU possibilities of the formation below the Dakota. This locality, being on the west side of the fault and near the crest of the great anticline, is most favorable for a test of the lower rocks.

The Upton-Thornton Oil Field, Wyoming,

By E. T. Hancock.

INTRODUCTION. LOCATION or THE FIELD.

The territory here designated the Upton-Thornton oil field (see PL VI) includes two small dome-shaped folds and a small tract that yields a moderate quantity of oil of excellent quality and is entirely separate from either of these domes. One of these domes will be referred to as the Upton dome and the other as the Thornton dome. The productive territory lies in Weston and Crook counties, Wyo., near the Chicago, Burlington & Quincy Railroad, about 3 miles north- west of Thornton. It is about 20 miles southeast of the Moorcroft oil field, 90 miles northeast of the Salt Creek field, and 80 miles almost due north of the very promising Lance Creek field. Most of the producing wells are in sec. 83, T. 49 N., R. 66 W., and sec. 4, T. 48 N., R. 66 W. The Upton dome is about half a mile southwest of the town of Upton, in sees. 34 and 35, T. 48 N., R. 65 W., and sees. 2 and 3, T. 47 N., R. 65 W. The Thornton dome, which lies about 2J miles southeast of Thornton, is included mainly in sees. 7, 8, 17, and 18, T. 48 N., R. 65 W.

Ackkowldgmekts.

The writer was assisted in the field work by Mr. Robert M. Camp- bell, for whose aid he desires to express his appreciation. He is also indebted for hearty cooperation to many of the citizens of Upton, especially to Messrs. R. C. Chappell and F. W. Palis, of the South- west Oil Co., for valuable well data and for courtesies shown in many ways.

PTJBFOSE or THE INVESTIGATION.

The purpose of the present investigation was to assist in the de- velopment of the field by making a detailed study of the stratigraphy in order to determine the stratigraphic position of the oil-bearing sands and the possibility of obtaining oil and gas in other sands, also to discover and locate such structural features as have elsewhere been found to have a definite relation to accumulations of oil and gas.

17

18 Contbibutions To Economic Geology, 1920, Part H.

Method 07 Field Work.

The investigation that furnished a basis for the present report was made in July and August, 1918. The field observations were made and the maps prepared under the immediate supervision of the writer. In the process of mapping nearly all locations were made by triangulation, and elevations were determined by means of vertical angles. A line 10,400 feet long was measured on the railroad track southeastward from the station at Thornton, and with this as a base, a system of triangulation was extended over the area. Beginning with the known elevation of the railroad track at Thornton the elevation of each of the stations was determined by vertical angle.

History Of Development.

An attempt was made to test the Thornton dome several years ago. Two holes were drilled near the top of the dome, and from the appearance of the cuttings near the holes the drill must have penetrated the red beds. The first apparent discovery of oil was made by the Southwest Oil Co. in its No. 2 well about three years ago. Since that time the company has drilled 12 more wells and has obtained oil in every one of them.

Topography.

This field has no very conspicuous surface features. It lies along the southwest flank of the Black Hills uplift, and its topography is mainly the result of the action of wind, rain, and running water on the long, narrow outcrops of beds that present different degrees of resistance. For example, the Greenhorn limestone, which occurs between the great body of soft shale in the upper part of the Gran- eros formation and that of the Carlile shale, forms a continuous ridge from one end of the field to the other. Near Upton and about 2i miles southeast of Thornton local uplifting of the strata has given rise to relatively high areas exhibiting a reversal of dip along the east side. The doming of the strata near Upton lias produced an elliptical hill nearly 100 feet higher than the surrounding area. That about miles southeast of Thornton has given rise to a simi- lar hill whose top is approximately 170 feet above the surrounding flat.

Upton-Thornton Oil Field, Wyo. 19

The drainage channels in this field occur, for the most part, in the valleys between the outcrops of the more resistant beds. The up- lifting of the strata in the formation of the Thornton dome has given rise to a somewhat elevated tract from which the streams flow in opposite direction. A portion of the sediment that is picked up by running water near the top of this divide is carried southeastward and another portion goes northwestward. These two portions together completely encircle the Black Hills, one on the south and the other on the norths After being transported several hundred miles the sediment is again mingled in eastern Meade County, S. Dak., where Belle Fourche River joins the South Fork of the Cheyenne to form Cheyenne River.

Geology.

Stbatigbaphy. General Section.

No sedimentary beds crop out in this field which are lower in the stratigraphic column than those about 100 feet above the Dakota sandstone, the oldest formation of the Upper Cretaceous series in this region, but in attempting to determine the possibilities of the accumulation of oil and gas it is necessary to consider all the beds that lie within reach of the drill. In this field the principal known concentration of oil is in beds that reach llie surface a short distance from the center of accumulation, but in most other fields the greatest accumulations are in porous sands which are sealed by the overlying impervious beds, especially where the entire series has been arched upward. Inasmuch as the beds in this field have been arched in two different localities outside of the productive area it is necessary to consider the relations, composition, and depth of some of the under- lying beds. The following table shows the rock formations which crop out in this field, as well as those which were penetrated in the bore hole at the Antelope mine at Cambria, Wyo., and in the deep well at Cambria. The same formations from the Morrison down are represented graphically in figure 1.

20 CONTRIBDTtONS TO ECONOMIC GEOLOGY, 1920, PABT II.

MonUooaiuif..

8pearfl>h tormatloli

Boll BDd Enrcl. LIght-graj to ptnklih (hale.

SiDdj plnklih ahale. Sand; light-era j ihio Light -grar ahale am Soft buff nnd atone. Dark greenUb-gra; ahBle.

Red aad dart-t; cIaj.

88S

00

Gypsum, Gyp-am

Hlnnekahta

llmealoDr

ess

Red clay. LlmeBtone.

Opeche formation...

lOBQ

Bed sandy clay, porpUah at top.

Buff Mndatonm,

pink Minds looe.

Hlnneluaa

HIDdatODC

iseo

SandstoDH and dark ahale.

IBBl

Dark Bhale, 4 feet.

Darkebale.

CalcareoDs gray and aandatonea.

!?iJ

Light-colored sandBtonea.

Gray BBodatoDea. caleareoua near top.

BrowD aandBtoDea, layers of gray Itmeatone.

id gray tlmeatoDea.

Upton-Thobnton Oil. Field, Wyo.

Section of rock formations in the Upton-TlMmton field.

System.

Series.

Group,

Formation and member.

Character.

Thick- ness (feet).

Upper Greta* oeooB.

Montana.

Pierre shale.

Dark shale including a tone of calcareous concretions near middle and a few thin beds of bentonite. Only lower 1,200 feet to top of sone of calcareous ooncre- is mapped.

2,500±

Cokndo.

Niobrara shale.

Chiefly lieht-yellowish to cream-colorea calcareous shale, with some impure chalk, clay, and sand.

Oariile shale.

Dark shale with thin beds of soft sandstone mainly near the base.

Greenhorn lime- stone.

Impure slabby limestone.

m

O

Dark*ray to black shale, including many large cal- careous concretions, es- pecially in the upper part.

CretaceouB.

Mowiy shale member.

Bard, light-gray, ssndy shales containing numer- ous fish scales. Bentonite beds near the top and to some extent near the base.

Dark sandy shale upward into typical Mowry shale.

Reddish to light-yeUow sandstone associated with black carbonaceous shale.

3 to 16

Dark-gray to black shale.

Dakota sandstone.

Thin -bedded to massive hard buft sandstone.

Lovrer Creta- ceous.

Fuson formation.

Shale and thm-bedded sand- stone.

Lakota sandstone.

Sandstone, in part con- glomeratic, with some coal beds near the base.

CretaceoiisC?).

(7)

Morrison formation.

Light-gray to pinkish shale.

Juraaolo.

U]>per JuTBflsio.

Smidance forma- tion.

Liight-gray to dark greenish- gray and pmkish sandy shale with a 25-foot sand- stone near the base.

TrteasftD (?).

SpeiBrflsh fonnatlon.

Gvpsum and clj beds in alternating Recession. Popularly known as the ''Red Beds."

Pennlaa (7).

Mizmekahta lime- stone.

LlghtFay to pinkish or purplish limestone.

CteYxjoiferDut.

Opeche formation.

Red sandy clay, purplish at the top.

Femisyhranian.

Minnelusa sand- stone.

light gray to buff calca- reous sandstone.

MlasissippiazL

Fahasapa lime- stone.

White, pale-buff, pinkish, and gray limestone.

306±

22 Contributions To Economic Gbology, 1920, Paet Ii.

Formations Not Outcropping But Within Reach Of The Drill.

The section from the top of the Dakota sandstone down into the Morrison is weU shown in the bore hole of the Antelope mine, at Cam- bria, about 23 miles southeast of Upton.

Section in bore hole of Antelope mine at Cambria, Wyo.

Dakota : Feet.

Sandstone, thin bedded, at top of table 20

Sandstone, hard, massive, buff colored 40

Fuson :

Shale and talus 20

Lakota :

Sandstone, light colored, conglomeratic in part GO

Talus and sandstone ledges 70

Sandstone, light gray, soft, fine grained 60

Coal J 7 .

Sandstone, hard, light brown 5

Sandstone, soft, dark brown 2

Sandstone, light gray, moderately hard li

Coal with sandstone, shale, and pebbly layers

Sandstone, dark gray, soft 1

Coal, shales, and sandstone 2

Morrison :

Fire clay, gray 3

Sandstone, light gray, moderately hard li

Fire clay 7J

Sandstones, gray, upper half very hard 4

Shales with some thin sandstones 54

The deep- well boring at Cambria probably furnishes as detailed and reliable information regarding the underlying formations as can be obtained. The well was begun just below the T-foot bed of fire clay in the above section and was continued to a depth of 2,345 feet. The log of the well, as shown in figure 1, was compiled by N. H. Dar- ton from samples sent to Washington and from a set of borings ad- mirably preserved in glass tubes by Mr. Mouck, the superintendent of the Cambria mines.

Inasmuch as the beds exposed at the top of the Thornton dome lie about 100 feet above the Dakota sandstone, it follows that the beds at the bottom of the deep well at Cambria are about 2,830 feet stratigraphically below the top of the Thornton dome. The Upton dome is not eroded as deeply by about 200 feet, and consequently the same beds are about 2,930 feet below the top of that dome.

A careful analysis of the logs of the bore hole in the Antelope mine and the deep well at Cambria shows that the principal sand-

iDartXm, N. H., U. S. Geol. Surrey Geol. Atlas, Newcastle folio (No. 107), p. 4, 1904.

Upton-Thobnton Oil Field, Wyo. 23

stones beneath the surface in this region are included in the Dakota, Lakota, and Minnelusa formations. At the Antelope mine the Dakota is composed of an upper thin-bedded sandstone and a lower hard, massive buff sandstone. The Lakota is composed mainly of sandstone, in part conglomeratic, with coal beds near the base. The Morrison consists mainly of light-gray to pinkish shale, with beds of sandstone and firer clay near the top. The Sundance formation is composed mostly of light-gray to dark greenish-gray and pinkish sandy shales but includes near its base one soft buff sandstone about 25 feet thick. Extending from the base of the Sundance formation down to the Minnekahta limestone is the Spearfish formation, com- monly known as the "Red Beds," including gypsum and red clay in alternating succession. The Permian series is probably repre- sented by the Minnekahta limestone, about 34 feet thick, and the underlying Opeche formation, composed of 74 feet of red sandy clay, somewhat purplish at the top, although the Permian age of these formations has not been established. The Carboniferous from the base of the Permian series to the bottom of the well is composed essentially of sandstones and limestones. The Minnelusa formation consists almost entirely of light-gray to buff calcareous sandstones, the total thickness of which is 851 feet. From the base of this formation to the bottom of the well there is 398 feet of massive lime- stone.

Outcropping Formations.

Upper Cbetageous Rocks.

OOLOBADO OBOTTF. t

Osansbos Shale.

Overlying the Dakota sandstone in this field is a mass of soft, fine-grained deposits about 1,225 feet thick. The greater part of the mass consists of dark-gray to black shale which is very soft and yields readily to the ordinary agencies of erosion. About 225 feet above the base of the formation is a reddish-brown, mod- erately soft sandstone, the outcrop of which encircles the central portion of the Thornton dome and occurs in isolated patches neai the top of the dome. It is apparently only 2 or 3 feet thick aroimd the northwest end of the dome, but on tJie east side of sec. 17 it is considerably thicker. In that locality there is about 15 feet of reddish to light-yellow sandstone associated with some black car- bonaceous shale, somewhat resembling a section of the sandstone member, and associated beds of the Graneros shale measured on the west side of a gully about 4 or 5 miles northeast of Upton and one-

24 Contributions To Economic Geology, 1920, Part H.

eighth of a mile east of the main road. At that locality some pros- pecting has been done, apparently in a search for coal, and a 12-foot bed of light-yellow massive sandstone overlain by dark shale is exposed. The sandstone is underlain by 5 feet of black carbonaceous shale, which in turn is underlain by 8 feet of sandy shale and sand- stone. Underlying the 8-foot bed is 16 feet of somewhat sandy car- bonaceous shale. East of the gully is a long dip slope rising toward the east on the surface of a sandstone which weathers reddish brown and which is believed to be a few feet higher than the 12-foot massive sandstone on the west side of the gulch.

From Stockade Beaver Creek, about 5 miles southeast of New- castle, northwestward to the north side of T. 45 N., R. 62 W., the sandstone member of the Graneros is much thicker and is so hard and resistant that it gives rise to very prominent hogbacks southwest of the main ridge formed by the Dakota sandstone, from which it is separated by a line of narrow valleys eroded out of the intervening black shale. In the vicinity of Newcastle, where it contains more or less petroleum, it is about 85 feet thick, and a short distance west of that town it forms a ridge about 500 feet above the railroad.

Encircling the outcrop of the sandstone member of the Graneros in the Thornton dome is an area underlain by dark shale. This shale, which overlies the sandstone and gradually merges upward into the typical Mowry shale, is about 50 feet thick. This shale area, which sustains a rank growth of sagebrush, can readily be distinguished because it lies between the barren dip slope formed on the top of the sandstone member of the Graneros and the outer encircling area imderlain by the Mowry shale and characterized either by a stunted growth of grass or by an abundance of evergreens.

The narrow zone of dark shale described in the preceding para- graph in,erges upward into the typical Mowry shale member of the Graneros. The Mowry shale underlies at the surface the outer nar- row belt in the Thornton dome and the entire central portion of the Upton dome. It comprises about 150 feet of hard light-gray sandy shales that contain numerous fish scales. These shales weather nearly white, in strong contrast with the softer dafrk-colctfed shales alxJve and below. Owing to their superior hardness they do not erdde as rapidly as the overlying and underlying shales. The soil derived from them is in places entirely barren, as is well shown by the upper portion of the Upton dome. Although the outcrops of the Mowry shale are rarely grass covered, it is very common to find them cov- ered by a moderately dense growth of evergreens. In the upper part of the Mowry shale there are several thin beds of bentonite. This mineral is a hydrous sili<5ate of alumina with tithr ddnstiCu-

Upton-Thobnton Oil Field, Wyo. 25

ents in small proportions. It is characterized by its high absorbent qualities, having the power of absorbing three times its weight of water. It is a light-gray to yellowish fine-textured soft massive clay. One of the beds occurs about 16 feet above the top of the typical Mowry shale and is exhibited as a light-colored band around many of the low banks of shale between the Thornton dome* and Upton and for some distance north of the Thornton dome. It was especially valuable as a horizon marker in the determination of structure, because it shows a striking contrast to the rusty, iron-stained beds a few feet above the Mowry shale and was therefore very easily recog- nized. When wet the material is exceedingly stict, but on drying it shrinks and breaks up into small irregular-shaped lumps.

The upper 800 feet of the Graneros formation is composed essen- tially of dark-gray to black shale, including many large concretions, especially in the upper part.

Oreenhobn Umestone.

Immediately overlying the upper dark shale of the Graneros for- mation is a thin but very persistent series of beds of impure lime- stone known as the Greenhorn limestone. In most places the entire formation does not exceed 50 feet in thickness, but these limestone beds and the sandstones in the lower portion of the Carlile shale are so much harder than those above and below that they give rise to a continuous ridge or northeastward-facing escarpment extend- ing the entire length of the field. On weathering the thin beds of limestone become very hard and resistant, and in consequence the outcrop of the Greenhorn limestone is in many places marked by a series of thin slabs projecting above the surface. These slabs are commonly characterized by numerous impressions of Inocenmvus labiatus a fossil which rarely occurs in the Carlile and Graneros formations.

Cablujb 8Halb.

The Carlile formation consists mainly of shales with some thin beds of sandstone near the base. The entire formation is about 700 feet thick. The lower portion of the formation is best exposed in the railroad cut about 2 miles northwest of Thornton. Although it was rather difficult to measure the beds accurately along the rail- road, nevertheless the separate units in the following section were examined carefully and the description should convey a rather defi- nite notion regarding the composition of the lower third of the formation.

154071**— 21— Bull. 716 3

26 Contributions To Economic Geology, 1920, Part H.

Seption of the lower portion of the CarlUe shale and the Greenhorn limestone in the railroad,cut about 2 miles northwest of Thornton Wyo.

Ft In.

Sandstone soft and unconsolidated 4

Shale, dark gray 6

Sandstone, soft brown 1 4

Shale, dark, inclined to be sandy In places 20

Sandstone, in thin beds forming a shelving ledge; strike

N. 20" W., dip 25* S. W 3

Shale, dark gray 83

Shale, including some very thin beds of sandstone 15

Shale, dark, containing a few sandstone concretions and belts of very sandy shale. These shales and sandy shales were examined at several horizons and with few excep- tions gave a very distinct odor of petroleum. The sandy shales near the base are in places nearly saturated with

oil 90

Sandstone 10

Sandstone, soft, unconsolidated, and shale in alternating

bands, giving distinct odor of petroleum 2 6

Sandstone, hard 6

Soft sand and dark sandy shale in thin alternating layers ;

distinct odor of petroleum throughout 15

.Shale, dark, somewhat sandy 20

Soft sandy beds of yellowish-brown color, including seams

of dark sandy shale 20

Shale, very sandy, and' soft sandy layers including large calcareous concretions cut by Irregular branching veins of caldte. Probably represents the Greenhorn limestone— 20 Shale, very sandy 40

In many places the sandstone in the lower part of the Carlile shale gives rise to sharp ridges, and if the dips are very steep these ridges have very ragged crest lines.

Niobbaba Shale.

Owing to the softness of the constituent materials and the conse- quent lack of good exposures, the Niobrara shale is the most indefi- nite of all the formations in this field, and consequently the bound- aries as shown on the geologic map (PL VI) are subject to the greatest amount of error. The formation is about 200 feet thick and is composed of soft calcareous shale with some impure chalk, clay, and sand. Where the formation is unweathered it is generally light gray, but upon weathering it acquires a bright-yellow colojr. It sometimes contains hard, limy beds made up largely of an aggrega- tion of shells of Ostrea ccngesta a fossil very distinctive of the forma- tion. Owing to the softness of the beds it commonly occupies a more or less shallow valley at the foot of the slope formed by the harder rocks of the Carlile shale.

Upton-Thornton Oil Field, Wyo, 27

XOVTAVA QfROVT.

Pierre Shale.

This field (see PL VI) includes only the lower portion of the Pierre shale, or from thebase up to the top of a well-defined zone of calcareous concretions, which, on the basis of the structure sections, appears to be about 1,200 feet above the base of the formation* The formation in general is made up of a rather uniform mass of dark- colored shale, but at certain horizons the shale contains more or less admixed sand. There are also other horizon markers in the shale, such as thin beds of bentonite and zones of calcareous concretions, some of which are very fossiliferous. The first well-defined ridge southwest of that formed by the Greenhorn limestone and overlying beds is developed along the outcrop of one of these zones of concre- tions, which is shown on Plate VI.

Stbttctube.

Method Op Representation.

In order to obtain a &irly adequate notion of the lay of the sedi- mentary rocks in the Upton-Thornton field the reader should care- fully examine Plate VI, which shows the long, linear outcrops of the different formations and by structure contours and structure sec- tions their angle of inclination and distance above sea level. The fol- lowing explanation is offered for the benefit of those who are un- familiar with the interpretation of structure' sections and structuie contours.

A structure section is based mainly on the degree of inclinaticm of the beds at the surface, on measured stratigraphic thicknesses, and on data derived from deep borings. It shows how a portion of the earth's crust would appear if it were cut along a vertical plane and the rocks on one side of the plane were entirely removed and exhibits the angle of inclination as well as the relation of the different formations to the surface and also to sea level. Four sections showing the structure along lines A-A% B-B', C-C', and D-D' are given on the map, and section D-D' shows the formations given in the table on page 21.

Structure contours are lines drawn on a map to show the eleva- tion of a chosen horizon or stratum above or below a certain datum plane, as, for example, mean sea level. They are like topo- graphic contours in that every part of any one contour is at the same elevation above the chosen datum plane. They are designed to show the shape and magnitude of the folds and in general the irregular warping of the beds. In the preparation of the accom- panying map, it was decided to use two sets of structure contours,

28 Contributions To Economic Geology, 1920, Part U.

as shown under " Explanation.'' One set is drawn on the top of the sandstone lentil in the lower part of the Graneros shale. The con- tours in this set are indicated by the unbroken lines, and each con- tour is 60 feet either above or below the adjacent one. The con- tours of the second set are represented by the broken lines and are drawn on the top of the principal oil sand in the lower part of the CarHle shale. It follows, therefore, that any particular contour is the line of intersection between the top of the sand which is contoured and a horizontal plane a certain distance (for example, 4,000 feet for the 4,000-foot contour) above sea level.

Structure Of The Upton -Thorn Ton Field.

The Upton-Thornton field as a whole occupies a portion of the southwest flank of the Black Hills uplift, and hence the prevailing dip is toward the southwest, but as the structure sections clearly show, the dip increases as the distance from the Black Hills in- creases. In the eastern part of the field the beds rise toward the Black Hills at a imiformly low angle, but in the western part the dips range rom 10° to 25°. The bedding in the Pierre shale is not as easily recognized as that in some of the lower formations, but by careful observation thin layers of sandstone, belts of con- cretions, and yellow beds of bentonite can be detected in many places. Such beds indicate a southwesterly dip in the southern part of the field of 17° to 20°, and the Pierre shale is inclined at a similar angle as far north, as Thornton. From that place northward, how- ever, the beds flatten out very materially. The true angle of dip can be determined with greatest accuracy from thin beds in the Greenhorn limestone. South of Thornton that formation is in- clined southwestward at angles ranging from 10° to 16°, but in the vicinity of the Chicago, Burlington & Quincy Railroad where the strike changes abruptly, the Greenhorn limestone and overlying beds are inclined as steeply as 25°. North of the railroad the beds soon flatten and the dip is as low as 10°. South of the railroad in sees. 8 and 4, T. 48 N., R. 66 W., the entire series from the Green- horn limestone to the zone of concretions in the Pierre shale dips very steeply, but the structure contours, which are based solely on the depth of the principal oil sand in the wells, indicate an abrupt flattening of the beds north of the railroad. Structure section A-A', which is based on the dip of the Greenhorn limestone at its outcrop, on the elevation of the principal oil sand in the wells, and on the total thickness of beds between the principal oil sand and the zone of concretions in the Pierre shale, shows a well-defined struc- tural terrace, or perhaps, to judge from the shape of the structure contours, an abrupt flattening along the axis of a low anticline*

Upton-Thornton Oil Tield, Wyo. 29

In line with the strike of the beds in this field and about where the beds begin to flatten in approaching the Black Hills were devel- oped two rather well-defined domes which, owing to their situation, are here named the Upton dome and the Thornton dome. The sur- face at the top of the Thornton dome about 180 feet higher than it is at the top of the Upton dome, but the beds exposed at the top of the Thornton dome are about 250 feet nearer the Dakota sandstone than those at the top of the Upton dome, so that corresponding beds are about 430 feet higher in the Thornton than in the Upton dome. The beds at the top of the Upton dome are about 100 feet higher than the corresponding beds at the axis of the syncline a mile to the ast and about 50 feet higher than the same beds at their lowest point between the Upton and Thornton domes, so that the amount of closure in this dome is small. The Thornton dome, on the other hand, is much higher, and the beds which crop out at the top are approximately 500 feet higher than the corresponding beds at the xis of the syncline between the Thornton dome and the Black Hills uplift.

The writer was unable, for lack of time, to study the structure far north of the line between Crook and Weston counties. The work there was confined mainly to the mapping of the Greenhorn lime- stone, and although structure section A~A' shows the beds dipping Westward from the top of the Mowry shale at a very low angle, nevertheless the wide belt of outcrop and the few dips recorded near the north edge of the field indicate the necessity for further study.

Oil.

0Cgt7Bbekces Op Oil Keab The Ufton-Thobntok 7Ieli).

Some of the beds that crop out along the southwest flank of the Black Hills have for many years been known to contain oil in small quantity. The most pronounced seepages occur in the vicinity of Newcastle and in the Moorcroft field, which extends northward from Moorcroft, in a general way from Belle Fourche River to the center of T. 52 N., R. 67 W.

The sandstone that occurs about 225 feet above the base of the raneros shale ranges from 10 to 30 feet in thickness in the vicinity of Newcastle. A small quantity of excellent petroleum oozes from this sandstone in at least two places. One of these oil springs is ear the railroad about 2 miles west of Newcastle, where the sand- stone underlies the long dip slope extending southward from the top of the high ridge west of Newcastle and dips beneath the surface in a small gully immediately north of the railroad. At the time of the writer's visit the oil had collected to considerable extent in an old cistern-like structure immediately southwest of the railroad, and

80 Contribxttioks To Economic Geology, 1920, Part H.

from all appearances it was being freely used as a lubricant by those living in the vicinity. The other spring is said to be about 2 miles farther northwest and a little farther north of the railroad. Sev- eral attempts have been made to develop the oil-bearing sand in its extension underground by means of wells a short distance west and southwest of Newcastle, but apparently these operations have not yielded a large supply of oil. The oil is very heavy and even in its crude state is reported to be a high-grade lubricant

A high-gravity oil also finds its way to the surface at several locali- ties in the Moorcroft field, and in order to convey some notion regard- ing the nature of the seeps, the probable source of the oil, and the ef- forts that have been made to develop the field, the following is quoted from a previous report :

In the SE. i sec. 2, T. 61 N., R. 87 W., at a smaU spring seeping from the shale and sandstone of the Fuscm shale, oil collects on the sorface of the water ; in the NB. i NE. i sec. 34, T. 52 N., R. 67 W., a very small amount of oU occurs in a ravine in the sandstone member of the Graneros shale; in the NE. i SB, J sec. 27, T. 52 N., R. 67 W.. there is a spring of water on the surface of which oil collects in sufficient quantity to be dipped up with a ladle; and about oneuarter of a mile farther north, in the next ravine, at another spring of water, oil coUects in very smaU quantities. In the sandstone member of the Graneros shale exposed in a ravine in the SB. i sec 22, T. N., R. 67 W., there is oil in sufficient quantity to give a brownish color to the rock and impart a distinct odor of petroleum. Oil also seeps to the surface in three of the old drill holes along the west flank of the anticlinal ridge, as follows : WeU No. 4, In sec. 36, T. 51 N., R. 67 W. ; well No. 14, in sec. 12, T. 51 N., R. 67 W. ; and well No. 90, in the NE. i sec. 34, T. 52 N., R. 67 W. Oil is obtained at a depth of about 600 feet from six wells in the NW. i sec. 34, T. 52 N., RL 67 W., where it occurs either in the sandstone member of the Graneros shale or in the Mowry shale member of the Graneros and is reported to have been struck at a depth of about 600 feet.

Of the 65 seeps and wells described in the following pages, 3 are oil springs, 21 re shallow holes which should not be considered wells, and 41 are wells which are perhaps fair tests for oil at the localities where they were drilled. Of these 41 test holes 15 are reported to have struck "showings" or smaU quantities of oil. One well is reported to have yielded a small amount of gas, and four wells gave flowing water. All the wells in the field but seven have been abandoned as oil wells.

The map accompanying the report on the Moorcroft field shows that the beds dip westward away from an irregular anticlinal axis at an angle of about Most of the wells were begun either in the Mowry shale or in the upper dark shale between the Mowry and the Greenhorn limestone, apparently with the hope of obtaining consid- erable oil in the sandstone member of the Graneros shale. The se- quence of beds is apparently the same as in the Upton-Thornton field, but the reader should bear in mind that the oil which is at

Barnett, V. H., The Moorcroft oil field, Crook County, Wyo.: U. S. Oeol. Survey Bull. 581, p. 86, 1915.

UPTOir-THORNTOK OIL FIELD, WYO.

present being obtained in the Upton-Thornton field comes from beds much higher in the sedimentary coliunn than those so thoroughly tested in the Moorcroft field.

Oil Nea& Thobnton.

The soft sandy shales and more or less pure sandstones near the base of the Garlile shale come to the surface and are well exposed in the railroad cut about 2 miles northwest of Thornton. These beds are petroliferous throughout and in places are thoroughly saturated with oil. It is reported that oil has been known to seep from these beds in sufficient quantity to accumulate in small pools in the bottom of the ditch along the railroad track. During the last two years con- siderable drilUng has been done north of the raih*oad, mainly by the Southwest and High Gravity oil companies, for the purpose of test- ing these sands, and at present a small quantity of high grade light oil is being obtained from the wells by pumping and also by bailing. The Southwest Oil Co. has erected a small refinery near the center of the field and is able to supply local trade with gasoline and other products. The wells are all shallow, their depth, of course, depend- ing on their distance from the outcrop. The oil is obtained mainly from a sand which ranges in thickness from 29 to 47 feet and is reached at depths ranging from 448 to 843 feet. The depth of the wells and the depths at which the principal oil sand was reached are shown below. A good showing of oil was also obtained in some of the wells from a sand 6 to 80 feet thick which occurs from 22 to 50 feet above the principal oil sand. The productive capacity of the wells that have already been drilled will probably range from 5 M 10 barrels a day.

Depth of tcells and depth to principal oil sand in Upton-Thornton field, ''.Vyd.

WeUNo.

Southwest OU Co.:

S

Depth of well (feet).

I>epthto

prrndpal

oil sand

/Ceet).

Well No.

North Central Oil Co.:

High Gravity Oil Co.:

Depth of well (feet).

DrUIing.

Depth to

principal

oil sand

(feet).

Quality Of The Oil.

The oil that is being obtained near Thornton is of medium light olive-green color and has a low specific gravity. Six samples of oil taken from wells 2 to 7, inclusive, of the Southwest Oil Co. were analyzed with the results shown below.

Contributions To Economic Geology, 1920, Part Ii.

AnalyseM of oils from toelU of the Southwest Oil Co., Upton-Thornton field, Wffo.

(Made in the laboratory of the Bureau of Mines. Distillation in Bureau of Mines Hempe!

flask. Amount distilled, 200 centimeters.]

Air distillation, with fractionating oohmin.

Vacuum diatf llation, without firactionating column.

OrsTlty at

To 150* C.

150*to300C.

175 to 300' C.

Wen

Ba- rometer read-

(mnil- meten).

No.

latlon

Total

per- centage

tilled

Specific gravity

at 125*-

Total per- centage tilled

Speclflo gravity

at

Pres- sure (miUi- meten).

Total

per- centage

tilled

Resld- uum (per

cent).

Sul- phur

aw

oent).

by vol-

150*C.

by vol-

300* C.

by vol-

ume.

ume.

ume.

a

a833

3Z4

jO.843

a 10

Oaioin Of The Oil.

The primary source of petroleum is not definitely known, but most oil geologists believe that it is of organic origin. It seems probable that most of the petroleum in the earth's crust has originated from plants rather than animals, for two reasons — in most rocks the car- bonaceous remains of plants are far more abundant than those of ani- mals, and the hydrocarbon-bearing portions of animals decompose more readily than the corresponding parts of plants. It has been e6ti|aated that more' than 99 per cent of the carbonaceous material in tSe earth's crust is of plant origin. Aside from the water which they contain, plants consist mainly of the elements that enter into the composition of petroleum and natural gas, namely, oxygen, hydro- gen, and nitrogen. It is true that the soft parts of animals are com- posed mainly of the same elements, yet they decompose much more readily and therefore are much more likely to be dissipated into the atmosphere or to be picked up by running water before being buried so deeply that oxidjktion and decomposition cease. In certain locali- ties petroleum and natural gas have been found intimately associated with plant remains ; in others they are more directly associated with the hard parts of animals, as, for example, the shells of moUusks. The great accumulations of petroleum and natural gas, however, indicate migration on a large scale, hence it is in general very difficult to say whether these substances originated where they now occur or whether they originated elsewhere and gradually migrated to their present position as a result of the chemical and physical processes that are continuously going on within the earth's crust

The oil-bearing sands near Thornton lie immediately above the Greenhorn limestone, in which the shells of mollusks are abundant.

Upton-Thoenton Oil Field, Wyo. 33

The limestone itself overlies a thick mass of dark shales, and the oil-bearing sands are overlain by similar material containing cal- careous concretions many of which are very fossiliferous. It seems to the writer reasonable to suppose that the oil now present in the sands originated, to some extent, from the soft parts of these sea animals but also in part from carbonaceous material included in the dark shales themselves.

CONDITIONS OOVEBNINQ THE ACCUMlTIiATION OF OIL AND GAS.

A careful examination of the structure of the rocks and its rela- tion to concentrations of oil and gas in many parts of the world has given rise to the structural or anticlinal theory. The conditions that control the accumulation of oil and gas, according to this theory, are briefly as follows: ,

1. A reservoir rock. This is commonly known as an oil sand, al- though it may be a very sandy shale, a fractured rock of some kind, a loose conglomerate sufficiently porous to allow the accumulation of oil or gas, or a porous limestone composed largely of interlocking crystals of calcite.

2. An impervious cap rock, to seal over the reservoir rock and pre- vent the upward escape of the oil and gas.

3. Folds in the rock favoring the accumulation of oil and gas in certain localities, these substances migrating from more extensive areas of adjoining beds less favorably situated for their retention.

4. Saturation of the rocks by ground water, on which the oil and gas will move on account of their lower specific gravity and be forced into the upper parts of the folds. According to the anticlinal theory, if a porous rock containing gas, oil, and water is folded between other rocks which are nonporous, these substances, imder the influence of gravity, separate and arrange themselves according to density. Gas, being the lightest, rises to the crest of an anticline, the oil separates out below, and the water seeks the deepest portions of the beds. Detailed field observations have shown not only that many of the concentrations of oil and gas are intimately related to anticlines and domes, but also that gas, oil, and water are related in the manner indicated. Although the recognition of these facts has caused most geologists to accept the anticlinal theory in its broader aspects, many of them are willing to accept it only in a modified sense, as recent study has shown that accumulations of oil and gas occur not only in the crowns of the arches but also in many places on the flanks of the folds where the dips are interrupted for some dis- tance, the interruptions forming structural terraces.

The accumulation of oil near Thornton bears a definite relation to such an area of local flattening of the beds, and the writer believes that this flattening is the principal cause of the accumulation. In- asmuch as the oil sands, where exposed at the surface, contain very

84 Contributions To Economic Geology, 1920, Part Ii.

little organic material, it seems reasonable to assume that the oil which they now contain had its origin in the dark shales and impure fossiliferous limestone above and below. It is believed that the surrounding shales and impure limestone far from the outcrop and for some distance along the strike have contributed toward the present accumulation. If the assumption is correct that the oil and a little gas originated in the surrounding beds, they must have grad- ually migrated through these beds into the porous sands, which were probably pretty thoroughly saturated with water. As the oil, gas, and water become mingled in the steeply dipping porous sands they in all probability separated and arranged themselves in the order of density, for although intermolecular attraction no doubt plays an im- portant part in the movement of these substances it is the writer's belief that where the sands dip steeply gravity is probably the domi- nant force. The oil, being less dense than the water was borne up- ward, but as it entered the sands that were nearly flat-lying the viscosity of the oil and the adhesion of the oil and sand were prob- ably almost equal to the greatly diminished force of gravity. In the gently dipping beds, where the opposing forces were active, the up- ward movement of the oil was retarded and the result was a greater concentration, but where a local flattening of the beds does not occur it is doubtful if the upward movement has been suflSciently retarded to produce any considerable concentration of oil.

SXIOaESTIOKS FOB DBILLINa.

The close relation which has been observed between anticlinal structure and accumulations of oil and gas suggests that the Upton and Thornton domes should be carefully tested with the drill. From the description of these domes given under the heading " Structure " it is evident that the Thornton dome offers the greatest possibilities for oil and gas accumulation, mainly for the reason- that it is a much higher fold, the closure being about ten times that of the Upton dome.

The sandstone lentil that occurs about 225 feet above the Dakota sandstone and is commonly oil bearing in this region has been eroded from the Thornton dome, but it lies beneath about 150 feet of cover in the Upton dome. Owing to its thinness in this locality, however, and the lack of a sufficiently impervious cap rock there is little prob- ability of finding much oil in that sand in the Upton dome. The Thornton dome has been drilled at two points with apparently un- favorable results, and both of the holes seem to have been well located. The writer was unable to obtain the logs of the wells, but from the appearance of the dried sludge the drill must have entered the red beds. Owing to the fact that considerable oil was encountered in the Minnelusa sandstone in the Old Woman anticline, about 75 miles to the south, the writer feels that the Carboniferous beds should also be thoroughly tested in so promising a fold as the Thornton dome.

The Mule Creek Oil Field, Wyoming.

By E. T. Hanoook.

Introduction. Looatiok And Extent Of The Field.

The Mule Creek oil field, as shown in Plate VII, is in the northeast- em part of Niobrara County, Wyo., about 4 miles from the east line of the State. It lies about 100 miles almost due east of the Salt Greek oil field and about 35 miles northeast of the Lance Creek field. The field, as mapped and described in this report, includes about 30 square miles of territory immediately south of Cheyenae River, in T. 39 and 40 N., Rs. 60 and 61 W. In this field there are two rather well defined anticlines, which for convenience of description will be referred to as the eastern and the western anticline. The top of the eastern anticline is about 18 miles almost due west of Edgemont, S. Dak., a flourishing town on the Chicago, Burlington & Quincy Railroad, from which most of the supplies going to the field are hauled. At a station called Aientine, some distance northwest of Edgemont, the railroad lies within 12 miles of the field.

ACXNOWLEDaMENTS.

In presenting this report the writer desires to express his thanks to David White for valuable suggestions and criticisms and to Carroll E. Dobbin for assistance in the detailed mapping. He also wishes to call attention to the publio service rendered by the oil and gas operators, who very willingly furnished the records of deep borings.

Fu&Pose Of The Znyestiqation.

A geologic investigation of this character requires, first of all, a thorough study of the outcropping strata. Such a study is made for two reasons. In the first place, a geologic report, to be of the great- est practical value, should describe each conspicuous bed or set of beds so vividly, with respect to composition, general appearance, effect upon topography, and other salient features that the oil oper-

36 CONTKIBXJnONS TO ECONOMIC GEOLOGY, 1920, PABT U.

ator, land owner, or prospective investor will be able to recognize it in the field. In the second place, it is very important to make a thorough study of the strata so as to be able to determine the struc ttire accurately. In working out the structure it is necessary to ascertain the elevation and dip of many of the beds that come to the surface, but there is nothing to be gained by making careful instrumental determinations unless the investigator is reasonably certain regarding the relation, in the stratigraphic column, of the beds that crop out in different parts of the field. After the outcrops of the different beds have been traced and located on the map, both as to horizontal position and as to elevation, and after such well logs as are available are examined, it is possible to show by means of structiu'e contours the attitude of any particiQar bed such as an oil sand throughout the field. The oil sand whose attitude is shown by contours on the map in this report is that in the Ohio Oil Co.'s producing well in the NE. i sec. 24, T. 39 N., R. 61 W. At this point the record of the well shows the elevation of the sand; and nearly everywhere else the elevation has been calculated by means of other criteria.

Field Wobx.'

The field investigation that furnished the basis for the present report was made between July 8 and 17, 1919. The observations were made and the maps prepared under the inmiediate supervision of the writer, who was ably assisted in the field by C. E. Dobbin.

In the process of mapping nearly all locations were made by the triangulation method and elevations determined by means of ver- tical angles. A base line (A-B, PI. VII) 7,900 feet in length was carefully measured along the high land from the south end of the western anticline to the SE. J sec. 24, T. 39 N., R. 61 W., and the extremities were designated by means of a white flag. After the plane table had been oriented at the points designated, certain monuments and a number of the drilling rigs were located by inter- section, and a system of triangulated points was extended through- out the field. In the absence of a permanent bench mark an eleva- tion of 1,000 feet was assumed for the flag at the northwest end of the base line, and all other elevations were based upon the assumed elevation. Later on the elevation of the sandstone in the NE. sec. 6, T. 39 N., R. 60 W., was determined by reading a vertical angle on the Chicago, Burlington & Quincy Railroad track at Argen- tine, S. Dak., and the assumed elevations were revised in accordance with the new elevation thus determined. It is apparent, therefore, that the elevations shown on the accompanying map (PL VU) are only approximately correct.

Mx7Le Creek Oil Field, Wyo. 37

In view of the purpose of the investigation, it was necessary to trace out and map the boundaries between the different formations and to determine the elevation and record the strikes and dips of the beds at many points. Where it was possible to trace a definite horizon within a formation and especially where the beds are in- clined at a very low angle the structure was determined by means of elevations taken at short intervals.

Land Surveys.

Only a small proportion of the section and quarter-section comers in this field are marked by pits and set stones. The locations of most of the comers have been established by local surveys and are at present indicated by means of plainly marked square posts.

Surface Features.

The Mule Creek oil fieldforms apart of a relatively high area bordered on the north and east by the broad alluvial valley of Cheyenne River. The elevations in this field range from about 3,550 to 4,100 feet. The highest land is at the top of the eastern anticline, and the lowest is in the broad valley along the Cheyenne River. The eastern and western anticlines are rather well defined, but they differ considerably in relation between structxu*e and surface form. A long period has elapsed since the sandstone which now forms the top of the eastern anticline was removed from the crest of the western anticline. Since the agencies of erosion swept this sandstone and the underlying Greenhorn limestone from the crest of the western anticline they have been actively at work removing the great body of soft shale between the limestone and the Dakota sandstone, and at the present stage of erosion the western anticline is marked by a drainage basin, whereas the eastern anticline is represented by a relatively high dome-shaped lull. The drainage basin of the western anticline is bordered on the south and west by a continuous ridge formed mainly by the Green- horn limestone. The surface of the field is rather rough, owing to the presence of numerous small gullies, most of which unite to form larger ones extending northward and eventually reaching Cheyenne River. Most of the field is covered with grass and sagebrush. There are nu- merous Cottonwood trees along the valley of the Cheyenne and an oc- casional Cottonwood along the principal gullies, but the remainder of the field is entirely barren of timber. The field is readily accessible either by way of an excellent graded road leading west from Edge- mont, S. Dak., or byway of the main road leading northwest from Edgemont along the west side of the valley of Cheyenne River. Most of the traffic seems to be over the road leading west from Edge- mont, which enters the field at the south end, follows closely the axis of the eastern anticline, and leads down the slope to the area of Mowry shale at the top of the western anticline.

CONTBIBUnONS TO ECOXf

ator, land owner, or prospoi :

in the field. la the seoon.!

thorough study of the str„ .

tore accurately. In nor

ascertain the elevation ;

2-Lzz-i izid .ie-rh-:.

the surface, but thcri'

instrumental detemii,

. , :ut* Tl.. 3 MTur Ln — :

certain regarding tl

beds that crop oui

- ffv-arr t - fL-;.ipr -mvii if -_ii-

of the different h,

. wdna'.

as to horizontal i

.1 I'll die UpTfC-TaumcijE. jii -if.;,

as are availalili

- . iinhwest tad bears a anuiiir .-ri;:*-

structure couf

wriliT tuis diicaifieii ji i.i-iir<.i:.

sand througl

.1. 'iiyse which were E>'cern,--i

by contour-;

;f at Cambria, Wju., i:iji "in

,.:i.inik Inasmuch aa :L:tf- J.-rums:

the recor-!

-- ji .ieid oiTur at pnc'Jiij -n iame

everywli'

\;tic*d in the t'ptoo-Ti;c- .c ztLi.i.

criteria.

. J .- :;:a[ rt'port iarepe*.!.;-; itsTf wtia.

:. writer's intfipTKuJi'it le* zhe

Til.

- :.'. -.lif well Ic given hl 52.

repo

- , -, T HIT ABE VTTBIS aiL\C£ OF

of 1

u.

riciil occur about 75 few iWnr .: si-owi locaUties not fiir di?3Aiit, . -r well exposed. Ihtse hods are - - h! alitrf the southwest £ank rf Uw , ,. (, and also in the vkiniij of -k oi the Old Woman aatidine, a I -,jij of this field, in the Tiani lh Dak>ta sandstmie about

til.

angle on tine, S. I with the that the are only

IFioni ouloopplng beds and dMp iKcliigi at Cambria, Wyo.]

38 Contributions To Economic Geology, 1920, Pabt H.

GEOLiOGY.

General Section.

The hlgliest beds in the sedimentary series mapped and described in this report are those which occur at the top of the Niobrara forma- tion. The lowermost beds exposed are those which occur in the Mowry shale, but in a comprehensive discussion of the possibilities of oil and gas concentration it is necessary to consider such of the deeper beds as are within reach of the drill.

In the recently published report on the Upton-Thornton oil field/ which lies about 60 miles to the northwest and bears a similar rela- tion to the Black Hills uplift, the writer has discussed, in addition to the formations that crop out, those which were penetrated in the bore hole at the Antelope mine at Cambria, Wyo., and also those in the deep well borings at Cambria. Inasmuch as the lowermost beds exposed in the Mule Creek field occur at practically the same horizon as the lowermost beds exposed in the Upton-Thornton fields the table of formations given in that report is repeated here, with certain alterations in the thicknesses of some of the units above the Dakota sandstone to conform to the writer's interpretation of the identity of some of the sands shown in the well log given on page 52.

Formations That Do Not Crop Out But Are Within Reach Of

The Drill.

The lowest beds exposed in this field occur about 75 feet below the top of the Mowry shale. At some localities not far distant, however, the underlying beds are well exposed. These beds are exhibited where they are upturned along the southwest flank of the Black Hills uplift to the north and east, and also in the vicinity of Wright's camp, near the north end of the Old Woman anticline, a few miles to the southwest. Northeast of this field, in the vicinity of Newcastle, there is immediately above the Dakota sandstone about 225 feet of dark shale that erodes very readily, producing a relatively low area between the long dip slopes formed by the Dakota sandstone and the more or less jagged ridge formed by a sandstone lentil that overlies this shale. The extent of development of this sandstone lentil along the flanks of the Black Hills uplift and in the adjacent area is a matter of vital interest to oil and gas operators, not only because oil issues from it in considerable quantities at Newcastle, but also because it is one of the main oil-producing sands at other local- ities in Wyoming. In the Upton-Thornton oil field it is a reddish- brown, moderately soft sandstone encircling the central portion of

the Thornton dome nd occurring as isolated patches near the top

J Hancock, E. T,, The Upton-Thomto9|(||gld, Wyo.: U. 8. Geol. Survey Bull. 718, pp. 17-34, 10 (BuU. 71&-B).

Mule Creek Oh. Field, Wyo.

Rock formations in the Mule Creek field, Wyo. [From outcropping beds and deep borings at Cambria, Wyo.]

Sjstem.

ja,,„, 1 Group, formation, and

Character.

Thick- ness (feet).

Upper Creta- ceous.

Colorado group.

Niobrara formation.

Soft shaly limestone or Impure chalk, Including some clay and sand.

CarlUe shak.

Dark shale with thin beds of soft sandstone (Wall Creek sandstone member) near the base.

Oreenhom limestone.

Impure slabby limestone. .

Bo

Graneros shale.

Dark-gray to black shale, in- cluding many large calca- reous concretions, especially in the upper part.

Cretaceous.

Howry shale member.

Hard light-gray sandy shales contaiining numerous fish scales. Contains bentonite beds near the top and to some extent near the base.

Dark sandy shale grading up- ward into typical Mowry shale.

Newcastle sand- stone member.

Reddish to -veDow sand- stone associatea with black carbonaceous shale.

3 to 15

Dark-gray to black shale.

Dakota sandstone.

Thin-bedded to massive hard buff sandstone.

Lower Creta- ceous.

Fus<m formation.

Shale and thin-bedded sand- stone.

Lakota sandstone.

Sandstone, in part conglom- eratic, with some coal beds near tne base.

Cretaceous (?) (?)

Morrison formation.

Light-gray to pinkish shale.

lao

Jurassic.

Upper Jurassic.

Sundance formation.

Light-gray to dark greenish- gray and pinkish sandy shale, with a 25-foot sandstone near the base.

TTiaas!c(?)

Spearflsh formation. Minnekohta limestone.

Gypsum and red clay beds in alternating suooession (" Red Beds").

Permian (7).

Light-gray to pinkish or pur- plish limestone.

'arbonUeroiM.

Pennsylvanian.

Opecho formation.

Red sandy day, purplish at the top.

Mlnnelusa sandstone .

Light-gray to buff calcareous sandstone.

Mlsslssipplan.

Pahasapa limestone.

W hite, pale-buff, pinkish, and gray Uznestooe.

40 Contributions To Bconomic Geology 1920, Part Ii,

of the dome. It is apparently only 2 or 3 feet thick at the northwest end of the dome, but on the south end it includes about 15 feet of reddish to light-yellow sandstone associated with some carbonaceous shale. In the vicinity of Newcastle, where considerable oil seeps from this sand, it is about 35 feet thick and forms a ridge about 500 feet above the railroad. It continues as a very conspicuous ridge as far southeast as the L. A. K. ranch, on Stockade Beaver Creek, but from that point southward it becomes thinner, appearing only at intervals as lenses in the shale. It seems to be rather well developed, however, near the north end of the Old Woman anticline, about 12 miles southwest of the Mule Creek field. The conditions there are as foUows: About three-quarters of a mile northwest of Wright's camp the Dakota sandstone forms a long dip slope. The sandstone is overlain by about 200 feet of dark shale. The shale is overlain by a succession of sandstones and carbonaceous shale beds which give rise to a very conspicuous ridge. This group of beds, the details of which are shown in the following section, is in part at least equivalent to the oil-bearing sand at Newcastle.

Section of sandstone and carbonaceous shale beds northwest of Wright'' s camp.

Ft. In.

Sandstone very hard, forming east dip slope 2 6

Mainly black carbonaceous shale 9 0

Sandstone, yellowish brown, maasiye 6 6

Shale, sandy, carbonaceous 9

Sandstone, rather thinly bedded 7 0

Shale, black, carbonaceous 5 6

Sandstone, yellowish brown, hard Imd massive 4 6

Shale, sandy 1-f

36+

The group of sandy beds described above is doubtless widely dis- tributed throughout Wyoming. It was recognized by the writer on the south slope of the Como Ridge, about 6 miles east of Medicine Bow, and is in all probability equivalent to the sand that occurs near the middle of the Thermopolis shale at different localities in the Big Horn Basin and is commonly known by drillers as the Muddy sand. These beds attain an unusual thickness at Newcastle and are oil bearing at that locality, so for convenience of description they are named the Newcastle sandstone member.

The beds immediately above the Newcastle sandstone are plainly exhibited along the north side of the Thornton dome, described in the report on the Upton-Thornton oil field. Encircling the sand- stone in the Thornton dome is an area which is underlain by dark shale. The shale that overlies the Newcastle sandstone and grad- ually merges upward into the typical Mowry shale is about 50 feet thick. The upper half of the Mowry shale is exposed in the Mule

Mule Greek Oil Field, Wyo. 41

Creek field at the top of the western anticline and for that reason the entire formation is described on succeeding pages along with the others which crop out in this field.

The section from the top of the Dakota sandstone down into the Morrison is well shown in the bore hole of the Antelope mine at Cambria, Wyo. At that locality, which is about 40 miles north of the MiQe Creek field, the following section is exhibited:

Section in bore hole of Antelope mine at Cambria Wyo}

Dakota: Feet.

Sandstone, thin bedded 20

Sandstone, hard, massive, buff .' 40

Fuson: Shale and talus 20

Lakota:

Sandstone, light colored, conglomeratic in part GO

Talus and sandstone ledges 70

Sandstone, light gray, soft, fine grained 50

Coal 7

Sandstone, hard, light brown 6

Sandstone, soft, dark brown 2

Sandstone, light gray, moderately hard

Goal with sandstone, shale, and pebbly layers

Sandstone, dark gray, soft 1

Coal, shales, and sandstone 2

Morrison:

Fire clay, gray 3

Sandstone, light gray, moderately hard

Fire clay , 7J

Sandstone, gray, upper half very hard 4

Shales with some thin sandstones 54+

The deep-well boring at Cambria probably furnishes as detailed and reliable information regarding the tmderlying formations as can be obtained. This well was begun just below the T-foot bed of fire clay in the above section and was continued to a depth of 2,345 feet. The log of the well as shown in figure 1, was compiled by K. H. Darton from samples sent to Washington and from a set of borings admirably preserved in glass tubes by Mr. Mouck, the superintendent of the Cambria mines. According to this log and the section from the bore hole of the Antelope mine there are 2,636 feet of beds between the top of the Dakota sandstone and the bottom of the deep well. In all probability there is a slight variation in the total thickness of the for- mations between Cambria and the Mule Creek field, but on the assump- tion that the total thicknesses are the same, the beds which occur at the bottom of the deep well at Cambria are about 2,900 feet below the surface at the top of the western anticline at Mule Creek and 3,770 feet below the surface at the top of the eastern anticlines.

*DvtOD, K. H., U. 8. Qeol. Sonrey Geol. Atlas, Newcastle folio (No. 107), p. 4, 1904. 154071*>— 21— BuU. 716 4

42 . Contributions To Economic Geoix)Qy, 1920, Part H.

A careful analysis of the logs of the bore hole and the deep well at Cambria shows that the principal sandstones beneath the surface in this region are included in the Dakota, Lakota, and Minnelusa forma- tions. At the Antelope mine the Dakota is composed of an upper thin-bedded sandstone and a lower hard, massive buff sandstone. The Lakota formation is composed mainly of sandstone, in part con- glomeratic, with coal beds near the base. The Morrison is composed mainly of light-gray to pinkish shale, with beds of sandstone and fire clay near the top. The Sundance formation is composed of light- gray to dark greenish-gray and pinkish sandy shales, including near its base one soft buff sandstone about 25 feet thick. Extending from the ba3e of the Stmdance down to the Minnekahta limestone is the Spearfish formation, commonly known as the Triassic ''Red Beds,'' including alternating beds of gypsum and red clay. The Permian series is probably represented by the Minnekahta limestone, about 34 feet thick, and the tmderlying Opeche formation, composed of 74 feet of red sandy clay, somewhat purplish at the top. The Carboniferous from the base of the Permian series to the bottom of the deep well is composed essentially of sandstones and limestones. The Minnelusa formation, of Pennsylvanian age, consists almost entirely of light-gray to buff calcareous sandstones, the total thickness of which is 851 feet. From the base of this formation to the bottom of the well there is 398 feet of massive limestone.

FORMATIONS EXPOSED. VmOL O&XTAOZOVS BSBIB8.

Colorado Group.

The Colorado group in this locality includes the Niobrara formation, Carlile shale, Greenhorn limestone, and Granerous shale. The last three formations are equivalent to the Benton shale of other axeas.

Graneros shale, — Overlying the Dakota sandstone in this region is a mass of softy fine-grained deposits whose total thickness is about 885 feet. According to Gilbert' the name Graneros was first suested by R. C. Hills for an equivalent group of beds exposed along Graneros Greek about 20 miles south of Pueblo, Colo. The greater part of the mass consists of dark-gray to black shale, which is very soft and which yields readily to the ordinary agencies of erosion. About 175 feet above the base of the formation there is conmionly what may be called a sandy zone. This zone of sandy material — here named the Newcastle sandstone member, from Newcastle, Wyo., where it is conspicuously developed — varies in thickness and also in composition in derent localities, as explained on pages 38-40, but it can gen- erally be recognized by anyone reasonably familiar with their strati- graphy. It is commonly overlain by 25 to 50 feet of dark shale, which merges upward into the typical Mowry shale.

Gilbert, O. K., The uxiderground water of the Arkansas Valleyln eastern Colorado: IT. 8.- Qaol. SarrcT Seventeenth Ann. Bept., pt. 2, p. 57D 1896.

Mule Cbeek Oil Field, Wyo. 43

The term "Mowrie beds" was first applied by Darton in his description of the Big Horn region to a group of beds exposed along Mowiy Creeky northwest of Buffalo, Wyo. The Mowiy shale in more or less typical form is exposed in this field at the top of the western anticline, where, as near as the writer could estimate, erosion has removed about one-half of the original thickness. Where the Mowry is upturned along the southwest flank of the Black Hills uplift it ordinarily includes about 150 feet of hard light-gray sandy shales, many of the individual plates of which exhibit fish scales. These shales, on weathering, become almost white, in strong contrast with the softer dark-colored shales above and below, and, owing to their superior hardness, they do not erode as rapidly as the overlying and underlying shales, so that the position of the Mowry shale member is commonly indicated by a more or less continuous ridge or by a suc- cession of low hills covered by a moderately dense growth of ever- greens. In this field some of the shale has been removed from the top of the western anticline, and certain thin layers of sandstone are laid bare for several hundred feet. The top of the Mowry shale is well exposed along the west side of the anticlines near the center of sec. 2, where it is marked by two 4-foot beds of bentonite separated by 8 feet of dark shale. This bentonite is a light-gray to yellowish fine-textured soft and massive clay. It is a hydrous silicate of alumina with certain other constitueixts in small proportions and is characterized by its highly absorbent qualities. The upper bed of bentonite is overlain by about 10 feet of dark-gray flaky shale, and this in turn by very black shale containing considerable heavy black, iron-stained material in thin layers and also in individual concretions. The bentonite and the associated beds are valuable horizon markers in eibstem Wyoming because of their persistence over wide areas.

From the Mowry shale member up to the Greenhorn limestone the Gb'aneros formation is composed essentially of dark shale containing scattered calcareous concretions.

Oreenhom limestone. — Immediately overlying the upper dark shale of the Graneros formation is a thin but very persistent series of beds of impure limestone known as the Greenhorn limestone. According to Gilbert,* this limestone first took its name from Greenhorn Creek and Greenhorn station, about 14 miles south of Pueblo, Colo. The entire limy series does not generally exceed 50 feet in thickness, but these limestone beds are so much harder than the beds above and below that they give rise to a more or less continuous ridge bordering the western anticline on the west and south and to a considerable extent on the east. They also give rise to a very prominent escarp-

Dartaa, K. B., Camparison of stratigmphy of Black HUb, Bigfaom Moantolns, and Rooky Hountaln Front BaniKe: GeoL Soc America BulL, vol. 16, p. 400, 1904.

Formerly sometimes spelled "Mowrie." QUbsrt, O. K., op. It., p. 670.

44 Contributions To Economic Geology, 190), Pabt H.

ment extending from east to west along the north side of Cheyenne River. Where the resistant beds of impure limestone have not given rise to a well-defined ridge their outcrop is indicated on the surface by a narrow belt having a distinctly lighter color and curving in obedience to the gradual change in the strike of the beds. On weathering the thin layers of impure limestone become very hard and resistant, and where the beds dip steeply the outcrop is commonly marked by a series of thin slabs projecting above the surface. Many of these slabs contain numerous impressions of Inoceramus lahiataSf a fossil that rarely oocurs in other formations of Benton age.

CarlUe shale. — The name Carlile shale was first applied by Gilbert to a body of shale resting upon the Greenhorn limestone in the vicinity of Carlile Spring and Carlile station; about 21 miles south of PueblO; Colo. In the more recent reports of the Geological Survey the same name is applied to a group of beds having the same strati- graphic position but differing considerably from those at the type locality. In the report on the Upton-Thornton oil field the writer calls attention to the fact that the lower 230 feet of the Carlile shale is composed essentially of soft sand and very sandy shale. These beds are all exposed in the railroad cut about 2 miles northwest of Thornton Wyo. The lowermost 200 feet of the Carlile shale is not well exposed in the Mule Creek field, and hence that part of the formation is believed to be composed essentially of shale and imper- fectly consolidated sandy beds. The upper portion of the section exhibited in the railroad cut near Thornton is represented in this field by a group of sandstones and carbonaceous shale beds about 35 feet thick. The beds of this series crop out in the western anti- cline a few hundred feet outside of the Greenhorn limestone and also along the gulches both east and west of the eastern anticlinal axis, and they occur at the surface at the producing well on the highest part of the eastern anticline. From the stratigraphic position of these sandstones and associated beds they are believed to represent the Wall Creek sandstone of areas farther west. The beds are weU exposed in the NE. sec. 7, TBO N., R. 60 W., where the following section was measured:

Section showing the beds which constitute the Wall Creek sandstone member in the NE, i

sec, 7, T. 39 N,, R, 60 TT., Wyo.

Fwt

Sandstones, yellowish brown, soft and very irregularly bedded 7

Shale, dark, sandy, and carbonaceous 4

Sandstone and dark carbonaceous shale, interbedded 5

Shale, dark, becoming very sandy near the top 9

Shale, dark gray and very sandy, including numerous thin beds of

sandstone 10

T OUbert, O. K,, op. clt., p. 570.

Mule Creek Oil Field, Wyo. 45

The following species of invertebrate fossils were obtained from the above-described beds near the main road about a mile farther west, in the NE. i sec. 12, T. 39 N., R. 61 W. They were examined by T. W. Stanton, who states that they belong to the Benton fauna and indicate a horizon within the Carlile shale.

Aporrhais sp.

Corbula sp.

InoceramuB fragilis Hall and Meek.

Limatia sp.

Prionocyclus wyomingensiB Meek.

Prionotropus sp. related to P. hyatti Stanton.

Scaphites warreni Meek and Hayden.

Throughout the eastern part of the Mule Creek field the sandy beds shown in the above section occur at or very near the surface, and either all or a large part of the upper portion of the formation is eroded, but in the western part of the field the upper portion is present. In that area the Carlile dips rather steeply beneath the Niobrara formation and, like that formation, presents very few exposures.

Niobrara formjoiion. — The Niobrara formation rests unconf orm- ably upon the Carlile shale and is exposed throughout a narrow belt along the south and west sides of the field. This formation was first named in the reports of the Hayden Survey, and the type locality is along Missouri River near the mouth of the Niobrara, in northeastern Nebraska. At that locality the beds form vertical cliffs from 90 to 100 feet in height. In the Mule Creek field the characteristics of the formation are best exhibited east of the main road, at the south end of the field. It includes about 200 feet of soft shaly limestone or impure chalk containing more or less shale, fine sand, and clay. It also includes some thin beds of hard limestone which consists of aggre- gations of Ostrea congesta, a fossil very distinctive of the formation. The unweathered exposures of the formation are usually grayish, but the weathered outcrops are decidedly yellow. The formation is therefore very conspicuous, although the constituent beds are soft and give rise to few noticeable ridges.

STBTTCniBE. GENERAL FEATURES.

The Rocky Mountain Front Range and the Black Hills uplift are connected by what is commonly known as the Hartville uplift, an irregular arch whose axis is indicated by exposures of granite, schist and limestone near Hartville and Lusk, at Rawhide Butte, and at a number of other localities. The position of the axis is also indicated by the Old Woman anticline, which brings to the surface the upper- most beds of the Sundance formation. The Mule Creek oil field lies in the direct continuation of this axis, about midway between the

46 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1920, PABT n.

Old Woman anticline and the rather steeply dipping beds along the southwest flank of the Black Hills. The great disturbance which brought the major uplifts into existence also resulted in the forma- tion of two well-defined anticlines in the Mule Creek field, but the strata involved in these folds were uplifted relatively little in com- parison with the arching of the same strata in the Old Woman anti- cline or the Black Hills uplift. The location and form of the two principal anticlines of the Mule Creek field are clearly shown on the accompanying geologic map (PL VII) . The smaller one of the two lies south and east of the larger, and for want of better names they are called the eastern and western anticlines.

Methods Of Representing Structure.

Different methods have been used from time to time by the €reo- logical Survey for the purpose of conveying to the reader an adequate notion regarding the folding, or what is frequently referred to by drillers and others as the "lay" of the beds. The structure is ordi- narily shown by means of either structure.sections or structure con- tours. The structure section is based mainly upon the degree of inclination of the beds at the surface, upon measured stratigraphic thicknesses, and upon data from deep borings. It shows how a por- tion of the earth's crust would appear if it were cut by a vertical plane and the material on one side of the plane were removed. The structure section is an excellent aid in the explanation of structure where the beds dip steeply, but where they are inclined only a few feet to the mile it is difficult to bring out certain structural features without exigerating the vertical scale more than is desirable. In oil and gas investigations, where the interpretation and representation of structure are extremely important, the method of representing structure by contours has been adopted because of its practical value and also because it is easily understood. The following explanation is offered for the benefit of those who are unfamiliar with the defini- tion, degree of accuracy, and practical application of structure con- tours:

Structure contours are lines drawn on a map to show the elevation of some particular stratum above or below a certain datum plane, as, for example, mean sea level. They are designed to show the shape and magnitude of the folds and, in general, the irregular warping of the beds. In the preparation of the accompanying map (PI. VII) it was decided to show, throughout the field, as accurately as the data available would allow, the elevation of the sand that yields oil in the Ohio Oil Co.'s producing well in the NE. i sec. 24, T. 39 N., R. Gl W. Any particular contour is the line of intersection between that sand and a horizontal plane a certain distance (for example, 2,000 feet for the 2,000-foot contour) above sea level. Each struc-

Mtjle Cbbek Oil Field, Wyo. 47

tiire contour represents a level 100 feet above or below that of the one adjacent, and hence it follows that where the contours are closely spaced the beds are steeply inclined, and where they are widely spaced the formation approaches much nearer to horizontality.

Structure contours furnish a convenient method for presenting to the reader a comprehensive idea regarding the structure of an entire field. Their practical value depends, of coiurse, upon their accuracy, and their degree of accuracy depends upon the number of data avail- able. In certain developed oil fields it is possible to obtain numerous well logs and recognize in them, either directly or from other beds, the position of the particular bed which it is desired to contour. After a structiu'e-contour map is made for such a field the depth to the contoured bed at any point can be ascertained very accurately by subtracting from the surface elevation at that point the elevation of the contoured bed as shown by the structiue contom*. In other fields, where little drilling has been done and especially where mai\y of the records were not preserved, it is necessary to depend almost entirely upon surface data, such as dips, measured intervals between beds, and elevations of traceable beds in making a structure-contour map. In such fields the structure contours are not likely to be drawn as accurately, but the demand for information is often so acute that it becomes necessary to sacrifice a certain degree of acciu-acy in order to insure more prompt publication. On the map of the Mule Creek field the structure contours are. drawn mainly on the basis of dips, measured intervals, and elevations of traceable beds. At the Ohio Oil Co.'s producing well at the top of the eastern anticline, in the NE. i sec. 24, T. 39 N., R. Gl W., the Wall Creek sandstone occurs at the surface and the oil sand occurs at a depth of 1,394 feet. For- tunately, it was possible to trace and determine the elevation of the Wall Creek sandstone throughout a large portion of the field and from it to determine the elevation of the oil sand. The top of the Green- horn limestone is very close to 200 feet below the top of the Wall Creek sandstone, and therefore it is about 1,200 feet above the oil sand. It follows, then, that the top of the Howry shale is about 570 feet stratigraphically above the oil sand if the thicknesses of the different formations and members are approximately those shown in the table of formations on page 39.

Stbuctube Of The Mule Creek Field.

The structural relation of the Mule Creek field to the sturounding region is discussed on pces 45-46. As a result of the forces which were active in this region, two well-defined anticlines were developed in the Mule Creek field. The axes of these two anticlines trend nearly due north, and the more pronounced of the two is a little north and west of the other. The two anticlines are separated by a sharply

48 Contributions To Economic Geology, 1920, Part H.

curving syncline. As shown on Plate VII, the axis of the western anticline extends from sec. 23, T. 39 N., R. 61 W., to the northeast comer of the same township and from that point in a sweeping curve to the northeast comer of sec. 30, T. 40 N., R. 60 W., and in all probability for some distance farther east. The beds involved in this anticline are at most points inclined from 5° to 15, but along the west side opposite the small area of Mowiy shale they dip as steeply as 26. East of the axis the beds are inclined from 14 to 16° at the south end, but farther north they become flatter as the fold broadens out. The axis of the eastern anticline extends from the synclinal axis southward to the Ohio and Midwest wells, at the top of the ridge near the west line of sec. 19, T. 39 N., R. 60 W., and thence it follows the township line closely for an indefinite dis- tance southward. From this axis the beds are inclined at angles ranging from 3° to 6°. The axis of the syncline extends from the NJJ. J sec. 23 to the SE. sec. 12, T. 39 N., R. 61 W., where it makes a sharp curve, and from that point it extends toward the middle of the north side of sec. 20, T. 39 N., R. 60 W.

When the two anticlines came into existence the same beds were forced up much higher in the western than in the eastern anticline, as is shown by the following facts. The Wall Creek sandstone, which crops out at the top of the eastern anticline, is about 236 feet higher than the Mowry shale, exposed at the top of the western anticline, but according to the thicknesses as given in the table of formations on pie 39, there are about 900 feet of beds between the Wall Creek sandstone and the uppermost exposed beds of the Mowry. If the tops of the two anticlines were at exactly the same elevation, it is evident that the difference in elevation of corre- sponding beds would be equal to the stratigraphic interval, or 900 feet, but inasmuch as the top of the western anticline is 236 feet lower than that of the eastern anticline, it follows that any par* ticular bed in the western anticline is 900 minus 236, or 664 feet higher than the corresponding bed in the eastern anticline. The reader should keep in mind, however, that this calculation is based on the log of the Ohio Oil Co.'s discovery well and the assumiption that some of the formations are considerably thinner in the Mule Creek field than they appear to be in the Upton-Thornton field,

oiij and qas.

FACTOBS THAT GK)VEBKr THE ACCUinJLATION OF OIL A2n> aAS,

A careful comparison of the structure of the rocks and its relation to concentrations of oil and gas in many parts of the world has given rise to the structural or anticlinal theory. The conditions that control the accumulation of oil and gas, according to this theory, are briefly as follows:

Mule Creek Oil Field, Wyo. 49

(a) A reservoir rock, commonly known as the oil "sand," although it may be a very sandy shale, a fractured rock of some kind, a loose conglomerate sufficiently porous to allow the accumulation of oil or gas, or a porous limestone -or dolomite composed largely of inter- locking crystals of calcite or oolitic grains.

(b) An impervious cap rock to seal over the reservoir rock and prevent the upward escape of the oil and gas.

(c) Folds in the rock favoring the accumulation and confinement of oil and gas in certain localities, these substances migrating from more extensive areas of adjoining beds that are less favorably situ- ated for their retention.

(d) Saturation of the rocks by groimd water, on which the oil and gas will move on account of their lower specific gravity and be forced along the more porous strata into the upper parts of the folds.

According to the anticlinal theory, if a porous rock containing gas, oU, and water is folded between other rocks which are non- porous, these substances, under the influence of gravity, separate and arrange themselves according to density in the porous zone. The gas, being the lightest, rises to the crest of the anticline, the oil separates out below, and the water occupies the deeper portions of the beds. It is a well-recognized fact that oil and gas have entered porous sands from adjacent beds and that they have in many areas migrated long distances to the points of concentration, but it is not absolutely demonstrated just what forces are the most active in causing oil, gas, and water to migrate from the fine clays and shales into the porous sands. Neither has it been proved beyond con- troversy to what extent gravity and capillary attraction influence the movement of those substances along porous sands that are inclined at an extremely low angle.

Detailed field observations have shoWn not only that many of the concentrations of oil and gas are intimately related to anticlines and domes, but also that gas, oil, and water adjust themselves in the strata in the manner stated above. Although the recognition of these facts has caused most geologists to accept the anticlinal theory in its broader aspects, many geologists are willing to accept it only in a modified sense, as recent study has shown that accumulations of oil and gas occur not only in t&e crowns of the arches but also in many places on the flanks of the folds where the dips are less steep for some distance, the local flattening forming structural terraces. Recent studies indicate also that the conditions of accu- mulation are entirely different in saturated and imsaturated rocks — that in thorouy saturated rocks the oil and gas are borne upward on the sheet of underground water and are caught in the crowns of the arches, whereas in dry rocks the principal point of accumula-

50 Contributions To Economic Oeologt, 1920, Pabt H.

tion of oil may be near the bottoms of the synclines or at any place where the forces obstructing the movement of particles of oil are equal to or in excess of those which promote such movement.

In saturated rocks the ideal structural form is the dome which includes a thick bed of porous sand that is effectively sealed above and dips gently for considerable distances, but such a form is not common in nature. In many domes the dips are limited by other structural features, and in consequence the collecting area is small. The oil sands may be lenticidar, or continuous sands may be offset along f aidt planes. If the fault remains partly open fluids migrating through the porous sands may rise to the surface and escape. It has been found that many oil seeps are characterized by deposits of asphalt. If the fault is sealed by clay, asphalt, or some other imper- vious substance the oil and gas may concentrate in the sand near the fault plane, and the result is practically the same as when the sand is lenticular. Thus an open f aidt fissure may prevent concentration at the top of an anticline or dome, and a fissure effectively sealed may produce local concentration at some point along the flank. The migration of oil, gas, and water through porous sands up along the flank of the most ideal structural featiu'e may be retarded where the beds abruptly flatten or where the porosity of the sand decreases, and it may be entirely obstructed where a dike of igneous rock cuts across the sands. From the facts above outlined it is not surprising that some concentrations of oil and gas occur in places where, from all surface indications, the conditions are unfavorable, whereas some areas that appear to have the most favorable structure are barren. These conditions are mentioned briefly, not with the object of depreciating the value of the anticlinal theory as a working hypothesis, but merely to emphasize the necessity for making in every field a thorough study of all the conditions which may in any way retard the movement of fluids and result in concentration.

Possible Pboditctive Sakds.

In an attempt to apply what has been said to the Mule Creek field certain facts become at once apparent. In the first place, a careful examination of the beds exposed along the southwest flank of the Black Hills shows that there ai% many porous beds in this field beneath the horizon of the Wall Creek sandstone and within reach of the drill. It is also apparent from the table of formations (p. 39) that many of these porous beds are overlain by impervious beds, and the geologic map (PI. YII) shows plainly that the entire series has been arched upward, forming two well-defined anticlines. With these facts in mind we should attempt to ascertain, from experience in adjacent fields, which of these porous beds are the most Ukely to yield oil and gas.

Mi7Le Creek Oil Field, Wyo. 51

In the description of the lowest beds exposed m the Mule Creek field (pp. 38-42) considerable emphasis is placed on the Newcastle sandstone, which at Newcastle occurs about 50 feet below the Mowry shale and about 225 feet above the top of the Dakota sand- stone. These sandy beds are widely distributed throughout eastern Wyoming, and they exhibit considerable variation from one locality to another, even along the southwest flank of the Black Hills. They contain oil at Moorcroft and Newcastle and gas in the Big Horn Basin, and are probably the main oil and gas sands in the Lance Creek and Rock Creek fields. The GreybuU sandstone member of the Cloverly formation produces most of the oil and gas of the Greybull field. In the Powder River field the approximate stratigraphic equivalent, which was designated the Dakota (?) sandstone, is the principal oil-bearing formation, but a small quantity of oil occurs in at least two sands in the Morrison, and it is also present in small quantity in the Sundance formation. The Carboniferous portion of the Embar group bears oil in the Lander field, and a 1,730-foot boring on the Old Woman anticline, about 15 miles southwest of the Mule Creek field, is reported to have found considerable oil, doubtless in the Minnelusa sandstone, also of Carboniferous age.

Development In The Mule Cheek Field.

Attention was first directed to the Mule Creek field by the recog- nition of the western anticline, and the earliest development was in the nature of shallow drilling, mainly for the purpose of validating claims. As usual, the interested persons reported the '' commercial discovery" of oil, but accurate records of the wells were apparently not preserved. The first important discovery of oil was made early in 1919 by the Ohio Oil Co. near the top of the eastern anticline, in the SE. 1 NE. i sec. 24, T. 39 N., R, 61 W. When the writer's field examination was completed this was the only producing well in the field, but since that time a number .of other wells have been brought in near the axis of the eastern anticline. The writer is in possession of very little information concerning the recently completed wells, and consequently the detailed descriptions are omitted. The loca- tion and character of the recent wells, as shown on the geologic map (PL VII), are based upon a map furnished by the Ohio Oil Co. According to a statement in the Oil and Gas News of November 6, 1919, the producing wells at that time averaged from 125 to 150 barrels a day and the total production of the field exceeded 1,000 barrels a day. Like most of the oil obtained from that horizon in Wyoming, the Mule Creek oil is of low specific gravity and, has a paraffin base. It is reported that the Illinois Pipe Line Co. has begun laying a pipe line Irom the field northeastward to Dakoming, a station on the Chicago, Burlington & Quincy Railroad near the line between South Dakota and Wyoming.

Contbibutions To Economic Geology, 1920, Part H.

In order that the reader may become familiar with the strati- graphic position of the sand from which the oil is obtained in the discovery well, the log of that well is given below.

Log of Ohio Oil Co.'s producing well in theSE.i NE.\uc. 24, T. S9 N., R. 61 W., Wyo.

[DrOtor's Interpratatlan.]

Depth.

Sandy shale

SheU

Blue hard shale

SheU :

Blue shale

SheU

Blue abate

SheU

Blue and gray shate

Sand: showing of gas

Bluesliale (Newcastlesandstone horlson 176 feet above base)

Dry sand

Water sand

Blugray shale

Bhie shale containing stveaka of sand

Sand

Bandy shale resonbling talc (oil sand)

The above log indicates that the drill penetrated more than 200 feet of sand before reaching the principal oil-bearing stratum. According to the thickness of the different members as shown in the table of formations accompanying the recent report on the Upton-Thornton field, the top of the Newcastle sandstone would be near the base of the water sand" in the above log, but where the Newcastle sand- stone crops out along the southwest flank of the Black Hills and in the Old Woman anticline it rarely exceeds 50 leet in thickness. In the Lance Creek field it is composed of an upper and a lower sand- stone separated by hard shale, and the combined thickness of the three beds is probably not greater than 50 feet. Owing to the fact that the Newcastle sandstone is scarcely recognized immediately east of this area, where the beds are upturned in the vicinity of Edgemont, it seems reasonable to suppose that this sandstone is very thin in the Mule Creek field, and furtJiermore, that the ''dry sand'' and ''water sand'' noted in the above well log together constitute the Dakota sandstone, that the imderlying blue-gray shale is equivalent to the Fuson shale, and that the oil is derived from an oil sand in the Lakota sandstone. In arriving at this conclusion it is necessary to assume that the formations above the Dakota are somewhat thinner at Mule Creek than they appear to be in the Upton-Thornton field, but never- theless the field evidence seems to justify such a conclusion.

Mule Greek Oil Field, Wyo. 58

Considerable drilling has been done on the western anticline, mainly for the purpose of validating claims. Some of these wells, in all probability, were drilled below the horizon of the Newcastle sand. More recently considerable drilling has been done near the axis of the anticline by the Ohio, Sterling, and other oil companies. According to recent reports, iiie Ohio Oil Co. has drilled two wells as deep as the ''Red Beds" (Spearfish formation). One of these wells is in the SE. i sec. 11; T. 39 N., R. 61 W., and the other is near the southwest comer of sec. 36, T. 40 N., R. 61 W. The company is now (January, 1920) considering drilling the latter well still deeper for the purpose of testing some of the lower sands. Both of these wells are called dry holes, and both are well located with respect to the axis of the anticline. Having reached the ''Red Beds/' they have penetrated the sand that produces oil on the eastern anticline. The horizon of the oil sand is much higher in the western anticline, as explained on page 48, and there is an extensive collecting area to the north and west, but the results of drilling seem to be rather discouraging. The failure to obtain oil near the top of the western anticline is probably due to a change in the thickness or porosity of the oil sand, but addi- tional subsurface data are necessary before the problem can be satis- factorily solved.

NATURAL-GAS RESOURCES AVAILABLE TO DALLAS AND OTHER CITIES OP CENTRAL NORTH TEXAS.

By E. W. Shaw and P. L. Ports.

NATURE OF THE PROBIiEM AND PREVIOUS WORK.

The acute shortage of gas in Dallas and other cities in north Texas during the winter of 1919-20 led to an urgent request from Mayor Frank W. Wozencraft, of Dallas, that the United States Geological Survey make an examination of the gas resources of the region with a view to determining whether the shortage was due to exhaustion of underground supplies or to some nongeologic cause such as inadequacy of wells or transportation equipment, lack of proper adjustment of prices, or wasteful consumption.

In 1915 a similar call had come from the cities of Dallas and Fort Worth, and an examination of the principal source of supply — the Petrolia field — and other more or less productive or promising ter- ritory led to the conclusion that all known Texas fields as at that time developed would not fully meet the growing demand of these cities for more than a year or two and that it would be wise to extend the pipe lines to fields in southern Oklahoma. This was done, and as a re- sult of the added supply thus made available and of the curtailment of industrial use the needs of the gas-consuming communities have been fairly well met for three years. The main conclusions set forth in the first report are as follows :

Petboua Fdeu).

Original quantity of gas in the field, — The volume of pore space occupied by gas and the original rock pressure and also the relation between decline in pressure and percentage of depletion indicate that the original quantity of gas in the PetroUa field, measured at 8 ounces above atmospheric pressure, was about 120 billion cubic feet.

Ratio between percentage of depletion 'and amount marketed, — Statistics of production Indicate that about 37 billion cubic feet of gas from the Petrolia field have been delivered to consumers. This quantity is about 75 per cent of the reduction of supply in the ground. The question whether or not this per-

Bliaw, B. W., liataon, G. C, and Wegemann, C. H., Natural-gas resaurces of parts of north Texas : U. & Gec. Survey BuU. 029, pfK 78-76, 118-119, 126 1916.

56 COlTRIBUTIONS TO ECONOMIC GEOLOGY, 1920, PABT H.

centage should be larger Is beyond the scope of this report, but it may be re- marked that many gas fields shoV a greater waste.

Present capacity, — The PetroUa field as now drilled and equipped Is capable of producing more gas per day than it has ever been called upon to produce. The limit of its daily capacity depends in part upon engineering considerations not discussed in this report, such as the handling of wells and pipe lines, but it is probably at least twice that of any demand which has been made upon it.

Capacity in near future of the field as now drilled. — The dally capacity of the wells In the field is steadily decreasing, and indeed the field as a whole Is doubt- less rapidly approaching Its limit In rate of production. While the demands upon it have been steadily growing, its capacity has been diminishing because of reduction of supply and pressure, and before many years have passed the supply will no longer meet the demand.

Capacity in distant future of the field as now drilled, — If no new gas wells were drilled the production would not only tM below the demand in a few years, but in 10 years the output would probably be too small to be worth trans- porting.

Increase of capacity through new wells to known sands Un the proved field, — The capacity of the field may be kept up for a few years by new wells drilled to known sands within the proved field, but the present wells are rather evenly distributed and closely spaced, so that Increase of output through new wells can not be great

Increase of capacity through finding new sands in the proved field, — More gas can probably be found in some parts of the field by drilling deeper, for sands having favorable structure, texture, and stratigraphlc and lithologlc relations lie below the sands now producing. A few small gas-bearing lenses of sand lie above the producing sand, and though these lenses contain much less gas than the so-called deep sands they should not be overlooked.

Increase of capacity through finding new productive area adjoining the field. — The daily capacity of the field may be increased by new wells drilled outside the proved field to sands now producing. The structure of the field indicates that the actual area of the gas pool Is probably twice that of the area now producing, though a part of the new area may yield oil instead of ga& The production can not, of course, be doubled by simply doubling the producing area, for gas has been slowly moving from the undrllled ground to the producing weUs, so that throughout most if not all of the undrllled parts of the pool the original gas content and pressure in the sands have been reduced, though not so greatly re- duced as in the developed part of the pool.

Increase in marketed supply through greater care in handling wells. — The depletion of the original supply of gas at Petrolia is evidently considerably greater than the quantity of gas marketed, the loss Incidental to the production of oil being especially noteworthy. The output could be increased by handling the wells somewhat differently, but the work of properly caring for the natural supply must be left to the engineers.

Life of the field. — If all the gas at Petrolia could be delivered to consHmers In Dallas and Fort Worth and other cities now drawing on the Petrolia supply it would probably last them, at the present rate of consumption, about 6i years. If an estimate is made of the increase in consumption that will probably occur if the supply is adequate and no advance is made in the price, proper deduc- tion being made for necessary losses in production and marketing, the estimate of years must be reduced to about 4 or 5, and if further allowance be made for unnecessary losses, it must be reduced to 8 or 4 yeaiB, and a shortage will be felt in cold weather still sooner.

Katubal-Gas Resources Of Central North Texas. 57

Otheb Fields.

Other discovered pools northwest and west of Dallas and Fort Worth, par- ticularly those at Strawn and Moran, have noteworthy quantities of gas/ though not so much as Petrolla, and these supplies would be available to the cities if the pools were near to each other or to the existing pipe lines.

Undiscovered pools of gas and oil undoubtedly exist in the area described Id this report, and some of them will probably be large enough to warrant the bailding of individual pipe lines. If several of them were developed at once, however, sufficient gas would be made available to justify the construction of lines to groups of pools. The search for new pools must be pushed with vigor if the present output is to be maintained or Increased.

Gas has been found at Baileyville, Koose, Thornton, Groesbeck, Mexia, Wortham, Currie, Richland, Corsicana, Powell, Chatfleld, Mabank, Gash, and Cooper. At only three of these places have wells furnished gas In commercial quantities, and at only two have wells furnished oil, but the significance of the presence of gas in the area between Bailesrville and Cooper is not affected by the conunercial value of the discoveries that have been made. These discoveries show the presence of gas-bearlhg sands through this belt, and investigations indicate that the dip of the beds here is not uniformly toward the southeast bat is interrupted by terraces and minor reversals of dip. Structure favorable to the accumulation of oil or gas, similar to that at Mexia, Groesbeck, Powell, and Corsicana, will no doubt ultimately be discovered in this region, which is therefore regarded as a possible oil and gas field.

Conclusions Beoabdino Oklahoma.

In conclusion, it may be stated that the gas resources of central and southern Oklahoma are sufficient, if protected from waste and properly handled, to fur- nish supplies to such cities as Dallas and Fort Worth for years to come. The Sas is, however, for the most part distributed over large areas in many pools of comparatively small size, and it may prove unprofitable under present con- ditions to build pipe lines of sufficient extent to collect it. Among the larger gas pools may be mentioned the field south of Checotah, in Mcintosh County, which is at present being drilled. The large supplies of gas in the immediate ▼idnity of the Healdton oil field are worthy of careful consideration, especially since the bringing in of the new gas well near Fox, north of the field, which suggests the possibility of the presence of other gas pools in this vicinity.

In 1918 an estimate of the quantity of gas remaining in the Pe- trolia field was made by G. S. Rogers,' in connection with an in- vestigation of the helium resources of the country. Rogers examined critically the data and methods used by Shaw three years before, checked the results, with the help of new facts ined from the be- havior of the field in the intervening period, and concluded that Shaw's estimates of original reservoir capacity and quantity remain- ing in 1915 were correct and that in July, 1918, between 13 and 20 billion cubic feet remained in the pool. He remarks that if the re- maining gas were used at an average rate of 15,000,000 cubic feet a

' Rogers O. S. Helium-bearlBg natural gas : U. S. GeoL Survey Prof. Paper 121 (In 164071— 21— Bull. 716 5

58 Contributions To Economic Geology, 1920, Part H.

day the field would last two and one-half to three years. Since his es- timate was made, however, the Lone Star Gas Co. has contracted with the Niivy Department to reduce the output of the field to 10,000,000 cubic feet a day. Also since that time gas has been discovered on the Martin farm, about 2 miles west of the main part of the field, and the question has arisen whether the Martin wells are to be regarded as being in the Petrolia field, and whether their gas is a part of that in the Petrolia pool.

The evidence at present available indicates that in the middle of. 1918 there was 20 to 25 billion cubic feet of recoverable gas in the Petrolia pool, including the Martin gas, and that at the end of March, 1920, there remained 8 or 10 billion cubic feet of recoverable gas, for at that time the entire field seemed to contain only 12 to 15 billion cubic feet of gas, and of this about 4 or 5 billion cubic feet will never reach the consumer, for the reason that some will be left underground and some lost on its way to market. The method of computation is outlined on the following pages.

In the matter from the previous report quoted above it is con- cluded on the basis of geologic evidence that undiscovered pools of gas and oil undoubtedly exist in the region, and in the text and figure on page 20 of that report the favorable general structure west of Fort Worth is pointed out. Since Bulletin 629 was published the great oil and gas bearing territory centering around Kanger has been de- veloped, and the question arises. What relief may Dallas and other communities suffering from gas shortage expect from these fields? The conclusion reached in the present report is that the discovered fields contain enough gas to supply the domestic demands of these communities for several years, and that there are imdoubtedly still some imdiscovered gas pools in the region.

A preliminary summary of the present situation was contained in a telegram from the Director of the United States Geological Survey to Mayor Wozencraft on February 8. The results of the investigation harmonize with this summary but allow particularization where at first only generalization was possible. The telegram follows :

Gas resources north Texas, although limited and being rapidly depleted, are not yet nearing exhaustion. If a well-considered drilling program be followed* adequate pipe line and compressors be installed, waste reduced, and industrial consumption eliminated, remaining supplies will meet needs of residences In Dallas and other cities now served probably five to ten years. With industrial consumption in summer cost of domestic service would be somewhat lower than otherwise, but life of fields would be correspondingly shortened. Geologic con- clusions of fuU report will therefore probably be favorable, for apparently Texas still has considerable gas, though it would have had much more if waste had been kept within reasonable bounds. Engineering problems of gathering and transporting gas and economic problems of rates, restrictions in classes of use

U. 8. GlOIiOGIci

BULLETIN 716 PLATB Vm

f'TtvOI

Explanation

Single weB small Held

Gad field.

Gad pipe line

Projected

*-T5jectea gas pipeline

7~"

Prpbable limit of producing

Structonal features of regional ectat

Katubal-Gas Resoubces Of Central North Texas. 59

reduction of peak load, and general conservation will then imain to be solved, though it is fairly obvious that gas can be supplied for a few years at prices and in quantities that will enable it to compete successfully with other fuels.

In a later telegram to Mayor Wozencraft dated February 25 the Director stated :

Conclusions will doubtless show sufficient gas economically available for several years' domestic demand. Petrolia, best pool yet discovered, now probably 90 per cent exhausted. West Texas pools promising but need careful development, pipe lines, compressors, and reduction of waste. Capacity south- ern Oklahoma pools medium to small, but their aggregate volume sufficient to supply reduced demand at least two years. Undoubtedly several important un- discovered pools in Texas, but several years necessary to find and develop them. Great need is reduction of waste and determination by business men of price for fair return to invested capital under good management tb stimulate search for gas Independent of oil and to conserve the large but limited supplies.

Acknowledgments.

The citizens of north Texas and in particular the officials of the city of Dallas and those of the Lone Star Gas Co. cooperated heartily in every way possible toward the success of the work. Mayor Frank W. Wozencraft and Chief Engineer Ed C. Connor were especially helpful. The officers of the Lone Star Gas Co., the Dallas Gas Co., and the Fort Worth Gas Co. allowed free inspection of their records, supplied maps, and assisted in making observations and collecting data. Numerous geologists and others connected with different com- panies have been called upon for aid, and all have assisted without reserve. Robert T. Hill, who has done many years of effective work on Texas geology, rendered especially valuable assistance.

Location And Area.

The region in which Dallas and other cities are interested as a source of natural gas may be arbitrarily defined as that portion of Texas lying east of the lOOth meridian and north of the 31st parallel, together with the southern two tiers of counties in Oklahoma, or it may be said to include all territory within 200 miles of Dallas. (See PI. VIII.) The assignment of precise limits is impracticable and un- satisfactory, for the reason that the availability of a gas supply de- pends not only on distance from points of use but on other factors, such as magnitude and compactness of market. The business of pro- ducing and marketing natural gas involves not only the cost of gath- ering, transporting, and distributing the gas and ordinary overhe&d expenses but provision to meet an irregular demand. As the under- ground supply in any field is not unlimited the expenses of these several classes must be distributed equitably over the supply avail- able. Pipe lines alone commonly cost more than $25,000 a mile and

60 Coktribtjtions To Economic Geology, 1920 Pabt H.

depreciate so fast that they may have to be replaced within a few years. The salvage of pipe and other equipment on the exhaustion of the gas supply is often very expensive. If the underground supply is large and occurs in a small area and if the gas sand is thick and large-pored, so that the wells yield a large amount per day, gathering costs will be correspondingly low. If the closed pressure is high and the supply large, compressing and transportation costs will tend to be low. If there is a demand for a large amount of gas at the delivery end of the pipe line and along its course, if the consumers require large quantities per day, and if the points of consumption are close together, or if there are many good-sized towns along the line, costs will tend to be low. The cost of reading meters and collecting bills is lower per thousand cubic feet for the large consumer than it is for the small consumer. Lastly, if there is a great variation in demand per day, pipe and other equipment must be installed for the peak demand, and the unit cost of service will be higher than if the demand were uniform.

These nongeologic considerations are cited to emphasize the fact that the geologic problems of existence, location, extent, and compact- ness of underground supplies and character of the reservoir are only a few of the factors that enter into the business problem of whether or not the supplies can be got to market for a price per thousand cubic feet that the consumer is willing to pay. Natural gas has been trans- ported with profit to markets considerably farther than 200 miles from the source of supply, but this has been done under favorable circumstances, such as a large quantity of available gas, many cities and towns along the line, and good-sized cities at the end of the line. Perhaps the most noteworthy example has been the transportation of West Virginia gas to cities in Indiana. The gas at Mexia is less than 100 miles from Dallas, but it can not be brought to Dallas at a profit because the amount is small. Indeed, it would not pay the cost of transportation and marketing if the quantity were several times as great as has been discovered up to the present time. On the other hand, if northwestern Louisiana, 200 miles from Dallas, had a large surplus, or even if the Amarillo field, 350 miles distant, included several very large pools in open-pored sands, it might be feasible to bring gas from these sources to Dallas.

The general problem, with one or more phases of which this paper has to do, is in part an examination of the prospects of finding new fids, in part an appraisal of known pools not yet connected with the pipe-line system, and in part the determination of means of adjust- ing the diminishing supply of natural gas in the old fields to the in- creasing needs of rapidly growing cities. When the gas fields of north Texas were first called upon to serve Dallas and other cities, the supply of gas in sight appeared to be ample for years to come.

Natural-Gas Resources Of Central. North Texas.

Now, even though additional supplies have been found, the growth in population, with the consequent increase in the number of gas con- sumers, has overtaken the rate of new production, and an acute short- age is felt.

The cities and towns of north Texas now using natural gas for fuel and lighting are Petrolia, Fort Worth, Bellevue, Bowie, Sunset, Al- vord, Decatur, Rhome, Bridgeport, Irving, Arlington, Dalworth, Dallas, Gainesville, Sherman, Denison, Whitesboro, Denton, and Mc- Kinney, which receive their supply through one company, the Lone Star Gas. Co. of Dallas, and Electra, Burkbumett, Abilene, Albany,

"W

100*

3— a

' u.

-n

o

— j

K-

t 'T

.T

' IiicnB 5

T

f — —r ! — ri—wsiar — h

i I

A

J

y

io5*

CXPLANATtON

6ttS9ii|ipbad

Local 8upFi)r.

"Tb"

Fiouu 2. — Map staowixig cities and towns In north Tttaa using natural gaai

Moran, Mineral Wells, Baird, Cisco, Eastland, Ranger, Thurber, Desdemona, Coleman, and others, which are served by local producing gas companies and are supplied by near-by fields. (See fig. 2.)

' FIEIiDS NOW SUPPLYING NORTH TEXAS.

PETBOIiIA YIELD.

HISTORY ANB PRESENT CONDmONS OF DEVELOPMENT.

The first important gas field to be developed in north Texas was the Petrolia field of Clay County. Although it had been known as an

62 Contributions To Economic Geoloot, 19, Fart U.

oil field for some years, its development as a gas field did not begin until October, 1907, when the first gas well was brought in. The next year two other gas wells were drilled, furnishing an ample supply for the town of Petrolia, about 2 miles distant, and for drilling opera- tions in the field.

By 1909 the gas development had reached a stage that demanded a greatly enlarged market, and a 16-inch pipe line was laid to Fort Worth and Dallas, respectively, 94 and 135 miles away. About the same time service was extended to Wichita Falls, 18 miles from Petrolia. This field furnished the entire supply of gas for a large number of towns in north Texas until the southern Oklahoma fields were connected with the system, in November, 1917.

The gas from the Petrolia field is supplied to Dallas and Fort Worth through a 16-inch line, and to Wichita FaUs through one 6-inch and one 8-inch line. The natural pressure of the gas is insufficient to force it through the pipe line in the quantities required, so a battery of five large compressors, each of 1,250 horsepower, has been installed at the Petrolia compressing station. The gas is compressed in two stages, first to a pressure of about 40 pounds to the square inch, and then to about 150 pounds, at which it is delivered into the lines. The low- stage compressors apparently do not raise the pressure above the average rock pressure. As a matter of fact, however, they produce a suction so that the pressure at their intake valves is only about 1 pound. This produces a differential between that point and the mouth of the well. Otherwise the gas would not flow in sufficient volume to feed the compressor. It should be noted, too, that at present many of the wells have a rock pressure very little above zero.

Mode Of Ocgtjrrexge Of The Qas.

Most natural gas occurs in porous layers or strata of sandstone; some, however, is found in limestone and other kinds of rock. The strata lie in general more or less nearly horizontal but in detail have an undulating or wrinkled form. The pay " sands," as the beds con- taining the gas are called, are usually overlain and surrounded by closer textured rock which prevents the escape of the gas. Wrinkles or arches of approximately circular form are called domes ; those of elongated outline are called anticlines. Innumerable variations and combinations of these forms occur. Where oil is associated with the gas, it is generally found below the gas, presumably because of its higher specific gravity; where water is present it commonly forms the lowest member of the series, for the same reason.

Examinations of specimens of the producing sands of the Petrolia field made in connection with Shaw's investigations in 1915 showed that they have an average porosity between 20 and 25 per cent. In

Kattjbal-6As Besoubces Of Central North Texas. 63

this field there are three principal producing sands, at different levels or horizons; their aggregate thickness is 30 to 40 feet. The total area underlain by these producing sands, as outlined more or less clearly by dry holes, considered in connection with the structure as inferred from well records and from surface outcrops, is 12 to 15 . square miles. With these data at hand it is a simple matter to com- pute the space originally occupied by the gas. At the time of the earlier estimate the average thickness of the pay sands was inferred to be 30 feet, the pore space 20 per cent, and the areal extent of the pool 15 square miles. From these figures the apparent total original volume of the reservoir was computed as about 2,500,000,000 cubic feet. Later developments and fuller knowledge tend to indicate that the average thickness of pay sands is perhaps a little more than 30 feet, the pore space possibly somewhat more than 20 per cent, the area underlain by gas-bearing strata less than 15 square miles, and the original volume of the reservoir about 250,000,000 cubic feet.

Previotis Estikates Of Gas Reserves.

The entire amount of gas originally present in the Petrolia field was estimated by Shaw in 1915 to have been about 120 billion cubic feet, measured at a pressure of 8 ounces to the square inch, the pres- sure at which gas is normally supplied to city consumers. The space underground in which the gas was stored was computed at 2,500,- 000,000 cubic feet, as indicated above. The gas is thought to have been originally under a pressure of about 725 pounds to the square inch, the average pressure shown in the first wells drilled. Applying the well-known law of Boyle, according to which the volume of gas is inversely proportional to the pressure to which it is subjected, and adding atmospheric pressure to each of the pressures stated above, we obtain the ratio of 740 : 15.5, or roughly 48 : 1. Thus the reservoir whose total capacity was approximately 2,500,000,000 cubic feet con- tained gas enough at a pressure of 725 pounds to the square inch to occupy 120 billion cubic feet at a pressure of 8 ounces to the square inch. Later developments and additional facts indicate a total volume of about 110 billion cubic feet (see p. 66), but the probable degree of correctness of the earlier figures is remarkably high considering the hazardous nature of attempts to estimate quan- tities of underground gas.

In 1918 Rogers made an estimate of the quantity of gas then re- maining in the Petrolia field, and concluded that Shaw's earlier inferences as to the original capacity of the reservoir and the volume of gas contained in it were both correct. Some of Rogers's conclu- sions are as follows :

1. A study of the curve showing decUne in rock pressure indicates that at the present rate of production the field will be exhausted at the end of 1920,

64 CONTRIBUTIONS TO ECONOMIC GEOLOGY, IWl), PART H.

but that if the production is decreased to 12 or 15 million cubic feet a day the field will probably last at leitst a year longer, provided water does not Invade the gas sands.

2. An estimate of the quantity of gas remaining in the ground indicates that 13 to 20 billion cubic feet is still available, or a supply of 15 million cubic feet a day up to some time in the year 1821.

3. There is reason to believe that a small pool may be found about 2 miles west of the field.

It is worthy of special note that Rogers clearly ipretold the dis* covery of the Martin gas.

New Estimate Of Quantity Of Gas Remaining.

The total amount of gas marketed by the Lone Star Gas Co. from the PetroUa field from 1910 to 1919, inclusive, is shown in the fol- lowing table :

Rock pressure, open-flow capacity, and production of Peirolia fleid, including

Martin weUs, 1910-1919.

Avenge

rock pfessuTB

JaiLl.

Open flow Jan. 1.

GasmailEeted

Year.

Number of wells tested.

Combined

open flow

(tnoosand

cable feet).

AveiBge per well (thou- sand CO- bic feet).

during the

year fay Lone

Star Gas Ca

(thauaand

cubic fwt).

1,583,080

5,175,196

7.186,322

10 089.135

9,663,893 8,999,837 8,945,522 6,101,167 6,579,088 3,602,686

365,090

373,345

190,503

75,855

34,604

8,904 6,484 4,141 1,686 1,081

igao

The total quantity of gas marketed from the field can not be stated with precision, but for 1915 to 1919, inclusive, it ranged from 7 to 10 billion cubic feet annually. The quantity produced from 1907 to 1910 is not known but may be estimated at about 10 billion cubic feet.

The decline in closed pressure is illustrated in figure 3 and that in open-flow capacity in figure 4.

The amount of gas lost from the reservoir but not marketed is not known, but enough data are available to make possible an estimate of value. It is known that for the TJnited States as a whole more gas has been lost than has been marketed — that the underground loss plus the loss from blowing off wells plus the quantity used more or less efficiently in the field but not sold, plus the large quantity lost along gathering lines, main lines, and distributing lines amounts to more than all the gas that has been delivered to both industrial and

Natural-Gas Resottrces Of Central North Texas.'

fuK 8. — Carve iboirlDK decUne In nKk preware, number of weiu li on test In Petiolla gas Beld, Tat. Curve nuuted repreaenta k IfarUn Held, rock pruiire 00 to BOS ponnda.

s"

in

:??

" 0

a 0

3 n n

2 H

',

/

/

d

/

K

onimzsisnwtseiwernermn

Zd

66 Contributions To Economic Geology, 1920, Part Ii.

domestic consumers. It is evident from a study of the Petrolia gas field and its history, however, that the waste in this field has been considerably below the average. Finally, it is known that the per- centage lost is much greater at the beginning of the life of a field than at any other time, declining rather continuously throughout the life of the field as the pressure declines and as the wells and their equipment are improved.

All things considered, it may be estimated that in the Petrolia field from 3 to 6 cubic feet of gas has been lost for every 10 cubic feet delivered to a consumer and that at the present time the ratio is still lower than this.

Another consideration of importance in estimating the quantity of recoverable gas remaining in the pool is the pressure at which wells are abandoned. In the Petrolia field the average rock pressure at abandonment has been perhaps 3 pounds to the square inch and in the fixture may be expected to average as low as 2 pounds to the square inch. Some wells have been abandoned at much higher pressures because they were "drowned out" by water, and occasional occur- rences of this sort may be expected in the future. On the other hand, some wells will produce until the pressure has declined to atmos- pheric pressure, and some will no doubt be pumped until it is con- siderably lower still.

The problem of estimating the gas remaining in a field may be worked out as indicated below? The underlying principle of this solution is, of course, Boyle's law.

Let V=volimie of gas originally in the field.

v=volume of gas not recoverable.

v'=volume of gas in field at any particular date,

v'— v=gas recoverable atlhe date indicated.

R=original rock pressure.

r=rock pressure at time of abandonment.

r'=rock pressure at the date indicated.

p=atmospheric pressure.

(r+p)V

(R+P)

The quantity of gas recoverable in the Petrolia field January 1, 1920, is computed from these formulas as follows :

V=110 billion cubic feet, original volume (revised estimate). j

Ki=725 pounds, original rock pressure. .

nA

UMSLOJJJknua mi rmi

mm

J

NATUBAL-GAS RfiSOUBCES OF CENTRAL. NORTH TEXAS. 67

pounds, rock pressure January 1, 1920 (average for entire

sand). r=2 pounds, rock pressure at which field is abandoned. p=14.4 pounds, atmospheric pressure, v'— v=10,900,000,000 cubic feet.

This is the theoretical quantity of gas recoverable and does not allow for losses or for the effect of water encroachment. The losses may be estimated at 20 to 25 per cent

Water Encroachment.

The past and probable future extent of water encroachment in the Petrolia field can best be inferred from the behavior and distribution of wells that have partly or wholly " gone to water." Eleven wells have been abandoned on account of flooding, and five wells are at present showing more or less water. The total number of gas wells drilled in this field is about 79, of which 48 are now producing.

The mode of water encroachment is fairly clear from a study of the individual wells that have " gone to water." Beatty No. 1, north of the center of the field and considerably off the structural axis, was abandoned about January, 1918, at a rock pressure of 90 poimds. Skelly No. 2, south of the Beatty well and near the highest part of the sand, was abandoned as early as 1913 at a pressure of 300 pounds. Other wells in other parts of the field were abandoned at pressures of 0, 50, 90, and 120 pounds. These observations indicate that water is advancing into the gas reservoir but that the principal mode of ad- vance is from below up rather than from the borders inward.

The wells that have " gone to water " are not scattered indiscrimi- nately over the field but are distributed in more or less well-defined groups. (See PI. IX.) The order in which water troubles devel- oped in the Miller and Donley wells, on the south edge of the field, indicates that water is creeping up the south flank of the dome. On the other hand, some of the earliest wells to be drowned out were near the top of the dome. In these wells, however, water from higher strata may have entered through faulty packing and penetrated, the producing sand. The effects of water encroachment, though seri- ous, are local, and the field as a whole is not being systematically inundated.

In view of the facts above stated some allowance should obviously be made for the retardation of the decline in closed pressure caused by water advancing into the gas reservoir. Apparently the area of the gas pool has been reduced by 1 or li square miles, and the capacity of the reservoir has been correspondingly reduced, being now about per cent as great as it was originally, if the sands are fairly uni-

68 OONTRIBUnONS TO ECONOMIC GEOLOGY, 1920, PART U.

form in thickness. At least 10 per cent should therefore be deducted from the estimate of 10,900,000,000 cubic feet given above, leaving 9,810,000,000 cubic feet as the estimated quantity of gas that in the future can be delivered into the mains from the Petrolia field.

There is no way of determining the future rate of water encroach- ment except by inference based upon the probability that a fairly uniform rate of flooding will be maintained and that wells near those already flooded will go out in their turn. As the rate of general de- pletion of the field has far exceeded the rate of water encroachment it is not probable that any large portion of the remaining supply will be cut off by this agency.

Mabtik Wei1J9.

The relation of the Martin wells to the main part of the Petrolia field is not definitely established and promises to be a matter of con- siderable controversy. In the foregoing discussion they are regarded as constituting a part of the Petrolia field for reasons set forth in the following paragraphs.

The wells are on the N. H. Martin farm, about 3 miles southwest of Petrolia. There are four producing gas wells, and a fifth is nearing completion.

Data oonceminff the Martin irella.

Namo.

Martin No. 5.

lfartlnNo.7.. ]iartUNa9.. Martin Na 10. MiaitinNan.

Dateoom- pleted.

May 31,1918

Jan. 27,1919 Oct 14,1919

Feb. 39,1990

Total depth (feet).

1,788

1,740

1,710

Deptttof pio*

dneinff Band

M, 783-1, 788

l,e8S-l,aB3 H, 718-1, 730

Initial

dosed

praasure

(pounds

square Inoh).

Initial open

Hovr capac- ity (eobic tlBet).

5,570,000

8,Soo,000 88,800,000

8,377,130 14,844,970

Notes.

Making water and oU.

Upper aand.

b Lower aand.

Sufficient data are not at hand for a complete and satisfactory com- putation of the total volume of gas for each sand, and the following figures must be regarded as tentative. It seems almost certain from the available well data that the structure precludes any great exten- sion of the present pool toward the north, east, or south, and that ex- tensions toward the west are problematic, with the best prospects toward the northwest. The fairly rapid decline of closed pressure with moderate output supports the inference that the reservoir is smalL

Natural-Gas .Besources Of Gentbal North Texas. 69

Apparently the wells are drawing gas from an area of about 1-| square miles. The sands seem to have an average total thickness of about 18 feet, and on the assumption that their pore space amounts to 20 per cent and that the original closed pressure was 550 pounds, the total volume of gas present would have been 5,500,000,000 cubic feet. This estimate seems to be moderate, and there is reason to believe that more complete data will raise rather than lower the figure. The gas marketed from these wells from November, 1919, to February 1, 1920, amounted to 937,081,640 cubic feet It seems probable that several hundred million cubic feet additional has been drawn from the pool but for various reasons unmarketed.' The original volume of gas has probably been reduced by 1,500,000,000 cubic feet. The de- cline in closed pressure of the wells has been nearly 50 per cent, but it is thought that at a distance from the weUs the pressure is much higher, especially as the gas has been withdrawn so rapidly that the pressure has not had time to become equalized.

possiBiLiTy or new pools.

Other outlying pools or arms of the main pool may be discovered. About 30 wells have been drilled in the territory immediately around the Petrolia pool, in a belt wide enough to include the Martin wells, and seven of these became producing oil or gas wells. This result would give a ratio of dry holes to producing wells of 4 to 1, and would suggest that extensions and new marginal pools should be sought at a greater distance.

The deep test well of the Lone Star Co., Byers No. 36, just west of the producing area, disclosed the fact that the strata underlying the known producing sands are similar in character and arrange- ment to those above, though at this point the whole series was barren. It might be well to drill a deep well in the center of the field at the southwest comer of block 5, near Culbertson well No. 5, whicli, ap- pears to have struck the " lime near its highest point. This would be approximately at the center of the dome.

Very few if any undrilled locations still lie within the known limits of the pool. A study of the map and other data leads to the sugges- tion that a well be drilled about the center of block 16. The suggested location would be about 2,250 feet southeast of Landrum wells Nos. 1 and 2, which have declined in rock pressure at a tmif orm rate from 295 poimds in 1915 to 40 pounds at the present time. The suggested location would be 2,600 feet northeast of Jackson well No. 1, which was abandoned several years ago : 3,000 feet northwest of HoUoway well No. 8, which came in at 110 pounds in 1918 and now registers

70 CONTRIBUTIOirS TO BCOKOMIC GEOIX>GY| IWD, PART H.

zero ; and about the same distance northwest of HoUoway No. 9, which came in at 140 pounds in 1918 and now has a pressure of 35 pounds. The best that could be expected from this location would be a well with a pressure of perhaps 50 pounds and a relatively small open flow.

Curves showing the decline in rock pressure and open flow for the Petrolia field are given in figures 3 and 4. Records of production are also shown for comparison in figure 4.

Summary For Petrolia Field.

Below is a summary of conditions in the Petrolia field, including the Martin wells, at three different periods in the history of the field :

Original closed pressure of pool, pounds to the square inch. 725 Original absolute pressure of pool (=gage reading+at-

mospheric pressure) pounds to the square inch— 740

Area of pool square miles— 12-15,

Average thickness of pay sand feet..- 30-40

Average pore space of pay sand per cent— 20-25

Original capacity of reservoir (revised estimate), billion

cubic feet 2i

Original gas content measured at 8 ounces above atmos- pheric pressure (revised estimate), billion cubic feeL. HO

September. 1916.

Average closed pressure of active wells, pounds to the

square inch 288

Average pressure midway between wells, pounds to the

square inch 875±

Average pressure in marginal territory and In lenses

having poor connection with wells, pounds to the square

inch 650db

Average pressure through entire pool, pounds to the

square inch 435

Average absolute pressure for entire pool, pounds to the

square inch 450

Quantity of gas marketed billion cubic feet— 37

Estimated quantity of gas lost , do IS

Estimated quantity of gas remaining (allowing for some

water encroachment) ,, billion cubic feet— 70

Katural-Gas Resources Of Central North Texas. ' 71

February, 1920.

Average closed pressure of active wells In old Petrolla

field pounds to the square inch 49

Average closed pressure of Martin wells do 305

Average pressure midway between wells in old Petrolia

field pounds to the square Inch 70±

Average pressure in marginal territory and in lenses having

poor connection with wells pounds to the square inch— 175±

Average pressure through entire pool including Martin

farm pounds to the square inch 85±

Average absolute pressure for entire pool do 100

Bstimated quantity of gas marketed billion cubic feet.- 70~S0

Estimated quantity of gas lost do 20-25

Estimated quantity of gas remaining (allowing for some

water encroachment) billion cubic feet 12-15

Estimated future underground loss, including gas finally left in sand and that lost to other sands, billion cubic

feet 2-8

Estimated future loss above ground billion cubic feet 1-2

Estimated quantity of gas remaining in pool, Including Martin wells, that can be delivered to the mains; billion cuMc feet 9-10

General Features.

The Fox field is in Tps. 2 and 3 S., Rs. 2 and 3 W., Carter County, Okla., about 10 miles north of the Healdton oil field, where there are several gas wells, one of which had an initial open flow of 40,000,000 cubic feet a day. The gas at Healdton, being considered of secondary importance to the oil, has not been conserved. In November, 1917, a 16-inch gas line was laid to Dallas from the southeast comer of Stephens County, Okla. This line is about 115 miles long. From its northern extremity an extension of 12-inch pipe, miles in length, taps the Fox field.

The Fox field now contains 12 wells, the first of which, northwest of the village, was completed in October, 1915. This well had an initial daily open flow of 18,000,000 cubic feet. The average daily open-flow capacity of the producing wells in the field on February 1, 1920, was 7,700,000 cubic feet. , As many as five producing sands, all of which are believed to be of Pennsylvanian age, are penetrated in some of the wells. These sands range in depth from 1,400 to 2,800 feet. One or two wells produce from shallow sands less than 1,000 feet deep. A typical well log showing the relative position of the five sands is given below.

72 CONTBIBtmONS TO ECONOMIC GBOIXKJY, IMO, PART H. Tvplcal veil log of Fox field, Otia.

to

K Ai

m

Js

loa

3M J80

is

era

7S8

g

Bm

rS

Ss"

-J"

White.

eIee;

gSS'"'

ffiT::::::::

EtEE

WliUi.

yoil,OOOniblofKof(W.

WlUte,

Sis:?

"X

33,000.000 ouUil (Vet of tks.

Pboddction.

The average closed pressure in the Fox field in November, 1917, was about 720 pounds to the square inch. By Fruary, 1920, it had fallen to 141 pounds. (See fig. 5.) This decrease would indicate that the Held is at present a1:>out 80 per cent depleted. The gas marketed from this field since November, 1917, amounts to about 17 billion cubic feet. All things considered it may be inferred that

NATDBAL-GAS RESOURCES OF CBKTRAl. NORTH TEXAS. 73

about 5 billion cubic feet can in the future be recovered and marketed from this field. A separate estimate of losses and of gas used in field operations is not needed for this preliminary estimate, because it is probable that the proportion of such gas to the total withdrawals from the pool will not change materially in the future. Any estimate must be regarded as tentative, for the available data concerning area, thickness, and porosity of sands, etc., are not as full as could be de-

sired, and there is always the chance of considerable error in determin* ing underground gas reserves.

There is a reasonable hope that the field may be extended, and much prospecting is now being done in adjacent areas.

WAIiTEB ITEU).

The Walter or Keys field lies in the northeast quarter of Cotton County, Okla., north of the town of Walter. The field supplies both oil and gas, many of the wells coming in as gas wells and later yield- ing oiL The highest recorded initial rock pressure was 825 pounds 164071"— 21— BuU. 716 6

74 Contributions To Economic Geology, 192D, Pabt H.

to the square inch. The Sanders well No. 1, in sec. 3, T. 2 S., R. 10 W., and the Skelton well No. 1, in sec 1, T. 2 S., R. 11 W., came in at that pressure. Each of these wells had an open-flow capacity of about 18,000,000 cubic feet a day. Several of the wells had a greater initial capacity, but the average for the field is about 10,000,000 cubic feet a day. The wells are 2,100 to 2,300 feet deep, and most of the gas is found in one sand, which is recorded in the well logs as ranging from 7 to 27 feet in thickness, with an average of about 12 feet. The producing sand is at least 600 feet below the base of the Permian and lies in the middle or upper part of the Pennsylvanian series.

The figures showing production by the Lone Star Gas Co. from tbis field are as follows :

Cubic feet

1918 (April to December, inclusive) 3/192,977,000

1919 10, 831, 193, 000

1920 (January) 539,222,000

14, 503, 392, 000

To this should be added at least 5 per cent for the gas consumed at Lawton and Walter. Gas for field operations is furnished mainly by shallow gas wells and by oil wells that supply a little gas, so this item may be omitted from the present computation. The original average rock pressure appears to have been about 700 pounds to the square inch, though a few wells came in at a higher pressure. The average rock pressure February 1, 1920, was 240 pounds. (See fig. 6.) In view, however, of the fact that new walls now coming in show pressures of 400 to 525 pounds, the average pressure in the sand throughout the pool is evidently between these limits, and there is reason for believing that it is not far from 375 pounds. This is a little less than the mean between the highest initial pressure among recently drilled wells (525 poimds in Schwalbe well No. 2, December, 1919) and the average of all the wells at the mouth (240 pounds). Eoughly, the data above recorded indicate that a little more than 50 per cent of the gas has been withdrawn from its natural reservoir. The recoverable and marketable supply remaining is therefore about 13 billion cubic feet. This must be regarded as only a very rough approximation, but it is probably not far from correct.

The problem of water encroachment and the fact that more than one company draws gas from this field add some uncertainty to the computation of the reserve supply. Competing companies in a field tend to increase the rate of depletion, owing to the fact that when one company gets a gas well the other companies that control adjoin- ing leases are practically forced to drill or their gas will be drawn out. The principle is not essentially different from that operating in oil fields, but the effects are felt more quicHy and extd over a larger area. Water troubles are already appearing in this field,

Natural-Oas Besottrces Of Central Nobth Texas. 75

and the utmost care should be taken by the operators to guard against them.

Other Fields.

The fields above described include all that have 'thus far furnished gas to Dallas, Fort Worth, and other north Texas towns, with the ex- ception of some small pools that have supplied gas to certain towns south of Dallas but are now so completely exhausted as to be negligible.

The rapid depletion of the fields in use at present is graphically ' illustrated by the accompanying curves of decline in rock pressure

(6gs. 3, 5, and 6). 'i'o counteract this exhaustion, pipe lines to other fields, described in the following pages, are being constructed as rap- idly as conditions permit.

Loco Field.

Special interest attaches to the Loco field at this time, as it is just being connected with the system that supplies the north Texas towns. It is a field of small area, lying almost wholly within sees. 9, 10, 15, and 16, T. 3 S., R. 5 W., near the southern edge of Stephens County,

76 CONTRIBUnOlSrS to economic OEOLOOYy 1920, PART H.

Okla. Wegeman and Heald' refer to it as lying along a curve of which the Healdton dome, 10 miles to the southeast, forms one extremity, and the Duncan dome, 15 miles north-northwest, forms the other. They state ihat this curve

appears to encircle the west end of the Arbuckle Mountains, forming, so to speak, a cross fold to the low arch which lies between the Arbuckle and Wichita uplifts. It is not meant to imply that the Healdton, Loco, and Duncan fields are situated on one long anticUne. They are in fact three separate domes, but they He in such a relation to one another as to suggest that they are more inti- mately connected in origin with the Arbuckle uplift than with the Wichita. The Duncan field Ues north of the low arch between the two mountain uplifts, and the Loco and Healdton fields lie south of It.

Oil and gas are found in beds covering a wide stratigraphic range in the Loco field, as is illustrated by the log of the J. B. Anderson well No. 1, though this well may be rather an extreme case.

Log of J, Anderson well No, 1 of Lone Star Ons Co,, sec. 16, T, S fif.,

R. 5 W., Loco fields Okl,

[DrUled about Jan. 1. 1918.]

Formation.

Sliale

Sand

Sliale

Sand

Shalo

Sand

Sliale

Sand

Shale

Sand

Shale

Sand

Shale

Sand

Shale

Sand

Shale

Sand

Shale

Sand

Shale

Sand

Shale

Sand

Shale

Sand

Lime

Sand

Do

Shale

Sand

Shale

Sand

Shale

Do

Do

Shell and aand.

Lime

Sand

Shale

Sand and lime. Sand

Color.

Ked.

Ked. Red!

Hed.

Blue.

Red.

Red.

Blue.

Brown.

Blue.

Blue.

Blue.

Ilardnoas.

Soft.

.do. .do. .do. .do.

Blue,

Blue.

Blue.. White. Blue..

Blue.

Hard..

Thick-

nes9

(feet).

Depth

(feOi).

45'

Co

85

1,000

Remarks.

Water.

Oil, gas, and water.

Show of gas and oiL

Do.

Show of oil.

Set 12Hnoh cadng.

6,000,000 cubic feet of

Dry.

Slight show of oil.

Do.

Show of gaa and water.

2.000,000 cubic feet of gas. Set 104nch casing. Shelly and broken.

Slight show of oU. Slight show of oil and

&QOO,000 cubic feet of gas. Set 6|-lnofa casing.

Water.

Show of oil.

Wegemann, C. H., and Heald, K. C, The Healdton oil field, Carter County, Okla.: U. S. Oeol. Surrey Boll. 821. pp. 2-24. 1916.

UiTUBAL-OAS RESOURCES OF CENTRAL NORTH TBXAS.

Log of J. B. Anderson icell So. 1 of Lor

I- Gas Co.— Continued.

Color.

Thick-

J

W

Rvauiia.

None of the producing sands in this well lie deeper than 851 feet, and throughout the field most of the producing sands are less than 1,000 feet deep. They lie in the " Kd Beds," of Permian age.

The gas of this field has not been used except for drilling opera- tions, yet since January 1, 1916, the rock pressure has decreased about

acid, Okla. In fomc

90 pounds. (See fig. 7.) Reports indicate that waste in this field has been about the average, of perhaps below the average. One well, the Ida Eilley No, 5, which had an initial open flow of 9 or 10 million cubic feet, blew off steadily for three weeks after the accidental opening of the gas sand by a shot of nitroglycerine. The well was drilled with a rotary drill, and the sand was penetrated without being noticed. A lower oil sand was struck, and after this was exhausted and the well abandoned the gas sand was opened by a shot set off in an effort to dislodge the casing. The well finally had to be plugged. No other important losses have occurred in this field.

The amount of gas used for drilling is roughly estimated at 7,500,000 cubic feet per well, which, for 35 wells, would be 262,600,000 cubic feet ; the amount of loss due to oil wells producing from the same sand and to leakage is estimated at 200,000,000 cubic feet for the Ida Billey well and 100,000,000 cubic feet for all others, or 300,000,000 cubic feet The original pressure in the pool was about 300 pounds

78 tWNTRIBUTlONS TO ECONOMIC GEOLOGY, 19, PART II.

to the square inch, and the present average closed pressure of the wells is above 185 pounds. At points distant from wells the pressure, to judge by initial pressures of new wells, is probably 225 pounds. It follows that the original volume was at least 1,465,000,000 cubic feet, and the amount remaining is at least 900,000,000 cubic feet, of which perhaps 700,000,000 cubic feet may be recovered and marketed. The decline in closed pressure is shown in figure 5.

The geologic conditions afford ground for hope that this field may be extended in a direction slightly west of oorUi and perhaps also to the southeast, though until a detailed surrey is made no great reliance can be placed on this inference.

Duncan Field.

About 10 miles north of the Loco field is the Duncan Geld. The curve of decline in rock pressure for this field (fig. 8) indicates that

FiauBB 6. — Curve Bhowlug decline In rock pTure Id tbe DuDcaa gas Beld, Okla.

as a prospecti\-e source of supply for. north Texas cities it may be disregarded.

Kinebal Wells Piels.

The promising gas fields of Palo Pinto County, Tex., have not yet been drawn upon except for local use, but pipe lines are rapidly being pushed toward them, and their supply will soon be available for the north Texas cities. The Mineral Wells field lies in the east-central part of the county, near the town of Mineral Wells. Perhaps the mineralized water at this locality was related to the same set of condi- tions that gave rise to the oil and gas pools.

The field produces mainly from one sand in the Strawn fonnation, at a depth of about 1,000 or 1,100 feet. The thickness of tlie sand, as calculated from available well logs, ranges from 8 to 21 feet, nd aver- ages 14 feet. The producing area covers about 8 square milea The data at hand do not show the original rock pressure, but it was prob-

Natubal-Gas Res0X7Rges Of Oentral North Texas. 79"

ably not far from 420 pounds to the square inch. The hydrostatic head for wells 1,050 feet deep is about 450 pounds ; hence this estimate may be a little low. The earliest wells of which complete records are at present available had initial rock pressures of 270 to 365 poimds. These wells were by no means the first in the field, so it must be as- sumed that the original rock pressure was well above that at which they came in. A porosity of 20 per cent is assumed. The total volume of gas is thus computed to be about 18 billion cubic feet. As the cor- rections to be made are nearly all of a plus character, arising from probable development of new territory, discovery of new sands, and the fact that the original rock pressure is conservatively estimated, it is probable that the estimate could safely be raised to 26 billions. Some of the supply has already been drawn for local use at Mineral Wells, and some has been lost through the more or less careless meth- ods usually attending the development of a new field. Still there seems to be good reason for believing that there remains available at least 15 billion and possibly 25 billion cubic feet. Relatively this is not a large aioiount of gas for the area of the field, but the wells are of rather small capacity. Fifteen representative wells of this field show an average open flow of only 1,820,000 cubic feet a day.

A much deeper sand, at about 4,000 feet, having a closed pressure of about 1,400 pounds to the square inch, has been penetrated in one or two places. After the exhaustion of the shallower sand, this sand will afford a new but at present unascertainable volume of gas in re- serve. It should be borne in mind that the difficulty and expense of recovering gas from a depth of 4,000 feet are considerably greater than for shallower depths.

-Kabtlajstd Fieu).

The Eastland County field lies mostly north of the town of East- land. The producing sands are in the Bend series, at an average depth of about 3,000 feet and extend eastward to the county line, merging into the Banger field. This field contains much oil, and as oil production is much more profitable than gas production, it is spoken of as an oil field. Nevertheless the high rock pressure and the large open flow of the "gasser " scattered throughout the field in- dicate an abundant gas supply, in spite of the waste that has been involved in an overdiligent search for the more valuable oil. The gas and oil are mainly in the same sand, and sooner or later most of the gas wells, if allowed to " blow," will begin to yield oil. It was in an attempt to obtain oil that the Barker No. 1 well was allowed to blow at the rate of about 42,000,000 cubic feet a day for three months. The Railroad Commission has lately put a stop to such practices in the interest of conservation of natural gas. This waste of gas in order to obtain oil emphasizes the need of conservation, which can be

80 CONTRIBUTIOKS TO ECONOMIC GBOLOOY, 190D, PABT n.

accomplished by enacting and enforcing properly drafted laws and by putting the prices of the two commodities more nearly on a parity, so that there will be as much incentive to save the one as the other.

The irregular occurrence of gas in this field makes estimation of the quantity extremely difficult. Very little gas from the field has been used commercially, but the large wastes have made a noteworthy depletion. Only the roughest sort of an estimate can be made of the amount available at present. The average open flow is about 20,000,000 cubic feet a day, and the average rock pressure is about 650 pounds to the square inch. The amount of gas originally in the field can hardly have been less than 100 or 200 billion cubic feet and of this 10 to 20 billion cubic feet has already been used or wasted.

Data regarding the wells in Eastland County are given in the fol- lowing table :

Data conceminff EMtUmd County tceUa.

Name and nmn- berofwall.

CookseyNo. 1

Summeral No. 1...

W.P.SnMdNo.!.

Barker No. 1

C.J.HaireUNo. 1.

Tbraves et al. No.

Harrell No. 1. MiUerNo.2..

Beard No. 1... Kincaid No. 1.

Owner.

Jackson Refining

AOUTo. States Oil Co

Texolean Co.

Mid Kansas Co.. Texas Co

Ranker

Mother Fool Oil Co.

FolsomOilCo Ardizone-Braden.

C. 7. HairelL Ranger-Texas .

Harmony Church Lot No. 1.

JimHamll.

J. C. HarreU.

Mildren Oil & Gas Co.

States Corpora- tlon.

.do.

Depth of

gas sand

(feet).

3,900 1,740

1,930-1,927

3,030 1,920-1,900 1,78S-1,790

1,700 1,768-1,701

1,730-1,733

1,720-1,781?

1,702-1,774

Tests.

Date.

Sept. 25, 1910 Sept. 23,1919

Oct. 10,1919

(Oct. 17,1919 Nov. 13,1919 Jan. 1,19?0 Oct. 10,1919

Nov. 1,1919 Nov. 21, 1919

Nov. 24,1919 Dec. 2,1919

Jan. 1,1920

Dec. 10,1919

Dec. 20,1919

Jan. 1,1020

Feb. 8,1920

Rock pres- sure (pounds

per square incii).

()pen- flow capac- ity (M cubic feet).

2,809 60,000

13,447

42,532 42,532 .Vt,000 47,000

40,000

100,000 700?

8,000 0,000

17,000

39,288 26,000

12,852

85,408 84,489 81,070 26,000

Remaps.

Oasdry.

Gas dry. Open flow Oct. 1, I919 11,640,000 cuble feet.

Well blowing open through ineh pip© supplying hi el for 20 rigs.

10 barrels of

[

oil a day. Mudding in gas to

drill deeper. Nov. 1, 1919, open

flow, 20,000, ooa

cubic feet.

Aug. 80, 1919. makinff 10,000,000 cubic leet of gas; shut in 8eiptei&> ber, 1919.

Sept 0,1919. drilled to 3,220 feet; 20 barrels of oil.

Tan. 2H, 1920. well leaking gas nadly.

Nov. 21, 1919, stm gas at 1,725 drilled 6 inch< into the sand.

Feb. 3, 1990, fixing to mnd-in to diifl deeper.

Gas slightly wet.

Gas dry.

BUilitly wet; Ing little salt w. ter.

Estimated.

KATUBAL-GAS RESOtJBCBS OF CENTRAL NORTH TEXAS.

Data concenUng Eastland County weUs — Ck>ntinued

Mftme and num- twrofwell.

O. E. Meador No. 1 BowImNo. 1

Hogg No. 5.

CowellNo. 1. CktyweliNo.3. Cypert No. 1.

Cypwt

Vkaght

aoghtNo. 1.

OwiMr.

Depth of

gas sand

(feet).

Tests.

Mid- Kansas Cp..

3,095-3,110

Sinclair OU A Gas Co.

VaaNo.3.

Emde No. 1. Foot No. 3..

W. B. Lewis No. 1. SbeUenberger No. 1

SbAlleDberger No. 2 fiheOenberger No. 1

BielsftaidNo. 1

Shorter White No.

B. A. DavsNo. 1.

Rlekaid No. 1. Blckard No. 2.

A. L. Duffer No. 1 . A. L. Duffer No. 2.

A. L. Duffer No. 6.

PattfloNo. 1

Atlantic Petro- leum Co.

Plains Oil & Qas Co.

Magnolia Petro- leiun Co.

Burmoeal Co

Southern Califor- nia Drilling Co.

Osceola Drilling Co.

Prairie Oa<bOas Co.

Quaklln Petrole- um Co.

Vulcan OU Co

Texas Co. do...

L. A. Hightower

No.1. DountainNo. 1...

BeottNo.!.. BehoorNal.

..do. ..do.

2,610-3,821

3,602-3,610

3,485

2,492,600

2,583-2,588

2,570-2,577 2,023-2,927 2,780-2,783

2,833-2,838 3,048,3,060

3,048,3,060

Date.

Oct. 16,1919 Sept. 5,1919

Sept. 5,1919

do.

Oct. 3,1919

Dec 5,1010 Sept. 8,1910

Feb. 281930

Sept. 4,1019 Sept. 5,1919 Dec. 3,1019

3,535-,542

do.

Humble Oil &

Refining Co. Texas Co

J. M. Sullivan Drilling Co.

Humble Oil &

Refining Co. do

3,122-3,148

Nov. 12,1919 Dec. 3, 1919

Feb. 13,1920

Dec. 22,1919

Feb. 111020

do

Nov. 25,1910

Nov. 8,1919

Rock pres- sure (pounds

per square inch).

Nov. 8,1010

Jan. 3,1920

Nov. 8,1919

Jan. 8, 1920

Jan. 3,1920 Dec 31,1919

Open- flow capac- ity (M cubic feet).

a 150

a 20,000

2,804

19,419

13,000 3,735

a25,000

5,443

20,000

11,000

19,000 1,042

4,186

13,678

5,253 31,000

a 8, 000 10,000

al4,000

03,000

6,500

5,213 2,522

Remarks.

Usinff this gas for bouer fuel.

26 drilUng wells oslnff gas; makes considerable gaso- line in drips.

15 drilling rigs using gas.

Slightly wet. Shows little water; nooil.

Sprays gasoline, ter, and oil when blowing; suppUes gas to 10 diUUng ngs. Later roo- ord, Feb. 29 193GL

Slves sand at ,490-3,497 ieet. total depth 3, feet, 30,000,00000- blo feet of fs: probably driliea deeper.

75 barrels of oil; total depth 3,600 feet

30 drilling rigi.

Notoompleted.

Total depth 3,700 feet: Dec. 8, 1919, fishing for tools.

Total depth, 3,860 feet.

Oas dry; leaking badly.

Not complete; fish- ing for tools.

Making a Uttle oil; blowing through trumble trap.

Oas leaking around

Totaldepth, 8,543 feet; making 100 barrels of oil.

Total depth, 3,605

feet Total' depth, 3,330

feet. Spraying oil.

Total depth, 3,606

feet. Qas dry; packing

blew out trring to

shut in well.

Gas wet; total depth 3,701 feet; plumed back to 8,2O0lMt.

Estimated.

82 Contributions To Economic Geology, 1920, Fabt Ii.

&Anos& Field.

No sharp line of demarkation exists between the Eastland and Banger fields. Each produces oil and some gas, the Banger field mostly casing-head gas. Immediately west and southwest of the town of Banger are two small groups of wells whose capacities are given in the following table :

Wells near Ranger.

Duffer No. 1

Duffer No. 2

Duffer No. 5

PattonNo.l

Patton No. 6

Rodr

pressure (pounds

per square inch).

Open-flow capacity

(cubic feet per day).

8,000,000

10,000,000

20,000,000

14,000,000

378,000

1,533,000

These weUs do not promise a large ultimate output. If there were a pipe line near by, and if their pressure were somewhat higher, so that they would feed into the line, they would add perceptibly to the supplies of the region.

Minob Fields.

The Mexia-Groesbeck field of Limestone County was not regarded by G. 0. Matson as of great promise and has followed the predictions of decline very closely. It may be disregarded, as it has practically reached the point of exhaustion.

The northern Louisiana fields are only about 160 miles from Dallas and are not beyond consideration so far as distance is concerned, but their available supply of gas is insufficient to warrant the expense of a line into north Texas. They produce little surplus above the de* mands of the markets they already supply.

West of Dallas and Fort Worth there are small scattered pools, none of which would justify a pipe line, but which are of interest owing to the encouragement they offer in the search for larger pools.

The Desdemona field, at the junction of Eastland, Comanche, and Erath coimties, contains 14 or 15 gas wells of moderate ca- pacity. A pipe line has been surveyed from this field to Stephenville and Dublin, both in Erath County. A few months ago this field was regarded by both oil and gas men as one of great promise, but the pro- duction of its wells has fallen off rapidly.

g-haw, B. W., Matson, G. C, and Wegemann, C. U., Natural-gas resources of parts of north Texas : U. S. Geol. Surrey Bull. 629, ppL 87-110, 1916.

IfATtJKAIiHSAS BESOURCBS OF CENTRAL NORTH TEXAS. 88

A well yielding 50,000,000 cubic feet of gas daily has recently been completed in Erath County, just north of Kxray, about 16 miles from the Desdemona field and but little farther from the Eanger and Min- eral Wells fields. It is close to the nonproductive belt across Erath, Comanche, and Brown counties indicated by geologic conditions and dry holes.

Stephens County does not at present afford evidence of much gas though it includes good oil territory, and the oil contains a consider- able proportion of gas. It is not unlikely that here, as in Eastland County, just to the south, there may be developed some as wells interspersed among oil wells. Some of the Eastland gas wells are very near the Stephens County line.

Shackelford and Callahan counties supply enough gas for the use of local towns but do not promise at present a supply for transmission to other points, though considerable portions of these counties have not been tested and it is quite possible that they may have one or more valuable gas pools. Coleman Coimty contains the Jim Ned field; and Brown County the Bangs field. These fields also are sufficient only for local use.

The only other developed gas pool west or northwest of Dallas is the AmarUlo field, a few miles north of Amarillo. This field is re- ported to contain one of the largest wells on record, a well with a daily capacity of 107,000,000 cubic feet. Six wells in the field have a total open flow reported as 171,000,000 cubic feet. This field can not be regarded as an immediate source of relief to Dallas if indeed it can be regarded as available at any time. It is 270 miles northwest of the western extremity of the 18-inch pipe line that extends westward from Dallas and is 210 miles from Walter, Okla. There are probably no engineering difficulties in the way of laying a connecting line, but it is somewhat doubtful if a sufficiently large yield could be developed to warrant the great expense of piping the gas to Dallas and other north Texas cities.

Prospective Territory.

In the report on the gas investigation of 1915, it was pointed out that the country extending 150 miles north and northwest of Dallas and Fort Worth offered great encouragement to the oil and gas pros- pector. Developments since that time have shown the correctness of this suggestion, and it may be safely assumed that there are still several undiscovered gas pools in this region. The reasons for this assumption are much the same as those stated in the earlier report, as quoted below. Testing has not yet been sufficiently thorough to show that all the pools of the region have been discovered.

U. S. Geol. Survey Bull. 629, pp. 62-65, 1916.

84 Contributions To Economic Geoloot, 190D, Pabt Il

Oeologioal indications. — The geology of the region extending north and west of Dallas and Fort Worth for 150 miles is, as already stated, generally favorable to the origin, accumulation, and preservation of gas and oil pool& All consider- ations, both practical and theoretical, point to ttie existence of undiscovered pools both of gas and of oil in the region. The favorable geologic conditions may be summarized as follows:

1. The rocks of the region belong to the Carboniferous and Cretaceous sys- tems, which contain much gas and oil in other regions. Sudi rocks as the pre- Cambrian, which nowhere contain valuable pools of gas or oil, are not found or lie so far below the surface that they may be left out of consideration.

2. Tlie neral structure is favorable. The layers of rock have the form of a broad, shallow basin or geosyncline, and most of the gas and oil of the world occur in such general basins. The rocks lie nearly flat and at some places, particularly between Fort Worth and Red River, have a broad terrace form.

3. The details of structure are locally favorable. Though the beds lie nearly flal, their general attitude is at many places modified by Irregularities of various kinds, and here and there they are undoubtedly arched up into well- developed domes and anticlines, as has been shown by observations made in similar basins elsewhere and by the conditions existing in those parts of this basin that have been tested.

4. The chemical composition of the rocks shows that they may have been the source of large quantities of oil and gas. Carbonaceous sediments, Includ- ing coal, though not so abundant as in some other regions, are very common.

5. The physical nature of the rocks also shows that they are well suited to accumulate and retain gas and oil pools. They Include many layers of open- textured sand of various degrees of porosity, in more or leas lenticular beds. These sands make up less than half of the rock, a fact favorable to their reten- tion of pools of oil and gas, because It makes the washing out of the beds with fresh water difficult or Impossible.

6. The history of the rocks has been favorable to the accumulation and reten- tion of poola With the exception of those underlying Dallas, they have appar- ently not been tilted back and forth until all the fluids in the sands have mi- grated elsewhere. Salt water, which is taken as an indication of slight or no underground circulation, is found almost throughout the region, and it may be fossil sea water which has not shifted far since the beds were deposited.

7. The rocks have been under sufficient pressure to induce the degree of meta- morphism required to separate the hydrocarbons that make up gas and oil but have not been so much compressed as to drive these fluids out of the region and leave nothing but carbonized remains. David White, in discussing this subject recently, has pointed out that the quality of gas and oil found in any rocks sliows a relation to the stresses to which the rocks have been subjected and has suggested that gas pools are likely to be most numerous on the sides of an oil region that lie nearest to regions that have undergone greater stresses. According to this principle, gas pools should be most numerous on the east side of this oii and gas region.

The discovery of new pools may undoubtedly be hastened by careful studies of the riK'ks, made to determine the most promising places for drilling. With- out such assistance in finding pools, the cities of Fort Worth and Dallas will probably full to obtain abundant supplies of natural gas unless they draw sup- plies from Oklahoma or other distant fields. As the country is developed, and as the oil and gas resources become gradually exhausted, wildcat wells will no doubt increase in number and greater care will be taken to drill in the most favorable places. The search for gas and oil pools should begin with domes

Natural-Gas Besouboes Of Central North Texas. 86

and anticlines, for they are by far most likely to contain such pool& I|ater explorations should extend to stmctures less favorable, and finally to regions in which the underground structure can not be determined because significant out- crops are poor or are lacking.

Inferences hosed on experience and an the doctrine of chances. — The propor- tion of wildcat wells that have been successful in the region under discussion indicates that if it were practicable to make tests of each square mile, a good many more gas pools would be found. Such a series of tests is, of course, as yet out of the question, but illuminating Inferences may be drawn from the results of the somewhat random wildcatting and the proportion of successful wells. The importance of these tests becomes more obvious when we apply to them the law of probabilities and remember the fact that some counties, especially Parker, have had scarcely one deep test If a township were known to contain a pool of oil a mile across, the chances of finding that pool by a random well would, of course, be 1 in 86. If a county covering 1,000 square miles contains one pool 8 or 4 miles across or having an area of 10 square miles, the chances of finding the pool by a random test are 1 in 100. Other considerations, of course, may enter into the problem, such as the fact that the well must be sufficiently deep and drilled with sufficient care to make an adequate test ; nevertheless a single unsuccessful wildcat well drilled at random does not throw a great deal of light on the existence of gas and oil pools in a considerable area.

Later developments and surreys have brought to light additional facts concerning the stratigraphy and structure of the region, but many details are not yet known and can not be learned except by de- tailed and expensive surveys and long and careful study. Plate VIII shows some of the known or probable structural features of the region. Prospecting guided by additional surveys may open up several gas pools. Many tests have already been made in some of the promising areas, and their results should be carefully studied in connection with the results of detailed surveys, to obtain a more intimate knowledge of the formations and their attitude.

The cross folding between the Wichita and Arbuckle mountains of southern Oklahoma, as referred to by Wegemann and Heald, has already been mentioned. The geographic relation between the Wheeler and Fox fields suggests another fold parallel to the one just mentioned. Wegemann and Heald speak of an anticline on the east bank of Bed Hiver 30 miles west and 8 miles south from the Healdton dome, in alinement with the Devol anticline of the Grandfield district.

Stephenson has described the Preston anticline and the Leonard- Celeste monocline, extending from Marshall County, Okla., south- eastward into Hunt County, Tex. The Preston anticline has pro- duced some oil and gas. It is not known by the writers that any deep wells have been drilled near the axis of the Leonard-Celeste mono- clinal " nose."

U. 8. Geol. Survey BaU. 621, p. 24, 1916.

' Stephenson, L. W., A oontribation to the geology of norttaeaatem Texas and Boatbem Oklahoma: U. 8. Qeol. Surrey Prof. Paper 120, p. 129, 1919.

86 Contributions To' Economic Geology, Iwd, Part H.

Te outline and structure of the Bend arch ' are now fairly well known, but prospecting has proceeded more rapidly on the eastern flank than on the western. The Bangs and Eastland fields lie very nearly on the axis. Pools of small extent may still be found on or near the axis, and possibly on smaller structural irregularities esLSt or west of the axis.

The Marathon fold, which is described by Beede and Liddle* as possibly extending from Brewster County northeastward into Foard Coimty (see PI. VIII), may prove favorable for the accumulation of oil and gas and doubtless will receive careful attention throughout its length.

CONCIiUSIONS.

A summary of the available contents of the fields that are either in use at the present time as sources of supply for the north Texas towns, or presumably available for connection before the winter of 1920—21, is given below. The figures indicate estimated recoverable reserves of natural gas January 1, 1920.

Cubic feet.

Petrolla field (Including Martin wells) 10,000,000,000

Fox field 4, OOOrOOO, 000

Walter field 13,000,000, 000

Loco field 700, 000, 000

Mineral Wells field 23, 000, 000, 000

Eastland and Ranger fields 150,000,000,000

200, 700, 000, Ooo

As shown by the curve of gross production of the Lone Star Gras Co. (fig. 9), the demand for 1920 may be estimated at 23,500,000,000 cubic feet. For 1921, a somewhat slower rate of increase being as- sumedy it may be 25,000,000,000 cubic feet. Predictions of this sort should not be carried too far into the future, owing to constant changes in conditions. If the necessary wells were drilled, pipe lines and compressors installed, and if the demand remained uniform at the estimated figure for 1920, the estimated supply of gas 200,700,000,000 cubic feet, would last about 8i years. There would be shortages in the winter due to the greater demand at that season. Figure 10 shows the seasonal variations in sales during 1919.

The present industrial consumption of gas in Dallas amounts to more than 50 per cent of the total amount of gas delivered. Any de- crease in the volume used in this manner would of course increase the

Hager, Doney, Am. Inst Min. Bn. Bull. 138, p. 1100, 1918.

Beede, J. W., Further notes on the straoture near Robert Lee, Coke County, Tex. : Texas Univ. Bull. 1847, pp. 3-7 [1920].

Liddle, B. A., The Marathon fold and Its influence on petroleum aGcmna]atlo& : Idem, pp. 9-16.

ITArUBAL-OAS BESOXTBCBS OF OBNTRAL KOBTH TEXAS.

l]20 U IB

Cd

o

lO

-J

Z

/

/

/

,

/

/

/

/

/

/

/

y

/

/

y

/

/

r

O 18

12

1(3 19

M- 19

18

120 Is

fZ\ I9Z2

FioUKE 9. — Curre showing production of gas by Lone Star Gas Co., 1910-1919, and esti

mated prodaction for 1920-21.

zpoo bJiaoo

(J 1,700

s

31,600 11,500

Oyioo

Z 1,300 Dl,20O

2i,ioo

re

/

/

/

'

/

/

/

/

n Felb Mar Apr Mnr Jurw Ji Ai Sept Oct. Nov Dec Jm

A.

So

Pxoosa 10.— Conre showing monthly sales of gas by Lone Star Qas Co., January, 1919,

to January, 1920.

88 CONTBIBUnOtTS TO ECONOMIC GEOLOQY, llOO, FABT U.

length of time that the remaining supply would last. The total leak- age is 20 to 25 per cent. It is questionable whether this loss con be reduced materially under present conditions. The expense of re- pairs is often far above the value of the product wasted, and> gas companies are loath to conserve the gas if conservation is of no eco- nomic advantage to themselves.

The curve in figure 10 is flattened out by the increased industrial consumption during the summer. Although the decrease of indus- trial consumption, if not its entire elimination, is regarded as an important step in the conservation of natural gas, it is only fair to point out the fact that the summer sates to industrial users have

t PM-t Worth,

enabled many gas companies to maintain a level of production throughout the year that was necessary in order fbr them to fulfill their contracts with well owners. ITie usual form of such a contract provides that the output of a well must never fall below a certain daily minimum. Owing to the extreme seasonal fluctuation of domestic consumption, the specified minimum would in the summer often not be attained if the company were supplying domestic consumers only. A curve showing domestic and industrial consumption at Fort Worth (fig. 11) is appended for comparison.

It seems probable that with rigid economy and scientific conserva- tion the present available supply of natural gas in the region around Dallas may be depended on to suffice for six to ten years, though there

Natural-Gas Resources Of Central. North Texas. 89

will be shortages nearly every winter. Little can be certainly pre- dicted for future developments until natural gas is elevated to an economic position side by side with its associate, petroleum, and frank recognition is given to the peculiar hazards of the gas industry. Natural gas to-day, owing to the low value placed upon it, is essen- tially in the position of being a by-product of the petroleum industry. This condition is neither in the interest of the gas consmners nor a stimulus to the conservation of this valuable natural product.

154071**— 21— Bull. 716 1

The Lance Creek Oil And Gas Field, Niobrara County,

Wyoming.

By E. T. Hancock.

Introduction.

The Lance Creek oil and gas field is situated in Niobrara County, east-central Wyoming, about 25 miles from the east line of the State. The center of greatest activity is about 45 miles southwest of Edge- mont, 80 miles northeast of the Big Muddy field, and 85 miles east and a little south of the Salt Creek field. The Lance Creek field can be reached either from Edgemont, on the Chicago, Burlington & Quincy Railroad, or from Lusk or Manville, on the Chicago & North- western Railway. The east end of the field, as shown on the geologic map (PI. X), is about 22 miles due north of Lusk, and the west end is about the same distance north of Manville.

History Of Development.

According to notes submitted to the writer by Dr. J. E. Hawthorne of Lusk, the early history of development in the Lance Creek field is briefly as follows:

. As early as 1912 Dr. Hawthorne made an effort, by advertising, to obtain the necessary funds to drill a hole on Buck Creek. He failed to interest anyone at that time, but on April 29, 1913, what is known as the Lusk, Wyoming, Oil Co. was incorporated. After consulting L. W. Trumbull, State geologist, the company decided to drill a hole m the extreme northeast comer of sec. 15, T. 35 N., R. 64 W. Drill- ing was begun in August, and by June, 1914, when the funds were exhausted, a depth of 2,250 feet had been reached. A California company, represented by H. A. Rispin, then attempted to finish the hole but did not drill deeper than 2,600 feet.

In April, 1913, Mr. McWhinnie, of Douglas, shipped a portable rig to Lusk. The rig was taken out to the SE. sec. 31, T. 36 N., R. 64 W., early in June, and on July 12 the drill had reached a depth of 268 feet. Later drilling was continued to 1,200 feet, and the hole was then abandoned.

In the summer of 1914 Edwin Hall organized the Pine Dome Oil Co., composed of Salt Lake mining men. A standard rig was pro- cured, and drilling was begun in the N. i sec. 33, T. 36 N., R. 66 W.

92 Contributions To Economic Geology, 1920, Part U.

Owing to the development of a crooked hole at a depth of 1,700 feet, this company also abandoned the field.

The Montana-Wyoming Oil Co. of California, represented by H. A. Rispin, started a well in the SW. SE. sec. 3, T. 35 N., R. 65 W., about the 1st of November, 1916. This company drilled about 200 feet and then abandoned the work until the following year. The well was finally finished in 1919 by the Western States Oil Co., which brought in a water well.

In 1916 Dr. Hawthorne procured from the State a lease on sec. 36, T. 36 N., R. 65 W., and subleased it for a period of seven months to the California company represented by Mr. Rispin. The lease was subsequently extended for five months. Later Dr. Hawthorne' ob- tained another lease from the State and subleased the tract to the Ohio Oil Co. This company erected a standard rig and commenced drilling on September 27, 1917. The driU penetrated the first oil sand at a depth of 2,689 feet on March 13, 1918. This sand yielded 80 barrels of oil during the first 24 hours. The company resumed drilling April 29, 1918, and reached the principal oil sand October 6, 1918. When the drill had penetrated the sand to a depth of 2 feet 6 inches the well flowed at the rate of about 1,500 barrels during the first 24 hours. Since that date a number of other wells have been drilled in the principal oil sand, with results set forth on pages

Acknowledghsnts.

In presenting this report the writer desires to express his thanks to David White for valuable suggestions and criticisms and to Robert M. Campbell for assistance in the field. He feels particularly indebted to Mr. R. F. Gray, county surveyor of Niobrara County,f or information relative to section and quarter comers. He also wishes to thank the oil and gas operators for their willing cooperation in furnishing the "records of deep borings. Finally, he wishes to express his apprecia- tion for the many acts of courtesy by the citizens of Lusk and vicinity.

FUBPOSE OF THE PBBSBNT DTVESTiaATIOK.

The principal object of the investigation was to procure all the information obtainable relating to the composition and structure of the sedimentary beds and the conditions controlling the accumulation of oil and gas, and to arrange that information in such form as to pro- mote the economic development of the field. To attain that object it was necessary to trace out and locate the beds on the surface and to determine their dip or degree of inclination at close intervals.

Lakce Gbeek Oil. And Gas Pield Wyo. 98

Fibld Wobk.

The field investigation that furnished the basis for the present re- port was carried on between September 11 and November 5, 1918, The field observations were made and the maps prepared under the supervision of the writer. In the process of mapping nearly all the locations were made by triangulation, and the elevations were de- termined by means of vertical angles. The instrument used was the ordinary 15-inch plane table and telescopic alidade. Two base lines were carefully measured by means of a steel tape, one in the valley of Lance Creek and the other near the east end of the field. After the plane table had been carefully oriented at the extremities of the base lines, the derricks and a number of previously constructed mon- uments were located by intersection. A certain elevation was as- sumed for the instrument at the south end of the base line on Lance Creek, and the elevation of each subsequently located point was determiaed from this assumed elevation. Later these elevations were adjusted to conform to the correct elevation of the top of the casing of the Ohio No. 1 or discovery well, as determined by the Illinois Pipe Line Co. In the process of mapping many of the land comers were located either by intersection or through the use of the stadia, after the instrument had been carefully located by triangulation. The section lines were then drawn to conform as nearly as possible to the located comers and to the data shown on the official township plats.

Surface Features.

GHABACTBB OF SUBFACE AS BELATED TO FUTtTBE DEVELOP- MENT.

Most of the development work that is being carried on in the Lance Creek field is confined to the relatively low-lying tract be- tween the more or less continuous ridge of the Fox Hills sandstone on the north and the escarpment formed by the White River beds on the south. The two principal points of supply are Lusk and Manville, on the Chicago & Northwestern Railway. The oil com- panies and Niobrara County have, at considerable expense, laid out and constructed an excellent graded road the entire distance from Lusk to the productive portion of the field, where the main camps of the Ohio, Buck Creek, and Midwest oil companies are located. A short distance south of the field is a secondary road that extends from the principal highway in a northwesterly direction over the ridge underlain by the White River beds and down to the valley of Lance Creek.

An excellent road has also been laid out from Manville to the oil field, and construction work is well underway. This road, which is to take the place of the one previously used, will furnish a direct

94 Contributions To Economic Geologt, 1920, Part H.

route from the Chicago & Northwestern Railway to the west end of the field.

Trails lead from the principal highways to the different parts of the field. These have received very little attention, but in general the streams have not cut their channels very deeply, and therefore it is not a difficult matter to reach most any part of the field even with heavily loaded trucks.

Dbaikaqb.

There are no perennial streams in the Lance Creek field. Even

Lance Creek, which has a well-defined channel, is dry the greater

part of the year. The long gullies in the western part of the field

either lead down to the valley of Lance Creek or to Little Lightning

Creek, its tributary from the west. The gullies that open into Lance

Creek from the east all head near the top of a divide which separates

the drainage system of the western part of the field from that of

the eastern part. The run-off from the east slope of the divide

either empties into Young Woman Creek or finds its way into Buck

Creek. Whichever course it takes, it finally reaches Lance Creek,

for Buck Creek joins Lance Creek about 7 miles north of the field,

and the drainage into Young Woman Creek reaches Lance Creek

about 6 miles farther down its course. Although the principal

streams in the Lance Creek field are without running water most of

the year, there is sufficient seepage so that the deeper portions of

their beds generally contain standing water, and even where the bed

is entirely dry water can be obtained by drilling to a very alight

depth.

Stratigraphy.

Oekebal Featubes.

The oldest beds exposed in the Lance Creek field lie about 1,650 feet below the top of the Pierre shale of the Montana group and are exhibited at the crest of the anticline in the western part of the field. In the Powder River dome, which lies about 15 miles west of Salt Creek, oil seeps are found in the Sundance, Morrison, and Dakota ( ?) (Cloverly) formations and in the Mowry shale member of the Benton shale, as shown in the coluxnnar section of the Powder River field on Plate XI. In a discussion of the strata of the Lance Creek field in relation to oil accumulation it is therefore necessary to consider the formations at least as low as the Jurassic. The nature of the beds between those that crop out and the oil and gas bearing sand is well shown in the log of the discovery well on page 113. The com- position the imderlying formations can only be inferred through comparison with other localities.

i WegBnuam, C. H., Tbe Powdflr Rivflr oil field, Wyo.: U. 8. Geol. Survey Boll. 471, pp. 56-, Mis.

Lance Gbeek Oil Akd Gas Field, Wyo.

The following section; which is believed to represent the stratig- raphy in the Lance Creek field as low as the base of the Sundance formation, was made up from data collected in the Upton-Thornton field, 80 miles to the north, and from the records of borings at Cambria.' The section from the top of the Dakota to the bottom of the second fire clay in the Morrison is taken from the log of the bore hole of the Antelope mine. The part of the section comprising the lower portion of the Morrison formation and the Smidance formation is taken from the log of the deep well at Cambria.

Rock formations in the Lance Creek fields Wffo.

SystoODL

Series.

Group.

Farmatian and member.

Character.

Thickness (feet).

Quatomary.

Beoent.

Allnvinm.

Sands and loams with some ad- mixtore of coarse material

Varlablei

Tortiftiy.

OHgooBoei

White River

Verv soft unconsolidated green- isn-oav to white sand,lnter- bedded with reddish to grav- Ish clay shale. Commonly overlain by greenish-gray, very coarse grained sandstone, In places coarsely conglomeratic.

Variable.

IVrtlaryC?).

Eocene (T).

Lanoe f ohna- Uon.

Sandstone and sandy shale, with thin beds of coal.

Only the lower beds were ex- amined.

Upper Creta- oeoas.

IContana.

Fox Hills sandstone.

Sandstones with some sandy shales. Some of the sandstones, especially those near the top, include numerous large red- dish-brown concretions, many of which are very f ossiliferous.

Plemsbale.

Dark-gray shales interbedded with thin beds of hard sand- stone and thicker beds of soft sandy shale.

Cretaoooos.

Dark-gray shale, including thin beds of sandy shale and beds of f ossiliferons calcareous con- cretions.

ShannonC?) sandstone member, coarse-grained greenish-gray sandstone with many yeuow- ish-brown iron-stained con- cretions.

Predominantly dark-gray shale, but including lenticular masses

and some venr thin beds of fos- slliferous calcareous concre- tions.

1,960

polorada

Niobrara for- mation.

Soft shaly limestone or impure chalk, including someday and sand.

aoo

Dartoo, M. H., U. 8. Geol. Survey QeoL Atlas, Newcastle folio (No. 107), p. 4, fig. 5, 1994.

--o/Vi tV BCONOMIC QBOLOQT, 1920, PABT U.

Onnp.

Formatlanand

Chaiaoter.

TllloklMK

Colorado.

CarlUe shale.

Dark shale with thin beds of soft sandstones (Wall Creek sand- stone member) near the base.

Too

Upper Ci- taoeoos.

Oreenhom lliiwrtona

Impure limestone.

Dark-gray to black shale includ- ing many large oaloareous con- cretions, espeoially in the up- per part.

Mowry

shale

member.

Hard Ugfatray sandy shales oontalning numerous fish scales. Bentonite beds near the top and to some extent near the base.

CrvtMMoa.

Dark sandy shale jrading up- ward into typical Mowry shale.

as

Newcastle sand- stone member.

Reddish to light-yellow sand- stone associated with black carbonaceous shale.

Dark-gray to black shale.

Dakota sand- stone.

Thin-bedded to massive hard buff sandstone.

60?

Lower Cre- taceous.

Anson forma- tion.

Shale and thin-bedded sand- stone.

stone.

Sandstone, in part conglomer- atic, with some coal beds near the base.

Orotaoeoi]8(r).

(?)

Morrison for-

Ught-gray to pinkish shale.

Tmaarfo.

Upper Ju- raaaic.

Sundaneefor-

Ught-gray to dark greenish-gray and TMiMri-*! AbiAwnh %

n

laoon.

3&-foot sandstone near the base.

X7Kexposbd Bocks.

Jurassic System.

8Undancb Formation.

The Sundance foimation is exposed at many places in the Black TTilla and at certain other localities in eastern Wyoming — for example, in the Powder River field, west of the Lance Creek field, and in the vicinity of HartviUe, on the south. By comparing the formation in these different localities it is possible to form a reasonably accurate notion of its composition in the Lance Croek field. As an aid in

Lance Gbeek Oil And Oas Field, Wto. 97

making such a comparison the reader is referred to the columnar sections on Plate XI.

At Cambria the Sundance formation is composed essentially of light-graj and pinkish shale, with one 25-foot buff sandstone near the base. Farther southeast, in the Edgemont quadrangle, the formation contains a much larger proportion of sandstone and is overlain by a fine-grained massive cliff-forming sandstone, known as the Unkpapa sandstone, whose maximum thickness is 225 feet. The greatest development of this sandstone in the Black Hills region is in the hogback east of Hot Springs and Cascade Springs, and it gradually decreases in thickness toward the west.

The Sundance formation as exposed near North Platte River, about 13 miles northwest of Hartville, Wyo., is reported to be about 200 feet thick. The lower part consists of about 140 feet of buff to nearly white sandstone, and the upper 60 feet includes a variable amount of more or less slabby sandstone with interbedded clays. The formation is exposed in the Powder River field,* in sec. 33, T. 41 N., R. 81 W., along the bed of a canyon that enters Salt Canyon from the north. Here about 10 or 15 feet of the formation is brought to the surface by a sharp minor fold. The exposure consists of argil- laceous limestone beds a foot or two in thickness which yield abun- dant fossils and, interbedded with the limestone layers, numerous beds of dark-gray shale.

Cretaceous (?) System. Mobribon Formation.

The Morrison formation, which is doubtfully referred to the Creta- ceous system, overlies the Simdance conformably. It represents fresh-water conditions of sedimentation, whereas the Sundance represents marine conditions.

The section of a drill hole at the Antelope mine at Cambria' (see columnar section for Upton-Thornton field, PI. XI) shows two beds of fire clay, one 3 feet and the other 7 feet thick, separated by sand- stone. The deep well at Cambria was begun just below the 7-foob bed of fire clay and penetrated 130 feet of Ught-gray to pinkish shale, also included in the Morrison formation.

According to the description of the formation given by Darton and Smith," it is 100 feet thick west of Minnekahta, S. Dak., but farther east it thins out and disappears. For the Edgemont quad-

Darton, N. H., and Smith, W. 8. T., U. 8. Geol. Survey Oeol. Atlas, Edgemont Iblio (No. 106), p. 4,

4 Smith, W. 8. T., U. 8. GeoL Survey Oeol. Atlas, HartviUe foUo (No. 91), p. 3, 1903.

WeeBmann, C. H., The Powder River oilfield, Wyo.: U. B. Oeol. Survey BulL 471, p. 61, 1912.

Darton, N. H., U. 8. QealL Survey Oeol. Atlas, Newcastle folio (No. 107), p. 4, 1904. r Idem, p. 8.

Darton, N. H., and Smith, W. 8. T., U. B. Qeol. Survey Oeol. Atlas, Edgemont folio (No. 108), p. 4,

98 GOKTRIBUTIONS TO ECONOMIC GEOLOGTy 1920, PART II.

rangle as a whole it may be said that the formation ranges in thick- ness from practically nothing to 125 feet and consists of grayish, greenish, and maroon massive shale, including thin beds of fine- grained white sandstone. Like the miderlying Sundance formatioa, the Morrison is exposed along North Platte River about 13 miles northwest of HartviUe,* and in that locality it contains about 100 feet of massive shales or hardened clays of various colors — green, purplish, reddish, light and dark gray to nearly black — with one or more thin beds ot moderately hard, compact light-grayish lime- stone.

In the Powder River field, according to Wegemann,® the forma- tion is about 250 feet thick and consists of shale with a few hard sandstone beds from 3 to 8 feet thick. The shale in the lower part of the formation has a greenish tinge, but that in the upper part is maroon. #

OBETAOEOUS SYSTEM. LOWS& OKBTACXOirS 8XBXSB.

The Morrison formation of northeastern Wyoming is commonly overlain by a rather massive sandstone. In the Powder River field, according to Wegemann," it is overlain by a coimse conglomeratic sandstone 56 feet in thickness with a thin bed of coal at its base. In that field the sandstone is a lithologic unit, but 25 miles to the north, where it crops out along the Big Horn uplift, it consists ot numerous thin layers of sandstone with interbedded shale. In the report on the Powder River oil field this sandstone was doubtfully referred by Wegemann to the Dakota sandstone. In his second report on the Salt Creek oil field,' however, the same beds are included in the Lower Cretaceous series under the name Overly formation, mainly on the evidence of fossil plants which were collected from layers of shale that lay between beds of conglomerate near the base. These fossils were identified by F. H. Knowlton as undoubtedly Kootenai species, and hence there is little doubt that the conglom- erate is equivalent in age to at least part of the Kootenai of Montana. Overlying the conglomerate is 80 feet of dark, unfossil- iferous shale, above which is a 14-foot bed of shaly sandstone whose top layers are strongly ripple marked. According to Wegemann, this bed, though comparatively thin, is foimd at many places throughout this region and appears to be of wide extent, and accord- ingly he suggests that if the formations of the Black Hills are all present in the Salt Creek field, the 14-foot sandstone may represent

f Smith, W. 8. T., U. B. Oeol. Survey Geol. Atlas, Hartville folio (No. 91), p. 3, 1008. 10 Wegemaim, C. fi., The Powder River oil field, Wyo.: U. 8. Qeol. Snrvey Boll. 471, p. 61, 1912. ( " Idem, p. 82.

u Wegemann, 0. SL, The Salt Creek oU field, Wyo.: U. 8. Oeol. Survey BulL 870, p. 15, 1017. u Fisher, C. A., Soathem extension of the Kootenai and Montana ooal-bearinR fonnatioos of northflm Montana: Soon. Geology, voL S, pp. 77-90, lOOB.

LA2!rGE GBEEK OK. AND QAS FIELD, WTO. 99

the true Dakota and the shale oveilyiag the conglomerate may be the equivalent of the Fuson shale, of Lower Cretaceous age; he also suggests that the Dakota may be absent and that the shale and sandstone referred to may belong to the Benton.

Above the Morrison beds in the locality about 13 miles northwest of HartviUe are from 250 to 300 feet of sandstones with several beds of shale and clay, which have been grouped together by Smith under the name Dakota sandstone. Smith says, however, regarding this method of grouping:

While it is possible and even probable that the lower part of this series of rocks corresponds to the Lakota (Lower Cretaceous) of the Black Hills, no formation corre- sponding definitely to the Fuson or Minnewaste was observed, so that the line of (vision between the Upper and Lower Cretaceous rocks (if the latter are represented) can not be drawn except arbitrarily. For this reason the rocks have been mapped without subdiviaioin.

Many of the sandstones show distinct bedding; a few of them exhibit cross-bedding, and several present ripple-marked surfaces. The beds of clay or shale occurring with the sandstones are from 2 to 8 or 10 feet in thickness and of reddish; yellowish; or grayish color. In the Black HillS; on the opposite side of the Lance Creek field from the Hartville region, 150 to 350 feet of beds generally intervene between the Morrison beds and the Dakota sandstone. These beds seem to be the equivalent of the Lower Cretaceous rocks in other localities.

Li the Newcastle quadrangle; for example, the Morrison is overlain by 150 to 200 feet of massive, cross-bedded; coarse gray to buff sandstone with local coal beds and conglomerate, known as the Lakota sandstone. This is overlain by 15 to 30 feet of gray to red shales with thin sandstones, known as the Fuson formation. Farther southeast, in the Edgemont quadrangle, the Lakota formation is from 200 to 350 feet thick, and between the Lakota and the Fuson formation is a limestone 25 feet in maximum thickness, which has been named in the Edgemont folio the Minnewaste limestone. This limestone ia, however, not of widespread occurrence in the Black Hills. Its principal outcrops extend from the vidnity of Cascade Springs to Buffalo Oap, S. Dak., and it thins rapidly toward tiie flouth and west.

VPPXa OBSTAOXOT78 8BBIS8.

Dakota Sandstone.

The Dakota sandstone, as it has been definitely recognized in the Black Hills, ranges in thickness from 50 to 150 feet. In some places it is thin bedded in the upper part and massive in the lower part; ui others it is entirely massive. It is ordinarily gray to buff and generally weathers brown.

i8iiiith, W. S. T., U. 8. aol. Bunrey Oeol. Atlas, HArtviUe foUo (No. 01), p. 8, 1908.

100 CONTRIBUTIONS TO ECONOMIC GEOLOGTy IMD, PART II.

Colorado Group.

The Colorado group in northeastern Wyoming includes the Nio - brara formation, Carlile shale, Greenhorn limestone, and Graneros shale. The last three formations are equivalent to the Benton shale elsewhere. None of these formations are exposed at the surface in the Lance Creek field proper. . They are well exposed in the Old Woman anticline, about 15 miles east of this field, and also in the Mule Creek oil field, about 30 miles northeast of the producing area in the Lance Creek field. The thickness and character of each of these formations aie shown in the table on pages 96-96.

Fobmatzok8 Exposed Ik The Lakoe Greek Field.

The lowermost beds exposed in the Lance Creek field are those at the highest point on the anticline, in the western part of the field. They occur about 360 feet below the top of a sandstone which is probably the equivalent of the Shannon sandstone in the Powder River and Salt Creek fields. The formations that have been exposed by erosion in the Lance Creek field are described below.

Obetacbous System. Pierre Shale.

The Pierre shale occurs at the surface throughout the compara- tively low area between the more or less continuous ridge formed by the Fox Hills sandstone on the north and the escarpment caused by the White River formation on the south. Being composed essentially of shale, it weathers down to a comparatively even surface. The bulk of the formation is composed of dark shale containing lenticular masses and more or less continuous beds of calcareous rock. The comparative hardness of the calcareous beds causes many of them to stand out above the general surface, and in places the succession of more or less independent jagged masses fiunishes the only available key to the structiu'e. These limy beds and lenticular masses, weathering, break up into a vast number of angular fragments and exliibit various kinds of fossil shells. Among the fossils collected from the upper portion of the Pierre shale during the process of the field work the following species were identified by T, W, Stanton:

Actaeon attenuatus Meek and Hayden.

Anchurasp.

Baculites ovatus Say.

Cucullaea shumardi Meek and Hayden.

Fiflh scale.

InoceramuB barabini Morton.

Lmgula nitida Hall and Meek.

Mactra gradlifl Meek and Hayden.

Modiola meekii (Evans and Shumard).

Lakge Grbek Ok. And Gas Field, Wto. 101

MytUus? sp.

Ostreasp.

Frotocardia subquadrata (Evans and Shumard).

Scaphites nodoeua Owen.

Syncydonema rigida (Hall and Meek).

Yoldia evansi Meek and Hayden.

In many places where the shale is exposed a careful observer is able to detect thin layers of sandstone or thin seams of gypsxmi. One conspicuous layer of sandstone is exposed in the bottom of the gully between Rabbit Mountain and the main escarpmment in the western part of sec. 4, T. 35 N., R. 64 W. A sandstone resembling it is well exposed at the north edge of the outlier of the White River formation near the north line of sec. 6 of the same township. Layers of sand- stone show how the beds are inclined at numerous places in the east end of the field and furnish some clue as to structure in the western part, where most of the shale is concealed by the overlapping beds of the White River formation. In certain localities beds of tiie yellow clay known as bentonite occur in the shale and assist very materially in deciphering the structure. One of these beds forms the dip slope in the W. i sec. 2, T. 35 N., R. 65 W., and appears to dip south at an angle of A similar bed of bentonite, in all probability the same bed, is exposed on the north side of the anticlinal axis in the SE. i sec. 26, T. 36 N., R. 65 W. There the bed of yellow clay dips north at an angle of 16. The structure and also the total amount of the Pierre shale exposed in this field are indicated by thicker sands which occur in the upper portion of the Pierre and which are traceable for some distance on the surface.

The Shannon ( ?) sandstone crops out along the small gully immedi- ately west of the No. 1 or discovery well, near the northwest comer of sec. 36, T. 36 N., R. 65 W. It rises gently toward the south, forming the dip slope, and arches over at the top of the anticline about 1,500 feet southwest of the discovery well. Scattered ex- posures of this sandstone were observed as far west as the center line of sec. 27. From dip determinations it is believed to lie about 1,300 feet below the base of the group of sandstones mapped as the Fox Hills sandstone. The gas well in the SW. i NW. i sec. 34 is*reported to have reached the first producing sand at a depth of 3,303 feet, whereas in the discovery well that sand was encoxmtered at a depth of 3,663 feet. It is evident, therefore, that the beds which reach the surface at the gas well are about 360 feet below the top of the Shan- non (?) sandstone, and accordingly about 1,660 feet of the Pierre shale is exposed in this field. Immediately overlying the Shannon ( ?) sandstone is a zone about 600 feet thick, including some soft sandy shale but composed mainly of dark shale with numerous fossiliferous calcareous concretions. Nearly all the. beds from the top of this

102 Contributions To Economic Geology, 1920, Part H.

zone up into the Fox Hills sandstone are exposed along the east bank of Lance Creek in the NE. i sec. 28, T. 36 N., R. 65 W., as shown in the following section:

Section showing the uppermost peart of the Pierre shale and the lowermost beds of the Fox Hills sandstone along the east hank of Lance Creek in the NE. sec. 38, T. S6 N., R. 65 W,

Fox Hills aandstone: Ft. in. Sandstone, very light colored and very soft, not well ex- posed 25

Sandstone, light yellow, soft and maasive; contains a few concretions and rather uniformly distributed beds of hard

reddish -brown sandstone from 6 to 18 inches thick 96

Soft sandstone and sandy shale in thin beds; contains three thin beds of hard brown shelving sandstone showing

numerous ripple marks 30

Sandstone, light yellow, fine grained 1

Sandstone and sandy shale in alternating layers of light

yellow and dark color 3 6

Sandstone, massive, yellowish 3

Sandstone, reddish brown, slabby ; dip 24® 7

Sandstone, containing thin seams of sandy shale 4

Sandstone, very massive, light yellow 7

Sandstone, soft, containing thin beds of dark sandy shale and a few thin beds of hard sandstone, especially in the

upper portion; strike east, dip 27® N 162

Pierre shale:

Shale, very dark, containing thin layers of reddish-brown sandstone; becomes much lighter colored near the top, as it merges into the Fox Hills formation; strike east, dip

27® N 72

Sandstone; weathers to rounded surfaces; cut off abruptly by

a shear zone 36

Shale, dark; contains ten separate layers of reddish-brown concretions. Baeulites fairly abundant. Strike east,

dipattop27i® 67

Shale, dark, slightly sandy; contains very few concretions

and is not very fossiliferous 120

Interval, not well exposed but in all probability composed

of very soft beds 100

Belt composed essentially of soft sand but includes many

thin seams of hard yellowish-brown sandstone 84

Shale, very sandy 85

Shale, grayish brown, sandy; weathers yellowish gray. Has many calcareous concretions which contain Inoceramus harabini Morton and Anchura sp. Dip 23® N . 40® W 34

A 30-foot bed of soft light-gray sandstone included in the Lanoe Creek section is exposed in the NE. i sec. 27, T. 36 N., R. 65 W. The bed was traced and mapped eastward to a point a few hundred feet east of the prominent butte composed of White River beds in sec. 25, T. 36 N., R. 65 W. Where the bed was last recognized it dips 20 N.

Lakge Cbeek Ok. And Gas Field, Wto. 108

Fox Hills Sandstone.

The great mass of Pierre shale is overlain with apparent con- formity by many hmidred feet of sandstones and sandy and carbona- ceous shales, including some coal beds. A long period of time elapsed after the beginning of the influx of coarse sediments before there was a complete change from marine to brackish and fresh waters, and during that period the beds of the Fox Hills formation were laid down. After the formations were uplifted to their present position they were attacked by the agencies of erosion, but the overlying sandy beds, being harder and more resistant, were not removed as rapidly as the soft shales. As a i'esult the area underlain by the Pierre shale is bordered on the north and west by a more or less continuous ridge underlain by the Fox Hills sandstone and the lowermost fresh and brackish water beds of the Lance formation. Most of the beds constituting the Fox Hills sandstone are exposed along the east bank of Lance Creek in the NE. i sec. 28, T. 36 N., R. 65 W., and are shown in the stratigraphic section on page 102. There is a gradual transition from the Pierre shale to the Fox Hills sand- stone, owing to the gradual influx of sandy material, but for the pur- pose of mapping the base of the Fox Hills was drawn at the base of the 162-foot zone as shown in the section, there being thus approxi- mately 330 feet of the formation exposed at that locality. Through- out most of the Lance Creek field the formation is not well exposed, but farther north the Fox Hills and overlying Ceraiops beds" (Lance formation) and also some of the Pierre shale are much better exposed and are well described by Hatcher as follows:

Along the southeastern border, especiaUy between Lance and Buck creeks, are many fine exposures of the Ceratops beds and the underlying Fox Hills. Perhaps the best exposure is that made by a smaU tributary emptying into Buck Creek, about 4 miles east of Lance Creek and one-half mile northwest of the Buck Creek pens used by the cattlemen for round-up purposes. This watercourse has here cut its way in a southerly direction at right angles to the strike down through the lower half of the Ceratops beds, through the underlying Fox Hills sandstones, and into the Fort Pierre shales. At this place the bed of Buck Creek and the rounded hills of that region at the head of this stream, embraced between the border of the Ceratops beds and Fox Hills sandstones on the north and the bluffs of Miocene clays and conglomerates on the south, are composed of Fort Pierre shales. All the strata of this entire section dip to the northwest at an angle of 16 degrees. The exposure is a continuous one, and, commencing from below, the section is as follows:

At the base are the Fort Pierre shales, of unknown thickness, several hundred feet of which are exposed. They consist of argillaceous, finely laminated dark shales, quite soft and easily eroded. They contain many limestone concretions and numer- ous invertebrates. Among others are BaculUes ovatus, B, compressusj ScaphUes nodo- 9u$f Plaeentieeras placenta NautUua dehayij etc.

Overlying the Fort Pierre deposits is an alternating series of sandstones and shales with an estimated thickness of 500 feet. In the lower portion of this series the shales

u Hfttcher, J. B., The Ceratopt beds of Conyerse County, Wyo.: Am. Jour. Bci., 3d a&r,, voL 46, p. 138

isn.

104 CONTRIBUTIONS TO ECONOMIC QEOLOQTy 1920, PART U.

predominate, but toward the middle the sandBtonee are in excesa, and in the uppr 50 feet they entirely replace the Bhales. The sandstones are of a yellowish-brown color, very fine grained, firm, and well stratified below, but softer and quite maaaive at the top, where they contain numerous large concretions and a rich marine inver- tebrate fauna. ♦ ♦

Next come the Ceratopa beds, with an estimated thickness of 3,000 feet, restiiig directly upon the Fox Hills series. Immediately above the Fox Hills is a very thin but persistent layer of hard sandstone, well stratified, and easily cleavable along the lines of stratification. This stratum of sandstone is about 6 inches thick and is regarded as the dividing line between the marine and fresh-water beds.

In the geologic mapping the top of the Fox Hills sandstone is drawn at the 6-inch bed of sandstone, which Hatcher regards as the dividing line between marine and fresh-water beds. The sand- stones which he mentions as containing numerous large concretions and a rich marine invertebrate faima are exposed almost continu- ously along the west side of Buck Creeki and from the Buck Creek narrows as far east as the formation was mapped. Thej were also recognized in isolated exposures from the vicinity of Buck CSreek as far west as Lance Creek. The appearance of these sandstones as they are exposed along the east side of Buck Creek valley is shown in Plate XII. The following fossils were collected from the Fox Hills beds at different localities in the Lance Creek field and identified by T. W. Stanton:

SE. sec. 33, T. 37 N., R. 63 W., from concretions in the sandstones near the top of the formation:

Anchura sp.

GaUistasp.

Crenella elegantula Meek and Hayden.

Gylichna scitula Meek and Hayden.

Dentalium gracile Hall and Meek.

Fish scale.

Protocardia eubquadrata (Evans and Shumard).

Scaphites conradi (Morton)?

Veniella humiBs Meek and Hayden. NW. i NW. i sec. 22, T. 36 N., R. 64 W., from concretions in the sandstones nesr the top of the formation:

Burrows of a boring mollusk.

Veniella humilis Meek and Hayden. NE. i SE. i sec. 20, T. 36 N., R. 64 W., from a sandstone about 100 feet above the base of the formation:

InoceramuB sp.

Nucula sp.

Protocardia subquadrata (Evans and Shumard).

Scaphites conradi var. intermedius Meek?

Tellina scitula Meek and Hayden.

Veniella humilis Meek and Hayden. SE. J SE. i sec. 12, T. 35 "N., R. 66 W., from thin beds of sandstone exposed in the east bank of Little Lightning Greek:

Avicula fibrosa Meek and Hayden.

Baculites ovatus Say.

B0lJ.ETtN 710 PIATB Xn

SANDSTONE INCLDDING LARGE HEDDISH-BROWN CONCRETIONS NEAR THE TOP OF THE FOX HILLS SANDSTONE. EAST SIDE OF BUCK CREEK VALLEY, SEC, S3. T.37N..R.63 W..WYO.

eadwring; fi, VlmloDkingDorthinal. TIh treenxivered rid at top ia '' —J-- — - j; — - — utwardon thoppiwt sida of tba valley.

daTdopad, lo tan, on tin aanw aBudaiooB di;

liANCB CKEEK OIL AND QA5 FIELD, WYO. 105

Ludna robundata Hall and Meek. Lunatia concinna (Hall and Meek)? Nucula cancellata Meek and Hayden? Scaphitee conradi (Morton). Veniella humilis Meek and Hayden? Yoldia evansi Meek and Hayden.

Tebtiaby (?) System. La.Nos Formation.

The light-colored massive sandstones at the base of the Lance fonnation fonn Pine Ridge, in the SE. i sec. 23, T. 36 N., R. 65 W. Thej crop out almost continuously as far east as sec. 12, T. 36 N., R. 64 W., but farther north and east they are not so conspicuous. West of Lance Creek these beds are well exhibited along the gulch extending southeastward through sec. 29, T. 36 N., R. 65 W., where the beds of the White River formation have been eroded and the uppermost Fox Hills and lowermost Lance beds appear, dipping 30 northwest. Toward the southwest they soon pass beneath the White River beds and are next seen in the SW. i sec. 31 of the same town- ship. Thence the beds can be traced continuously as far as the NE. I sec. 12, T. 35 N., R. 66 W., but farther southwest they are entirely concealed. Where they were last recognized a brackish-water bed composed mainly of the shells and casts of Ostrea svhtriganalis dips 24 W. A similar brackish-water bed was seen near the east side of sec. 29, T. 36 N., R. 65 W., and sheUs of Corhicvla planumbona Meek were collected near the control point at the top of the high ridge in the NW. i sec. 22, T. 36 N., R. 64 W., from a layer of sand- stone near the top of the conspicuous white sandstones that form Pine Ridge, about 4 miles farther west.

The writer was unable, for lack of time, to study the details of even the lower portion of the Lance formation in this field. He did, how- ever, measure a section at Pine Ridge, in the SE. i sec. 23, T. 36 N., R. 65 W., which shows fairly well the composition of the lower part of the formation. The base of the Lance formation is not well de- fined here, owing to the lack of good exposures, but the bottom of the following section is probably not far from that horizon.

Section of the lower hedi of the Larice formation in the SE. i sec. 23, T. 36 N., R. 65 W.

Feet. Soft sand and sandy shale containing thin beds of rusty-colored

sandstone. The entire mass presents a pinldsh color 9

Sandstone, light yellow, soft; weathers into cavern-like forms — 3

Shale, sandy; weathers pinkish 2

Sandstone, light colored 3

Sandstone, rusty colored; weathers into rounded forms 4

Sandstone, light brown, hard; forms conspicuous bed; weathers

out into iQglike forms 3

154071'— 21— Bull. 716

106 Contributions To Economic Geology, 1980, Part H.

Feet

Shale and sand containii thin layers of aaadstoiie; in weatheiiiig

farmfl a pronounced pinldah to lightrgiay belt 35

Sandstone, lighter colored and softer than that below 18

Sandstone, yellowish brown, maasive, very much in contrast with

the white sandstone below ; exhibits considerable cross-bedding . 60 Sandstone, very soft, containing a large amount of carbonaceous

materud 25

Sandstone, soft, thin bedded 6

Shale, dark gray; contains some carbonaceous material, very sandy

at top 8

Shale, carbonaceous 2

Shale, dark gray 4

Sandstone, light yellow, soft and massive

Coal (sandstones above and below show many fragments of fossil

plants) 5

Sandstone, soft; contains considerable carbonaceous shale 5

Sandstone, white, very massive; crops out at top of Pine Kidge. . 15 Interval not well exposed but seems to consLst mainly of sandy

and carbonaceous shale, including thin beds of sandstone 25

Shale, black, carbonaceous; contains thin seams of coal and many

thin streaks of sulphur 10

Sandstone, very white and massive; erodes into rounded sur- faces 63

Sandstone, soft; contains several thin layers of hard reddish- brown sandstone which project above the surface 80

Shale, very sandy 40

Sandstone, rusty colored and hard 5

Tertiary System. Whitb Biveb Formation.

After the Upper Cretaceous beds and those of the Lance formsr tion, of doubtful Tertiary age, were uplifted to theu* present attitude they were deeply eroded, and finally, as a result of the oscillatory movements of the land, the waters again encroached upon the land area, and a considerable thickness of light-colored beds, now known as the White River formation, was laid down. That formation, in all probability, covered all of the Lance Creek field and lay as a horizontal sheet over the great arch of Cretaceous beds, but the agencies of erosion, such as wind, rain, and running water, have swept the beds from the crest of the arch and revealed that fold as a possible trap for the acciunulation of oil and gas. If erosion had progressed still further the westward extension of the great anticline would be better known, for at present its west end is completely obscured by these horizontal beds. The northward limit of these beds is indicated by a rather well-defined escarpment and by outliers which form isolated buttes still farther north within the broad area occupied mainly by the Pierre shale. The formation is composed essentially of very soft, unconsolidated greenish-gray to white sand,

LANCE GBEEK OIL A2!n> GAS FIELD, WTO. 107

interbedded with reddish to greenish-gray shales. These beds are commonly overlain by greenish-gray, very coarse grained sandstone, in places coarsely conglomeratic. The reddish sandy shale near the base of the formation is sometimes mistaken for the 'Red Beds" by those who are unfamiliar with the stratigraphy of the region.

QUATEBNARY SYSTEM. ALLUnUM.

The only notable deposits of alluvium in this field are those which produce the rich, level land along Lance Creek. There the admixture of silts, sand, and gravel has heen spread out from time to time as the stream has shifted its course.

Structure. Salient Fbatubb8.

The Rocky Mountain front range and the Black HUls uplift are connected by what is commonly known as the Hartville uplift, an irregular arch whose axis is exhibited by exposures of granite, schist, and limestone near Hartville and Lusk, at Rawhide Butte, and at a number of other localities. The position of the axis is also indicated by the Old Woman anticline, which brings to the surface the upper- most beds of the Sundance formation. The Lance Creek field occupies a great arch or anticline of sedimentary beds west of the Old Woman anticline, from which it is separated by a shallow syn- cline. The crest of this arch can be traced with considerable accuracy for about 18 miles. It forms a reversed or sigmoid ciue and extends from sec. 5, T. 35 N., R. 65 W., northeastward to the Ohio No. 1 or discovery well, near the northwest corner of sec. 36, T, 36 N., R. 65 W. ; thence almost due east to a point one-eighth of a mile south of the center of sec. 25, T. 36 N., R. 64 W.; and thence a little easi of north to the point where Buck Creek cuts across the Fox HUls escarpment, in sec. 29, T. 37 N., R. 63 W. The southwestward exten- sion of the crest of the arch is obscured by the overlapping White River beds. The dip of the beds on the northwest flank of this great arch gradually steepens from 3° near its north end to 27° on Lance Creek, and from Lance Creek southwestward the dip is fairly uniform. The beds on the opposite flank of the arch dip south- eastward for an indefinite distance at angles of to 5°.

The Fox HUls sandstones, which at one time arched over the. Lance Creek anticline, have been eroded away, leaving at the surface along the crown of the arch beds that lie several hundred feet below the top of the Pierre shale. The relatively low and even surface eroded on the shale is limited on the north by the conspicuous ridge formed by the Upper Cretaceous Fox Hills sandstone and on tb'

108 Contributions To Economic Qeoloqy 1920, Part U.

south by younger Tertiary beds, which conceal the older formations in that direction for many miles. The great arch of sedimentary beds is doubtless separated from the Hartville uplift by a broad syncline, but the western part of the syncline is obscured by the overlapping White River beds. The position of the east end of the synclinal axis can be recognized by opposite dips in sec. 36, T. 36 N., R. 64 W., and the SE. J sec. 3, T. 36 N., R. 63 W.

METHOD OF BBPBBSBNTINa STBTTCrrUBB.

Different methods have been used from time to time by the Geo- logical Survey for the purpose of conveying to the reader an adequate notion regarding the structure, or what is frequently referred to by drillers and others as the '4ay" of the beds. The structure is ordi- narily shown by means of either structure sections or structure con- toiu. The structure section is based mainly upon measurements of the degree of inclination of the beds at the surface and of strati- graphic thicknesses and upon data from deep borings. It shows how a portion of the earth 's crust would appear if it were cut along a vertical plane and the portion on one side of the plane were removed. The section is an excellent aid in imderstanding the structiu'e where the beds dip steeply, but where they are inclined only a few feet to the mile it is difficult to bring out certain structural features without exaggerating the vertical scale of the section, which is imdesirable. In oil and gas investigations, where the interpretation and representa- tion of structure are extremely important, the method of showing structure by contours has been adopted because of its practical value and also because it is easily understood. The following explanation is offered for the benefit of those who are unfamiliar with the defini- tion, degree of accuracy, and practical application of structure contours.

Structure contours are lines drawn on a map to show the position of some particular stratum above or below a certain datum plane— for example, mean sea level. They are designed to sho\/ the shape and magnitude of the folds and in general the irregular warping of the beds. In the preparation of the accompanying map (PL X) it was decided to show throughout the field, as accurately as the data available would allow, the elevation of the top of the sand that yields most of the oil and gas. Any particular contour is the line of inter- section between the top of the sand and a horizontal plane a certain distance (for example, 2,000 feet for the 2,000-foot contour) above sea level. Each structure contour represents a difference of 100 feet in position above or below the one adjacent, and hence it follows that where the contours are closely spaced the beds are steeply in- clined, and where they are widely spaced the sand approaches much nearer to horizontality.

Lanoe Cbeek Oh. Ad Qas Field, Wyo. 109

Stnicture contours furnish a convenient method for presenting a comprehensive idea regarding the structure of an entire field. Their practical value depends, of -course, upon their accuracy, and the de- gree of accuracy depends upon the number of data fivailable. In certain developed oil fields it is possible to obtain nimierous well logs and to recognize in them, either directly or through the relation to other beds, the position of the particular bed which it is desired to contour. In such a field the depth at any point to the contoured bed can be ascertained very accurately by subtracting from the surface elevation the elevation of the bed as shown by the structure contour. In other fields, where little drilling has been done and especially where few of the records have been preserved, it is necessary to depend almost entirely upon surface data, such as dips, measured intervals between beds, and elevations on traceable beds. In such fields the structure contours are not likely to be drawn as accurately, but the demand for information is often so acute that it becomes necessary to sacrifice a certain degree of acciu*acy in order to insure more prompt pubUcation. In the Lance Greek field the structure contours shown by broken lines are drawn on the basis of dips, measured intervals, and elevations on traceable beds. Those which are represented by imbroken lines are based entirely upon well records.

Throughout the field the contours near the base of the Fox Hills sandstone are reasonably accurate, because the Shannon (?) sand- stone crops out near the discovery well, and, as explained on page 101, the dip determinations indicate a thickness of about 1,300 feet between that sandstone and the base of the Fox Hills formation. Southeast of the outcrop of the Fox Hills formation, in the eastern part of the field, the dips can be easily recognized, but there are very few beds in the Pierre shale that can be traced more than a few hun- dred feet. The writer obtained no well data from that portion of the field, and consequently the structure contours for it are less accurate. Practically all of the southwestern part of the field is overlain unconformably by the White River formation, of Oligocene age, Bind it seemed inadvisable to the writer to continue the structure contours any farther in that direction for fear of misleading those who studied the map without reading the text. The writer's views concerning the structure in the southwestern part of the field are stated briefly, however, under the heading 'Suggestions for develop- ment" (p. 120).

ouj and oas.

obnbral pbmoipias concbbnina thb obiqin, hiobatiok,

and ooncbntbatiok of oil and qas.

The primary source of petroleimi is not definitely known, but most oil geologists believe that it is mainly of organic origin. It seems probable that most of the petroleiun in the earth's crust ha

110 Contributions To Economic Geology, 1920, Part H.

originated from plants rather than animals, for two reasons — first, that the carbonaceous remains of plants are far more abundant than those of animals in the rocks; second, that the hydrocarbon-bearing parts of animals decompose more readily than the corresponding parts of plants. It has been estimated that more than 99 per cent of the carbonaceous material in the earth's crust is of plant origin. Aside from the water which they contain, plants consist mainly of elements that enter into the composition of petroleimi and natural gas, namely ogen, hydrogen, and nitrogen. Although it is true that the soft parts of animals are composed mainly of the same elements, yet they decompose much more readily and therefore are more likely to be dissipated into the atmosphere or picked up by running water before being buried so deeply that oxidation and decomposition cease. In certain localities petroleum and natural gas have been found intimately associated with plant remains; in others these substances are more directly associated with the hard parts of animals, such as the shells of mollusks; but the great accu- mulations of petroleum and natural gas show conclusively that they migrate extensively. Hence it is generally very difficult to say whether these substances originated where they now occur, or whether they originated elsewhere and gradually migrated to their present situation as a result of the chemical and physical processes that are continuously at work within the earth's crust. The oil-bearing "sands'' in the Lance Creek field are overlain and imderlain by shales containing calcareous concretions, many of which are very fossiliferous. It seems possible that the oil now contained in the sands originated to some extent from the soft parts of the sea fmimiilg represented by the fossils, but probably it was derived mainly from carbonaceous material included in the dark shales themselves.

A careful examination of the structure of the rocks and its relation to concentration of oil and gas in many parts of the world has given rise to the structural or anticlinal theory. The conditions that con- trol the accumulation of oil and gas, according to this theory, are briefly as follows:

1. A reservoir rock. This is commonly known as an oil sand, and as a rule it is porous, although it may be a very sandy shale, a fractured rock of any kind, a loose conglomerate sufficiently porous to allow the accumulation of oil or gas, or a limestone composed largely of interlocking crystals of calcite.

2. An impervious cap rock to seal over the reservoir rock and prevent the upward escape of the oil and gas.

3. Folds iQ the rock favoring the accumulation of oil and gas in certain places, these substances migrating from more extensive areas of adjoining beds that are less favorably situated for their retention.

LANCE OBEEK OH. AND GAS FIELD, WYO. Ill

4. Saturation of the rocks by ground water, on which the oil and gas will move on account of their lower specific gravity and be forced into the upper parts of the folds.

According to the anticlinal theory, if a porous rock containing gas, oil, and water is folded between other rocks that are nonporous these substances, imder the influence of gravity, separate and arrange themselves according to density. The gas, being the lightest, rises to the crest of an anticline; the oil separates out below; and the water seeks the deepest portions of the beds. In accordance with the theory of organic origin it is believed that these substances were originally disseminated in the carbonaceous shales and limestones adjacent to the oil sands. Experience has shown, however, that the principal concentrations of oil and gas occur in the sands near the upper part of a fold. It is evident, therefore, that the -fine particles of oil and gas have been forced out of the denser beds into the more porous sands and that this movement was followed by a slow migra- tion up through the sands into the upper part of the fold.

Capillary attraction is in all probability an effective agent in the concentration of oil and gas. llie size of the opening in rocks varies approximately with that of the constituent grains, being greatest in conglomerate and coarse sands and least in the clay shales. Inasmuch as water has about three times the surface tension of crude oil, capillary attraction must exert about three times as much force upon it. As the amount of the capillary pull varies inversely as the diameter of the pore, the tendency is for capillarity to draw water rather than oil into the smaller openings and to crowd the oil and gas into the more porous sands. It is believed that when, as a result of surface tension, the oil and gas have become segregated into bodies of considerable size, they arrange themselves under the influence of gravity and move upward through the pores of the sand under hydro- static pressure. It has been shown by experiment that if a bubble of gas, in rising through water, comes into contact with a globule of oil the two unite and the oil forms a thin continuous film aroimd the gas bubble. It seems, probable, therefore, that the upward migration of oil is influenced considerably by the upward movement of bubbles of gas.

Detailed field observations have shown not only that many of the accimiiidations of oil and gas are intimately related to anticlines and domes, but also that gas, oil, and water are arranged in the manner indicated above. Although the recognition of these facts has caused most geologists to accept the anticlinal theory in its broader aspects, many of them are willing to accept it only in a modified sense, as recent study has shown that the accumulations of oil and gas occur not only in the crowns of arches but also in many places on the flanks where the dips are interrupted for some distance, the local flattening of the beds forming structural terraces.

flatten or where the porosity of the sand decreases, and it may be entirely obstructed where a dike of igneous rock cuts across the sand. From the facta above outlined it is not surprising that some accumu- lations of oil and gas occur in areas where from all surface indications the conditions are imfavorable, and that some areas which appear to have the most favorable structure are barren. These conditions are mentioned briefly, not with a view of questioning the value of the anticlinal theory as a working hj'pothesis, but merely to emphasize the necessity for making in every field a thorough study of all the con- ditions that may in any way retard the movement of fluids and the result in concentration.

B.EOENT DEVELOPUBKT IN THE LAHOE CB.EEE SIEUi.

A few of the principal facte regarding early development in the Lance Creek field are given on pages 91-92, under the heading "His- tory of development." Since the completion of the field work in June, 1919, several new wells have been completed, and before this report is available others will doubtless be drilled to the principal oil sand, so tliat, with respect to development, the facts shown on the accompanying geologic map (PI. X) are incomplete. Wells at which,

Uge Cbeek Oil And Gas Fielj), Wto.

according to recet reports in the oil journals, drilling has been dis- continued are represented on the map as inadequately drilled. At certain wells the discontinuance was probably due to unfavorable resxdts in neighboring wells; other wells may be only temporarily shut down. It will be some time before the limits of the pool are definitely determined, although the surface geology, together with the records of some of the wells that have already been drilled; strongly suggests the location of the most promising territory.

CHABACTBB AlTD RELATION OF THB SANDS AS BXHIBITED IN

Wbll Beoobds.

Most of the wells that have been completed in the Lance Creek field range in depth between 3,300 and 4,000 feet, and the formation penetrated is almost entirely shale. There are, however, certain sands whiph- were recognized in some of the wells and which doubtless could have been recognized in others if the driU cuttings had been more carefully preserved. The log of the discovery weU is complete, and as it is probably typical of the field, it is given below.

Log of well No, i Ohio Oil Co., in the NW. sec, 36, T. 36 N., R. 66 W.

Driller's interpretation.

Ifnddy ahale

Hard sandrock

Sandrock

Shale and soft sand.

Hard rock

Hard shale and sandrock ,

Shale and mud.

Muddy shale

Qunmiy shale.

Gray shale*

Shale.

(Shannon (7) sandstone].

Tough gray sha le

Shale; showing of gas at 2,070 feet. . . .

0ray shale with shells.

Hardshell

Shale.

Gray shale

Whiteslate

Shale.

Shale with shells; gas at 2,425 feet . . .

Sandy shale..;

Hardshell

Sandy shale.

Gray sandy shale

BroKen sand; trace of oil at 2,615 feet .

Sandy shale.

Shale

Oilsand (Wall Creek sandstone]

Shale

Sandy shale ,

Shale.

Soft shale

Shale, color changeable

Soft black shale

Shale

Hard sheli.'Ill. !]!'-'.!"...

Shale

Dark lime.

Shale.

Hardshell

Band (oil sand)

Thickness.

Feet.

1,720

2J+

Depth.

Feet.

2,070 2,105 2,U5 2,290 2,330 2,350 2,425 2,440 2,505 2,507 2,565 2,580 2,630 2,660 2,680 2,701 2,720 2,730 2,808 2,986 3,076 3,206 3,233 3,250 3,333 3,460 3,657 3,663 3,665i+

The Ohio Oil Co. has several wells designated No. 1, and to identify the well the number should be read in connection with the location.

114 Contributions To Economic Qeologt, 192D, Part H.

It is possible to recognize in the above and other logs the several sands in the Lance Creek field, and for convenience they are dis- cussed below in the same order as they aro encountered in drilling.

Shannon (T) Sandstone,

The sandstone that is regarded as probably the same as the Shannon sandstone of the Salt Creek field crops out along the gully immedi- ately west of the discovery well, near the northwest comer of sec. 36, T, 36 N., R. 65 W. It rises gently toward the south, fonning a dip slope, and arches over the top of the anticline about 1,500 feet southwest of the discovery well. Exposures of this sandstone were observed here and there as far west as the center line of sec. 27. In some places along the outcrop the sandstone is only about 16 feet thick, but in others it is much thicker. It is coarse grained, has a greenish-gray color, and contains many yellowish-brown iron- stained concretions. At the top there are many small dark-colored concretions which, upon weathering, become light gray. The log of the discovery well as given above shows sandy beds extending from 6 to 145 feet beneath the surface, but the exposures along the outcrop did not indicate so great a thickness.

In the Ohio Oil Co.'s well No. 1 near the northwest comer of sec. 31, T. 36 N., R. 64 W., the Shannon ( ?) sandstone is probably represented by a 38-foot sand whose top lies at a depth of 195 feet, and in the Midwest Refining Co.'s well No. 3, in the SW. i sec. 25, T. 36 N., R. 65 W., it is represented by 40 feet of gray sandrock beginning at a depth of 40 feet. It is also exhibited in the log of the Ohio Oil Co.'s well No. 1 in the SW. i NW. J sec. 32, T. 36 N., R 64 W., as a hard sand containing a little water and extending from 30D to 330 feet beneath the surface. The sandstone lies near the surface at the Ohio No. 1 and Buck Creek No. 7 wells, near the center of sec. 35, T. 36 N., R. 65 W., and is eroded from the higher portion of the anticline farther west, where the gas wells are situated. If, as explained on page 101, the two bentonite beds on opposite sides of the anticline are the same, the Shannon ( ?) sandatone should dip beneath the surface on the southeast side of the anticline, near the Midwest weU No. 1, m the NE. sec. 3, T. 35 N., R. 65 W., but it was not recognized there.

Wall Creek Sandstone.

It is possible to recognize in many of the weU logs in this field a sandy zone approximately 1,050 feet above the principal oil sand. In the discovery well this zone extends from 2,580 to 2,701 feet beneath the surface, and its top is 1,083 feet above the top of the principal oil sand. In some of the well logs this material is recorded as sand, in others as sandy shale, and in a few as alternating beds of

Lance Creek Oil And Gas Field, Wyo. 115

shale and sand containing some oil and gas. The stratigraphic position of these sandy .beds is similar to that of the Wall Creek sandstone in the Powder River and Salt Creek fields, the sandstone at the top of the eastern anticline in the Mule Creek field, and the sands that yield oil in the Upton-Thornton field. Although none of the wells in the Lance Creek field are producing oil from this sandstone, it has given promise of yielding a fair output in some of the wells and should be watched carefully and recorded in the logs as accurately as possible.

Principal Oil And Oas Sands.

The formations included between the base of the Sundance and the top of the Dakota are discussed in considerable detail on pages 96-99, and the subdivisions of the Colorado group are mentioned on page 100, but inasmuch as the sands near the base of the Colorado do not crop out in the Lance Creek field but are exposed not far distant, it seems appropriate to study some of the lower beds first as they are exposed elsewhere and later as they are exhibited in some of the well logs of this field. Northeast of this field, in the vicinity of Newcastle the Dakota sandstone is immediately overlain by about 225 feet of dark shale that erodes very readily, producing a relatively low area between the long dip slope formed by the Dakota sandstone and the more or less jagged ridge formed by a sandstone that overlies this shale. The eictent of this sandstone along the flanks of the Black Hills uplift and outward from that uplift is a matter of vital interest to oil and gas operators, not only because oil issues from it in considerable quantities at Newcastle but also because it is one of the main oil-producing sands at other local- ities in Wyoming. In the Upton-Thornton field it occurs as a reddish-brown, -moderately soft sandstone encircling the central portion of the Thornton dome and occurring as isolated patches near the top of the dome. It is apparently only 2 or 3 feet thick at the northwest end of the dome, but at the south end it includes about 15 feet of reddish to light-yeUow sandstone associated with some car- bonaceous shale. In the vicinity of Newcastle, where considerable oil seeps from the sand, it is about 35 feet thick and forms a ridge about 500 feet above the railroad.

It continues as a very conspicuous ridge as far southeast as the L. A. K. ranch, on Stockade Beaver Creek, but from that locality southward it bec(Hnes thinner, appearing only at intervals as lenses in the shale. It seems to be rather well developed, however, near the north end of the Old Woman anticline, a few mUes east of the Lance Creek field. The conditions there are set forth below.

About three-fourths of a mile northwest of Wright's camp the Dakota sandstone forms a long dip slope. The sandstone is overlain

116 CONTBIBUnOKS TO ECOKOMIC GEOLOOY, 1920, PABT II.

by about 200 feet of dark shale, and the shale is in turn overlain by a succession of sandstone and carbonaceous shale beds almost 38 feet thick, which give rise to a very conspicuous ridge. This group of beds, the details of which are shown in the following section, is in all probability equivalent to the oil-bearing sand at Newcastle.

Section near north end of Old Woman antiidine.

Ft. In.

Sandstone, very hard, fonning east dip slope 2 6

Interval, mainly black carbonaceous diale.- .' 9

Sandstone, yellowish brown, massive 6 6

Shale, sandy, carbonaceous 9

Sandstone, rather thinly bedded 7

Shale,' black, carbonaceous 5 6

Sandstone, yellowish brown, hard and massive 4 6

Shale, sandy... 1+

36 9+

The group of sandy beds described above is doubtless widely distributed throughout Wyoming. The beds were recognized by the writer on the south slope of Como Ridge, about 6 miles east of Medicine Bow, and are in all probability equivalent to the sand that occurs near the middle of the Thermopolis shale at different locali- ties in Big Horn Basin, commonly known by drillers as the Muddy sand. In the writers recent report on the Mule Creek oil field this sand was named the Newcastle sandstone member of the Graneros shale, because at Newcastle it is of imusual thickness and contains oil. It is the writer's opinion that the principal oil and ga sands in the Lance Creek field are the stratigraphic equivalent of the Newcastle sandstone and should be called by that name.

In the Lance Creek field the Newcastle sandstone is usually com- posed of two distinct beds of sand separated by a layer of hard sandy shale, and in that respect it resembles a portion of the section near Wright's camp, at the north end of the Old Woman anticline. (See above.) The upper sand varies considerably in thickness and averages about 20 feet. The shale interval between the upper and lower sands also varies considerably, but the average thickness is about 15 feet. Evidence concerning the thickness of the lower sand is lacking, for in most borings the drill has penetrated only a portion of the sand, but the total thickness of the two sands and the intervening shale is probably not greater than 50 feet. As a result of lenticularity, variable porosity, or some other property of these sands, the results of drilling have in certain places been somewhat disappointing. The behavior of gas, oil, and water in the wells is a subject that requires special study, and after more data are available such a study should be made for the purpose of determining how the physical and cbem-

u Hanoock, E. T., The Mule Creek oil field, Wyo.: U. S. QeoL Survey Bull. 716, p. 42, 1990 (Bull. 716-€).

liANCB CBGEK OIL AKD GAS FIELD, WYO. 117

ical properties of the sands influence the migration and accumulation of these substances.

pSSUIiTS OF DBILLmG.

At present it is impossible, with the meager data at hand, to tabu- late more than a few of the results of the drill. The facts set forth in the following table have been obtained from various sources, mainly since the field work was completed, and although some of the depths shown may be slightly in error they are believed to be essentially correct. The information relating to well logs obtained by the writer in the course of the field work was supplemented by additional data obtained through F. B. Tough and B. H. Scott, of the United States Bureau of Mines, relating to the composition of the principal oil sand in some of the wells recently completed.

I i" I

!

! Nii i

! ! li ! i I

lit.

ikll I tlililHlltlil !

Iplllll

§ se ! s gg s; §3 g : li m is s

}!iii i M II II !i II II in

iii i tiiiiiiiSii i

n

yHMyjUl

I H M I Jl N I Mi 2 i I i

IdM i tun iiili

Lance Cbeek Oh. And Gas Field, Wyo. 119

Most of the figures of production in the above table indicate the sup- posed production September 6, 1919. Some of the estimates of flush production, as given in the oil journals, are probably too high. The Wyoming Oil News summarizes the situation in the Lance Creek field by saying: "The present production of oil is around 4,650 barrels per day, with some of the wells pinched down. The capacity of the gas wells is around 150,000,000 cubic feet per day."

Most of the oil from the Lance Creek field is conducted through a pipe line to the Chicago & Northwestern Railway at Lusk, Wyo., and there emptied into tank cars ready for shipment to the refineries. According to the Oil Trade Journal of November, 1919, the Ohio Oil Co. then expected to have in operation in about three months the first imit of what will eventually become a large absorption plant for the manufacture of casing-head naphtha. The original plan was to install a high-pressiire plant that would treat 10,000,000 cubic feet of gas a day, but later it was decided to install a low-pressure plant that will handle the gas at a pressure of 30 pounds instead of 80 to 100 pounds.

On the higher portion of the anticline the upper sand generally shows high gas pressure. In wells Nos. 1 and 27 of the Buck Creek Oil Co., in sec. 34, T. 36 N., R. 65 W., and in well No. 1 of the Ohio Oil Co., in sec. 4,. T. 35 N., R. 66 W., the gas seems to occur in large volxmies and the rock pressure is reported to be nearly 1,000 pounds to the square inch. This is probably also true of the two gas wells of the Midwest Refining Co., one near the south quarter comer of sec. 27 and the other in the NE. sec. 33, T. 36 N., R. 65 W., but the writer is imable to verify this statement. It is probable that the lower limit of gas in the upper sand on the axis of the anticline is not far west of the group of wells in the NE. sec. 35, T. 36 N., R. 65 W., as well. No. 28 of the Buck Creek Oil Co. is reported to have given a strong showing of gas when the drill entered the first sand, but as the well was drilled deeper the proportion of oil greatly increased. Farther west the body of gas lies structurally as low or even lower along the northwest flank of the anticline but apparently not as low along the southeast flank.

After the discovery well was drilled in, the oil rose to the surface and discharged into the earthen storage reservoir with great force, as shown in Plate XIII. This flow took place at intervals of approxi- mately one hour and lasted for about 30 minutes each time. Tanks to hold the oil were constructed as rapidly as possible, and finally the oil was turned into the pipe line. There is in all probability a body of oil below the gas which is trapped in the upper part of the fold, but neither the upper nor the lower limit of the oil can be determined untU further drilling is done. The few wells that have been drilled

120 CONTRIBUTIONS TO BOONOIOC QEOUOGY 1920, PABT n.

indicate that the main body of oil occurs at a lower level along the northwest flank of the anticline than it does along the southeast flank.

The two weUs (Nos. 30 and 33) near the southeast comer of sec. 34, T. 36 N., R. 65 W., are shown as water weUs, as it is reported that water was encountered in each well in the upper sand. Deeper drill- ing may prove that the lower sand contains oil, and if through skillful manipulation the upper sand is properly cased off, these wells may stUl become producers. It was reported that early in Januaiy the Ohio Oil Co. was at work cementing off the water in the upper sand in its No. 2 well in the NE. sec. 4, T. 35 N., R. 65 W. The peculiar occurrence of oil and water in the upper and lower sands, as shown in the above table, indicates that the upper sand should invariably be carefully tested. If the supply of oil is not satisfactory this sand should be mudded and a string of pipe put through it and cemented before drilling into the lower sand. If the upper sand is nonproduc- tive and yet does not contain water, this practice will prevent the oil and gas under high pressure from the lower sand from escaping into the upper sand. If the upper sand is water bearing and tiie lower sand is productive it will prevent the productive sand from being flooded as soon as the rock pressure in this sand becomes lower than the water pressure exerted from the upper sand.

Suggestions Fob Development.

According to the 'writer's interpretation of the structure there is little probability of finding in the area east of T. 36 N,, R. 65 W., pools of oil comparable to that which lies in that township and the one immediately south, and yet it seems reasonable to expect that some oil may have accimiulated near the axis of the anticline, at least as far east as the east line of sec. 26, T. 36 N., R. 64 W. North- east of that line the anticlinal axis is more steeply inclined and the conditions are not quite as favorable. The two water weUs in sec. 31, T. 36 N., R. 64 W., one near the northwest comer and the other near the north quarter comer, surest a slight lowering of the anticlinal axis at that locality. If such is the case there is probably a corre- sponding rise in the axis immediately east of that place and a slight closure a short distance west of well No. 1 of the Midwest Refining Ck). in sec. 28. The field evidence seems to indicate that the anticlinsd axis pitches eastward rather rapidly from that point. If the structure is as shown, the gas, oil, and water would naturally migrate up the steeply dipping sands, mainly from the northwest, and finally tend to accumulate where the axis becomes more nearly horizontal or where it is gently arched. If the Newcastle sand is reasonably thick and porous and continues northwestward from the anticlinal axis for a considerable distance, it is reasonable to expect a certain amount of

BULLBnN Tia PU,TB zut

DISCHARGE OP OIL INTO A DAMHED-UP GULCH AT THE OHIO OIL CO.'S DISCOVERY WELL IN THE NW. H SEC 36, T. 36 N., R. 65 W., LANCE CREEK FIELD, WTO.

Lance Creek Oil And Gas Field, Wyo. 121

concentration in the sand near the anticlmal axis and for some dis- tance down the dip, especially north of the axis. The most prom- ising territory lies west of the east line of sec. 26, T. 36 N., R. 64 W., because there the anticlinal axis is more nearly horizontal and also because farther east the depth of the sand increases very rapidly. The best part of this promising territory appears to lie southwest of the developed portion of the field, more or less in line with the hypo- thetical anticlinal axis, as indicated on Plate X by the broken line ex- tending across sees. 5 and 8. The abrupt rise in the anticlinal axis from the vicinity of the discovery well westward is the natural result of the abrupt change in the strike of the beds. If the strike continues in a southwesterly direction for a considerable distance beyond this abrupt change, then the anticlinal axis in all probability also pitches toward the southwest. The trend of the structure contours southeast of the anticlinal axis seems to indicate that the higher contoiurs close around the fold rather quickly and that the axis pitches in a south- westerly direction, very much as it does from the highest portion of the anticline eastward toward the discovery well.

Other sands lower than those which have been tested in the Lance Creek field should ultimately be tested near the highest portion of the Lance Creek anticline. It is the writer's belief that in the Mule Creek field the oil comes from a portion of the Lakota sandstone. In the Greybull field the Greybull sandstone member of the Cloverly forma- tion produces most of the oil and gas. In the Powder River field the approximate stratigraphic equivalent of the Cloverly, which was designated the Dakota (?) sandstone, is the principal oil-bearing formation, but a small quantity of oil occurs in at least two sands in the Morrison and also in the Sundance formation. In the Lander field the Carboniferous portion of the Embar group bears some oil, and a 1,730-foot boring on the Old Woman anticline, a short distance east of the Lance Creek field, is reported to have found considerable oil, doubtless in the Minnelusa sandstone, also of Carboniferous age.

In an area structurally so promising as the producing portion of the Lance Creek field, it seems advisable for the diflferent operating com- panies to combine, if possible, and drill at least one well near the top of the fold in order to test all the sands, or at least all including those in the Sundance formation. According to the table of formations on pages 95-96 all these sands could be tested by drilling to a depth of approximately 4,200 feet.

Quality Of The Oil Anb Qas.

The following analysis of a sample of oil from the Ohio Oil Co.'s discovery well is fairly typical of most of the oil in the Lance Creek field. A much heavier black oil is reported, however, from the Buck Creek Oil Co.'s No. 7 well in the NW. i sec. 35, T. 36 N., R. 65 W.

154071°— 21— Bull. 716 9

122 Contributions To Economic Qeologt, 192D, Part U.

Analysis o/(nl/rom discovery well of Ohio Oil Co, in the NW. J see, S6, T. S6 N.,R.65 W,

[Hade in the laboratory of the Baxwa of lOntB. DiftlUatloo in Boxeaa of Mines Hempel flask. Amomt distilled, 200 cublo centlmetera. Depth of well, 8,666) feet; depth to principal oil sandi 3,663 feet.]

Gravity at C:

Specific 0.807

Baum drees. . 43. 5

Air distillation with fractionating column:

Barometer reading millimeterB. . 740

Distillation begins degrees C. 25

To C. :

Total distilled by volume per cent. . 29.8

Specific gravity (125M50**) 0. 760

150® to C. :

Total distilled by volume per cent. . 32. 9

Specific gravity (276''-300*) 0. 825

Vacuum distillation, without fractionating column (175-300®):

Pressure millimeters. . 39

Total distilled by volume per cent.. 21

Residuum do 16. 3

Sulphur.. do 0.043

The gasoline content of the gas from three of the wells of the Ohio Oil Co. in the Lance Creek field, as shovni by an absorption test made by J. K. Gibson, of the Hope Natutal Gas Co., is shown by the follow- ing data, which were furnished by the Ohio Oil Co. :

Data on gas toells of Ohio Oil Co.

Location.

Well No.

Quarter.

Section.

Town- Rhip N.

Range W.

Nw

Nw

Ne

6$

Volume of

gas (cubic

feet per day)

800 Odd 4,500,000 8,000,000

Pressure at which test was made (pounds to the square inch).

Qas(rfin oont€Ot (gallons per 1,000 cubic feet ofgM).

1.1S4

Coal In Eastern Idaho.

By George R. Mansfield.

Introduction.

The general coal shortage in the winter of 1916-17 was particu- larly acute in eastern Idaho, notwithstanding the relative proximity of this area to the coal fields of western Wyoming. The mines of the Horseshoe district, on the west side of the Teton Basin, afforded some relief but were unable to supply the demands of the region.

In the summer of 1917, in response to urgent requests by residents of eastern Idaho, the United States Geological Survey undertook the investigation of certain reported coal fields in that part of the State to determine if there were any lands that could be classified and appraised as coal land and thus made available for local mining, so that the threatened shortage for the ensuing winter might be averted.

The writer, who was detailed to make the examination, spent about two months in the summer of 1917 with camp outfit and two helpers visiting the reported localities and mapping the geology of' portions of the country,

Scope Of Investigation.

The territory examined falls in general within four districts — (1) the Willow Creek-Caribou district, southwest of Snake River, including prospects on Willow Creek, on Grays Lake Outlet, and in the Fall Creek basin ; (2) the Pine Creek district, northeast of Snake River, including the land between the head of Pine Creek on the northwest and Palisade Creek on the southeast and also Bums Canyon; (3) Teton Basin, Teton County, including the valleys of Horseshoe, Mahogany, Patterson, and Trail creeks; (4) the Conti- nental Divide district, Fremont County, in T. 14 N., Rs. 38 and 40 E.

In addition to these districts, two prospects were reported to the writer while he was in the field— one at Heise, in the SE. sec. 26, T. 4 N., R. 40 E., and the other at Barney's ranch, 4 miles up Canyon Creek from the former Canyon Creek post office. At Heise condi- tions proved to be similar to those seen at the Willow Creek locali-

124 Contributions To Economic Geology, 192D, Pabt 11.

ties, but the prospect at Bameys ranch, which was stated by the writer's informant to be probably on an occurrence of obadian, was not visited.

In this report only such geologic data are presented as have a direct bearing on the occurrence and usability of the coaL

Maps.

The general map (PL XI Y) shows the location of the region ex- amined and the distribution of the general geologic and other fea- tures. This map also shows the location of the principal prospects and exposures examined where detailed work was not done. Plate XV and figure 13 show, respectively, on a larger scale the Pine Creek and Teton Basin region and the area in T. 14 N., B. 38 and 39 E., near the Continental Divide.

Summary Of Results.

The results of the examination are disappointing. In the Willow Creek-Caribou and Pine Creek districts coaly shale, with some im- pure coal, is present in beds ranging in thiclmess from a few inches to 7 feet or more. As a rule the coaly portions of these beds are not persistent but wedge in and out. Lumps of usable coal may be ob- tained here and there, but commercial development seems to be impracticable. The rock formation in which these coal beds occur is not the one in which the active mines of western Wyoming are located.

The only part of the Teton Basin that is producing coal at the present time is the Horseshoe district. Though conditions in this district are such that large-scale development is probably imprac- ticable, work now in progress will doubtless make possible a some- what greater yield than that of previous seasons. There is little chance that workable coal beds will be discovered elsewhere in the basin.

On the Continental Divide in T. 14 N., R. 38 E., a 82-inch bed of good coal was found, but the area in which it crops out is not large and its remoteness from lines of transportation and a suitable market make its early exploitation doubtful.

In the districts examined two substances occur that are commonly mistaken for coal, namely, phosphate rock and obsidian, a black volcanic glass. The phosphate rock in these districts when distilled yields a small quantity of petroleum, is unusually black, and has a gloss that makes its appearance very deceptive, as in the Patterson Creek, Burns Canyon, and Palisade Creek localities, where this rock has hitherto been regarded as coal.

Goal In Eastsrn Idaho. 125

During the examination of the Teton Basin several reported oc- currences of oil were investigated, but these do not indicate the pres- ence of oil in paying quantities.

Ackno.Wledgments.

The writer is indebted to the United 'States Forest Service and particularly to officers of the Caribou, Palisade, and Targhee national forests for maps and the free use of their field facilities. A. R. Schultz, D. D. Condit, and E. H. Finch of the Geological Survey, have kindly permitted the use of manuscript maps and reports re- lating to portions of the region visited. The published work of earlier geological surveys has been drawn upon in the preparation of both the general map and the text and will be specifically ac- knowledged on later pages. Mr. J. A. Cloward, whose ranch is on Willow Creek, in sec. 6, T. 1 N., R. 40 E., furnished valuable in- formation. Mr. L. Hillman, of Driggs, Idaho, manager of the Teton Valley Coal Co., was kind enough to show personally the workings of the Brown Bear and Boise mines. Mr. L. Perry, of Bates, Idaho, took the writer to see several prospects oh Mahogany Creek and in the vicinity of Tetonia. Information from other sources will, so far as practicable, be acknowledged below*

Surface Features Of The Country.

The region here described lies in the southeastern part of Idaho, in Fremont, Jefferson, Madison, Teton, Bonneville, and Bingham counties, and includes the east end of the Snake River plains, with their mountainous borders, which have been so vividly and admirably described by Russell.*

The Blackfoot, Caribou, Snake River, and. Big Hole ranges, which form, the rugged mountain border in the southeastern part of the district, are composed of folded and broken sedimentary rocks that represent many geologic periods and vary considerably in resistance to weathering and erosion. These rocks have been subjected to more than one cycle of uplift and erosion, so that broad valleys or basins have been excavated along the strike of the relatively weaker rocks, such as certain sandstones, shales, and clays, while harder rocks, such as massive limestones, sandstones, or quartzites, have formed prominent peaks and ridges 7,000 to 9,000 feet or more in general elevation and cut by narrower transverse canyons or gulches. The broader valleys, 1,000 to 3,000 feet lower and occupied in part by lava, together with the adjacent transverse valleys and gulches,

*Mr. Schaltz'R report has Blnce been published as V. S. Ceol. Survey Rull. 680, 1018. 'Rawell, I. C, Geology and water resources of tbe Snake Biver plains of Idaho: U. S. QeoL Survey BulL 199, 1902.

covered in some places to a considerable extent by soil that has largely been deposited by the wind, alluvium and stream gravel, and drifting sand or dunes. Elsewhere the somber basalt forms the sur- face in large or small exposures, locally' rough with low broken ridges, and elsewhere with low, relatively smooth, dark surfaces marked by polygonal cracks. Over considerable areas the thin, grass-covered soil, with intervening dark ledges, resembles in the fall the surface of a yellowish sen with black waves. Bold cliffs of black basalt with columnar aspect border the principal stream valleys and in places, as in the lower canyon of Snake River, form high canyon walls. The old broken cone and crater of Sand Moun- tain, near St. Anthony, with the adjacent group of sand dunes, are conspicuous topographic features. Elsewhere volcanic cones with craters rise above the surface of the plain. Some of them consist of basaltic debris, but others, notably Big and East buttes, northwest of Blackfoot. are composed of rhyolite and stand as volcanic islands in the basaltic sea.

The drainage of the region south of the Continental Divide is all gathered by Snake River and delivered through Columbia River to the PaciBc Ocean. North of the ContineDtal Divide are the head-

COAJj IN EASTERN IDAHO. 127

waters of the Missouri. The mountains have many springs and per- manent streams which on the Idaho side supply the two forks of Snake Biver and their larger tributaries, such as Blackfoot Eiver, Willow Creek, and Teton Eiver.

In the vicinity of the mountains these streams are rather closely spaced and water for camping or other purposes is available at nu- merous places along the roads. In the bench lands underlain by lava, however, the permanent streams are much farther apart and water may be had at comparatively few places. On the road from Tetonia to St. Anthony, a distance of about 30 miles, Canyon Creek is prac- tically the only watering place between the two crossings of Teton Biver, some 24 miles apart. Eanchers who occupy dry farms on these benches must sink wells through the lava perhaps 200 feet or more until a suitable supply of water is reached, or haul it for long distances. The water wagon and water barrel are familiar sights throughout the dry-farm district.

The low alluvial lands adjoining Snake River and the lower courses of its tributaries are supplied with water by means of irri- ting ditches, some of which are themselves large-sized creeks. Northwest of Snase River the Continental Divide is also well sup- plied with permanent streams, but most of the surface drainage sinks through the porous and shattered lava so that comparatively little reaches the river directly, though much is doubtless supplied by springs. On the direct road from St. Anthony to Kilgore, a dis- tance of approximately 30 miles, no water is seen after leaving the ditch a mile north of Parker until Camas Creek, at the lower end of Camas Meadows, is reached, some 25 miles beyond.

Industries.

The alluvium along Snake River and some of the larger creeks at elevations of 4,500 to 5,000 feet furnishes considerable areas that are suitable for irrigated fields, which produce a variety of valuable crops. Locally these lands are subject to local frosts or are too wet for cultivation but yield abundant crops of hay and support large numbers of cattle. All the larger soil areas, whether irrigable or not, are being rapidly taken up for cultivation, and forlorn home- steads are even perched here and there among the lava ledges where only a few square rods or acres of cultivable soil is available. Ow- ing to the scarcity of water, much of the lava country must remain waste until through a system of wells or otherwise water is furnished for stock and for domestic use.

The mountains are heavily timbered with aspen, red fir, and other conifers, which yield local supplies of fuel and building material. Several sawmills supply the demand for rough lumber, but dressed

128 Contributions To Economic Geology, 1920, Pabt

lumber is largely shipped in by rail. The mountains also, through the grazing regulations of the United States Forest Service, are made available for the summer pasturage of large numbers of sheep and cattle.

Coal is mined in the Horseshoe district of Teton Basin. The coal beds and their development are described on pages 137-145.

St. Anthony and Idaho Falls, the two principal cities in the dis- trict, owe their location to the presence of falls where Snake River has cut through the alluvium and plunges over basaltic ledges, and Blackf oot, just to the southwest, is located favorably at the confluence of Snake and Blackfoot rivers. All three cities are railway junc- tion points and distributing centers for the increasingly important agricultural products of the region.

Many details regarding the settlements, industries, scenery, and general geology of the district are given in the guidebook of the Overland Soute published by the Geological Survey.'

Geology. Sedimentaby Bocks.

The sedimentary rocks of the region have a wide range both in character and in geologic age. All the great geologic periods from early Carboniferous to the present are represented. In southeastern Idaho these rocks have been subdivided into many formations, which are rather fully described in some of the published accounts of that region.* They are summarized in the accompanying table, which is given for reference. Some of the formations that occur in the southern part of southeastern Idaho were not recognized here, and others were not differentiated. An additional column has therefore been placed in the table to show the units mapped.

The Phosphoria formation deserves brief description because it has been prospected and mined for coal at several places in the region here described. The formation occurs in many bands distributed through the mountain ranges. (See PI. XV.) The phosphatic shale

Lee, W. T., Stone, R. W., Gale, H. S., and others. Guidebook of the western United states. Part B, The Overland Route: U. S. Geol. Survey Bull. 612, pp. 130-147, 1915.

Gale, H. S., and Richards, R. W., Preliminary report on the phosphate deposits in southeastern Idaho and adjacent parts of Wyoming and Utah : U. S. Geol. Survey Bull. 430, pp. 457-535, 1910.

Richards, R. W., and Mansfield, G. R., Preliminary report on a portion of the Idaho phosphate reserve : U. S. Geol. Survey Bull. 470, pp. 371-439, 1911.

Schultz, A. R., and Richards, R. W., A geologic reconnaissance in southeastern Idabo: V. S. Geol. Survey Bull. 530, pp. 267-284, 1912.

Richards, R. W., and Mansfield, G. R., Geology of the phosphate deposits northeast of Georgetown, Idaho : U. S. Geol. Survey Bull. 577, 1914.

Mansfield, G. R., and Roundy, P. V., Revision of the Beckwlth and Bear River forma tlons of southeastern Idaho : U. S. Geol. Survey Prof. Paper 98, pp. 75-84, 1916.

Mansfield, G. R., Geography, geology, and mineral resources of the Fort Hall Indivi Reservation, Idaho: 17. S. Geol. Survey Bull. 713 (in press).

Northern part.

Syitflni*

Quaternary. Unconformity Tertiary. Unconformity

Cretaceous.

Unconformity Cretaceous (7)

Series.

Pttooene (probably).

Eocene.

Remarks.

sons lomerate, probably also rhyoUte and basalt, idetermined.

Upper Cretaceous.

lored sandstone and clay aggregating 5,800 feet, al beds and some calcareous beds tentatively cor- the Frontier and Aspen formations of south-

n Wyoming.

ored sandstone and shale with some calcareous aggregating 5,000 feet; typical Bear River (basal :)retaceous) fossils.

erentiated; conglomerate much reduced in topo- c prominence and thickness.

Jnrasslo

ons recognized but not dilTerentiated.

Triassic.

Oaiboniferous.

jnitely recognized.

Lower Triassio.

Ued but not differentiated.

Initely recognized.

Permian.

: the phosphatic shale of the Phosphorla formation i a little petroleum when distilled, is black and : and is mbtaken for coal. Rex chert member developed but without limestone; quartzite in I part.

PannsylTanian.

-erentiated.

Kississippian.

1640n*-dl— Boll. 716. (Tof

Coal In Eastern Idaho. 129

member is distinctly nodular or even conglomeratic at the base, and there is a bed of hard phosphate a foot or more thick that is some- what siliceous and furnishes large float fragments with the charac- teristic bluish- white bloom. The main phosphate beds lie above this bed and are dark colored, locally coaly black, and yield upon dis- tillation a little petroleum. The characteristic oolitic texture, how- ever, may be clearly distinguished, the tiny rounded grains or oolites being readily visible to the naked eye. The disturbance that the shale has undergone in assuming its usual inclined position has made it shiny and smooth in some places so that it might readily be mis- taken for coal. The thickness of the phosphatic shale, where exposed in Palisade Creek, is estimated at more than 100 feet.

The coal of the region occurs in formations known or supposed to be of Cretaceous age. Some of it is hardly more than carbonaceous or lignitic shale. Several of these formations were recognized but are not differentiated on the map. The lowest corresponds with the Gannett group (Cretaceous i) and Wayan formation (Cretaceous) of southeastern Idaho. There is a distinctive dark conglomerate about 25 feet thick at the base, composed chiefly of chert pebbles. Above this are variegated beds with some limestones, succeeded by yellowish and dark-grayish sandstones with interbedded carbona- ceous shale, the whole aggregating about 1,300 feet in thickness.

The second formation consists of dark-grayish sandstone and shale, with carbonaceous shale and some calcareous beds aggregating perhaps 5,000 feet in thickness. Typical Bear River fossils have been found in it at a number of places, but there is uncertainty about the position of the upper and lower limits of the formation.

Above the beds assigned to the Bear River is gray clay of unde- termined thickness which may correspond with the Aspen formation of southwestern Wyoming. Above this are generally light-gray sandstone and clay, with some coal beds, which together with the underlying clay apparently aggregate more than 5,800 feet in thick- ness if there is no duplication. There is a suggestion, however, as shown in figure 12 (A) j that the coal beds in the Horseshoe district may be folded into a syncline. If they are, the thickness is only 3,600 feet.

Fossil invertebrates and leaves have been found in these beds. The invertebrates were collected from calcareous beds at the Brown Bear mine. T. W. Stanton states that they probably belong to the fauna of the Colorado group and may have come from the Frontier forma- tion. An earlier determination of perhaps more scanty material from the same locality gave the age as that of the younger Mesaverde formation (of the Montana group) of the Rock Springs district, or the Adaville formation of southwestern Wyoming.'

Woodruff. E. O., The Horseshoe Creek district of the Teton Basin coal field, Fremont County, Idaho : U. S. Geol. Survey Bull. 541, p. 382, 1914.

130 Contributions To Economic Geology, 1920, Pakt H.

The evidence of the fossil leaves collected in the Horseshoe field and on the Continental Divide in T. 14 X., R. 38 E., as determined by F. H. Knowlton, is equally inconclusive. The field relations and lithology favor Frontier rather than Mesaverde age, and the beds are tentatively so referred. This provisional assignment is in ac- cord with the views of R. Schultz,' who is familiar with the formations at Rock Springs and Adaville, Wyo., and in the Horse- shoe district of Idaho.

1,000

z

3 Miles

FiouBB 12. Geologic structure sections of parts of the Horseshoe, Teton Basin, and Con- tinental Divide districts, Idaho. A, Section across the Horseshoe district in the vicinity of the Brown Bear and Boise mines ; B, section in the region of the Horseshoe Creek- Mahogany Creek divide ; C, section along the divide between Mahogany Creek and Pat- terson and Henderson creeks; D, section across Cottonwood Creek, Continental Divide district, in the vicinity of the Scott & Bucy mine, a, Iava and conglomerate; b. Frontier (?) ; c. Aspen ( T) ; d. Bear River ; e, Wayan formation ( ?) and Gannett group ; J, Stump sandstone, Preuss sandstone, and Twin Creek limestone ; g. Nugget sandstone to Thaynes group ; ft, Thaynes group and Woodslde formation ; i, Phosphoria foramtion ; ;', Wells, Brazier, and Madison ( T) formations.

The occurrence of clay in the supposed Frontier formation gives rise to frequent landslides.

The other formations of the region are sufficiently described for the purposes of this report in the preceding table.

aEKEBAIi STRUCTITBE.

Three broad structural areas may be distinguished in the general region — (l)the mountains of the southeastern part; (2) the Snake River plains, occupying the great central portion; and (3) the Con- tinental Divide, on the north. The first and third areas are com- posed largely of sedimentary rocks that have been deformed to a greater or less extent by folding and faulting. This is particularly

Personal communication.

Coal In Eastern Idaho. 131

true of the southeastern area, where the structural features represent the northwestward continuation of great folds or faults, some of which extend many miles to the southeast. The dominant faults of the region appear to be northeastward oyerthrusts. The names ap- plied to faults on the maps indicate their supposed relation to well- known faults farther southeast. The folds are generally open and upright, but a certain tendency to overturning may be noted. The inferred details of structure in the sedimentary areas are shown on the accompanying maps and geologic structure sections.

Little attention was paid in the present examination to the struc- ture of the Snake River plains. Locally near the margins, as in the Willow Creek district, sedimentary rocks exposed through the re- moval of the lavas by erosion indicate the continuation of the folded and faulted sedimeitary rocks beneath the lavas. The lavas that underlie the plains have been built up by a succession of practically horizontal flows, between which at certain places there were inter- vals of time sufficient for the deposition of alluvial or lake deposits or for the formation of soils. Along the canyon walls of Snake River and in wells at various places the composite nature of the lava series is revealed. A well sunk in the lava several miles east of Teton passed through a number of layers of soil between beds of basalt and rhyolite. One bed of soil was encountered at a depth of 400 feet.

Coal Beds.

Oekekal Occubbence And Chasacteb.

Coal occurs at a few places in eastern Idaho in two or perhaps three of the Cretaceous formations. It is definitely known to be associated with the Bear River formation and with less certainty is believed to occur also in the Wayan formation. In neither of these formations is it of commercial value. Better coal is found in a higher formation, thought to be the Frontier, though the paleon- tologic evidence of its age is not entirely conclusive. The distribu- tion of the Cretaceous strata is shown in Plate XIV and the inferred position of the workable coal beds is indicated in Plate XV and figure 13.

The coal of the Wayan (?) and Bear River formations is hardly more than carbonaceous shale in which the carbon is locally abun- dant enough to bum. The moisture and ash are high and the heat- ing value is low, as shown by the analysis of a sample from Pine Creek Pass, No. 29280 in the table on page 152. (See also section 1, fig. 14.) The coals of the Willow Creek-Caribou and Pine Creek districts are of this class.

Lee W. T., Stone, E. W., Gale, H. S., and others, op. clt., p. 139.

132 Contributions To Economic Geology, 1920, Past U,

The coal of the Frontier( i) formation in this region, however, is of bituminous rank, fairly pure, and of relatively high heating value. The areas of known conmiercial coal are not sufficiently large and the beds are not thick enough to be worked on any great scale. Even if the mines were fully developed they would probably not supply the local demand, at present prices. They are grouped in two districts— the Horseshoe district, in Tps. 4 and 5 N., Bs. 43 and 44 E., and the

Cottonwood Creek district, in T. 14 N., Rs. 38 and 39 E., on theon- tinental Divide. The Horseshoe district has been productive for several years, but the other district is not yet developed.

Willow Cbeek-Cabibou District.

Vloward entry.— In the SE. sec. 6, T. 1 N.. R. 40 E., on the hill slope a few rods back of the house of J. A. Cloward, is an entry that was opened in the winter of 1916. It is about 100 feet long and trends about N. 50° E., curving slightly toward the south. The " coal " consists of the more carboniiceuiis jwrtions of earthy ai"i carbonaceous shaly lenses that wedge in imd out and have a white

Coal Ix Eastern Idaho. 133

powdery substance in the partings. Nine* layers were counted at one place, ranging in thickness from about one-sixteenth of an inch to 18 inches. It is doubtful, however, if enough fuel of this character can be obtained for local needs without involving prohibitive expense.

Brinson mine, — The Brinson. mine, in the NE. J SE. J sec. 34, T. 2 N., R. 40 E., is probably the property described by Schultz as the Miller mine. A man named Miller is reported to have been as- sociated with Mr. Brinson. According to Schultz, work was begun at the Miller mine in 1900 by the Canyon Coal Mining Co., which constructed a shaft, tunnel, road, and buildings, and installed machinery, the whole at a cost reported at $6,000. In 1910 Mr. Milder, one of the members of the former company, filed application to pur- chase and was permitted to make payment for 160 acres of coal land at $10 an acre. Work was continued. A shaft 40 feet deep was sunk and an engine and hoisting machinery were installed at an additional cost of about -$2,500. The developments just described tally well with those seen at the Brinson mine, which is the only mine known to such residents of the vicinity as the writer was able to consult.

The tunnel is about 115 feet long and trends N. 76 E. at the entrance. About 61 feet from the portal is a shaft in nearly vertical carbona- ceous and gypsiferous shale 7 feet 6 inches thick, the so-called coal bed. Two other coaly layers 6 inches and 11 inches thick, respectively, were noted. As in Cloward's prospect, the shale is probably carbona- ceous enough in places to bum, and such material is reported to be excellent for blacksmithing. At the time of the writer's visit the shaft was largely filled with water and the exposed parts of the shale were intensely sheared and weathered. The shaft is reported to end in gravel like stream gravel. A fault by which conglomerate beds were brought against the shale might give rise to such a report and is not improbable. No coal of promising appearance was seen. Several other prospects occur in the vicinity.

The road, which is cut in the steep and rocky canyon wall at a uni- form grade for nearly a mile, is now out of repair, and it is evident that no recent work has been done at the mine. No reports are avail- able regarding the amount of coal extracted from this mine, but from the character of the so-called vein it is clearly negligible and the pros- pects of successful development are slight.

Croley mine. — The carbonaceous shale of the Wayan (?) formation along Grays Lake Outlet has been prospected here and there for coal. Perhaps the most extensive development is the so-called Croley mine, in the SE. J SW. i sec. 27, T. 1 S., K. 41 E. The workings

, A. R., A geological reconnaissance for phosphate and coal in southeastern Idaho and western Wyoming: IT. S. Geol. Survey Bull. 680, p. 74, 1918.

134 Contributions To Economic Geology, 1920, Part Ii.

consist of two caved tunnels and several prospects. The bed can not now be seen, but according to one report it is 8 inches thick, and according to another 18 inches thick. It was stated that material was obtained that would burn, but it crumbled and would not form lumps. Fragments of dark shale and of carbonaceous matter, somewhat lig- nitic in character, were seen on the dumps.

Another prospect, known to some as Croley's mine, is reported farther down the valley in the northeast face of Pine Mountain, oppo- site a small island in Grays Lake Outlet and on the south side. Thib prospect was not found in the time available for search. It may perhaps be the one indicated as the Croley mine by Schultz and Rich- ards on their map and shown as a coal tunnel in the SE. SE. i sec. 24, on the plat of T. 1 S., K. 40 E. The structural relations of the region suggest that it lies on the strike of the beds already described. Unless unsuspected faults intervene it is clearly in the same formation.

Fall Creek basin and Heise. — The coal prospects of the Fall Creek and Heise districts are in carbonaceous shale that contains lignitic material and is of either Wayan or Bear River age.

Pine Creek Distbict.

Pine Creek Pass. — The old prospect at Pine Creek Pass, approxi- mately in the SW. i NW. i sec. 24, T. 3 N., R. 44 E. (unsurveyed), was reopened in September, 1917, by John Nocker and an associate, of Kemmerer, Wyo. At the time of the writer's examination the slope excavated on the dip of the coal bed had been cleared to a depth of about 15 feet from the surface. A tiny fault was noted. The fol- lowing section was measured at a depth of 12 feet :

Section of coal bed at Pine Creek Pass prospect,

Pt- In. Limestone, dark; Bear River fossils 8-h

Olay, sandy and rusty 6±

Gi>al, mashed, sUckenslded 1 10

Clay, dark, sheared.

The coal bed strikes N. 56° W. and dips 55° SW. About 2 leet higher along the dip the thickness of the bed is 2 feet. The coal ap- parently contains much clay, for when moist it becomes plastic. A sample from the place measured was analyzed with the results in- dictated in the table on page 152 (analysis 29280). The section is graphically shown in figure 14. The content of moisture and ash is high, and the heating value (7,376 British thermal units for the air- dried sample) is below the minimum allowed (8,000 British thermal

Schultz, A. R., A geologic reconnaissance for phosphate and coal In southeastero Idaho and western Wyoming : U. S. Qeol. Survey Bull. 6S0 p. 74, 1918.

Coal' In Eastebn Idaho.

units) for workable coal according to present rules of the United States Geological Survey for coal-land classification."

drift. — About a mile east of Pine Creek Pass, on the north side of the road, is a cared drift in Bear River carbonaceous shale. The writer is indebted to Mr, Joseph Kunz, of Victor, Idaho, for the following data regarding it. This drift was driven about four years ago by Samuel and Joseph Kunz and their associates. The " coal " occurs in a 6-foot bed, channeled with boulders and gravel, lying above a black clay and below a limestone which is sugary just above . the Coal but hard farther above.

The writer's examination showed a black shale with carbonaceous lenses. Several lenses, ranging in thickness from 2 to 8 inches, were aoted, and above them lay a black fossiliferous limestone. The rocks at this prospect appear to be near the axial region of a subordinate

Explanation

a .s H

SampM.AnilyinzMlO

iSDU 14. — Coal McUoiiB ill tbe Pin* Creek and Tetn Budn diUrlcta and kt Cotton- wood Creek In tbe Continental DlTlde diatnet, Idaho. 1. Pine CreA Pus; 2, Boise mine; 8, Brown Bear mine; 4, WoodmlTB locallt? 10; 6, mine; 6, BorMehoe nine ; 7, Scott Bnc7 mine.

fold and to strike N. 84° E. and dip 19° X. The atratigraphic rela- tions suggest that this is the same bed as the one exposed at Pine Creek Pass. The greater thickness of coal noted by Mr. Kunz may be in part due to the location of the bed in the fold or to irregularity of the bed.

Other prospects. — About 1,000 feet west of the Kunz prospect, and on the south side of the road, is another caved drift opened by the

136 CONTBIBUnOKS TO ECONOMIC GEOUOGYy 1820, PABT II.

same prospectors. The caving is so complete that only fine dark shale fragments are to be seen. In a neighboring canyon south of the Pine Creek road other coal prospects are reported. A cabin and one or two openings so badly caved as to be scarcely recognizable were all that were found.

Bainy Cbesx.

Southeast of Pine Creek the rocks of the Cretaceous basin continue across Rainy Creek. About 100 yards southwest of the point where the trail from Pine Creek to Fogg Hill crosses Rainy Creek there is a group of coal prospects. Two of the prospects occur on the same bed at different heights, and the third is a tunnel about 100 feet west. The bed at Rainy Creek has been locally reported as 10 feet thick, but this appears to be an error. The bed in which the first two pros- pects are made is a dark shale with a carbonaceous stratum about 7 feet thick. The f ootwall at the entrance of the lower prospect, a caved drift, is a gray sandstone which strikes N. 64 W. and dips 66 E., and the hanging wall is a black shale. No coal was exposed, but some fine carbonaceous matter lay distributed through the dump. No fossils were seen. The upper opening was also caved. According to A. E. Harris, of Rexburg, Idaho, who is familiar with much of this region, the prospector who dug the main drift struck a fault and stopped. He then started a tunnel, the third prospect above men- tioned, and after digging a short distance ran into his previous work- ing and stopped again. The tunnel is now caved.

llast of the coal prospects and over the hill between the forks of the creek the Fogg Hill trail descends a long point on which a fos- silif erous ledge of brownish-gray limestone occurs. Fossils were col- lected from this, ledge, among which species of Ostrea and ModioU were identified by T. W. Stanton, who states that they may have come from the Bear River formation, though he thinks it more probable that they came from the Frontier formation. The stratigraphic relations appear to favor the Bear River rather than the Frontier formation, but it is possible that a small local syncline of the Frontier is present.

Palisade Cbeek.

Reports from several sources* of a fine natural exposure of coal in Palisade Canyon led to the extension of the reconnaissance to that exposure. No difiiculty was experienced in reaching it, and there is no doubt of the identity of the locality visited with that of the reports. About a mile below the forks of the creek a black, coaly- looking rock extends along the south side for perhaps 100 feet and rises abruptly from the water for 40 or 60 feet. The beds are ver- tical and strike N. 55° W., and their smutty and shiny surfaces are certainly suggestive of coal. A closer examination, however, re-

COAL .J EASTERN IDahO. 137

veak the oolitic texture of phosphate rock, which, with interbedded shale and black, fetid limestones, makes up the exposure. The phos- phate rock is part of the Phosphoria formation, which here lies along the west side of a fault between Carboniferous formations and Jurassic limestone. The line of the fault is marked by small canyons that extend northwest .and southeast from the main creek. This is probably the same fault that separates the Cretaceous and Carbonif- erous rocks in Pine Creek. Palisade Canyon was not traversed above the Fogg Hill trail, but there seems little reason to suppose that Cretaceous rocks or coal beds occur there.

Burns Canyon.

The General Land Office plat for T. 4 N., E. 43 E., shows indi- cations of coal in sec. 2 and near the southwest comer of sec. 19. The locality in sec. 2 is in Carboniferous rocks and was not visited. The locality in sec. 19 is in Coal Mine Canyon, a tributary of Burns Canyon, and is reported to have produced "coal that would bum." This mine was visited. It lies near the head of the canyon, in the phosphatic shale of the Phosphoria formation, like the fine natural exposure in Palisade Creek. Masses of phosphate rock, black, smutty, dossy from rock shearing, and superficially resembling coal, lie scat- tered on the dump, but the characteristic oolitic texture of the phos- phate is readily seen, and on some pieces the bluish- white bloom may be detected.

Teton Basin. Horseshoe District.

The coal deposits of the Horseshoe district have been described by Woodruff, who gives details of the mines and prospects, including analyses and sections, some of which are reproduced in the table on page 152 and in figure 14. The Horseshoe district, which is the only producing coal field in eastern Idaho, lies on the west side of Teton Basin and includes portions of Tps. 4 and 5 N., Rs. 43 and 44 E. (See PL XV.) The district as a whole may be considered as including all the Cretaceous rocks with their intervening formations north of the line of Mahogany Creek, an area of nearly 20 square miles. The part that carries coal beds that can be profitably mined, however, is much smaller and probably does not exceed 3 or 4 square miles. The distribution of the formations of the district is shown on the map, and the general structure of the coal-bearing portion as here interpreted is shown in the geologic structure section, figure

My

° Woodruff, E. G., Tbe Horseshoe Creek diatrlct of the Teton Basin coal field, Pre- nBt County, Idaho : U. S. Geol. Survej' Bull. 641, pp. 370-388, 1914.

154071°— 21— Bull. 716 10

138 Oontbibutions To Economic Geology, 1920,' Part H,

8TSTJ0TU&AL rEATTTXSS.

The fault along the west side of the Cretaceous area is here con- sidered a thrust rather than a normal fault, as shown by Woodniflf. In the line of the section given in figure 12 (1) it would be difficult and perhaps even impossible to discriminate between normal and thrust faults by inspection. Great orerthrusts are, however, more characteristic of southeastern Idaho and western Wyoming than great normal faults. Notable overthrusting has also taken place in this region, as is well illustrated by the little Carboniferous outlier on the Cretaceous rocks of sees. 10 and 15, T. 4 N., B. 44 E. According to Schultz the parallel normal fault farther west shown by Wood- ruff is not evident in a traverse along the line of structure section A- A' but may represent a subordinate strike fault more clearly shown at its junction with the main thrust. Such a fault would be difficult to detect in beds similar on both sides.

The rocks east of the coal-bearing beds as mapped by Woodruff are not Paleozoic, as he suggests, but belong to lower portions of the Cretaceous, as shown by the characteristic Bear River fauna from sec. 19, T. 5 N., R. 44 E. Similarly the supposed Paleozoic ledges in sec. 32, T. 5 N., R. 44 E., are Jurassic or Cretaceous. The fault in the eastern part of the district as mapped by Woodruff may be pres- ent, but as the strata west of it are not Paleozoic his argument for it has little weight. Several minor cross faults occur in the Cretaceoos, as noted by Woodruff, but no strike faults were recognized in the rocks of that age north of Horseshoe Creek. Such faults might be present and easily escape detection because of the lithologic similarity of the beds.

The structure south of the general line of Horseshoe Creek differs considerably from that to the north. The Jurassic ledges that form the backbone of the ridge east of the south fork of the' creek terminate abruptly south of the main creek. The productive coal beds also have not been traced much south of the Horseshoe mine in the north- east comer of T. 4 N., R. 44 E. This may be due to the extensive mantle of debris composed of older rocks, but there are numerous gullies in which such beds might be exposed. Because of these dif- ferences a normal fault with downthrow to the north is tentatively drawn south of the Horseshoe mine and of the main creek, although other considerations, which can not be entered upon here, indicate that such a fault may not be required.

The generally troughlike structure east of the great thrust fault, and clearly shown at the south end of the district, has an important economic bearing, for it leads to the suggestion that the two coal beds mapped by Woodruff may in reality be the same bed caught in a

Schultz, A. R., personal communication. Woodruff, E. G., op. clt., p. 383.

V. i. OKOIOOICAL BUSTBT

GEOLOGIC MAP OF THE H0n9ESH0I

Coal In Eastern Idaho. 139

rather closely folded syncline of which the two beds would represent the opposite limbs, as indicated with a query in structure section A-A'. Such a structure would naturally limit the depth to which the coal could be worked, even if no other limiting factors were in- volved. Certain differences in the coal beds at the Boise, Brown Bear, Bellcut, and Horseshoe mines seem at first sight to oppose the synclinal suggestion, but they may not be so serious as to disprove it. For example, the section at the Bellcut mine (probably Woodruff's locality 10) shows 7 feet 4 inches of coal with a parting of sandy cky 10 inches thick near the middle. A similar sandy clay bed oc- curs in the coal bed 10 feet 3 inches thick at the Horseshoe mine but nearer the top. It is thought by Woodruff and by L. Hillman, manager of the mine at the time of the writer's visit, that the bed at these two localities is the same. The bed at the Brown Bear mine ranges from 4 feet 5 inches to 5 feet 3 inches in thickness, and the bed at the Boise mine is only 3 feet 2 inches thick. These beds do not show the sandy clay bed. The Brown Bear bed contains a thin layer of shale and the Boise bed is clear coal. Available analyses of the coals from Brown Bear, Bellcut, and Horseshoe mines show consider- able similarity in the quality of the coal. Clay and shale beds are generally lenticular, though at many places attenuated, and may be expected to thicken, thin, or disappear even if the strata suffer no deformation.

If the coal beds are parts of a closely folded syncline they would he likely to vary in thickness with their location in the fold. Parts of the bed nearer the axial region or bottom of the trough would 1)6 thicker than parts of the bed on the limbs or sides. The thick- ness of the portions on the limbs would vary with the amount and character of the shearing stresses developed during the deforma- tion of the rocks. These stresses would also cause the thinning or disappearance of clay or shale beds on the limbs of the fold and their thickening in the axial region. The same stresses would also develop throughout the coal lines of cleavage or parting which would cause it to break easily or crumble when extracted. The crumbling of the coal is one of the disadvantageous features in mining in this field.

In a northward-pitching syncline the axial portion with thicker beds would be exposed at the south end. The Horseshoe mine with the thickest beds of the district is so located. Farther north the axial region would be deeper and the exposed portions would lie along the limbs where the beds are thinner. If the axial plane of the syncline were tilted or bent, as suggested in the structure section, the exposed portions of the limbs would not be symmetrically located with reference to the axial plane and might be expected to differ

140- COXTRIBUTIOXft TO ECONOMIC GEOLOGY, 1920, PART Ih

somewhat in character and thickness. These reasons seem sufficient to account for the differences noted in the coal bed at the different mines. The hypothesis of synclinal structure of the coal bed appears to be supported by such facts as are available, but owing to the heav cover of debris and the thick growth of vegetation in the region where the bed should be exposed, confirmation of this hypothesis must await more extended exposure of the strata by mining operations.

At the westernmost opening of the Horseshoe mine the slope follows the dip of the sandstone, about 33° NW. About 100 yards west of this slope is a broad ledge of massive sandstone, whose atti- tude is obscure but which seems to strike X. 55 E. and dip about 10° NW. These exposures appear to be near the axis of the sup- posed syncline, and give suggestions of its pitch. On the assump- tion of the steeper dip, which seems justified by the somewhat steeper dip given by Woodruff for a locality near by, the bottom of the synclinal coal bed at the Brown Bear and Boise mines should lie about 4,800 feet below the surface, as indicated in figure 12 {A). On the assumption of the 10° dip, it should lie about 1,200 feet below the surface. The dip of the bed at the Bellcut mine, 70°, suggests that the dip steepens down the limbs of the fold, as shown in the structure section.

The structure of the southeastern part of the Horseshoe district is apparently anticlinal, with the axis near the western edge of the lava and largely concealed by it. The rock between the Jurassic beds and the lava along the line of the structure section B-B in figure 12, is Cretaceous sandstone, rather poorly exposed but appar- ently dipping southwest. The southeast face of the prominent lava- capped hill in the southeast comer of sec. 33 gives an excellent exposure of the sandstone with a northeasterly dip of 21°. The stratigraphic position of the sandstone is not known, but it is assumed to be possibly of Bear River age. No fossils were found in it.

Charaotee Of The Ooal.

Woodruff states that the coal is bituminous and rather free from impurities but is noncoking according to the agate-mortar test. A large part of the coal breaks down to fine fragments. It is thus not adapted to long-distance transportation.

Owveeship.

The properties recently consolidated under the name Teton Valley Coal Co. were transferred in December, 1917, to mineral operators from Seattle and Spokane.*'

Bell, R, N., Nineteenth annual report of the mininir industry of Idaho, for the year 1917, IK 101.

Coal In Eastern Idaho.

Coal Beds.

According to Bell " 20 beds ranging in thickness from 6 inches to 10 feet have been identified by surface work throughout a linear ex- tent of 2 miles, and three of these beds have been ratl\er extensively developed. The number of beds present can only be conjectured until much underground work has been done and a detailed knowledge of the structure obtained. The beds can not well be traced at the surface because of the thick cover of rock debris and jegetation. There may be as many as 20 beds or even more, but practically all of those pros- pected, except the beds on which the four mines described below are located, have given little or no promise of commercial value. Prob- ably some of the openings now regarded as exposures of distinct beds may prove to be on the same bed. There seems little doubt that the Horseshoe and Bellcut mines are so located. On page 139 reasons are given for thinking that the Brown Bear and Boise mines may be on the same bed as the Horseshoe and Bellcut mines.

Kives.

Brown Bear mine, — The coal bed at the Brown Bear mine varies somewhat in thickness and character, as shown by the following sec- tions measured by Woodruff, who also recognized and mapped sev- eral faults in the coal bed :

Sections of coal bed in Brown Bear mine.

North end of mine.

Shale." Ck)al" Shale- Coal"

Ft.

In.

Soath end of mine.

Shale. Ft. In,

CJoal 2 10

Coal, crushed 1 7

Shale.

The general plan of the Brown Bear mine comprises a horizontal crosscut tunnel 825 feet long with drifts and stopes north and south along the coal bed. The south drift, which is about 800 feet long, has caved. The north drift is 1,700 feet long. Further extension in that direction is unprofitable both because of the cost of handling the material by present methods and because of the deterioration of the coal by the northward thickening of a parting.

In August, 1917, work was undertaken to extend an inclined air shaft, then 80 feet deep on the dip of the coal bed, 44°, to a depth of 200 feet below the surface. This shaft was to be used for hoisting the coal from stopes at the new level. A hoist, track, and car of about 1-ton capacity were to be installed. According- to Bell the

"Bell, R. N., op. cit., p. 103.

See anaylslB No. 15115 (p. 152), and also section 3, fig. 14.

Bell, R. N., op. clt.. pp. 101-104.

142 Contributions To Economic Geology, 192D, Part Ii.

shaft was sunk to a depth of 250 feet by the former owners and ex- tended to 400 feet by the present owners, who plan to extend it to the 500- foot level. The owners also plan a crosscut tunnel 6,000 feet long, which will afford natural ventilation, drainage, and means of handling the *coal by gravity. It is claimed that 4,000,000 tons of coal is available above the 500-foot level, but no statement is made regarding the basis of the estimate. A spur track to the mine from the Oregon Short Line Kailroad and equipment to handle 500 tons a day are among the plans for future development.

Water is rather abundant in the mine and will require pumping until the crosscut tunnel is completed. Before the deepening of the shaft it was removed by gravity along the tunnel.

Horseshoe mine, — The coal bed at the Horseshoe mine is thicker than at any other recorded locality in the district, and the heating value of the coal is relatively high. The following section was meas- ured by Woodruff :

Section of coal bed in the Horseshoe mine.

Ft. in. Shale.''

Coal 1 11

Sandstone . 10

Coal " cru8he<l .3 4

Coal, bony 1 9

Coal" crushed 1 3 3

Shale.

This mine, which consists of a single entry 500 feet long, is badly caved but can still be entered for a distance of about 200 feet. An attempt was made in the winter of 1916 to reopen the mine, and a small amount of coal was extracted. The attempt was abandoned on account of the unsatisfactory condition of the old workings.

Bellcut mine. — The Bellcut is a new mine opened in the fall of 1916 in what is probably Woodruff's locality 10. The workings con- sist of an open cut perhaps 100 feet long leading to a crosscut tunnel 80 feet long to the coal bed. Drifts extend north and south 170 and 815 feet, respectively, each timbered to the end. The north drift is very wet. The coal at the face is crushed fine, forming mud that has slumped forward at least 10 feet into the drift. The miners are said to have struck a fault here. The south drift is fairly dry. The coal at the face is hard and breaks unevenly without any special tendency to follow bedding planes. The dip of the bed is 70° W. The following section was measured at the south face:

IT See analysis 15116 (p. 152), and section 6, fig. 14.

Coal In Eastern Idaho. 143

Section of coal bed at Bellcut mine.

Ft. in. Clay, slickensided.

Coal, hard 3 4

Bone 2

Clay, sandy, gray 8

Coal, including 2-inch bone irregularly distributed*

about 1 foot from top 4 0

Clay, slickensided 8 2

At the portal the coal-bearing formation is exposed for about 45 feet along the open cut, showing buff-colored sandstone and clay with dark shale, much weathered and somewhat carbonaceous.

About 100 feet up the gully above the Bellcut mine a 20-inch bed of poor coal, much weathered, is exposed in the north bank. About 200 yards above the mine in the same gully is a bed 22 inches thick, said by Mr. Hillman to be good coal for blacksmithing. The bed strikes N. 33® W. and dips 69° W. It was too thoroughly weathered for sampling. Streaks of iron-stained clay were seen in it but no parting or bone. The hanging and foot walls are both clay.

Boise ndne. — The coal bed at the Boise mine is 38 inches thick, without bone or parting, and lies between beds of shale. (See section 2, fig. 14.) Unfortunately it has caved so that further production is delayed or perhaps even prevented.

Pxz0E8 Abb Peoduotzov.

The coal from the Bellcut mine was sold in the winter of 1916 as run of mine coal at $1.50 a ton at the mine. The lump coal from the Brown Bear mine brought $4.50 a ton at the mine during the same sean. The fine coal on the dumps at the Brown Bear was selling in the summer of 1917 for $1 a toi;i at the mine.

The production has always been small, a few tons a day. The total production in 14 years, including the output of the Horseshoe mine, amounted, according to Mr. Hillman (August, 1917), to ,000 tons.

00V0Lusi0V8.

The area in which coal beds of conunercial grade occur is not as large as was formerly supposed and probably does not exceed 3 or 4 square miles. The shattered condition of much of the coal, due to rock movements, is unfavorable for handling and transportation. For this reason only a relatively small proportion of the output is likely to command a favorable price, and much of it must continue to be sold locally as run of mine or fine coal at low prices. The steep dip of the coal bed makes mining difficult and expensive and induces caving, such as has already blocked workings that might otherwise

See analysis 29182 (p. 152) and section 5 (compare with section 4), tig. 14.

144 Contributions To Economic Geology, 1920, Part Ii.

be productive. The variable and faulted character of the coal limits the extent to which a given mine can be worked. The disposal of water in the mines will increase the cost of production in those work- ings that lie beneath the level of the tunnel. If the projected im- provements are completed and sufficiently favorable prices can W obtained for the product to offset the installation, operation, ami amortization charges, there is prob8|,bly enough coal in the ground to keep the mine running for a number of years. The future activity of the mines will depend in large measure on how well the operators are able to compete with Utah or Wyoming coals of equal or better grade (see table, p. 152) shipped in by rail.

An account of the Horseshoe district by G. W. Evans,** published since the completion of the present paper, gives a description in which the geologic features are based on WoodruflTs report. Although an estimate of 11,000,000 tons is given by Evans, he is careful to add the following qualifying statement, which should not be overlooked: No one is justified in assuming that this amount of coal has been proved in this district. ♦ ♦ ♦ The actual tonnage can be deter- mined only by actual gangway and slope development." The fol- lowing analyses are .given :

Analyses of coals from Horseshoe district.

BeU Gnldi bed.

[See p. 04 of report dted for section.

Air dried.

As received.

Moisture free.

IToistiire

and ash

free.

Bi 01 sture

Per cent.

&6

Percent.

a4

Percent*

Per etnt.

Volatile matter

Fixed carbon

Ash

Air-dry loss 6.2 per cent.

Brown Bear bed.

(See p. 94 of report cited for section.]

Ifoistore

Volatile matter

Fixed carbon

Ash :

Air-dry loss 4.6 per cent.

Boise bed.

Hoisture

Volatile matter- T...,

Fixed carbon

Ash

Air-dry loss 6.1 per cent.

Varley, Thomas, and others. A preliminary report on the mlninic dlBtrlcts of Idaho : Bur. Mines Bull. 166, pp. 90-103, 1919.

Goal In Eastern Idaho. 145

Mahogany Creek.

Several coal prospects in the Cretaceous rocks on the north side of Mahogany Canyon, in the NW. i sec. 15, T. 4 N., R. 44 E., were opened in carbonaceous shale of probably either Bear River or Wayan age. They give little promise of workable coal. A reported " coal " pros- pect in the south fork, which was not visited, is with little doubt in the phosphatic shale belt of the Phosphoria formation, which crosses iLe creek in the NE. J sec. 21.

Patterson Greek.

One of the two reported " coal " prospects in the basin of Patterson Creek was visited. This is approximately on the township line, in the SW. I sec. 35, and proved to contain phosphate rock but not any coal. The other .prospect is about a mile farther northwest, in the same belt of phosphatic shale.

South End Of Teton Basin.

The road to Jackson ascends the valley of Trail Creek. Beyond the rhyolite the first ledges encountered are light-gray limestones that may be Cretaceous (Wayan). The road follows the strike of the beds rather closely but gradually cuts across Jurassic and lower beds. To the west lie Carboniferous rocks. Thus a fault of considerable magnitude passes up the valley of Trail Creek, cutting out the Cre- taceous coal-bearing rocks.

North End Op Teton Basin.

The north end of Teton Basin is closed by rhyolite that forms prominent ledges in the vicinity of Tetonia. Associated with the rhyolite are beds of volcanic ash, including fragments of grayish- white pumice and black volcanic glass (obsidian). The glass has been mistaken by some persons for anthracite or coal.

On the Breckenridge ranch at Haden, in the NE. J SE. J sec. 35, T. 6 N., R. 44 E., a well was sunk 15 years or more ago for oil. It has been commonly reported that 10 feet of coal was struck in this' well at a depth of 600 feet. Upon visiting the locality the well was found in good condition with parts of the old broken derrick still standing. The writer is indebted to Mr. Preston K. Breckenridge, 8on of the former owner, for the following details regarding it.

The well was drilled under the direction of a man named McDon- ald from Florence, Colo. It had been intended to sink 3,000 feet but drilling stopped at about 700 to 760 feet. On the last day of drilling, when the men went to dinner, Mr. McDonald and one other Dian remained a few minutes at the well. The others after their

146 OOKTBIBTTTIOKS TO BOONOHIC GBOIiOOT, 1920, PABT IL

return from dinner resumed drilling and at once struck coal. After 10 feet of coal had been penetrated drilling stopped. Mr. McDonald then went to Denver to obtain further funds and additional ma- chinery, but while there sickened and died. Some three or fear years later Mr. Spencer Clawson, of Salt Lake City, had the well cleaned out and expended about $1,000 in sampling and casing it. Special devices were employed in exploring the well for coal, but none was found. Both the elder Mr. Breckenridge and Mr. Clawson have since died. Mr. Preston Breckenridge states that his father had always felt that the well had been fixed " before the reported coal was found. The well is cased to bedrock, 240 feet, and is 10 inches in diameter at the top and tapers to 8 inches at the bottom. No record of the character of the rock penetrated is available. Water stands in the well at a depth of 40 or 50 feet, as estimated by drop- ping a pebble. The well has been kept locked until recently but is now open.

BBOADER STEircrnRAL FEATUBES.

St. John,*® Blackwelder,* and Schultz have observed and figured the gently westward-dipping Paleozoic strata that pass beneath the lava along the west flank of the Teton Range on the east side of the basin. Schultz has made out anticlinal structure along the west side. Thus the structure of the basin appears with little doubt to be synclinal, as figured by Schultz. It was the opinion of Schultz that the syncline was deep enough to include coal-bearing Cretaceous beds and that commercial coal might be found by drilling at favor- able points in the basin. The reported occurrence of coal in the Breckenridge well at Haden seemed to support this view.

Probabiutt Op Coal.

One of the principal objects of the present examination was to procure data to test, if possible, the validity of the hypothesis just mentioned. As the basin is completely covered with Quaternary deposits to a depth of 240 feet at one locality, at least, and possibly to greater depths elsewhere, and is fringed with lava, inferences regarding the probability of the occurrence of coal beneath the cover must necessarily be drawn from the exposures igid structure of the rocks surrounding the basin.

The Paleozoic exposures to the east have a structure so simple that they suggest equally simple structure for the concealed portions of

St. John, Orestes, U. S. GeoL and Oeog. Soryey Terr. Eleventh Ann. Bept, pp. 411- 424, pi. 34, 1879.

Blackwelder, Bliot, A reconnaissance of the phosphate deposltfl In wealam Wyoming : U. S. Geol. Saryey Boll. 470, pp. 46&-464, 1011.

**SchaltE, A. R., A geologic reconnaissance for phosphate and coal In sontbeastem Idaho and irestem Wyoming: U. 8. GeoL Surrey BulL 680, pw 69, 19ia

Coal In Eastern Idaho. 147

the basin. The west side of the basin, however, exhibits many com- plications of structure, including pitching folds and branching thrust faults of considerable magnitude. It seems probable, too, that along the west side of the Horseshoe district close folds occur in the Cre- taceous beds. Doubtless the more intensive effects of the thrusting may die out eastward, but it seems that a simple synclinal structure for the basin can not safely be assumed.

Again, the Cretaceous formations below the commercially im- portant beds have a thickness of possibly more than 9,000 feet, so that there is no assurance that the syncline is deep enough to have carried the coal beds beneath the level of erosion, where they could have been preserved. If, as seems likely, the basin is a large com- plex syncline containing smaller folds, one or more synclines might be present and deep enough to hold coal measures, but the positions of these synclines could be determined only by systematic drilling, and the possibility of faults would add much uncertainty to the problem. The record of the Breckenridge well is inconclusive, because it now affords no information regarding the character of the bedrock.

If one were disposed to spend the necessary money to test the syn- clinal hypothesis the place to drill would be on the eastern slopes of the f oothilb east of the Horseshoe district or somewhat farther north and in the region between those slopes and Teton Biver. A few wells sunk on a northeast-southwest line to depths of 200 to 500 feet would probably suffice to indicate the geologic formation upon which the lava rests. If this should prove to be the FroQtier formation, coal beds that could be profitably mined might be expected. Because of the gentler dips in the broad syncline the coal if present would prob- ably be relatively free from the objectionable crumbling that char- acterizes the coal in the Horseshoe district and would thus be better adapted for transportation and marketing.

Continental Divide.

Two districts were visited on the Continental Divide, one at the headwaters of Cottonwood Creek in T. 14 N., Rs. 38 and 39 E. (un- surveyed) , and the other at the head of Sheridan Creek, chiefly in T. 14 N., R. 40 E. (unsurveyed). Coal was found in the Cottonwood district but not in the Sheridan district.

Cottonwood Cbeek.

osvEBAL rsATtrass.

The rocks of the Cottonwood district are chiefly Cretaceous sand- stone, shale, and clay. The stratigraphic position is not definitely blown, but they are presumed to be of Frontier or later age. They

148 Contributioks To Economic Geology, 1920, Part Ii.

have been exposed by the partial erosion of the overlying Tertiary conglomerate and lava. One coal bed of probable commercial im- portance is exposed, and there are several others each a few inches in thickness. Numerous landslides with fresh scars afford exposures of the rocks here and there, but debris accumulations of similar origin and patches of Tertiary conglomerate conceal much of the bedrock of the region. The Cretaceous rocks and some of the larger areas of Tertiary formations are shown in figure 18.

The strata have a general northwesterly to westerly strike and a dip of 13-39° SW. At the Scott & Bucy entry the strike is X. 69° W. and the dip is 16° SW. Toward the northeastern and south- western parts of the district the dip steepens. These structural features are shown in structure section D-D figure 12, for which, as well as for figure 13, sheet 4 of the United States Forest Service map of the Targhee National Forest was used as a base.

The outcrop, of the coal can be traced for only about a quarter of a mile, and a traverse through the country to the east failed to strike the continuation of the bed in that direction. The accumula- tion of debris above noted and the vegetation might readily conceal it There is no apparent reason, however, why the coal should not continue eastward. In fact, it is desirable that the approximate area presmned to be underlain by it outside the Tertiary cover should be shown on the map. Accordingly, on the basis of the available read- ings of strike and dip and the topography, the inferred position of the line where the bed should crop out is indicated on the map by a dotted line. The region southwest of this line may be tentatively regarded as underlain by the coal bed at depths varying in the man- ner suggested by the structure section. The exact position of the bed at any particular locality will have to be determined by drilling.

A dike of dark amygdaloidal lava occurs in the SE. NW. sec. 18, T. 14 N., R. 39 E. (unsurveyed; location estimated from topog- raphy). It is accompanied on the west by a breccia 5 or 6 feet thick composed of sandstone and clay cut by stringers of lava and contain- ing pieces of lava. The sandstone to the south strikes N. 55 W. and dips 23 S. A small pocket of black, coaly shale occurs in the breccia. Thin pieces of sandstone float containing carbonaceous flakes were found on the south side of the dike. Beneath the sandstone is a light gray clay. The dotted line representing the theoretical position of the projected coal bed crosses the line of the dike. The coal was not found here, but the pocket of coaly shale suggests its proximity.

Northwestward the coal bed probably continues an unknown dis- tance into Montana. Two traverses were made north of the divide, but the bed was not found. The region is thickly timbered and ob- structed by landslide debris and bogs, and one might readily pass within a few feet of an exposure or prospect without being aware of

Coal In Eastern Idaho. 149

its presence. A large slide was found about three-quarters of a mile northwest of the Scott & Bucy entry, in which occur fragments of coal and a massive bed of fossiliferous light-gray sandstone. The fossils here are different from those at the entry, and the horizon is therefore probably not the same but perhaps stratigraphically lower. The coal bed, though not exposed, is probably much thinner than at the entry. The northward continuation of the Cretaceous formation and other geologic data in Montana, as shown on the general map (PL XIV), are taken from a map by Condit and Finch.'

Bevelopiceht.

The Scott & Bucy entry is driven in rock down the dip of the coal bed and is untimbered. It trends N. 47° E. and is 110 feet long. The roof of the entry is of slabby sandstone, in places somewhat broken and dangerous. Some falls of rock have already obstructed the passage. At the time of the writer's visit no work had appar- ently been done within two or three years. The location notice is dated July 24, 1912, and the locators are C. W. Scott, of Dillon, and M. W. Bucy, of Monida, Mont

Ohahaoteb Of Coal.

The coal bed is exposed along the walls of the entry its entire length and shows little change in character or thickness. About 50 feet from the portal a small normal strike fault lowers the bed 2 feet on the west. The coal at the face of the entry is relatively fresh and fairly hard. It did not appear to break more easily in one direction than in another. The following section was measured at the face of the entry, where the strike of the coal is N. 60° W. and the dip 16° W. :

Section of coal bed at Scott d Bucy mine in the SW. 1 SE, sec. 11. T, 14 N.,

R. S8 E, (unaurveyed) Boise meridian, Idaho.

Ft. In.

Clay, gray; grades upward into sandstone 6

Coal, sheared and sUckenslded ; pinches out eastward-- 6

Clay, gray -- 6

Coal,** hard, dense 2 8

Clay, black, partly bone 7

Clay, gray 3

The following analysis of coal, presumably from the same open- ing, is contributed by Mr. Scott in correspondence with the Survey :

"Coodit, D. D., and Finch, E. H., personal communication. MSee analysis 20281 (p. 152) and section 7, fig. 14.

ritetl for, comparison in the table uii li>2. To judge from the t'ondition of the exposure along the walls of the entry it would not sliick readily on exposure to weathering and would probably stand hauling and transportation.

ACCEBBIBILtTY.

Although in an air line the mine lies within 15 miles of Beaver or Iluniplirey. on the Butte bnmcli of the Oregon Sliort Line Rail- road, the actual haul to the railroad would be much longer. By way of Kilgore tlie distance from tlie coal bed to Spencer, the nearest railroad point south of the divide, is approximately 27 miles. On the north side of the divide the distance to Monida, by way of Jones Creek and Centennial Valley, is approximately the same. Fur- ther exploitation of the field north of the divide might disclose more favorable points of access nearer Centennial Valley, but even then the distance from the present railroad would exceed 15 miles.

A well-traveled and well-graded wagon road leads up East Camas Creek to a point within about 2i miles of the coal entry. On the north side of the divide a road, now somewhat out of repair, has

Ooal Is Eastebn Idaho. 151

been constructed up Jones Creek to the divide. The grade for the last mile is very steep.

Oittlook.

The country both north and south of the divide is so sparsely settled that there is doubt if it could soon afford a sufficient market to warrant the development of mines in this field. The thickness of the bed, the quality of the coal, and the size of the field would not in themselves justify the construction of spur tracks to the mine, but should other causes cooperate in bringing a railroad sufficiently near profitable mines might be developed

Analyses.

The accompanying analyses were made at the Pittsburgh labora- tory of the Bureau of Mines. Four forms of analysis are given for each sample. A represents the material as received at the laboratory, essentially as it is found in the mine. B represents the coal after drying to a constant weight at a temperature of 30° to 35 C. This form of analysis is best adapted to general comparisons. C repre- sents the coal after all moisture has been removed. D represents the coal after both moisture and ash have been eliminated. C and D are theoretical forms derived from A and B by recalculation.

The samples analyzed have all been collected in accordance with the regulations of the Bureau of Mines, which require, in brief, that the face to be sampled must be cleared of weathered coal, powder stains, and other impurities and channeled across the bed to obtain the sample. Materials from large partings and liunps of impurities are rejected. The sample is collected on a sampling cloth, broken up to pass through a inch mesh sieve, thoroughly mixed and quar- tered, and the alternate quarters rejected. Mixing and quartering are repeated until the sample is reduced to about 4 pounds. This residue is then placed in a can, which is sealed and forwarded to the laboratory.

Analyses of two Wyoming coals are included in the table for comparison.

Goal In Eastern Idaho. 158

Occurrence Of Oil.

Reported indications of oil were investigated on Mahogany Creek, on the west side of Teton Basin, and in Darby Canyon, on the east side. On Mahogany Creek swamp slime with iridescent iron films was mistaken for oil and in Darby Canyon the gently undulating and faintly westward-dipping Carboniferous limestone near the old saw- mill was thought to have a favorable structure for the accumulation of oil. It was also reported that oil scum was common on the creek at certain seasons of the year. The stream at the time of the ex- amination was exceptionally free from scum of any kind, although a collapsed bridge near the sawmiU afforded excellent opportunities for the gathering of oil. The Carboniferous rocks alluded to are part of the thick Paleozoic strata that form the west flank of the Teton Kange. With the exception of the phosphatic shale of the Phosphoria formation, which yields small amounts of petroleum on destructive distillation,'' the Paleozoic rocks are not known to bear significant amounts of oil in this portion of the Rocky Mountains. Many of them, however, when struck with a hammer or freshly broken, give a fetid odor like that of crude petroleum. The dip and exposure of the strata are such as to afford ready opportunity for the escape of such hydrocarbons as may have been present in these rocks.

The coal bed and some of the shale beds at the Brown Bear mine yield small quantities of petroleiun upon destructive distillation.*

The anticline along the west side of the basin east of the Horseshoe district, as noted by Schultz,** furnishes the most promising structure in the region for the accumulation of oil. The axial portion and eastern limb of this fold are largely concealed by lava, and to the west faults occur in parts of the district. The gathering area for oil apparently is not large. The presence of oil could be determined only by drilling, which should not be undertaken without full realiza- tion of the cost and the great chance of failure.

—

" Condlt, D. D., Oil shale in western Montana, soatheaBtarn Idaho, and adjacent parts Wyoming and Utah : U. S. Geol. Survey Boll. 711, p. 81, 1019. Scholtz, A. B., op. cit, pp. 80. 81.

"Condlt D D., op. dU 82, 88.

154071— 21— Bull. 716 11

Cx>Al In The Middle And Eastern Parts Of San Juan County, New Mexico.

By Oltde Max. Baueb and John B. Beeside, Jr.

Introduction.

From the earliest settlement of southwestern Colorado down to the present tune the great coal bed, nearly 50 feet thick, exposed in the canyon of Animas Biver, 2 miles below Durango, Colo., has attracted general attention. It is true that this bed is not all coal, and at- tempts to mine it in competition with the better coals lower in the geologic sequence have proved failures. Nevertheless, many persons have speculated regarding its southward extension, and this has led to prospecting in the strip of land lying between the Colorado bound- ary and San Juan River. The character and size of this and asso- ciated beds north of the river have thus been ascertained, but until recently little exact information has been available concerning these beds in the inhospitable region south of San Juan Biver. In the summers of 1915, 1916, and 1917 the writers procured detailed in- formation regarding the coal beds north of the San Juan, crossed the river, and traced the coal-bearing formation as far as Alamo Arroyo, on the south line of T. 22 N., B. 9 W., where the formation ceases to bear coal beds of comjnercial value, and thus were able to delimit the field on the west side of the San Juan Basin.

From the Colorado-New Mexico boundary line this field extends through the central and southern parts of San Juan County, which occupies the extreme northwest comer of New Mexico. The out- crop of the coal-bearing Fruitland formation trends southwestward from the State boundary, near the point where it is crossed by La Plata Biver, to San Juan Biver. Beyond the San Juan the outcrop paraUels Chaco Biver very closely the entire distance to Alamo Arroyo, near the south side of San Juan County. (See PL XVI.) The coal is chiefly of subbituminous rank and is similar to that of the Gallup district, but in the northern part of the field it is good enough to be ranked as bituminous. The beds, numbering from two to six at most localities, range in thickness from a few inches to 40 feet. In the following pages the thickness of various beds at many places is given, and the quality and character of the coal and the inclosing strata are described.

156 Contributions To Economic Geology, 190), Part H.

Accessibility Of The Field.

The field may be reached from the north by the Denver & Rio Grande Railroad, a standai:d-gage branch of which extends from Durango, Colo., to Farmington, N. Mex., on San Juan River in north-central San Juan County. Access to Durango may be had by several routes. Travelers from the west may go from Grand Junc- tion, Colo., on the main line of the Denver & Rio Grande Railroad, by way of Montrose, Vance Junction, and Mancos. The total dis- tance from Grand Junction to Farmington is 300 miles, and the trip requires transshipment of passengers and freight from standard- gage cars to narrow and then from narrow to standard. From the east the traveler may go from Denver and Pueblo, by way of Walsen- burg or Salida to Alamosa ; thence over the Cumbres Pass (elevation 10,000 feet) to Durango. The total distance from Denver to Farm- ington is 496 miles, and two transshipments are required because of changes in track gage. Another route goes from Denver by way of Salida, Marshall Pass (elevation, 10,850 feet) , Montrose, Vance Junction, and Mancos. The total distance from Denver by this route is 585 miles, and two transshipments are required. On aU these routes grades are heavy, maintenance and operation costs are large,< and transportation is therefore relatively slow and expensive.

From the south the field may be reached by wagon from stations on the Atchison, Topeka & Santa Fe Railway. Roads run from Guam, Thoreau, and Bacd through several passes in the high ridges that lie a few miles north of the railroad. The trail from Thoreau through Satans Pass as far as the Pueblo Bonito Agency and Indian school at Crownpoint is well kept, but elsewhere the roads are unim- proved. The distance from the railroad to the southern edge of the field is 60 miles ; to Farmington it is 100 miles. This route requires a hard trip through nearly uninhabited country in which water is available at only a few points, and there are many arroyos to cross— a difficult task when heavy rainstorms or melting snow have supplied enough water to flow or erosion has cut the banks to steep angles.

From Gallup an automobile stage runs northward along a line about 10 miles west of the field, crossing the San Juan at Shiprock. in T. 30 N., R. 18 W., and thence following up the river to Farm- ington. More direct wagon routes from Gallup to the field are also available but have all the disadvantages of those from other points.

Field Work And Acknowledgments.

The field work on which this report is based was done during the summers of 1915, 1916, and 1917. In the absence of a suitable base map, several base lines were measured, from which control points were located by triangulation with plane table and telescopic alidade. From these points detailed mapping was extended through the field.

I Rio Arriba Co

Sandoval Co

MCKINLSry CO

Coal In San Juan County, N. Mex. 167

The field party of 1915, in charge of the senior author, was com- posed of H. B. Bennett, J. C. Brittain, Boyce Brown, and the authors. The party of 1916 included Frank B. Clark, J. E. Heald, J. H. Eiseman, and the junior author, and that of 1917 included Harvey Bassler, K. N. Garard, J, F. Gibbs, and the junior author. Acknowledgment of the efficient aid rendered in the prosecution of the project is due to all these men, particularly Mr. Bassler, who procured all the field data for the region north of T. 30 N., B. 15 W. The authors also wish to thank many residents of San Juan County for hospitality and for courtesies rendered the field parties, and M. B. Campbell for advice and assistance in the field and office work.

Surface Features.

Land 70Bms.

This field has a maximum relief of nearly 2,500 feet. The lowest point is on the San Juan near the western edge of the field and is about 5,000 feet above sea level; the highest point is on the south- eastern edge of the field and is about 7,500 feet above sea level.

Along the western edge abrupt tilting of resistant rocks and subse- quent erosion of the softer materials has formed a striking ridge known as the Great Hogback, Hogback Mountain, or simply the Hogback — a sharp ridge of sandstone whose eastern face is a steep dip slope rising as mueh as 700 feet above the adjacent country. To the north the Hogback passes into a series of lower parallel ridges and ceases to be a prominent feature.

North of San Juan Biver the country for some distance east of the Hogback is a fairly even surfaced shale valley, which is known locally as the Meadows. It contains some low sandstone ridges and some badlands. It is unoccupied, though it could probably be suc- cessfully cultivated if water were available. Wells drilled for oil in this part of the field have found only salt water.

The remainder of the field is essentially a dissected plateau. (See Pis. XVII and XVIII.) The drainage lines are all intrenched be- low the upland plain and are separated by flat-topped divides which are clearly parts of a former continuous surface. Here and there isolated remnants stand out prominently — or example, Pinyon Mesa, in T. 30 N., B. 14 W. Along the arroyos there are extensive bad- lands, which are all cut below the general surface and are invisible from it at relatively short distances. (See PL XVIII.)

Sand dunes are abundant on the interstream areas. Sand from the arroyos and dry creek beds is blown in enormous volume out upon the flats and forms large dimes and sand ridges. The surface forms m some parts of the field are much modified in this way. Along the cast bank of Chaco Biver, owing to the prevailing westerly winds, dunes and sand flats are abundant and form a barrier in many places diflScult to cross with a team.

Indians of the region have built a number of reservoirs and sunk shallow wells near the arroyos, which are easy to reach when their location is known and which form the main reliance of the traveler for his water supply. At a few points in Gallego Arroyo wells have been drilled that supply water by pumping. Most of this water car- ries enough alkali or salt to make it unpalatable.

Climate And Vegetation.

This field is part of an arid region whose climate is marked by great variability. Very hot days may be followed by very cool nights; no rain may fall for a month, and then a single shower may bring a normal month's rainfall ; the normally rainy months may be absolutely dry and the normally dry months relatively wet. The normal annual precipitation is about 7 inches for the San Juan Valley, though in exceptional years it may rise to nearly 20 inches or fall as low as 3 or 4 inches. For the entire field it is usually under 10 inches. The temperature fluctuates widely — below O'' for the minimum and well above 100° for the maximum. The mean

'See also firegory, H. E., Tbe Navajo country; a gweraphlc nud hydroerapblc recon- nalBsance of parts or Arizona, New Mexico, and lltab : V. S. Ceol. Survey Water-Sapidj Paper 380. IBIC. French. J, A. (Slate euBineer), Surtsci- water supply of New Heilco, 1888-lOlT, Albuquerque, N. Mri., 1918.

Goal In San Juan County, N. Hex. 159

annual temperature at Fruitland is 52.6, and the annual range is about 115. A daily range of 40 is not uncommon. The summer storms are usually short but violent, with high winds, lightning, and sometimes heavy rain and hail. The winter storms are often accom- panied by snow.

The native vegetation is entirely of types adapted to arid con- ditions of life. The lowest lands bear greasewood (Sareobahis) sagebrush {Artemisia), and bunch grasses. Higher lands (up to 6,000 feet) bear rubberweed (Hymenoxya), cactus (mainly Opuntia), sagebrush, grasses, and scattered juniper {Juniperus Trumoapermus) and piiion {Pintis edtdis). Where very sandy they support a growth of joint fir (Ephedra) and redtop grass. Above an elevation of 6,000 feet the chief elements of the flora are juniper and pinon and the minor elements are sagebrush and other shrubby plants, with some jack pine and scrub oak.

By means of irrigation it is possible to raise a number of plants not native to the region. Fruit of various kinds thrives and in most years brings abundant returns. Alfalfa grows well, and some grain, potatoes, tomatoes, and other vegetables are produced. Mar- kets forearm produce are strictly limited by the transportation con- ditions, and in the best years much more can be raised than there is any possibility of selling.

The Navajo Indians, by means of a system of storm-flood irriga- tion, succeed in raising fair crops of certain varieties of maize, melons, beans, and a few potatoes in bottom lands, where the soil is rich and gets the benefit of any heavy rains which may fall.

Settlements And Roads.

Aztec and Farmington are the two main towns of the field. Aztec is the county seat and has a population of 500. Farmington is the terminus of a branch of the Denver & Bio Grande Bailroad and has a population of 800. Both are essentially trading centers and supply points for the country about them and are well supplied with stores, banks, and other necessary institutions.

Beside these larger towns there are several scattered settlements on San Juan Biver, including Blanco, Bloomfield, Kirtland, Fruit- land, and Liberty; several on La Plata Biver, including La Plata and Pendleton; and several on Animas Biver, including Flora Vista, Inca, and Cedarhill. Most of these are post offices, with one or two stores. South of San Juan Biver there are a number of isolated trading posts outside of the Navajo Beservation which depend on the Indians for their existence. The location of many of these posts is shown on the map (PL XVI). There are very few white settlers outside of the irrigated districts.

Along the perennial streams the roads are kept in good condition and are normally passable for automobiles as well as wagons, but

160 CONTRIBXJnOKS TO ECONOMIC GBOLOGY, IMO, PART H,

outside of these districts they are usually mere unimproved wagon trails. These trails are numerous, thanks to the Indian propensity for moving about, though badlands, sand dunes, and rapidly eroding arroyos present many difficulties to the traveler. It is possible to take heavy camp wagons over most of the roads shown on the accom- panying maps, but automobiles meet with difficulties in crossing deep arroyos and steep- walled ditches.

Animas and La Plata rivers may be forded at many places, but the San Juan is treacherous and difficult to ford in the spring and summer. The two smaller streams are bridged at a number of places, and the San Juan at Blanco, 20 miles east of Farmington, at Farmington, and at Ship Rock, 35 miles by road west of Farmington. At Bloomfield a ferry operates during periods of high water, and at Fruitland there is a footbridge.

Land Surveys.

The land surveys of parts of the region covered in this report were made in recent years, and the monuments are easily found. Tps. 24 to 28 N., K. 13 W. ; part of T. 23 N., Tps. 25 to 28 N., R 12 W.; Tps. 27 and 28 N., Rs. 11 and 10 W.; and Tps. 29 and 30 N., Rs. 16, 17, and 18 W., were surveyed in 1913. T. 30 N., Rs, 16 and 14 W., was surveyed in 1909. Tps. 21 and 22 N. and part of T. 23 N., R. 13 W., were surveyed in 1893, and although no comers for thest townships were found in the field, the geographic details shown on the plats are accurate. The townships between San Juan River and the Colorado-New Mexico State boundary were surveyed mostly dur- ing the eighties, and though the comers are not easily found the details shown on the plats are fairly accurate. In the area included in Tps. 21 to 24 N., R. 12 W.; Tps. 21 to 26 N., Rs. 9 to 11 W.; and Tps. 21 to 24 N., Rs. 7 and 8 W., however, no authentic corners were found, and the details shown on the official plats disagree so pro- foundly with the districts they are supposed to represent that it seems doubtful if the surveys were ever made. The lines shown for this portion of the area mapped are based on relocations of a few cor- ners by local surveyors and the Office of Indian Affairs and must be considered provisional. In the part of the field covered by the net based on the Navajo meridian the lines must also be considered provisional, as little evidence of their position was obtained in the field.

Gbology.

Oenebal Featttbes.

The stratified rocks of this region consist of a succession of sand- stone, shale, coal, and conglomerate, laid down originally as marine,

Botxetin Tib

Coal Ik San Jt7Af C0Ukt7, 17. Mbx. 161

brackish-water, and fresh-water sediments. The rocks here have been depressed or those in surrounding regions have been uplifted until they lie in the form of an immense basin that stretches from Durango, Colo., on the north, a distance of 125 miles to Gallup, N. Mex., on the south. From the Hogback eastward to Cuba or Gallina, N. Mex., the basin is more than 100 miles across. In the center of the basin the rocks are supposed to be practically flat, but in the rim they are sharply upturned. This is illustrated by a dip of 45 E. in the Great Hogback, which near Liberty post office forms the western rim, dips of only 1° to 3® in the outcrop of the Fruitland formation near by, and dips of 1° or less in the younger beds.

Minor structural features superimposed on this general basin are not numerous in the San Juan County field. Several broad, low anticlines cross the rim at right angles north of San Juan River, but they are noticeable chiefly in the bulges they make in the outcrop lines of the formations. A small, sharper anticline occurs in T. 30 N., R. 16 W., and another in T. 26 N., R. 16 W. (unsurveyed). In T. 30 N., R. 15 W., there is some evidence of a flattening of the dip to form a structural terrace parallel to the basin rim ; in T. 29 N., R. 16 W., likewise an obscure structural terrace is observable in the Lewis shale. The only fault large enough to map was seen in T. 22 N., R. 7 W. but it is relatively small.

The Great Hogback is formed by the tilting of the resistant rocks

of the Mesaverde group in the sharp monocline known as the San

Juan fold. The dip flattens very quickly in the Lewis and Mancos

shales, so quickly that at first glance the structure looks as if faulted.

However, good exposures show only a rapid but continuous change

in the dip. Toward the north the axis of the fold shifts eastward,

and in T. 31 N., Rs. 13 and 14 W., and T. 32 N., R. 13 W., the steepest

dips are in the Fruitland formation and the Kirtland shale, while the

rocks of the Mesaverde group flatten to form the prominent southern

extension of the tableland known as Mesa Verde. Farther to the

north the fold is not very distinct.

The following table ves the names and thicknesses of the f ormar tions and summarizes tne stratigraphy :' '

—

' For a description of the fossils and a discussion of the correlations see Bauer, C. M., and others Contrilrations to the geology and paleontology of San Juan County, N. Mex. : tJ. 8. Geol. Survey Prof. Paper 98, pp. 271-858, 1916 ; Gilmore, C. W., Reptilian faunas of the Torrejon, Pueroo, and underlying Cretaceous formations of San Juan County, N. Mex. : U. 8. Geol. Survey Prof. Paper 119, 1919 ; Sinclair, W. J., and Granger. Walter, Paleocene deposits of the San Juan Basin, N. Mex. ; Am. Mus. Nat. Hist. Bull., vol. 83, pp. 297-316, 1014 ; Granger, Walter, Notes on Paleocene and lower Eocene mammal horizons of northern New Mexico and southern Colorado: Am. Mus. Nat. Hist Bull., vol. 37, pp. 821-830, 1917.

162 CONTRIBUTIONS TO ECONOIOO GEOLOGY, 1990, PAST IL Oeoloffic formatUma in middle and eaatem San Juan County, N, Ifex.

Age.

Ghanoter.

ThioknasB (iBSl).*

%

WaaBlob fannatioo.

m

ICassIve buff to yellow oon- mnentic sandston inter- bedded with vaifecited shale: red shale abundant. FluTistilfi.

(?)

(?)

(?)

Booone.

Fonnation undetsmined.

Lixht-gray shale with some darker-gray and some red layers and some soft white ccoiglomeratic sandstone. May be part of Wasatch for matian. Fluyiatile.

(?)

(?)

2S0

Qray shale and lentloular soft wUte sandstone with bands of colored shale; yellow firmer sandstones. wiQi con- cretions. Fluviatile.

1,400

(?)

390-1,140

OJo Alamo BandstoiDe.c

White, gray, or brown cod- glomeratio sandstone con- taining varicolored shale lenses. FhxviatUe.

(?)

Kirtland shale (Including Fannlnfton aandatone member).

Blue-gray shale banded with vellow and brown. Fann- mgton sandstone member, near middle of the Kirtland. made up of a number of -channel sandstones. Flu- viatile.

TOO-l.lM

Fmitland formatian.

Grav sandy shale and gray- White cross-bedded sand- stone and buff sandstone, with coal beds. Of fresh and brackiah water origin.

Oretaoeous.

Pictured CUflh sandstone.

Buff to light-yellow and grav sandstone interbedded with thin gray shale. ICbrine.

37S

fiO-70

Lewis shale.

61,100- 1,710

with scattered lenses of buff sandy limestone, liarlne.

7S-1I0

t

Cliff House sand- stone.

Kainly buff to copper-red sandstone, with some shale. Some beds massive cliff forming. Marine.

Menefee fonnation.

Shale with some sandstone and coal. The coal beds are grouped near the top and the bottom of the formation. Of fresh and brackish water orljdn, with some marine

1,076

(?)

Point Lookoutsand- stone.

Massive buff to cream-colored sandstone, with some sand- stone; weathers a copper- red. Marine.

aoo

(?)

Hano

08 shale.

Dark-gray and dark-drab shale. Marine.

(?)

(?)

(T)

a 1, Northern San Juan County, N. Max., and southern 1a Plata County, Colo.; 2, central Ban Juas County (San Juan River}, N. Mex.: 3, southern San Juan County, N. Mez. 6 Unpublished data oolleoted by max A. Plshel in Colorado, c See footnote 5b, p. 173.

BUtLETIN Tie PLATE X

GOAL IK SAN JUAN COUNTY, K. IfEX. 168

Thb Vobmations. Mah008 Shale.

The Manoos shale, the lowest formation exposed in the field, is a dark-gray to dark-drab marine shale. Its upper part contains a little sandstone, but it is a relatively homogeneous shale. The con- tact with the overlying Mesaverde group is gradational. No meas- urements of its thickness were made by the writers, but in the type region to the north it reaches 2,000 feet.

Xz8Avebde Obovp.

The rocks of Mesaverde age in this field, though considerably thicker than those farther north, show the same tripartite character as in Mesa Verde National Park, the type locality. Becently Collier ' has named the formations, in ascending order, the Point Lookout sandstone, the Menefee formation, and the Cliff House sandstone. The Point Lookout is a marine sandstone with some shale, the Mene- fee formation is chiefly shale but includes some thick sandstone beds and contains both marine and fresh-water faunas and a flora, and the Cliff House consists of sandstone and shale. The thickness and character of these formations are best shown in the sections through the Great Hogback, in T. 29 N., R. 16 W., where it is cut by San Juan River and Chaco River. (See PI. XIX.) Both are given below:

Bedion of Mesaverde group on San Juan River, [Meamred by Harvey Baasler.]

Liewis shale. Mesaverde group:

CUtf House sandstone: Ft In.

Sandstone, heavy, reddish brown to buff 4

Shale, gray, sandy, with a few thin beds of sand- stone 96

Sandstone, massive, heavy bedded, reddish brown to buff, with thin layers of shale seiia-

rating the sandstone beds 830

Shale and sandstone, interfoedded. Sandstone tn thin layers and more abundant in upper part of unit ; some layers ripple-marked. Both

shale and sandstone gray 196

Ck>ncealed ; probably sandy shale 73

Sandstone, soft, buff 8

Shale, gray, sandy 11

Sandstone, massive, pisolitlc, dark brown on weathered surfaces, gray on fresh surface 83

'Collier, A. J., Coal sonth of Manoos, Montexama Coonty, OoIck: U. S. Oeol. Soxrey Boa 681, p. 296, 1919.

164 Contributions To ' Eoonomio Geology, 1990, Pabi Il

Mesaverde group— Contlnned.

Menefee formation: Ft. in.

Shale, gray, sandy 6

Coal 7 6

Shale, sandy, brown, carbonaceous 20

Bone 6

Shale, carbonaceous 2 6

Coal 1

Shale, carbonaceoQs 1

Coal 1 2

Shale, carbonaceoQS 4

Coal 4

Shale, sandy, brown, carbonaceous 28

Shale, soft, light colored, sandy 6

Shale, sandy, brown, carbonaceous 12

Shale containing 18 beds of sandstone. The sandstone layers range in thickness from 8 to

12 feet but average 5 feet <tl0

Coal 1 2

Sandstode 15

Shale 25

Sandstone 7

Shale 8

Sandstone 80

Shale 125

Sandstone 35

Shale 1

Coal 1 4

Shal0 1 2

CoBl 1

Shale and sandstone 10

Coal 1 1

Shale 26

Sandstone 12

Shale 1

Coal 1

Shale 20

Coal 1 1

Shale 2 6

Sandstone 1

Coal . 2 2

Shale 2

Coal 2 1

Sandstone and shale 10

Coal 2

Shale and sandstone 5

Coal 1 2

Shale 21

1,076

COAL, IN SAlSr JUAN COUNTY, N. MBX. 166

Mesaverde group — Continued.

Point Lookout sandstone : Ft In.

Sandstone 82

Shale, sandy-w — , 16

Sandstone, with some layers of thin sandy shale. 252

Total Mesaverde group 2, 126

Mancos shale.

Section of Mesaverde group in T, 29 N,, R. 16 W., where Chaco River cut$ the

Great Hogback.

[Measured by C. M. Bauer.] Lewis shale. Mesaverde group:

Cliff House sandstone: Ft in.

Shale and sandstone 60

Sandstone, brown, pitted 18

Shale, yellow, sandy 8

Sandstone, light gray, pink in places 6

Shale, blue and gray 1 5

Sandstone, yellow, massive in upper part, carry- ing a few thin beds of shale; Halymenites

major in lower part 318

Shale, sandy, interbedded with yellowish sand- stone layers, each 1 foot thick 133

Sandstone, reddish brown, hard 10

Shale, Wue-gray 40

Sandstone, massive, thin bedded on top, massive and nearly white below 25

Menefto formation :

Shale, blue and gray, interbedded with lenses of buff sandstone. Shale beds are carbonaceous

and contain thin streaks of coal 900

Sandstone, massive, light gray 20

Shale, gray; contains beds of sandstone 1 foot

thick . 80

Sandstone ligjit gray, massive 12

Shale, blue-gray, containing several carbona- ceous streaks 92

Sandstone, massive 20

Shale, drab 6

Coal 10

Shale, carbonaceous, black 8

Shale, blue-gray, containing carbonaceous

streaks 246

Sandstone, gray 10

Shale, gray 8

Coal 8

ShalQ, gray 7

166 CONTBIBUnONS TO ECONOMIC GBOIiOGTy IMO, PABT II.

Mesaverde group— -Oontlnaed.

Menefiee formation — Continaed.

Goal (moisture, 11 per cent; ash, 22 per Pt in.

cent) 2

Shale and sandstone with thin beds of coal which are burned out 126

1,132 10

Point Lookout sandstone:

Sandstone, light buff and cream-colored, mas- sive 67

Sandstone, buff to brown, weathering red-brown. 158 Shale and sandstone, thin bedded, yellowish gray 20

Total Mesa verde group 2,000 10

Mancos shale.

Lbwi8 8Kau.

The Lewis shale is of marine origin and is very similar to the shale at Fort Lewis, Colo., the type locality/ In Colorado this formation reaches a thickness of 2,000 feet, but in New Mexico it is thinner, being 1,100 feet thick 10 miles north of San Juan Biver 475 feet thick on San Juan River, and decreasing further in thick- ness southward as far as Coal Creek, where it is 76 feet thick. It in- creases again to 103 feet on Meyers Creek and 140 feet on Escavada Wash. The Lewis shale has the same lithologic characteristics throughout the field. It is a greenish-gray sandy shale with local streaks of yellowish calcareous shale. On San Juan River it has also a prominent layer of buff limy concretions about 100 feet above its base.

PIOTiniED 0LIFF8 BAHDBTOirE.

Overlying the Lewis shale conformably is the Pictured Cliffs sand- stone, of near-shore marine origin. There is no sharp line separating this sandstone from the underlying Lewis shale, but the shale be- comes more sandy upward and passes into the sandstone by insensible gradations. Considered in a general way, the Pictured Cliffs sand- stone is very different from the beds beneath. As the name indicates, it is a cliff-making sandstone, particidarly on San Juan River imme- diately west of Fruitland, where it forms prominent oopper-colored cliffs 20 to 40 feet high. Farther south it is a yellowish to light-gray or brown sandstone and not so massive. The formation is variable in -thickness, owing in part to the nature of its boundaries. It is 200 feet thick near the State boundary, 187 feet 6 miles farther south, from 200 to 220 feet 6 miles north of San Juan River, 245 feet on the river, 49 feet on Brimhall Wash, 91 feet on Meyers Creek, and 70 feet on Escavada Wash.

CroB, Whitman. U. S. Geol. Survey Gool. Atlas, La Plata folio (Aow eO), ISM.

B. CHARACTERISTIC WEATHERING OF VARIABLE SANDSTONE OF THE FRUITLAND FORMATION, MEYERS CREEK, N. MEX,

Coal In San Juan County, N. Hex, 167

nVXTLAVB FOBKATzbv.

Confonnably above the Pictured Cliffs sandstone lie the brackish and fresh water beds of the coal-bearing Fruitland formation. The contact, like that between the Lewis shale and Pictured Cliffs sand- stone, is gradational. The name Fruitland is derived from that of a settlement on San Juan Biver that is on the outcrop of this forma- tion. The formation consists of sandstone, shale, and coal, very irregularly bedded. In constitution the various beds range from shale to sandstone with every conceivable intermediate phase of sandy shale and shaly sandstone. The marked variation both lat- erally and vertically is shown in many places by the imequal resist- ance to weathering and consequent production of fantastic assem- blages of pillars, knobs, mushroom rocks," and other forms. (See Pis. XX and XXI.) This irregularity is most marked in the gray- white sandstone and gray sandy shale, but it affects to some degree the coal beds also. Nevertheless, although the coal beds are lenticular, they are much more persistent than the individual sandstone and shale layers with which they are associated. Some of the coal beds have been traced along their outcrops with considerable certainty for 15 or 20 miles and are of sufficient thickness and good enough quality throughout to be of commercial value when transportation facilities become available. The coal beds are distributed through- out the formation but are more abundant and generally thicker in its lower portion. They are described in detail in the later pages of this report. The Fruitland formation is further characterized by the presence of large concretions of iron carbonate which weather dark brown or black. Many of these concretions have been con- verted by veins of crystallized barite into large septaria. The Fruit- land formation is more sandy than the lower part of the Kirtland shale, from which it is separated by a gradational zone marked in many places by sandstone lenses apparently of river origin. The thickness of the Fruitland formation varies somewhat in this field, ranging from 196 to 416 feet. It is thicker in the northern part of the area than in the southern part. (See sections, PL XXII.) The following sections of the Fruitland formation are given to illustrate its character and the thickness and position of the coal beds :

Section of the Fruitland formation on divide between La Plata and San Juan

rivers, Kirtland shale.

Fruitland formation: Ft. in.

Shale and sandstone 80

Sandstone 5

Shale 20

Sandstone 10

168 CONTBIBITnONS TO ROONOMIC OSOLOGT. 1990, PABT n.

FraitlEDd formation — Continued. Ft. in.

Shale, carbonaceous in part 80

Coal, high in ash 1 6

Shale, carbonaceous 2 6

Coal 8

Shale, carbonaceous 6

Coal 5

Shale, carbonaceous 2 3

Coal 1 2

Shale, carbonaceous 10

Coal 7

Shale, carbonaceous 1

Coal 2

Shale, carbonaceous 9

Coal 7

Shale, carbonaceous 8

Coal 6

Shale, carbonaceous in part 75

Coal, with many shale and bone partings ( see sec.

32, PI. XXVI, for details) 14 2

Shale, sandstone, and some concealed intervals 125

Coal 2 6

Pictured Cliffs sandstone.

Section of Fruitland formation on San Juan River,

Kirtland shale.

Fruitland formation: Ft. in.

Sandstone, gray, fine grained, irregularly bedded 7

Shale, gray to black; contains fragments of carbon- ized wood and is streaked with limonite 8

Shale, light gray to drab, with limonite streaks ;

sandy in lower portion 11

Shale, very sandy, light grtiy to buff 12

Sandstone, buff, friable ; contains concretions of light- gray fine-grained sandstone 15

Shale, drab, sandy 1

Shale, brown, carbonaceous; contains plant frag- ments 2

Shale, light gray, very sandy, with streaks of pearl- gray calcareous shale and drab platy concretions— 14 Shale, dark brown, carbonaceous ; contains plant frag- ments and g3i)sum in small flakes 7

Shale, light gray to drab 10

Sandstone, platy, fine grained, very light greenish

Shale, light gray, sandy, locally carbonaceous 15

Shale, dark brown, carbonaceous ; contains thin lenses

of bone 6

Sandstone, very light gray, fine grained, carbona- ceous 18

Shale, gray to drab, with carbonaceous bands which are burned locally (probably coal beds elsewhere). 80

Goal In San Juan County, N. Mbx. 169

Fniltland formation — Continue. Ft fa. Sandstone, light gray, fine grained; contains lenses of carbonaceous shale ; sandstone is gray to white,

cross-bedded, and locally stained brown 25

Shale, brown to black, carbonaceous 3

Coal I 8

Shale, brown, sandy 6

Bone 5

Coal, good 1

Shale, buff, sandy 5

Coal and bone in thin lenses 9

Shale, carbonaceous, black 1

Coal; contains resin 3 7

Shale, sandy, gray and carbonaceous in places 3

Coal, impure , — 4

Shale, gray, sandy 1

Bone 6

Shale, gray, sandy 1

Coal, impure 1 4

Shale, gray, sandy 3

Coal, impure 2 11

Bone 4

Shale, gray, sandy 1

Bone 5

Shale, carbonaceous 3

Shale, clayey and carbonaceous 2 3

Bone 3

Shale, brown 5

Coal 4

Shale, sandy, brown 1 5

Shale, light gray, sandy 2

Sandstone, greenish, cross-bedded 3 6

Shale, brown 1

Sandstone, nearly white 6

Coal 6

Sandstone 1

CoaJ 6

Pictured Cliffs sandstone. .

246 61

Section of FnUtland formation on Cottomaood Arroyo.

Kirtland shale.

Fruitland formation: Ft. in.

Sandstone, brown, platy 13

Shale, sandy, gray 31 6

Sandstone, brown, cross-bedded, concretionary 5

Sandstone; contains concretions of iron carbonate 4

Sandstone, irregularly bedded and unequally in- durated 8

Shale, gray, sandy, concretionary 28

Coal 10

Shale, sandy 1

CoaU 5

Sandstone, carbonaceous 1

154071*— 21— BuU. 716 -12

170 Contributions To Economig Geology, 19, Fabt Il

Frultland formation — Continued. Ft. lik

Coal 6

Sandstone, carbonaceous 6

Coal 2 2

Shale, carbonaceous 1

Shale, gray 15

Sandstone, buff to gray, cliff -forming 20

Shale, carbonaceous 10

Shale, gray 85

Sandstone, gray, easily eroded 11 9

Coal 1 7

Sandstone 8

Coal X 2 1

Shale, carbonaceous, brown and gray 12 ft

Sandstone, gray; contains lime concretions 4

Shale, sandy 8

Shale, brown, carbonaceous 10

Bone 3

Coal, impure 8

Sandstone 1

Coal 8 S

Bone 2

Coal 11

Shale, carbonaceous 6

Sandstone, nearly white, soft, cross-bedded, streaked

with llmonite 15

Shale, gray, sandy 2

Coal, impure 1 T

Ash (from burned coal) 5

Shale, gray 7 ft

Ash (from burned coal ) 1

Shale, bluish gray, sandy 16

Sandstone, nearly white, soft; contains streaks of llmonite i Inch thick and in places irregular masses

of brown cross-bedded sandstone 25

Coal ft

Shale, blue-gray, sandy 15 0

Sandstone, shaly in places, light colored, platy 12

Shale, carbonaceous 4

Coal 8

Shale, sandy 5 4

Coal 2 7

Shale 1 6

Bone 5

Shale, sandy, carbonaceous 8

Pictured ClifCs sandstone.

328 0

Section of Fruitland formation on north fork of Meyers Creek,

Kirtland shale.

Fruitland formation:

Sandstone, soft gray at base, capped by hard brown

coarse-grained layers 4

Shale, gray, sandy, streaked with yellow; occasional lenses of sandstone containing iron concretions 42

U. 8. 6B0L0Gicajl

Feet

s

Bulletin 716 Plate Xxh

Explanation

Coal

Shale

Sandstone

C25) Figures alon coal beds refer to detailed secikme

COLUMNAR SaiiNG OF THE FORMATION SOUTHWARD

Coal In San Juan County, N. Mbx, 171

Fniitland formation — Continiied. Ft in.

Shale, black, carbonaceous 6

Shale, gray, sandy, banded with yellow, locally a soft

gray sandstone, concretionary 10

Shale, light gray, sandy 25

Shale, dark brown, carbonaeeous 8

Shale, gray, with iron concretions and barite 5 6

Shale, black, carbonaceous 6

Sandstone, yellow, clayey 4

Shale, dark brown, carbonaceous 1 6

Sandstone, clayey, gray, streaked with yellow; con- tains brown platy concretions of coarser sandstone

and some aragonite concretions 12 6

Coal 2

Sandstone, black, carbonaceous 6

Bone 1

Shale, sandy; contains brown and gray lenses of sandstone and ferruginous concretions with barite

and lenses of carbonaceous shale 32 6

Sandstone, soft, gray with brown streaks, cross-bedded

and platy at top 6

Shale, brown, carbonaceous, locally sandy 3 3

Coal, impure jt 11

Bone : 4

Coal, impure 1 2

Bone, sandy 3

Coal 4

Bone, sandy ; contains lumps of resin 1 1

Coal, impure, with resin 1 7

Shale, gray and yellow, sandy 10 6

Shale, gray, sandy, and lenses of yellow sandstone,

concretionary 10

Sandstone, light gray, fine grained, unequally in- durated ; contains dark-brown sandstone concretions. 7

Shale, dark brown, carbonaceous 6

Shale, dark gray ; contains iron concretions locally 5

Sandstone, light gray, cross-bedded; contains iron concretions with barite ; grades laterally into shale. 7 6

Bone 6

Coal 7

Bone 5

Coal, impure 2

Shale, black, carbonaceous 2 10

Coal, impure . 5

Bone, sandy 1

Pictured Cliffs sandstone.

196 1

Kibtlahd Shale.

The Kirtland shale, named for a post office on San Juan Biver, lies conformably upon the Fruitland formation. It is composed mostly of gray shale, with some brown and black carbonaceous layers, bluish, greenish, and yellowish shales, easily weathering gray-white sand-

vidiiiii li'us will tiMUillv have a maximum thickness of 20 feet and 8 k-nfh of several hundred yards.

The upper part of the Kirtland shale is a thin unit, ranging from 40 to 110 feet in thickness, and is composed of shale and eaalj weatliered gray-white sandstone lenses, very similar to the lower shale unit but can-ying in many places relatively high-colored layers of yellow, blue-gray, and purple shale. Its persistence throughout the. lield is believed to signify a lack of erosion and consequently a -small or even no time interval between the deposition of the Kirt- land shale and that of the Ojo Alamo samistone."

Ojo Alako Sakdeioite.

The Ojo Alamo sandstone," composed of white, gray, or brown L-onglomerate sandstone with lenses of soft whitish sandstone and frniy or dral> shale, overlies the Kirtland sliale with apparent con- formity. The contact is at many places sharp and well marked, but at other places it is difficult to determine just exactly where in the

" Kee footQOH- '". p. 17,1.

*For n more mmplcte description ot tbis sandstone nee Baar. M.. StraUsT*pl>T of a port of llie Caco RlTor valley : V. 8. Geol. Surrey Prof. Paper 8, pp. 27B-27, 191S.

GOAL IN SAN JTJAN GOtJNTY, H. MEZ. 173

section the formation boundary lies. There does not seem to have been any considerable amount of erosion before the Ojo Alamo sandstone was laid down in the area covered by this report. The Ojo Alamo sandstone is of fiuviatile origin. In southern San Juan County it ranges from 60 to 129 feet in thickness. Farther north it increases to nearly 400 feet.

In Colorado the volcanic Animas formation lies above the Lara- mie formation " of older authors, which is equivalent to the Pictured Cliffs sandstone, Fruitland formation, and Kirtland shale, inclusive. The relation of the Animas formation to the Ojo Alamo sandstone is not yet known.**

Piteboo Astd Tobeejov Vobxatiovb.

The Puerco and Torrejon formations are very similar lithologi- caUy, and their respective faunas are limited to a few narrow but widely separated zones. No mappable plane of separation between them has yet been recognized, and the formations are therefore mapped and considered together. The Puerco formation every- where rests with imeven base on the Ojo Alamo, and it is believed that the contact is an unconformity, though the amoimt of erosion was not great.

At the head of Escavada Wash the lower 250 feet of beds is com- posed of lenticular light and dark gray shales with bands of pur- plish, bluish, black, and rarely claret-colored shale and of soft gray- white sandstone. This part carries Puerco fossils in its lower strata. It is overlain by 600 feet of lenticular cream-colored to yellow and brown, more indurated sandstone with reddish-brown concretions. The sandstone beds are separated by greenish-gray and lead-gray shales and some soft white sandstone. Fossils are very scarce. The upper 450 feet of beds includes very dark slate-colored shale with two prominent and several fainter red bands and also soft gray- white sandstone. This upper part contains Torrejon fossils.

Near Ojo Alamo the Puerco and Torrejon are only 890 feet thick. The lower 140 feet is composed of much the same material as the lower part on Escavada Wash and carries Puerco fossils near the. base. The overlying 250 feet consists of gray shale with bands of brown, greenish-gray, and dark slate-colored shale, soft gray-white sandstone, and some layers of more resistant yellow and brown sand-

Field work done by the Janlor author In 1920 has shown that a thlnnlnir wedge of tbe AnlmaA formation extends as far sonth as San Joan River. The Ojo Alamo sandstone extends northward upon the Animas wedge as far as T. 31 N., R. 13 W., where Puerco or Torrejon beds rest directly on Animas beds. The base of the Animas wedge in New Mexico is apparently conformable, though in Colorado it is clearly unconformable on the Kirtland shale. Southeast of Escavada Wash the OJo Alamo sandstone U also clearly unconformable on Kirtland shale, and it is likely that both Animas and OJa Alamo belong with the later rather than with the earlier beds. A full discussion of these new data wUl be glyen in a paper now in preparation.

174 C0Ntribx7Xi0Ns To Eookomig Gboloot, 1M>, Part Il

Stone. This upper part bears Torrejon fossils. Layers and concre- tions of dark-green to black manganitic sandstone and concretions of barite occur abundantly in the group, also thin layers of a dense cream-colored flintlike material that is full of plant stems. Silici- fied wood is common.

On San Juan River at and above Farmington* the Ojo Alamo sandstone is overlain by a succession of white to buff, in places rusty- brown sandstones which carry lenses of pebbles and are separated by light-gray, dark-gray, and brown-banded shales. Layers of fine green sandstone and a dense flintlike material are common, as is also silicified wood. The material in many respects is different from that farther south and contains very few fossils. By its position in the section and the fact that it dips eastward under beds containing Torrejon fossils, it is shown to belong to either the Torrejon or the Puerco formation, although direct connection with the southern ex- posures can not be traced. In the country north of San Juan Biver the Puerco and Torrejon formations have much the same character as on the river and reach a thickness of 1,400 feet.

The fossils of the Puerco formation and the Torrejon formation differ enough to indicate the lapse of a long period of time during which there may have been erosion, now represented by an uncon- formity, but there is little indication on the ground of such a break

Fobkatiov Vvdetebkived.

In the southern part of San Juan County the beds containing the Torrejon fauna are overlain by a banded deposit, 250 feet thick, of dove-colored shale, lighter-gray sandy shale, and soft white sand- stone. A few reddish bands occur near the top, and rarely dark shale is present. One or two more resistant light-gray sandstone lenses carrying pebbles were observed. No fossils were found. The lower boundary of this unit is a clean-cut line with marked irregu- larities. In its lithology and position the unit suggests strongly the beds in southern Colorado recently described by Granger' as the Tiffany beds. These beds at the type locality carry a fauna inter- mediate in character between those of the Torrejon and Wasatch formations and reach a thickness of at least 300 feet.

In the map by the senior author published as Plate LXIV of United States Geological Survey Professional Paper 98 these beds in the district southeast of Chico Springs are shown as within the

*The rocks now referred to the OJo Alamo sandstone and overlylnsr beds on San Juan River were assigned by the senior author to the Wasatch formation on a map poUlshed as Plate 64, U. S. GeoL Survey Prof. Paper 08, 1916. Later and more detailed work faither east has shown that this assignment was in error. It is probable that no true Wasatch beds occur in the territory shown on that map.

Granger, Walter, Notes on Palcocene and lower Eocene mammal horisons of northern New Mexico and southern Colorado : Anu Mas. Nat Hist. Bull., vol. 27, pp. 821-S30, 1917.

Coal, In San Jtjan County, N, Mbx. 176

Wasatdi formatioiL, but later work has suggested the desirability of Beparatifig them from the true Wasatch of the region.

Wa8At0K Vobxatiov.

At the southeastern extremity of the field the highest rocks ob- served comprise a very massive, cliff- forming copper-red basal sand- stone with lenses of pebbles which is about 50 feet thick, overlain by 150 feet of light-gray and red shales and soft white sandstone, over- lain in turn by another prominent cliff-forming sandstone similar to the first. The basal contact of the lower sandstone is not notice- ably irregular. No fossils were observed in these beds. The Wasatch formation farther east has been described by different observers as consisting of a basal conglomeratic sandstone overlain by a succes- sion of shales and sandstones with marked coloring. The writers have not traced te horizons, but there would seem to be little doubt that the rocks at the head of Escavada Wash are continuous with the CoryphodoTirheBxing Wasatch of the southeastern part of the San Juan Basin.

Age Op The P0Bmati0Ns.8

The Mancos shale typically contains invertebrate faunas of Colo- rado age in the older part and of Montana age in the younger part. Only Montana species were found in the small area of upper Mancos shale examined in this field.

The Mesaverde group has a flora and an invertel;)rate fauna of Mon- tana age.

The Lewis sdiale and the Pictured Cliffs sandstone likewise contain invertebrate faunas of Montana age, though with elements not known in the latest Montana faunas, such as that of the typical Fox Hills sandstone.

The Fruitland formation and Kirtland shale contain a homoge- neous flora and vertebrate and invertebrate faunas. The flora is of Montana age and closely related to that of the Mesaverde and allied formations of the region. The vertebrate fauna is entirely reptilian and of types known elsewhere only in beds of Montana age. The invertebrate fauna consists of fresh and brackish water forms, in the main of types known elsewhere only in post-Montana beds, though several of the brackish- water species occur only in beds of Montana age and several range from Montana beds into post-Montana beds. It seems most logical, in the light of present knowledge, to consider the Fruitland formation and Kirtland shale as of late Montana age.

The Pictured Cliffs sandstone, the Fruitland formation, and the Kirtland shale together make up the 'Laramie formation" of the

For isef erenoeg to literature ee footnote, p. 161.

176 COKTRIBUTIOKS TO ECOKOMIG GEOLOGY, ld0D, PAST IL

older works dealing with the San Juan Basin* The Ojo Alamo sand- stone wa also included by some authors. There is still considerable uncertainty as to what part, if any, of the section in San Juan County is equivalent to the typical Laramie of northeastern Colorado.

The Ojo Alamo sandstone has furnished a few poor specimens of plants of little value in correlation and has supplied evidence of a considerable dinosaurien fauna. The only specimen complete enough to identify occurs also in the Kirtland shale. Other specimens are definite enough, however, to be recognized as unlike any known post- Montana species.* The abrupt appearance of conglcHnerate lenses and coarse sandstone in the Ojo Alamo, above the Kirtland shale, has been interpreted as marking a great change in conditions of deposi- tion, considerable lapse of time, and therefore a closer relation of the Ojo Alamo to the later formations than to the earlier, particularly as such a condition exists elsewhere in the general region.® However, there is little evidence of an erosional break at the base of the Ojo Alamo sandstone — the persistent thin upper shale of the Kirtland does not show it — and no other evidence of a time break in the succession except the change in lithology. The apparent relationship of the fauna woidd place the deposition of the Ojo Alamo sandstone in Mon- tana time, though it is not conclusive. This view demands a hiatus between the sandstone and the overlying Puerco formation to account for the interval represented elsewhere by the Laramie formation, which is of post-Montana age but still within the Cretaceous.**

The Puerco and Torrejon formations have furnished a small flora that is interpreted as of Tertiary age and a considerable vertebrate fauna. This fauna consists chiefly of primitive mammals and turtles but no dinosaurs and is unversally regarded as of early Tertiary age. The base of the Puerco formation lies on an irregular surface that shows the effect of some erosion, though not enough in this field to indicate by itself a long time interval. The Puerco else- where is said to overlap older formations, and certainly its fauna has nothing in common with those of older formations. The fauna of the Torrejon is of the same type as that of the Puerco but is dis- tinct from it and definitely advanced toward modem mammals.

The Tiffany beds of Sinclair and Granger at their type locality carry a fauna intermediate between that of the Torrejon and Wasatch. The beds in this field that may be equivalent to them occupy the same stratigraphic position and are similar in lithology but yielded no fossils by which to verify the correlation.

Gllmore, C. W., personal communication.

W. T. and Kziowlton, P. H., Geology and paleontology of the Raton Hcea and tlicr regions in Colorado and Nev Mexico : U. S. Geol. Survey Prof. Paper 101, p. 55,

Coal In San Juan County, N. Mbx. 177

The highest rocks in this field are correlated with the Wasatch of the region on the basis of stratigraphic position and lithologic simi- larity.

Coal.

Distbibutign.

Coal occurs in the Menefee formation of the Mesaverde group and in the Fruitland formation. There are also local deposits of lignitic material at the base of the Puerco formation, such as that prospected just south of Farmington, and reports are current locally of coal in higher formations. The writer studied in detail the coal of the Mene- fee formation only in a small area just north of San Juan River, and most of the following description will therefore be devoted to the coal of the Fruitland formation. The coaly material of the younger formations is of very little value in this general region and may be dismissed from consideration.

The coal beds of the Menefee formation are in two groups— one near thtop, the other near the bottom of the formation. The beds are lenticular and are variable in purity and thickness. Most of them are relatively thin, but at some places a considerable thickness of minable coal is present.

The coal beds of the Fruitland formation are scattered throughout the formation but are thicker and more persistent in the lower part* The thickest beds lie north of San Juan River, though the total amount of coal is large in some places south of that stream, notably at the mouth of Klaychen Arroyo. Locally extensive burning of the coal beds has taken place and their former positions are marked by red baked shale and clinker. The very thick coal bed low in the Fruit- land formation in northern San Juan County has been correlated with that formerly mined at Carbonero Junction, near Durango, Colo., but jextensive correlations are doubtful south of the San Juan. In the extreme southern part of the field the coal beds decrease in number, thickness, and extent, and the coal is of poorer quality than it is in the northern part. Owing to this tendency to deteriorate southward, the coal on Escavada Wash possesses very little economic value.

Cha&Acteb.

Phtsioal Pbopebties.

The coals of the Menefee and Fruitland formations are very simi- lar in character. Both are black with a bright luster and are hard and brittle and break readily in handling. They check and break

Shaler* M. K., A reconnaissance survey of the western part of the Durango-Gallap coal field of Colorado and New Mexico : U. S. Geol. Survey BuU. 316, pp. 392-398, 1906.

178 C0Ntbibt7Ti0Ks To Eookoboc Geoix>Qt, 1930, Past Il

on exposure to the air and sun but with some protection may be stored almost indefinitely. The suitability for storage is an impor- tant feature in estimating the value of a coal. Resistance to dete- rioration on exposure is the chief difference between bituminous and subbituminous coaL* The chemical differences, though well marked if the two classes are considered as entities, are small be- tween many high-grade subbituminous coals and low-ranking hi- tuminous coals. Subbituminous coal, owing to its larger percentage of moisture, breaks down or slacks " readily on exposure to weather and must be protected or it will disintegrate to a dust, whereas bituminous coal is relatively unaffected on exposure. South of San Juan River all the coal of the Fruitland formation and that of the Menefee formation away from the Hogback is subbituminous. Ib the Hogback and north of the San Juan the coal of the Menefee for- mation is all bituminous. North of the San Juan the coals of the Fruitland formation pass from subbituminous to bituminous in rank, but they are of somewhat poorer quality than the older coals.

All the coals of this field bum to a gray ash without clinker. Nothing is known of their coking qualities, though the higher-grade coals a little farther north, in* Colorado, are coked and used at the smelter at Durango.

The coal of the Fruitland formation at many localities contains a considerable amount of the fossil resin wheelerite, in the form of clear brown or yellow grains about the size of a pea. It has been mistaken for sulphur, though in coal sulphur does not occur as such, but in combination with the coal substance or with iron as the brassy minerals marcasite and pyrite (fool's gold). These minerals were not seen in this field.

OHSmCAL OHABAOTEB.

An analysis of a coal sheds much light on its value, though various properties not indicated by the analysis are important also — for exam- ple, resistance to exposure and suitability for storage and shipment without deterioration, behavior.in handling and resistance to break- age and production of fine coal, capacity for coking, fusibility of the ash, and presence or absence of clinker. Yet much may be learned of a coal from a knowledge of the percentages of moisture, volatile mat- ter (gases), fixed carbon, ash, and sulphur determined in what is known as a proximate analysis,'' the percentages of the actual ele- ments composing the coal determined in an ultimate analysis," and

For a dlBcassion of Uie damiflcation of coals see CampbelU R, The ooal fields of the United States — General introduction : U. S. Geol. Surrey Prof. Paper 100, p|k. MO, 1917 (Prof. Paper 100-A).

U. S. Geol. Surveys W. 100th Mer. Rept., vol. 3, pp. 630-631. 1875.

Ooal In San Juan County, N. Mbx. 179

the heating efficiency expressed in calories or British thermal units. Inasmuch as coal owes its economic value primarily to its ability to produce heat, the heating efficiency is perhaps the most important. As it is in a sense resultant of the chemical composition, the sum of all the other factors of the analysis, it is used (p. 181) as the basis of comparison of the coals of this field with those of other fields.

In the production of heat the volatile matter and the fixed carbon are to be OMisidered as the valuable constituents, and the moisture, ash, and sulphur as injurious constituents. Moisture and ash are inert, absorb part of the heat produced by other constituents, and re- place heat-forming substances in such proportion as they are present. Sulphur produces in burning objectionable and harmful gases.

The table on pages 183-187 shows analyses made by the Bureau of Mines of 15 sampled of coal from San Juan County and 15 from other fields for comparison. Twelve of the samples from San Juan County were obtained from local mines of the drift type and three from open pits representing the freshest and least-altered coal ob- tainable. The small amount of adherent moisture — that is, moisture which may be removed by drying — as well as of total water in most of the samples is probably due to the aridity of the climate and con- sequent low position of the water table during most of the year. The absence of water in and over the coal, however, has the effect of per- mitting freer access of air and the consequent weathering of the coal much farther back from the outcrop than where the beds are moist the year round. On weathering there is a loss of volatile matter and of heating value, as is shown by the analyses of samples 17750 and 29006, the former from a point 100 feet from the mine mouth, the latter 350 feet from the mine mouth.

All these samples were obtained by the regulation method pre- scribed by the Geological Survey and the Bureau of Mines, which involves selecting a representative face of the bed to be sampled ; cleaning the face, making a cut across it from roof to floor, and re- jecting or including impurities according as these are included or excluded in mining operations j reducing the gross sample, by crush- ing and quartering, to about 4 pounds; and immediately sealing 'the sample in an airtight container for shipment to the laboratory."**

The four forms of analysis given for each sample are not different determinations but merely four forms of one analysis. Form A is the analysis of the coal exactly as it comes from the bed. Owing to the fact that the original moisture content of a sample is largely a matter of accident and depends partly on the amount of water in and around the place from which it came, it is best for comparisons to use Form B, which is the analysis of the sample air dried under

A calorie 1b the amount of heat reqalred to raise the temperature of a gram of pure water centisrade at or near C. A British thermal unit is the amount of heat re- quired to raise the temperature of a pound of water Fahrenheit at or near 30* F.

Bur. Mines Bull. 22, p. 8, 1913.

180 Contributions To Economic Geology, 1920, Past Il

uniform conditions. Form C is the analysis of the sample after all moisture has been theoretically eliminated. Form D is also com- puted and is the analysis of the sample after all moisture and ash have been theoretically removed. Forms C and D are useful chiefly to engineers.

Five of the analyses represent the coal of the Menefee formation of this field, collected at locations 104 and 548 and at points near Tiznatzin and Putnam (Pueblo Bonito). (See PL XVI.) The coal, as represented by analyses 17750 and 29006, is very low in ash and sulphur and relatively high in heating value. Compared with coal mined at Durango, on the north side of the San Juan Basin (analysis 14772), it is lower in fiixed carbon and heating value and higher in moisture; compared with that mined at Gallup, on the south side of the basin (analysis 19135) , it is higher in heating value and lower in ash. The analyses of samples collected in southern San Juan County show that the coal there is not so good as that in the northern part, being relatively high in ash and sulphur and, as mined, in moisture. It is lower in heating value and about equal to that mined at Gallup.

Ten of the analyses represent the coal of the Fruitland formation, collected at locations 9, 10, 58, 61, 67, 69, 301, and 419. (See maps.) The coal of this formation is low in moisture and sulphur. Two samples show a high sulphur content, which is due possibly to the accidental inclusion of coal with adhering powder residue but pos- sibly also to some local variation in the coal. In ash this coal is uniformly higher than the older coal. The samples collected in the northern part of the field are as high in heating value as the older coal of the same area and higher than the older coal of the southern part. The samples collected in southern San Juan County are about equal to the Gallup coal, though as they come from shallow open pits they may not represent as high-grade coal as that under thicker cover at the same localities.

At present the coals of this field are mined only for local use and consequently come into competition only with that shipped in from Durango, Colo. Should better railroad communication with tlie north or south, or both, become available the question of competition with other coals of Colorado and New Mexico would become of great importance to one attempting the development of mines in the San Juan field. If a railroad were built into the field from the south anv coal mined here would have to compete directly with coal mined in the vicinity of Gallup and indirectly with that of the Raton field, in Colfax County. If better railroad connection were made with the main line of the Denver & Rio Grande Railroad on the north, the local coal would have to compete with the Colorado coals mined near Porter and Hesperus, La Plata County ; near Somerset and Crested

C50Al In San Juan County, N. Mbx.

Butte, Ofumison County ; and near Newcastle and Sunlight, Garfield County; and with the Utah coals mined at Thompson, Sunnyside, and Castlegate. If facilities for shipping coal to the East were improved the local coal would have to compete with coal of the Trini- dad and Canon City fields, east of the mountains, and possibly with the subbituminous coal of the Boulder region, which is an important factor in the Denver market. Analyses of representative samples from all these fields are given for comparison on pages 185-187, but the sample from Crested Butte does not represent the highest-ranking coal of that field, for even anthracite is found there.

Other elements entering into value being disregarded, it is of in- terest to compare the coals of San Juan County and other fields on the basis of their heating value (1) as they come from the mine, (2) air dried, (3) with the deleterious moisture and ash theoretically removed. The first condition is perhaps the nearest to the average coal actually purchased by the consumer; the second avoids the accidental dif- ferences due to the local conditions in the mine, drying in storage and shipment, etc ; the third shows how much of the difference in heating value is really due to difference in the pure coal substance. In the following table, for simplicity in comparison, the best coal of San Juan County is taken as having a value of 100, and the heating values of the other coals are expressed in proportionate figures :

ComparaiUje heating values of coals of San Juan County and other fields.

Ban Jvam County.

1. Menefee lonxiatian, northeni part

2. Fniitland formation, northern part,bltu-

minoos

1 Fruitland formation, northern part, sub- bituminous

4. Fruitland formation, southern part

6. Menefee formation, southern pcut

OTHER nSLOS.

fti Duranco. Colo

7. Crested Butte, Colo. 8.Ca8tIef!ate,Utah 9. Trinidad, Colo

10. Hesperus; Colo

11. Koehler. K. Mex. . . .

12. Sunnyside, Utah

13. New Castle. Colo.. . .

14. Somerset, Colo

15. Sunlight, Colo

16. Thompson, Utah. . .

17. Canon City. Colo. . . .

18. Qalhip.N.Mex

19. Lafiiytte, Colo

Analy- sis

Na

As mined.

British

thermal

units.

12,010

11,720

U,140 10,360 10,130

13,710 13,430 13,060 13,000 12,670 12,620 12,620 12,620 12,430 12,420 11,720 11,420 11,100 9,940

Ratio.

AlKlried.

British

thermal

units.

12,270

12,060

11,570 11,020 11,090

13,990 13,620 13,200 13,060 13,170 12,870 12,810 13,090 12,650 12,810 11,950 12,120 11,770 11,080

Ratio.

Ash and mois- ture free

British

thermal

units.

14,020

14,880

13,950 13,680 13,300

15,220 14,960 14,430 16,270 14,550 14,960 14,490 14,400 14,600 14,470 14,210 13,710 13,940 13,120

Ratio.

a See table of analyses on pp. 185-187.

b Average of analyses 17749, 29249, 29250.

c Average of analyses 22026, 29025, 2464, 22506, 22509.

d Average of analyses 22685, 22807.

e Average of analyses 3811, 23003, 23004.

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188 CONTRIBUTIONS TO BOONOBnC GEOLOGY, 1920, PART H.

The sections of the coal beds at the points sampled, except those shown below, are given in the plates of graphic sections, and the parts included in the sample are marked by an asterisk.

Section of coal beds in Tiznatzin mine, on Coal Creek 2 miles above mouth, in

T. 2S AT., R. U ir., unsurveyed. . '

[Analysis 3811.] Sandstone. . Ft in.

Coal 1 8

Bone 5

Coal 3 2

Shale.

5 S

Section of coal heda in Pueblo Bonito mine, 1 mile southwest of Putnam {Pueblo

Bonito), in T. 21 N., R. 11 W.

[Analysis 28004.]

Sandstone. Ft In.

Bone 2

Coal* - 2 8

Bone, sandy 6

Coal 1 7

Shale, carbonaceous 2 6

Coal, impure 2 4

Shale.

Section of coal beds in Blake's mine, sec. 13, T. 22 N., R, IS W.

[Analysis 23008.] Sandstone. Ft in.

Coal 1 7

Shale, carbonaceous 1 1

Coal - 1 5

Sandstone.

A8H Tx8T8.

Tests were made in the field of the ash content of samples from a number of beds, and at the same time note was made of the air-dry- ing loss. The tests were made with a small portable outfit, devised by C. E. Lesher.* Samples collected at locations 140, 145, 154, 155, 230, 235, and 545 represented beds or benches of coal whose purity was uncertain and whose value the geologist wished to know in the field. The other samples were tested as representative of the coal at the outcrop. Each sample for the ash test was taken from a clean

Lesher, C. B., Field apparatus for determining ash. in coal : U. S. Oeol. Survey Bull. 621, pp. 1-12, 1016.

COAL IN SAN JUAN COUNTY, N. BflBX.

face of the bed by picking off, as nearly as possible, an even amount from all parts of the face so as to obtain a fair representation of the character of the bed.

The high ash content of samples from locations 158, 167, 224, and 231, as compared with that of samples from mines, would seem to in- dicate the presence of some foreign material in the weathered part of the coal bed, possibly mineral salts deposited by the evaporation of ground water.

A$h tests of coal from the Menefee formatUm,

LoeaUon 145.

Section.

Ash (per cent).

MoistiirB (percent).

Shale.

CoaL

Ft. in,

n.i

Shale.

Location 2S5.

Shale.

Coal, bony 1 7

Bone. 4

Shale. 1 11

Ash tests of coal from the Fruitland formation.

Location 140, NaTio nine, aoi aide of San Joan Rhrer.

Section.

Ash (per cent).

Moisture (per cent).

Shale, carbonaceous.

Coaly bony

Ft. in.

Shale, sandv

Bone.

CoaL

Shale. . . X . . . a

Coal and bone

Shale, carbonaceous

fioal . iTni>™pp - - . - T - .

..: 3 7

Shale, sany . r ... r .

Coal, immire

Shale, sanc'y

Bone

Coal

Shale, sandy

Coal.immire

Bone

Shale

Bone

Shale.

Location 1S4.

Shale, carbonaceous.

Bone 2 5

Shale, carbonaceous.

190 OOHTBIBUnOir S to EOOKOMIG GBOUyOYy 1930, PAST n. Ash tetts of coal from the FruitUutd formation — Gontiiiued.

w.

SecUon.

Ajh

(per cent).

(per cent).

ShAtet bteek, carbcmAceoin. Bone

FLin.

Coal

s

Bone

Shale

Coal . im Dure

Rhftlfi

Coal

Rhale

&

Bme

::

las

Coal

Bone

CoaL

Bliale.

Bhale . carbonaceoas.

C6al

Bone

Sandstone.

Shale.

SandBtoDe.

Coalytmpnre 7

Shale 3

Bone 1 10

Sandstone 5

Coal, bony 1 2

Shale 1 4

Coal, bony 2 10

Shale.

Location 153.

Shale, carbooaoeoos. CoaL

Shale.

Location 167.

Shale.

Bone 7

Coal, impure 3 8

Bone 1

bandstone 1

Bone 1

Coal 8

Bone and shale 3

Coal 2 2

Shale 1

Coal 1 0

Bone 2

Shale.

&3

Coal In San Juan County, N. Mex. 191

Ah teU of coal from the Fruitland formation — Continued.

Locmtioa 224.

Section.

Shale, carbanaoeoiu. Ft. in.

Coal, impore 2 7

Sbale, carbanaoeoiifi 1 5

Bone 4 5

Shale.

Ash (per cent).

Mdstare (percent).

Location 231.

Sltale, carbanaoeons.

Coal, impure 3

BanoBtane 1

Coal, impure 3 8

Bone 2

CoaL 11

Shale.

17.7 3.8

Quantity Of Coal In The Fbuitland Fobmation.

By asHiiming that the average conditions at the outcrop of a coal- bearing formation persist in depth it is possible to estimate the amount of coal present. The value of the estimate of (x>urse de- pends on the amount and character of the information available. Where good contour maps of the field exist and the position, dip, and thickness of the coal beds and overlying strata are known, fairly ac- curate estimates may be made. Where less detailed information is at hand, more assumptions are necessary, and the result is of course less exact. The method used depends on the chaiucter of the coal beds, their attitude with reference to the surface, and the topography of the field.

In estimating the amount of coal in the Fruitland formation of San Juan County only the area under which the coal is not deeper than 1,000 feet was considered. This area was divided into a number of narrow strips running perpendicular to the outcrop, the total thickness of coal at the outcrop and the area were obtained for each strip, and on the assumption that an acre- foot contains 1,800 tons of coal the tonnage was calculated for each strip. The sum of these amounts gives the coal beneath 1,000 feet or less of cover as 16,288,000,000 tons and the total area underlain as 747 square miles.

It must be remembered, however, that these figures represent the total amount of coal and not necessarily the amount that may be mined. The recoverable amount is variable, depending upon mining practice and the care exercised in extracting the coal. As it is prob- able that the percentage of recovery will constantly tend to get

192 Contributions To Econobcic Geology, 1920, Part U.

nearer and nearer 100, it is not thought wise to make an estimate on that basis.

Another estimate was made by taking an average of the total thickness of coal exposed at a number of places on the outcrop, the figure for each place being weighted by multiplying it by the sum of half the distances to the two adjacent places. The average thickness thus obtained (21 feet) was then multiplied by the total area underlain by the coal beds and the product reduced to tons. The resulting figure was 18,069,000,000 tons. This method does not take into account the relatively small size of the 'area underlain, within the depth limit, by the thick coal beds of the northern part of the field, and the estimate is therefore larger than that obtained by the first method.

The figures given above include all the coal beds observed. As some beds undoubtedly are not exposed and escaped observation, the estimate is not unwarrantedly high for the total coal content. Per- haps one-third of the coal represented in the estimates is in beds less than 14 inches thick and is therefore of small value under present economic conditions. Furthermore, no account was taken of partings, which in some parts of the field considerably reduce the value of the thicker beds. Locally the partings make up a third or more of the total thickness, but on the average they are very much less than that amount. If a tenth is allowed, however, for these partings the amount of usable coal at a depth of less than 1,000 feet is still nearly 10,000',000,000 tons.

Sufficient data are not yet available concerning the area in which the coal lies deeper than 1,000 feet to estimate the quantity, but it is probable that* between the depths of 1,000 and 2,000 feet at least as much coal is present as there is at a depth of less than 1,000 feet.

COAIi IN THE MEKEFEE FOSMATIOK OF THE MESAVEBDE GBOITF.

The Mesaverde group was examined in detail only in T. 30 N., R. 16 W., and small adjoining tracts to the east and south. Its upper boundary is elsewhere the limit of the field studied. However, sec- tions of coal beds were measured at several places south of San Juan Biver, samples of the coal were obtained for analysis (see table, p. 183), and where Chaco River cuts through the Great Hogback a sec- tion through the entire group was examined. These data are con- sidered below.

Goal In T. 80 V., B. 16 W.. Ahd Adjacent Tba0T8.

The coal beds of the Menefee formation in T. 30 N., R. 16 W. (H. XXIII), are in two groups, one near the top and the other near the base. This grouping is well shown in the section on San Juan Biver. (See p. 163.) Individual beds in both groups are lenticclar, though

Coal. In San Juan County, N. Mex. 193

some may be traced for several miles along the outcrop, and one was followed for nearly 6 miles. Some beds show in places a consider- able thickness of clear coal, the maximum observed being 11 feet 6 inches, though as a whole partings are numerous and the value of the beds is thereby lessened.

The only mine in the township is that at location 104 (see PI. XXIII), which supplies the Indian school and agency at Ship Eock. Production is limited to the needs of this institution. The coal bed mined here is 6 feet 2 inches thick and without partings.

The lower group of coal beds includes at most points two major beds, also some short lenses and locally a number of thin beds of small value.

Near the north side of T. 80 N., R. 16 W., and in R. 15 W. two sections were measured on a short but valuable lens of coal. At loca- tion 71 it is 3 feet 6 inches thick with a streak of coal above and another below it, and at location 72 it is 7 feet 8 inches thick. (See PI. XXIV.) The bed thins out north and south of these locations.

In sec. 10 two beds crop out whioh may be traced southwest- ward into sec. 29. The lower of these beds is represehted by sections at locations 88, 90, 94, 102, and 106. (See PL XXIV.) It has nu- merous partings and is not of high value. A short lens of small value 5 feet above the last-mentioned bed is represented by the sec- tion at location 106. The higher of the two beds, 20 to 25 feet above the lower, was examined at locations 89, 91, 95, 103, 104, 107, 108, and 109. The sections are shown on Plate XXIV. At location 89 this bed is split by 5 feet of shale into two thin beds, but the' shale thins southward and disappears, and at locations 95, 103, and 104 there is over 6 feet of clear coal. Location 104 is the mine of the Ship Rock ' Indian Agency, from which two samples have been taken for analy- sis. (See table, p. 183.) Farther south, at locations 108 and 109, the bed pinches down to about 2 feet of coal and is overlain by a thin, valueless lens. Neither of these beds can be traced farther south, though they may be connected with those shown in the section at location 122.

Above the higher bed represented by the sections at locations 91 and 95 a number of thin beds of small lateral extent are present. These are described in the following stratigraphic sections but are not shown on the map :

Section of strata above the higher bed at location 91.

Ft. In.

Sandstone 15

Shale, carbonaceous 10

CJoal 4

Shale, carbonaceous 3 6

Coal 8 6

194 Contributions To Economic Geolooy, 1920, Past H.

Ft, In.

Shale, carbonaceous 14

Coal 3 8

Shale, carbonaceous 4

Coal 5

Bone 1 6

Coal 4

Shale, carbonaceous 1 6

Coal 1 8

Shale, carbonaceous 10

Sandstone 8

Shale, carbonaceous 6

Coal bed of section 91, Plate XXIV. .

Total section 82 5

Total coal 9 11

Section of strata above the higher bed at location 95,

Ft in.

Sandstone and shale, yellow 15

Shale, carbonaceous 4

Coal 1 6

Shale, carbonaceous — 1

Coal — 1 1 1

Shale and sandstone 10

Coal r. 1

Shale and sandstone 30

Coal 1 3

Shale and sandstone 15

Coal 6

Shale and sandstone 10

Coal bed of section 95, Plate XXIV.

Total section 1 89 4

Total coal 4 4

A coal bod crops out in sec. 29 which may be traced southward to San Juan Biver. It is shown in sections at locations 122, 127, 129. 131, 133, 135, and 138. (See PI. XXIV). It is variable in thickness and purity, though locally, as at location 138, it reaches 5 feet in thickness and has few partings. At locations 122, 127, 131, and 138 it is overlain at a distance ranging from 4 to 6 feet by a thin bed of small value.

Beneath the bed represented by sections 122 and 138, and sepa- rated from it by 5 to 10 feet of shale, is a thin bed of coal which was examined at locations 128, 130, 132, 134, and 139. It is less than 2 feet thick in most of the sections. (See PI. XXIV.)

In sec. 29 the coal bed of section 122 is overlain by two lenses. The main bed at location 123 is separated by 12 feet of shale and sandstone from the first bed above, which is 8 feet thick. (See PI. XXIV). At 30 feet higher is the second lens, which is shown in the section at loca- tion 124 and is 3 feet thick at that point. These lenses can be traced laterally only a short distance.

u. s

Ft. t

Ft/m. iBi

in.

ft. in.

3 Z

I

Coal Impure (

N., San Jua

Coal In Sak Juan County, N. Mbx. 195

Above the higher bed of section 138 at the same locality several thin lenses are present, which are shown in the following section :

Section of strata above the higher bed at location 13S.

Shale. Ft In.

Coal 1 2

Shale and sandstone 246

Coal 4

Shale, carbonaceous 1 2

Coal 1

Shale and sandstone 10

Coal 1 X

Shale 26

Sandstone 12

Shale 1

Coal 1

Shale 20

Coal bed of section 138, Plate XXIV.

Total section 320 9

Total coal 4 7

The upper group of coal beds contains one rather persistent bed overlain and underlain by lenses of varying extent. In sec. 32, T. 30 N., and sec. 4, T. 29 N., practically no workable coal was observed in the upper part of the Menefee formation, though the exposures are very good.

The persistent coal bed of the upper group is represented on Plate XXIV by sections made at locations 74, 76, 79, 81, 83, 84, 86, 92, 96, 98, 100, llO-A, llO-B, llO-D, 111, 112, 113, 115, 116, 118, 120, and 121. It is the thickest and most valuable coal bed of the township. At location 74 it is either absent or represented by a layer of coal 6 inches thick. At location 76 it is 1 foot 1 inch thick; at location 79, 2 feet 10 inches; at location 81, 5 feet; at location 83 it thins to 2 feet. From this point it increases toward location 98, where it is 11 feet 6 inches thick and free from partings. Southward from location 98 it decreases in thickness and value, and at location 121 it is 3 feet 3 inches thick. Beyond this point it vanishes.

In sec. 5, T. 30 N., R. 15 W., the persistent bed is underlain by a lens which at location 73 is 4 feet thick, its maximum. (See PI. XXIV.) The intervening strata are 28 feet thick.

In sec. 6, T. 30 N., R. 15 W., the persistent bed is underlain by two lenticular beds, which were mapped, and several minor lenses. The lower bed, measured at location 77 (see PI. XXIV), is of small extent and 3 feet thick at its maximum. Ten feet above it lies the second lens, examined at locations 75, 78, 80, and 82. This bed in- creases from 2 feet 2 inches in thickness at location 75 to 4 feet 8 inches at location 80 and decreases to 1 foot at location 82. At location 75, between the bed shown in section 77 and that in section

can not be traced southward because of alluvial cover, but, to judge by other very variable beds, it is probably not extensive. Twenty feet below this bed at location 137 the following section was measured :

SeciioH of lenticular coal tied at location 137. Stiiile, carbonuceouK, snnJy. Ft. In,

Bone 6 0

Sliale, cLirbonncpous 2 6

Coal 1 0

Shiile. forboDflceous 1 0

Conl— 1 2

Shnle, carhouaceuus 4

Coal : 4

SliQle, CHrlwinnceoiiH, sanii)-.

Total section 18 0

Totitl coiil — - .- - 2 6

Coal South Of Ban Joan Eives.

A section of the Mesaverde group where Chaco River cuts through

the Great Hogback is given on page 165. This section exhibits very little coal. Only three thin beds are exposed, at locations 145, 146,

Coal. In San Juak County, N. Mbx. 197

and 147, in the zone covered by the lower group of beds. It seems possible that, owing to the abrupt folding of the strata, any coal beds present in the upper part of the Menefee formation have been squeezed out, though it is true that at some places north of the San Juan no coal can be found even where exposures are unusually good* The lowest coal bed at location 145 shows 2 feet of coal (moisture 11 per cent, ash 22 per cent). At location 146 there is 8 inches of coal, and at location 147 the coal bed is 10 inches thick. At all three of these locations the coal is overlain and underlain by shale.

Sections of coal beds and inclosing strata of the Menefee forma- tion at other places are given below. They all fall within the zone of the upper group of beds.

Section of coal beds at location 179, miles soutfieast of mouth of Ojo AmariUo

Arroyo.

Ft. In.

Sandstone, nearly white, easily weathered 45

Sandstone, buff, fine grained 18

Shale, light gray and yellow, sandy 18

Sandstone, buff, massive 56

Shale 2

Coal 3 5

Shale, brown, carbonaceous 2 2

Coal 3 4

Shale, blue-gray, with thin streaks of coal 26

Coal 3 5

Shale, blue-gray, with streaks of coal 18 6

Coal 3 7

Shale 12

Sandstone, massive.

Total section 209 7

Total coal 13 9

Section of coal beds at location 235, 5 miles tcest of mouth of Cottonwood Arroyo,

Ft, in.

Sandstone, massive, Ught yellow, weathering pink 65

Shale, gray, carbonaceous .' 15

Shale, gray 12

Coal 1 7

Bone - 4

Shale, carbonaceous 2 3

Coal, weathered 3 §

Shale, carbonaceous 8

Sandstone 4

Shale 6

Coal 2 8

Shale, gray 16

Sandstone, hard, platy 4 6

Shale, carbonaceous 3

198 Contributions To Economic Geology, 1920, Part H.

Ft. in.

Sandstone, forming cllflP 22

Shale, carbonaceous 3

Coal 1

Shale, carbonaceous 2

Sandstone, pink 14

Shale, gray, sandy 10

Shale, dark gray, containing several 3-inch beds of coal 5 6

Shale, black, carbonaceous 4 6

Coal 10

Shale, dark gray 61

Coal . - 3

Shale, carbonaceous 2

Coal '- 5

Shale, dark gray 18

Coal 10

Shale 12

Sandstone 15

Shale, gray, with carbonaceous streaks 21

Coal 1 5

Shale, carbonaceous 3

Sandstone 8

Shale, carbonaceous 4

Coal 1 2

Shale, carbonaceous 35

Sandstone 5

Shale, dark, carbonaceous 87

Shale and sandstone in alternating thin beds 195+

Total section 661+

Total coal 13 10

Section of coal bed at Tiznatzin mine, on Coal Creek 2 miles above mouth,

[Highest coal bed of Mesaverde gnonp.]

Sandstone. Ft. in.

Coal - 1 8

Bone : - 5

Coal, sampled 3 2

Shale.

(See analysis 3811, p. 183.)

Section of coal bed at location 548, at Blake*8 store.

Sandstone. Ft in.

Coal, sampled 1 7

Shale, carbonaceous 1 1

Coal, sampled 1 5

Sandstone.

(See analysis 23003, p. 183.)

Coal In Sak Juak County, N. Mbx. 199

Section of strata at location \549j on Meyers Creek 1 mile above mouth.

Ft. In. Cliff House sandstone 360

Menefee formation:

Shale, brown, carbonaceous 14

Coal, Impure 1 e

Shale, brown, carbonaceous 40

Sandstone, brown 15

Shale, carbonaceous 12+

451+

Section of coal bed at Pueblo Bonito mine, 1 mile west of store at Pueblo Bonito,

[Highest coal bed of Mesaverde group.]

STandstone. Pt. in.

Bone 2

Coal, sampled 2 8

Bone, sandy 6

Coal, sampled 1 7

Shale, carbonaceous 2 6

Coal, Impure 2 4

Shale. :

(See analysis 23004, p. 183.)

Another section of the bed represented by the last section, taken at a different point in the same mine, shows the following :

Section of coal bed at Pueblo Bonito mine.

Sandstone. Ft. in.

Bone 1 6

Coal, sampled 3 8

Bone 4

Coal, sampled 2 4

Shale.

COAL IK THB FBUITIiAND FOBMATION. GEHEBAL FEATURES.

In the following description of the coal of the Fruitland forma- tion the field will be treated arbitrarily as a number of districts, sug- gested by the surface features or by the continuity of exposures of the beds themselves. These districts are not distinct divisions, and their boundaries are therefore in large part indefinable. They are selected simply for convenience in presenting details that could not be set forth so readily if the field were treated as a whole.

Certain general features of interest, however, may be noted con- cerning the coals of the Fruitland formation. The outcrop, as shown

200 Contributions To Economic Geology, 192D, Part Ii.

on Plate XVI, is confined to a narrow belt running from the boundary between Colorado and New Mexico at first south westward, then westward, then southward to San Juan River. From the San Juan it runs parallel to Chaco Biver as far as the south boundary of San Juan County. The beds dip southeastward in the northern part of the field, eastward in the central part, and northeastward in the southern part to relatively slight depths beneath the overlying rocks. This surface distribution and attitude are, of course, to be expected, inasmuch as the field is part of a great structural basin. (See p. 161.) The Fruitland formation continues beyond the limits of this field and completes a great circuit, of which the part here described forms nearly the western half. The exposures are best in the arroyos. The thickest and most valuable beds of coal are in the northern part of the field, though there is considerable coal in the middle part. In the southern part the beds are thin and very lenticular and the coal is poor. (See PL XXII.)

La Plata Tallst.

The coal in the La Plata Valley district, which extends from location 1 to location 15 (see PL XXV) , occurs in two main beds with a number of minor lenses. At location 1 a lens of coal 2 feet thick rests directly upon the Pictured Cliffs sandstone. It was not noted elsewhere in the district. From 6 to 30 feet above this horizon lies the bed which was examined at locations 1, 3, 4, 9, 10, and 12. It is from 23 to 38 feet in total thickness, being thus the largest observed in the whole field, and has been correlated with the Carbonero bed, formerly mined at Carbon Junction, near Durango, Colo. Whether this cor- relation is valid or not, the bed is certainly thick and valuable in the district just north of the State boundary line. Its character is shown in the sections on Plate XXVI. Parts of it are being mined at five places in this district, from three of which samples have been ob- tained for analysis. (See p. 184.) The product from the bed is used entirely for local consumption.

From 100 to 125 feet above the Carbonero bed lies another bed which was measured at location 2. It is extensively developed to the north, in Colorado. In this district it is much split by partings and can not be traced very far. The section is given graphically on Plate XXVI.

Farther south a lenticular bed about 180 feet above the Carbonero bed can be traced for some distance, but it is of small value except at location 5 because of partings. The section is given on Plate XXVI. At location 11-A it shows the following section :

''Shaler, M. K., A reccHinaissance surrey of the western p&rt of the DurangD-Oallap coal field of Colorado and New Mexico : U. S. Geol. Survey Bull. 816, pp. 892-898, 1906.

r. S. OCOLOGICAL 8USVEY

Explanation

H

S

Outenip of cod bed and locstion

I Coal In San Juan County, N. Mbx. 201

I Section of coal bed at location 11-A.

Shale. Ft In.

Coal 2

Shale, carbonaceous 4

Shale carbonaceous 6

Coal 3

Shale, carbonaceous , 1

Coal 5

Shale 1

Coal 1

Shale.

Total section l 3 4

Total coal - 2 4

Beneath the bed examined at location 5 there are several unmapped taises of coal whose value is small because of thinness or partings, rhe character of these beds is indicated in the following section :

Section of coal hed8 beneath that examined at location 5,

Ft in.

Sandstone 10

Shale 2

Coal bed of location 5 (see PL XXVI) 5 7

Shale 40

Sandstone 2

Shale 40

Coal and bone 1 6

Shald 2 6

Coal 1 . 3

Shale '. 5

Coal 1

Shale 9

Shale 1

Coal 8

Shale 1

Goal 2

Bone 1

Shale 6

Coal 4

Bone 3

Coal 5

Shale , 9

Bone ; 2

Coal I 3

Shale 15

Coal 2

Shale 5

Total section 137 81

Total coal 12 8

ir>4071°— 21— Bull. 716 14

202 Contributions To Economic Geology, 1920, Pabt Ii.

At location 11-B a thick coal bed is 'exposed, but it is of sj lateral extent and much cut up by partings. The section is sl on Plate XXVI.

Between the coal bed of location 11- A and that of location several lenses are present, which are shown in the following sect

Section of coal bedA between locations 11-A and 11-B.

Shale.

Coal bed of location U-B (see PI. XXVI). Ft. in.

Shale, carbonaceous 4

Sandstone 10

Shale, carbonaceous . 40

coai ao

Shale 9

C5oa; 1 9

Ck)al, Impure 1

Shale, carbonaceous 4

Coal 9

Bone and shale 8

CJoal 5

Shale 4

Bone and bony coal 8

Shale 3

Bone 6

Shale, carbonaceous 37

Sandstone 5

Shale - 5

Coal bed of location 11-A (see p. 201).

Total section 103 9

Total coalL . 4 9

At locality 6 two lenses are present close together at about the die of the Fruitland formation. At locations 7 and 8 two len the upper part of the Fruitland formation about 1(X) feet apa shown. None of these lenses are extensive enough to be of value. The sections are all shown on Plate XXVI.

A short lens is represented by the section obtained at locati (See PI. XXVI.) At 12 feet above this lens is another one mapped. Its character is shown 7 the following section:

Section of coal lens bettce locations 14 and 15.

Shale, carbonaceous. Pt in..'

Bone 1 :

Shale i 3 !

Shalo 5

Coal 9

Shale 1

N

y-

fi.m.

2

ft.

'

Irvoir

Ft. in. gaaaFt.

a

n

N San

t

Coal In San Juan County, N. Mbx. 203

Shale, carbonaceous — Continued. Ft in.

Coal 10

Coal, bony 2

Coal 7

Shale.

Total section 4 7

Total coal 2 10

At locations 13 and 15 a lens was examined which has but small value because of numerous partings. The sections are shown on Plate XXVI. It lies about 70 feet above the bed shown at location 14 and may be the same as the bed at location 11-B.

LA FLATAp-SAN JUAH DIVIDE.

Along the La Plata-San Juan divide, from location 16 to location 37 (see PI. XXVII), the lowest coal-bearing bed rests immediately upon the Pictured Cliffs sandstone. Higher up in the Fruitland formation there are three other fairly persistent beds and some minor lenses. Between locations 36 arid 37 an abnormal development of sandstone occurs and little coal can be found, though the exposures are favorable.

The basal bed was examined at locations 21, 25, 28, 31, 34, and 37. It is variable in thickness and character, as the sections on Plate XXVI show. At location 37 the bed is only 1 foot thick.

The Carbonero bed in this district can not be directly connected with that in the district to the north, but the covered interval is short, and there is little doubt as to their identity. The bed was examined at locations 16, 19, 22, and 26. It lies from 30 to 50 feet above the Pictured Cliffs sandstone, and though some of the sections are incomplete it evidently decreases in thickness southward. For some miles southwest of location 26 no sections of it were obtained. Near location 37, in the zone where it ought to be found, only a little bone and dark shale are present, and it very probably thins out between locations 26 and 37.

From 100 to 120 feet above the Carbonero bed a higher bed was measured at locations 17, 20, 23, 29, 32, 35, and 36. It is of consider- able thickness but much cut up by partings and consequently of small value.

From 75 to 100 feet above the last-mentioned bed occurs another bed which was measured at locations 24, 27, 30, and 33. It is thin and split by partings.

At location 18, 85 feet above the bed of location 17, a lens is present which may represent the horizon of the bed at location 24. It con- tains 4 feet 5 inches of coal with one thin parting. The section is shown on Plate XXVI.

i'

/j

r X

/

Nty, New I

Coal In Sax Juan County, N. Mbx. 205

Aiother bed 50 feet above the Carbonero bed was examined at locations 62, 63, and 64. The sections are shown on Plate XXVI. It is of small value.

At location 58 a lens 2 feet 6 inches thick occurs 8 feet above the Carbonero bed. It could not be traced far laterally.

Sah Jvah Biveb.

The district near San Juan Kiver (see PI. XXVIII) produces a large share of the coal mined in the field, though the developments are not extensive and the product is all consumed locally. Two mines are in operation north of the river, both of which were sam- pled for analysis (Nos. 2464, 22508, and 22509, p. 184). An open pit on the south bank of the river opposite Fruitland furnishes the Navajo Indians with fuel. The two beds found in the district to the north are present here.

The lower bed was examined at locations 66, 67, 69, 140, and 144 (PL XXVI). At location 67, at the Black Diamond mine, north- west of Fruitland, the bed is over 15 feet thick and contains a num- ber of partings. At location 69, at the Hendrickson mine, the bed is 16 feet thick, contains partings, and is overlain by another bed, 4 feet higher in the section, which is so split by partings as to have little value. At location 140, the open pit south of the river (see PL XX, A), the bed is much poorer in quality and more cut up by partings. No further exposures of this zone are met until location 144 is reached, but here only a small amount of coal is to be found at the horizon of the Carbonero.

At locations 68, 70, 141, 142, and 143 a bed 30 to 50 feet above the Carbonero bed was examined. It is from 3 to 4 feet in thickness but at some points contains many partings. At location 141 the coal bed is partly burned and the best section obtainable is probably unreliable on that account.

Section of coal "bed at location HI.

Sandstone. Ft. in.

Coal 6

Sandstone r 1

Coal 6

Sandstone.

At location 66 a thin coal bed rests upon the Pictured Cliffs said- stone, and at location 140 the same horizon shows coaly material of no value.

South of this district a stretch of several mUes is so deeply cov- ered with wind-blown sand and river-terrace materials that ex- posures are rare, and though coal is probably present, it is not exposed and correlations of the beds are uncertain.

206 CONTRIBUTIONS TO EGONOMIO GEOLOGT, 1990, PAST n.

Ojo Axabiixo Abboto.

The coal in and near Ojo Amarillo Arroyo (see PI. XXIX) oc- curs in six beds, none of which can be definitely correlated with the beds on San Juan River, though they lie largely in the lower part of the same formation. The lowest bed, about 15 feet above the Pictured Cliffs sandstone, was measured at location 156 as follows :

Section of coal bed at location 155.

Shale. FL in.

Shale containing gypsum 1 1

Shale 1

Bone 3

Shale.

This bed pinches out both to the north and to the south in a dis- tance of several hundred yards. A similar lens appears at about the same horizon a mile farther south, at location 166, where 1 foot 9 inches of coal is exposed. Overlying it and separated from it by 34 feet of shale is a coal bed which was mapped for several miles and was measured at locations 149, 150, 152, 156, 161, 168, 172, and 175, in the vicinity of Ojo Amarillo Canyon. The bed is best de- veloped south of the arroyo, where an upper bench averages about 4 feet thick. North of the arroyo the bed is split by numerous part- ings, as shown by sections 149 and 150. The measurements of this bed are shown graphically on Plate XXX.

The next higher bed of coal in the section is represented by meas- urements at locations 148, 151, 153, and 162. At location 148, about 2 miles north of the arroyo, it shows the following section :

Section of coal bed at location H8, Shale. FL in.

CJoal 1 9

Bone 4

Shale.

The bed thins southward to 11 inches at location 149 and to U inches at location 153, on the north side of the arroyo. A field test here shows that the coal is impure, containing 16.2 per cent of ash. South of the arroyo, at location 162, the bed is 13 inche& thick, and farther south it thins out and disappears.

Separated from the bed just mentioned by 10 to 20 feet of sand stone and sandy shale is another bed, whose average thickness is less than 3 feet and which was measured at locations 154, 163, and 170. The sections are shown on Plate XXX, except section 163, which contains only 1 foot 6 inches of coal.

South of the arroyo two higher beds which are not present on the north side were examined and measured. One of these was meas-

V. flBOUIQICAL SUSTXT

MAP OP DISTRICT BETVKEN TOU SAN JUAN BIVEB, SAN JDAN CCj

Coal In San Juan County, N. Mbx. 207

ured at locations 159, 164, 167, 169, 171, 174, 176, and 178. The bed is variable in thickness and is split by many partings. It lies 30 feet above the bed of section 154, just mentioned. All the sections are given on Plate XXX except those at locations 159, 164, and 174, which are given below.

Section of coal bed at location 164.

Shale, brown. Ft. in.

Coal , 3

Bone 3

Coal 3

Bone 7

Shale - 1

Coal 10

Shale 1

Sandstone 1

Coal 1 1

Shale.

Total section 5

Total coal 2 5

Section of coal bed at location 159.

Shale, carbonaceous. Ft. in.

Coal 6

Shale, carbonaceous 5

Coal 10

Shale, carbonaceous.

Section of coal bed at location 174.

Shale, carbonaceous. Ft in.

Bone 1 1

Coal, impure 6

Shale 2

Coal 11

Shale.

The highest bed of coal exposed in this locality is a lens whose thickness was obtained at locations 158, 160, 165. It lies about 30 feet above the bed last described. The fact that this is a lens is shown by the middle measurement being 3 feet 10 inches, the northern 2 feet 11 inches (see PL XXX), and the southern 1 foot 11 inches.

DIVIDE BETWEEH OJO AXABILLO AHD OOTTOrWOOD ABBOTOS.

On the divide between Ojo Amarillo and Cottonwood arroyos, from location 180 to location 206, inclusive (see PL XXIX), the coal beds crop out in the bluff facing Chaco River. Two beds are gen- erally of sufficient thickness to be mapped across this district ; other

208 Contributions To Econobcig Geology, 192D, Part H.

beds are lenticular and are thick enough to warrant mapping only locally.

The lowest lenses mapped lie at the base of the Fruitland forma- tion, and although they are not continuous they occur at the same horizon throughout this portion of the field. These lenses are repre- sented by measurements obtained at locations 191, 194, and 201. At location 191 1 foot 8 inches of coal overlies 10 inches of bone, at loca- tion 194 there is 2 feet 2 inches of coal, and at location 201 there is 1 foot 6 inches. These lenses are overlain by 10 to 15 feet of light- yellow sandstone very much like the Pictured Cliffs sandstone below, but because of the presence of coal and the brackish-water fossils simi- lar to those of the Fruitland formation at location 191 these rocks are included in the Fruitland. Above this sandstone is a lens of coal which is very irregular in thickness. At location 180 8 inches of coal overlies 6 inches of bone ; at location 183 the same lens contains over 4 feet of good coal. (See PI. XXX.) This lens is separated by a few feet of gray sandstone and shale from another coal bed which is represented by sections at locations 186, 188, 190, 192, 193, 195, 196, 198, 202, 203, and 206. These sections, except Nos. 196, 202, and 206, are shown on Plate XXX. The bed is very irregular in thickness and in some places is split by many partings. However, it averages over 3 feet of coal. Measurements at locations 196, 202, and 206 are given below :

Section of coal hed at location 196, Shale. Ft. In.

Coal 1 5

Shale.

Section of coal bed at location 202,

Shale, carbonaceous. Ft in.

Coal, dirty 1 0

Shale 1

Coal 2

Shale.

Section of coal bed at location 206, Shale, carbonaceoua Ft. hL

Coal 1 10

Bone 3

Shale, carbonaceous.

From 16 to 18 feet higher is a bed of coal that is more regular and perhaps more persistent than any other bed in this part of the field. It was measured at locations 181, 182, 184, 187, 189, 197, 200, and probably also 204. The sections of this bed show an average thick- ness of to 4 feet of coal. They are all given on Plate XXX

Al In

ART n.

Oq

COAL IN SAN JUAN COUNTY, N. MEl. 209

except No, 204, which shows only 1 foot of coal, and No. 181, which is given below.

Section of coal hed at location 181.

Shale, carbonaceous. Ft. in.

Coal, containing resin : 1 2

Shale, carbonaceous 1

Bone 6

Shale 2

Coal, containing resin , 5

Shale, carbonaceous.

Total section i 8 3

Total coal 1 7

This bed is supposed to be the same as the bed at location 178, in the district immediately to the north.

Lenses of coal higher in the formation were measured at locations 186, 199, and 205, representing probably one horizon.' Sections 186 and 206 are given on Plate XXX, and 199 is given below :

Section of coal bed at location 199,

Shale, carbonaceous. Ft. in.

Coal . 5

Shale- 1

Coal 11

Shale, carbonaceous.

Oottohwood Arroyo,

In the Cottonwood Arroyo district there are five coal beds that crop out more or less continuously. These were examined at loca- tions 207 to 251, inclusive. (See PI. XXIX.) The lowest is at the baseof the Fruitland formation and rests directly on the Pictured Cliffs sandstone. Sections of it were measured at locations 209, 212, 216, 224, 226, 234, and 236. With the exception of Nos. 212, 225, and 234, these sections are given graphically on Plate XXX. At location 212 an incomplete section shows more than 1 foot of bony coal; at location 225 the bed contains 1 foot of good coal ; and at location 234 it shows 1 foot 3 inches of impure coal. The bed is thickest at loca- tion 236, where it consists of a lower bench 3 feet 2 inches thick and a higher one 1 foot 10 inches thick, separated by 3 feet of shale. Farther south these benches are more widely separated and are there- fore considered as two distinct beds, though they are mapped as one, owing to the proximity of their outcrops.

Between 40 and 50 feet of cross-bedded gray- white sandstone and gray shale separate this coal bed from the one next above. This upper bed was measured at locations 215, 217, 223, 226, and 237. Sections at locations 217, 223, and 237 are shown on Plate XXX, and those at locations 215 and 226 are given on page 210.

210 Contributions To Economic Geology, 1920, Part Ii.

Section of ooal bed aft lociUion 215.

Shale. ' Ft. In.

Bone 1

Shale J 1 2

Coal, containing resin 1 2

Shale 3

Bone 4

Shale, carbonaceous.

Total section 3 11

Total coal 1 2

8&i<m of coal bed at location 226,

Shale, carbonaceous. Ft. in.

Coal 9

Shale, carbonaceous 3

Sandstone, gray 3

Shale, carijonaceous 1 1

Coal 8

Bone 6

Shale, carbonaceous.

Total section 6 3

Total coal 15

As can be seen from the sections on Plate XXX, the bed averages over 3 feet in thickness near Cottonwood Arroyo but is split by part- ings at the north and south sides of this district.

Between the bed described above and the next bed of importance higher in the section there is about 15 feet of sandy shale. Near the top of this shale a thin lens of coal crops out for a short distance north of Cottonwood Arroyo, with the thickness and character shown in the following section :

tn

Section of ooal bed at looaiion 208,

Shale. Ft. In.

Coal 1 2

Sandstone 1

Coal 3

Bone 4

Coal 9

Shale, carbonaceous.

Total section 2 7

Total coal 2 2

Section of coal bed at location 210,

Shale, carbonaceous. Ft. in.

Coal 1 8

Shale.

A few feet above this lens lies a bed which has an extensive distri bution in this district and the districts to the south. Sections of if obtained at locations 211, 213, 219, 227, 231, 233, and 238 are shown

(28

R.irt

Ft. in.

Bulletin 716 Plate Xxx

Brim Hall Wash

35S 350

H.'tn. sFt.

Z 7

n

Ft. in. aaFt.tn.

t 8 Z

t 10

Ft. in.

Fl in. sd Ft. in.

I S

1 S

Ft. in.

S

Ft. in.

$ yn

S 6

Ft. in.

2

I 10

t

Ft.

Medio Arroyo

Divide

Ft. in. t 6

75

3

Ft. in.

359 563 368

I Ft.in. i=a Ft. in. Ft. in.

2

Impure cdal

2

t

! 7

I 2

t S

I 7

Ft. in.

Kh-

IKCaRAV-eo AND Bv rMK II S 9I.OU>'>lCAL Ol'

ft. in.

Z

Coal In San Juan County, N. Mbx. 211

on Plate XXX ; at location 207 it contains only 1 foot 10 inches of coal. It averages feet in thickness, and it is exceptionally pure at location 233, where it contains over feet of clean coal.

Another bed of coal which also averages about Bi feet in thickness lies 30 feet higher in the section. Measurements of it were obtained at locations 214, 218, 220, 228, 230, 232, and 239. These are shown graph- icaUy on Plate XXX.

About 70 feet higher lies the highest coal bed of importance in this district. Sections of it at locations 221, 222, 250, and 251 show many partings. As a whole, the bed consists of very impure coal. With the exception of section 221, these measurements are given on Plate

Section of coal hed at location 221,

Shale, carbonaceous. Ft. ' in.

Bone 8

Shale, carbonaceous, with streaks of bone 1 6

Shale, gray 6

Bone 1 7

Shale 1

Bone 3

Shale 1

Bone 3

Shale, sandy 1

Coal , 8

Shale 2

Coal, containing resin 8

Shale, carbonaceous 3

Coal 1 2

Coal 8

Shale.

Total section 8 71

Total coal 3 2

A lens with a lateral extent of only a few hundred yards occurs midway between this bed and the next one beneath at location 229, where its maximum observed thickness is about feet. (See PL XXX.)

Piha Veta Ohiha Abboto.

Five coal beds exposed at the mouth of Pina Veta China Arroyo are correlated directly with the five beds in the distri' immediately to the north, and a new bed is present. These beds were examined at locations 240 to 283, inclusive. (See PI. XXIX.) The lowest bed in Cottonwood Arroyo, as mentioned above, is here a group of two beds and several benches separated by 3 to 15 feet of sandy shale. The two principal beds of the group are thin and irregular, and the coal varies in quality and is commonly high in ash. Measure-

212 Cxdntbibutions To Economio Geology, 192D, Pabt H.

ments of the group obtained at locations 240 and 244 are given below.

ScotUm of coal bed at looaticn 240.

Shale, carbonaceous. Ft. in.

CJoal, much weathered 1 0

Shale, carbonaceous 3 4

CJoal 1 1

Shale, carbonaceous.

Total section 5 5

Total coal 2 1

Section of coal bed at location 244*

Shale, carbonaceous. Ft in.

Ck>al, Impure 1 4

Shale, carbonaceous 1 8

Coal 1 8

Shale, carbonaceous 5 5

CJoal, impure 1 8

Bone 10

Total section 11 9

Total coal 8 10

Only one bench of coal 1 foot 6 inches thick was observed at loca- tion 252, and one 1 foot 8 inches thick at location 253.

The next coal bed, 35 feet higher in the section, was measured at locations 241, 243, 247, 254, 258, 259, and 263, as shown on Plate XXX. In these sections it averages about 4 feet in thickness, but at location 241, as shown below, it has one bench over 4 feet thick and two other benches which are separated by thick partings.

Section of coal bed at location 241'

Shale, carbonaceous. Ft in.

Coal 4 10

Shale 1 3

Bone 6

Coal 1 6

Shale - 1 8

Bone 2

Coal, impure 1 2

Shale.

Total section 11 1

Total coal 7 6

This bed contains a large quantity of coal, its maximum thickness (at location 259) being 7 feet 10 inches.

About 15 feet above the coal bed just described is the bed which is thought to be the same as the one measured at location 238, in the district to the north. Measurements of this bed were obtained at

OOAIi IN SAN JUAN COUNTY, N. MBX. 213

locations 242, 245, 246, 248, 255, and 260 and are shown graphically on Plate XXX. The bed is very irregular, its minimum observed thickness, at location 248, being 2 feet 9 inches, of which 10 inches is bone and shale, and its maximum observed thickness, at location 245, being 6 feet 2 inches of coal. However, the upper bench at loca- tion 245 contains a high percentage of ash.

The next higher coal bed in the section is the same as the one measured at location 239, in the district immediately to the north. Measurements of it were obtained at locations 249, 261, and 266. This bed averages feet, but at location 261 it is split into two benches by a parting which is over 4 feet thick, as shown in the following section:

Section of coal beds at location 261,

Shale. Ft. In.

Coal - 11

Sandstone . 1

Shale, carbonaceous 5

Shale 3 9

CJoal 1 3

Total section 6 5

Total coal 2 2

The other sections of this bed are shown on Plate XXX.

Near location 261 a bed of coal appears midway between the bed just described and the highest bed in the section. It was measured at locations 262, 271, 275, 267, and 270 and was found to contain many partings, as shown in the sections on Plate XXX.

The highest bed in this district is the same as that measured at location 251, in the district to the north. Measurements of it at locations 256, 257, 283, and 269 are given on Plate XXX; at loca- tion 268 it contains 2 feet 1 inch of good coal. This bed averages nearly 4 feet in thickness.

Klatokzv Abboto.

Very good exposures of the Pictured Cliffs and Fruitland forma- tions are to be found on Klaychin Arroyo between locations 264 and 314 (see PL XXIX), and the coal beds can be measured in consider- able detail except where they have burned along their outcrops and are now covered with red baked shale or clinker. The following section extending from location 284 to location 287 gives the thick- ness and character of most of the coal beds, as well as the intervening sandstone and shale, and indicates the great amount of coal here present in the Fruitland formation :

Coal —

Shalp, bn)wri

Sondstnne, pinty, hniwii

SMiile, Iniriieii rwl iinJ whlti'

FIftli lied:

Ash ( from burned conl ln-il 1 .

SliHle, hnnrted hrown nnd crny

SiLiidtilonii, buff, pluty, leDticiilar

, croeiiisli cray, sandy

Fourth bl ;

Coal

Slinli'. sandy

Coal

Sliale, brown. cartKni melius.

Coal

Shale, brown

Coal, confalniiic rt-sin

Slinlc. brown, windy

Sliiile. blai-k. carboDaceoiis

Tlilrd lied :

Con!

Shale, brow-H, ver; Coat, contain in); n

Coal In San Juan County, N. Mbx. 215

/

Ft In.

Shale, brown, carbonaceous 2

Sandstone, brown, platy 2

Shale, brown, carbonaceous 1

Second bed:

Coal 1 3

Shale, brown 2 6

Lowest bed :

Coal 2 11 .

Shale, brown 1

Coal 2 7

Bone 3

Coal w 2 8

Shale, brown, carbonaceous 2

Pictured Cliffs sandstone.

Total thickness 121 4

Total coal 34 8

The lowest bed of coal is the same as the lowest one in Pina Veta China Arroyo. It measured at locations 272, 273, 278, 282, 284, 292, 293, 294, and 300. The sections at locations 273, 278, and 293 are given below; others are shown on Plate XXX. Its variability in thickness and character is marked.

Section of coal bed at location 273. Shale. Ft. in.

Coal 1 9

Shale.

Section of coal bed at location 278.

Shale. Ft. In.

Coal 2 4

Shale 1 6

Coal 2 8

Shale 3 4

Coal 1 10

Shale,

Total section 11 8

Total coal 6 10

Section of coal bed at location 203, Shale. Ft. In.

Coal 1 9

Shale.

The second bed, as shown in the section on this page, is 1 foot 3 inches thick and only feet above the lowest bed at location 284. Apparently it is a thin lens which extends only a short distance.

The third bed averages nearly 4 feet in thicfaiess and is correlated with that measured at location 263, in the district immediately to the north. Measurements of it were obtained at locations 264, 274, 281, 285, 290, 291, 298, 307, 302, and 310. Except the sections at locations 290 and 291 these are given on Plate XXX. At location 290 all the

216 CONTRIBUTIONS TO ECONOMIC QEOLOGT, 19aa, PABT H.

beds are burned and their outcrops are covered with baked shale and clinker, and at location 291 the bed contains only 1 foot 3 inches of coal. South of this point this bed is thin and does not warrant mapping.

The fourth coal bed is split by many partings, as shown particu- larly at location 297. Itflji represented by sections at locations 27T, 280, 286, 296, 297, 303, ik311, 313, and 314. With the exception of those at locations 311 and 818, all are shown on Plate XXX. Although sections 311 and 313 are separated by less than a quarter of a mile they differ much and illustrate the great variability of some of the coal beds of the Fruitland formation. At location 811 the bed con- tains only 1 foot 9 inches of coal, but at location 313 it contains 5 feet 6 inches of coal of fair quality, though considerably weathered where measured. The other measurements show an average thickness of about 4 feet for this bed.

The fifth coal bed, which is 12 to 15 feet higher than the one last mentioned, was measured at locations 276, 279, 287, 295, 299, 304, 308, and 312. The sections not shown on Plate XXX are given below.

Section of coal bed at location 299,

Shale, brown, sandy. Ft. in.

Coal 1 9

Shale, carbonaceous.

Section of coal bed at location 308.

Shale. Ft. in.

Coal, weathered 1 0

Shale.

At location 287 the bed has been burned and is represented by a 6-inch bed of ash.

The next higher coal bed in the section was measured at locations 289, 305, 309, 315, and 319. It averages over 4 feet of coal. These sections are given on Plate XXX, except the one which follows.

Section of coal bed at location 315.

Shale, carbonaceous. Pt. In.

Ck)al, good 1 10

Shale, carbonaceous 1 6

Coal 10

Sandstone, gray 4

Coal, impure 3

Shale, sandy 1

Coal 3

Sar 6

O uch resin l 2 7

( 1 8

! 1

Coal In San Juan County, N, Mbx, 217

Shale, carbonaceous — Continued. Pt in.

taoal ; contains resin 1 6

Sandstone, gray 4

Coal, good 6

Shale, carbonaceous.

Total section 13 3

Total coal 9 2

The seventh or highest coal bed in the Fruitland formation in this locality is correlated with the highest coal bed in Pina Veta China Arroyo, which was measured at location 283. This bed is mined on a small scale by stripping at location 301, where it con- tains an upper bench 3 feet thick and a lower bench feet thick. Technically these two benches are distinct beds, for they are sepa- rated by about 7 feet of shale. However, they are worked together at this place and are parts of the same bed to the north and to the south. A sample was obtained from the lower bed at this location, and an analysis of it is given on page 185 (No. 22685). The bed is only about 2 feet thick at location 320, as shown in section on Plate XXX.

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On the divide between Klaychin Arroyo and Brimhall Wash the lower coal beds crop out in a low bluff extending in a nearly north-south direction. The higher beds, on the other hand, are concealed in the broad, low divide and can be seen only about low hills or in " blowouts " where the wind has removed the loose surface material. The district extends from location 316 to location 333. (See PI. XXIX.)

The lowest coal bed is at nearly the same horizon as the lowest in the district immediately to the north. It is represented by a series of lenses and was measured at locations 316, 327, and 332. Between these three localities the bed is less than 1 foot thick. Sections at locations 316 and 327 are shown on Plate XXX, and that at location 332 is given here :

Section of coal bed at location 3S2. . Shale, sandy. Ft. In.

Coal 1 2

Shale, carbonaceous.

The coal bed next higher in the section is the same as the one measured at location 314. Sections of it at locations 321, 322, 329, 331, and 333 are given on Plate XXX; at location 317 the bed is burned and shows 1 foot of ash. The average thickness of this coal bed in this district is nearly 4 feet.

The third bed of importance in this district is represented by sections at locations 818, 323, 324, 326, 328, and 330. In the noi'**'

1540710—21— Bull. 716 16

218 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1920, PART n.

em part of the district it is in reality two beds, the parts being separated by 5 feet of shale, but each bench is thick enough to 'be valuable. The sections are all given on Plate XXX, except that; at location 330, which is given here.

Section of coal bed at location SSO,

Shale, carbonaceous. Ft. In.

Ck>alt impure 10

Bone, sandy 1

Coal, Impure 8

Shale, carbonaceous 1

Coal 4

Bone 4

CJoal 1 4

Bone 2

Coal 1 3

Bone 2

Coal, impure 11

Shale, black . 8

Coal, impure 7

Bone 4

Coal, impure 4

Shale, carbonaceous.

Total section 7 8

Total coal 6 3

About 6 feet below this section is a lens containing 1 foot 6 inches of coal. Also, 15 feet higher than the bed just described, at location 326, a lens crops out which contains nearly 6 feet of coal, but it thins within a short distance to the north and south of this point.

Two coal beds which are present in the district to the north are believed to be present in this district also, but owing to the evenness of the surface of the divide they are not exposed. It is believed, however, that they crop out on Brimhall Wash, and they will be con- sidered in the following description of that district.