Geology of the Bushrod Island-New Georgia clay deposit near Monrovia, Liberia

Blade, Lawrence Vernon · 1970 · Report

The Bushrod Island-New Georgia clay deposit near Monrovia, Liberia, consisted of interlensing clay and very fine to fine quartz sand

Public-domain full text preserved in the Mountain Man Mining Library. Original source: pubs.usgs.gov.

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co) wrI(f.TNITED STAILS D TMENT OF THE INTERIOR 74,5,GEOLOGICAL SURVEY ) PROJECT REPORT IR-LI-26 Liberian Investigations ,bA (9 THE BUSEROD ISLAND-NEW GEORGIA CLAY DEPOSIT NEAR MONROVIA, LTRERIA by trl LAURENCE V. BLADE, U.S. Geological Survey OPEN FILE REPORT L:

z .1. 4 4 tat .2.. This report is preliminary and has not been edited or reviewed for conformity with Geological Survey standards or nomenclature.

LIBERI1N GEOLOGICAL SURVEY BUREAU OF NATURAL RESOURCES AND SURVEYS MEMORANDUM REPORT NO. 34 (USGS IR-LI-26) THE BUSHROD ISLAND-NEW GEORGIA Miff DEPOSIT NEAR MONROVIA, LIBERIA by Lawrence V. Blade U.S. Geological Survey Monrovia, Liberia

e9) 7 ,L-- Weld- mt. 7;005 coLoGicAL s vo,sHINGToN U. S. GLCLOGICJ,L 5F71 TASKINCTCN, D. C. Ji-kki 5 1970 20,242 For release JiiNUAILY 22, 1970 The U. S. Geological Survey is releasing in open files the following reports. Copies are available for inspection in the Geological Survey Libraries, 1033 GSA Bldg., Washington, D. C. 20242; bldg. :ederal Center, Denver, Colo. 8L225; and 345 Eiddlefield id.,!.e-R1O Park, L,alif. 94025. Copies are also available for inspection in other offices as listed: Palynological investigations in the Upper Cretaceous and Tertiary of the idssissippi Embayment Region--VI, by Robert H. Tschudy. 25 p. USGS, 710 West High St., Lexington, Ky. 40508; Kentucky Geological Survey, 307 :iineral Industries Bldg., University of Kentucky, 120 Graham Ave., Lexington, Ky. 40506. Preliminary structure map of the Blackford quadrangle, western Kentucky, by Dewey H. Amos. 1 sheet, scale 1:24.,000. USGS, 710 West High ,5t., Lexington, Ky. 40508; Kentucky Geological Survey, 307 mineral Indus­ tries Bldg., University of Kentucky, 120 Graham Are., Lexington, Ky. 40566. LJ.;ateriai from which copy can be made at private expense is available in the two Lexington offices listed. This map supersedes the version openfiled in June 1968 by the same author, entitled HPreliminary map showing faults in the Blackford quadrangle, western Kentucky.L/ Availability of palynological material from Naval Petroleum Reserve No. 4, XIX: Umiat Test Wells Nos. 3 and 11, Simpson Core Tests 21, 27, 3u, 30A, by Richard A. Scott. 2 p. Remote detection of geochemical soil anomalies, by F. C. Canney. 6 p., plus 1 sheet tabular data. Geology of the Bushrod Island-New Georgia clay deposit near Nonrovia, Liberia, by Lawrence V. Blade. 35 p., including 7 figs., 4 tables. Seismic-reflection records from a survey at the Rocky ilountain Arsenal near Denver, Colorado, by A. B. Ilattick and D. B. Hoover. 4 p., 1 pl. Liqaterial from which copy can be -lade at private expense is available in the USGS Library, Bldg. 25, Federal Center, Denver, Colo. 80225.1/ 7. Digital computer terrain mapping from mvitispectral data, and evalu­ ation of proposed Earth Resources Technology Satellite (L­2.TS) data channels, Yellowstone National Park: preliminary report, by Harry W. Sn,edes, Kenneth L. Pierce, and Roger i,.. Hoffer. 43 p., 19 figs., I colored photo. 1012 Federal Tldp., Denver, Colo. 80202; 8102 Federal Office Bldg., Salt Lake City, Utah 84111; Geological Survey of ayoming, University of Tc:yo4ing, Laramie, ;57-o. 82070 Lp.O.Pox 3008, Univ. Sta2./.

COTTENTS Page Abstract Introduction Purpose and scope Location and accessibility Previous investigations Geologic setting Geology of the clay deposits Sand New Georgia clay Potential reserves Commercial uses References Appendix I - Logs of hand auger holes ILLUSTRATIONS Figure 1.- Geologic map of the Bushrod Island-New Georgia clay deposit Figure 2. Isopach map shoring thickness of New Georgia clay Figure 3. Sketch showing section along A-A' and B-B' Figure 4.a,b,&c. Differential thermal analysis curves of samples Figure 5. Isopach map shawl.ng thickness of combined units 1,3, and 4 Figure 6. Isopach map showing thickness of combined units 2,5, 6, 7, and 8 Figure 7. Isopach map showing thickness of unit 9 TABLES Table 1. X-ray mineralogical analyses of clay from the Bushrod Island-New Georgia deposit Table 2. Chemical analyses of clay samples from the Bushrod Island-New Georgia deposit Table 3. Averages and ranges of the oxides and volatiles in the three subdivisions of the clay in the Bushrod IslandNew Georgia deposit Table 4. Physical properties of the raw and fired clay as determined in the laboratories of the Refractories Industry Research Center, Department of Ceramic Engineering, Ohio State University

THE BUSHROD ISLAED-NEW GEORGIA CLAY DEPOST nAR MONROVIA, LIBERIA by Lawrence V. Blade U.S. Geological Survey ABSTRACT The Bushrod Island-IZew Georgia clay deposit near Monrovia, Liberia, consisted of interlensing clay and very fine to fine quartz sand; it ':ras deposited in elongate subparallel troughs that had been eroded in coarse-grained sediments. The troughs are interpreted as abandoned stream channels on a former delta of the St. Paul River. The clay of the deposit is essentially a quartz-rich kaolinitic clay that has undergone sufficient weathering in the upper part of the deposit to redistribute iron and alumina. The clay may be divided into three groups: an iron-rich group (A) in which total iron expressed as Fe203 averages 6.5 percent and ranges from 4.4 to 9.2 percent, a group (B) relatively lower in iron in which total iron expressed as Fe2 03 averages 2.7 percent and ranges from 1.6 to 7.4 percent, and a group (C) high in both organic material and iron in which total iron expressed as Fe203 averages 3.9 percent and ranges from 3.3 to 4.9 percent. Potential indicated reserves for the three groups are estimated at 1,800,000, 5,300,000, and 470,000 tons, respectively. Tests of the physical properties of the raw and fired clay indicate the clay is suitable for the following commercial uses: building brick, hollow tile, drain tile, roofing tile, quarry tile, flower pots, porous earthenware, low to intermediate dut refractory products, and probably stoneware and small diameter sewer pipe.

INTRODUCTIOU Purpose and scope This study was part of the Geological Exploration and Resources Appraisal Project, a cooperative effort of the Government of Liberia and the U.S. Agency for International Development, carried out through activities of a combined Liberian Geological Survey and U.S. Geological Survey staff. The investigation of the Bushrod Island-New Georgia clay deposit was designed to determine the approximate quantity and quality of the clay. The vertical extent of the deposit. was determined by exploration drilling with a hand auger and the lateral extent was determined by reconnaissance mapping. In the urban areas surface mapping was difficult because of contamination 1,y fill material. Forty-seven hand-auger holes ranging in depth from 4 to 24 feet were drilled during the investigation. Seven clay samples were analysed by x-ray methods, 27 clay samples were analysed by chemical methods, 38 samples were studied by differential thermal analysis, 3 clay samples were tested to determine potential commercial uses, and the age of 1 clay sample was determined by radiocarbon measurement. Rocks are described by hand lens observation, and size classifications are those of the Wentworth scale. Most of the colors of the burned powders from the differential thermal analyses were determined with the aid of a rockcolor chart. (Geological Society of America, 1963). Location and accessibility Most of the clay deposit is located on both sides of Stockton Creek (figs. 1,2) about 5 miles northwest of downtown Monrovia and is readily accessible. The road from Monrovia to Harrisburg crosses the main part of the deposit on the north, the freeway from Monrovia to Paynesville crosses the deposit on the south, and the main road north from Monrovia to Btimi Hills crosses the deposit on the northwest. Previous investigations The Battelle Institute (1963) investigated the deposit as part of a larger study of the Monrovia district. 'They found the clay in the New Georgia area suitable for brick, and the clay on Bushrod Island suitable for form-pressed wall tile and pottery, as well as for brick. Worrall and Dinkins (1965) made a soil map of the area. Two of their soil units fit the outlines of the clay deposit in parts of the area.

EX P I .AN ATION Qs\ `1`tiTh t Q. Wbs ) ,:\,,Qci (4 r lieach sand ,i / ."/ Qci / A ' ' Qcl Qfg / A Q. 1 '- ' \-j ' - 1711 I / / ( Clay and sand / Qs 1813"1j / / ' Clay and sandy clay (Qc1) ' locally with abundant St. Q plant fragments inter­ p€gn /

i / f, .1311 3 3 k

lensed with very fineto fine-grained quartz

sand and clayey sand (Qfs) '. QC1 ' / Medium-to coarse-grained quartz sand and clayey sand, locally with gran­ y1-1A.Ac.\161:

ules and pebbles of Qs 4(s quartz. Parts of this s unit are younger than

7.6A 6151kNet.w Qcl-Qfs, and parts are older but the litho­ Qh New: Qci logies cannot be differ. Krutowin 18A eorgial entiated (Qs) Qcl

'11B n-p+-;;-1

Gneiss Weathered

Qc1 Contact o Bushrod 12A( (871/ 3/1))

(H Long dashed where approximately located . short dashed where I; Island inferred, dotted where concealed 181). Qfs Strike of vertical foliation )

/ a Minor fold axis ' , 7/ -i horizontal :Logan Town // Kb)/ Qs , — // Qs Outcrop , (Qc1) Covered formation Clay pit, inactive / / Qs// Drill hole, preceded by 111. - in text Qs ) I CD , 18(.

Qcl Qs tn [y r- .j IVORY I Qb,

3, ( COAST Z / Qci M.!: K., IA sQfs 177,c— CO

/ 1, r — — QS / Index map of Liberia 2 KILOMETERS it 4 I MILE 13°Approx. Declination 1969 CONTOUR INTERVAL 5 METERS PRECAMHR1AT QtATERN.\RY Figure 1. - Geologic map of the Bushrod Island-New Georgia clay deposit

2 KIL()METERS I NIILE 13°Approx. Declination 1969 CONTOUR INTERVAL 5 METERS ISOPACH INTERVAL 5 FEET Figure 2. - Isopach map showing thickness of New Georgia clay

GEOLOGIC SETTING The New Georgia clay forms an elongate body about 1 1/2 by 4 miles in size along both sides of Stockton Creek (fig. 1). The fine-grained sediments which form this body were deposited in shallow troughs to a thickness exceeding 20 feet (fig. 2). These troughs had 'seen eroded in coarse-grained sediments, and the fine-grained deposit has been partially covered by similar coarsegrained sediments that are inferred to be partly deltaic and partly littoral in origin. The Battelle Institute (1963) report proposed that the clay was deposited in abandoned stream channels. The present work supports this inter­ pretation for the tro major troughs. However, some of the fine-grained sediments may have been deposited in marginal lagoons, particularly in that part of the deposit near the ocean. Along the west side of Bushrod Island the coarse-grained sediments have been formed into arcuate ridges parallel to the shore and were mapped separately as beach sands because of this topographic expression. Weathered Precambrian gneiss crops out sparsely along the St. Paul River, and laterite has been developed on what was probably gneiss at one spot in the north-central part of the area (fig. 1). GEOLOGY OF THE CLAY DEPOSIT Sand More than half of the 40 holes that were drilled in the clay deposit penetrated the underlying coarser-grained sediments (mapped as sand); of these, one hole (BL-16A, fig. 1. app. 1) penetrated 2 feet of light bluish-gray clay containing medium to very coarse sand grains and 1/2 foot of light-gray clayey, sandy, quartz pebble gravel. The remaining holes drilled through the clay penetrated predominately medium-to coarse-grained quartz sand that is commonly silty or clayey and locally contains generally sparse quartz granules and/or pebbles. Colors are light to dark gray except where the overlying clay is thin, and there the color is light brown° Two drill holes penetrated silty and/or clayey medium-to coarse -grained quartz sand colored dark gray and mottled gray and reddish-brown, before penetrating the clay deposit. The material encountered in the seven holes drilled in sediments outside the clay deposit ;sere similar to the coarse-grained sediments described above. Thus, there is a problem that on the basis of lithology, the sediments below, above, and adjacent to the clay deposit cannot be diffetentiated. Hence, they are all included in the map unit Qs.

New Georgia clay Lithology and age The New Georgia clay is composed of interlensing clay, sandy in part, and very fine to fine-grained quartz sand, clayey in part. In one drill hole (BL-15A, app. 1) a foot of very coarse to medium-grained quartz sand was observed within the very fine to fine-grained quartz sand; such coarsegrained units are apparently not abundant ithin the deposit. Colors of the units vary from browns to grays. The uppermost horizon commonly is gray because of the humus content (and charcoal if the area has been under cultivation); where the humus is not abundant or is absent and the level of the water table varies widely between the Jet and dry seasons, the color varies from light to moderate brown; where the water table remains high, the color varies from very light gray to medium gray. Deeper in the section the browns are lighter and change to light gray which in turn shades to dark gray as the amount of organic material increases or the material is below the influence of oxygen in the water. In parts of the section, organic material in the form of plant remains is very abundant (fig. 3). The color changes described above occur as bands of varying width and depth; they were used as a basis for differentiating nine separate, recognizable units in the clay, described below in descending order of occurrence (all units are not present in every hole): Unit Description Platic cl?y, medium to dark gr,,:y and light to moderate brown and combinations of gr,ys of gray and brown; generally contains humus, and on cultiv:Aed land fragments of charcoal; andy. Platic clay, very light gray t) medium gray, locally sandy. This is the upper unit in low, generally s:Itur.lted, ground. Plastic clay, light to moderate brown, gr,tyih brown, and brownish gray; locally sandy. Pla -Aic clay, mottled light to moderate brown; locally light gray and reddish br wn. locally sandy. 5. Plastic clay, mottled light gray and light brown (loc,Illy reddish brown): locally sandy. Plastic clay, very light gray to medium gray. Plastic clay, medium dark gra,/ to dark gray, locally brownish grlv and moderate graj_-lh brown; locally sandy, and locally with abundant plant remains. 8. Plastic clay, grayish brown, dusky brown, anj dark gray; generally changes to dark gray or gra,riqh black on exposure to air, locally with abundant plant remains: locally sandy. Plastic clay, moderate to dusky brown, changes color to dark gray or grayish black on exposure to air, Plant remains abundant, locally sandy. The fine-grained sand is similarly banded.

A " EXPLANA'11(IN .20 FE1"F f - fill material ,ery filwtn medium-grained ,:an lU uc - 1.1y, units 1, 3, an.! 4 lc - clay, combined units 2, i, 6, 7, and 8 SEA LEVEL pc - clay . unit 9 Alth abundant plant remains cs - medium - to coarse-grained sand 18A - Drill hole (preceded by BI. - in text) B'F20 FEET f 7C f HA f 8 i Ile "1-1 fs 'K. pc. it CS le ; til: fs cs CS / lYl 4000 FEET Figure 3. - Sketch showing sections along A-A' and B-B'

Unit 9, the interval from 14 to 15 fc t in hole BL-16A was sampled , for radiocarbon age determination, Meyer Rubin, U. S. Geological Survey, reported a radiocarbon age of 6160+-600 years B,P, for this sample (lab. No. W-2238). As stated previously some of the coarser sediments are younger than the NeJ Georgia clay- and some are older; hence, it seems best in this report to assign the whole seauence of sediments to the Quaternary Period. Mineralogy and chemirtry Differential thermal a_lalyser; re-0e made on 34 samples of clay and 4 samples of fine-grained sande :hc resulting curves are shcwn in Figure 4 a, b,c. These samples wera tested by the author in a portable Eberbach DTP apparatus heated at a rate of about 40° C per minute by controlling the voltage with a variable transformer, The color of the sample powder after the test is shown with each curve, as the colo17 dspends in part on the iron content of the sample. In lieu of a TiantI..tative test, the iron content may be roughly estimated from the color of the powdcl:. 0 The largest peak on these culves is an endothermic one between 620° and 645 C and indicates the presence of kaolinite. The exothermic peak between 950 and 10004-° C also indicates the presence of kaolinite. Another endother­ mic peak that iay indicate the presence of kaolinite, montmorillonite, or illite is between 20 and ;75°C. The second most notable endothermic peak, occurs between 310 and 340 C, and0indicate8 the presence of iron oxide. A small endothermic peak between 540 and 560 C indicates the presence of quartz. That this peak is missing on many of the curves is probably the result of operator error, as quartz p-robably is lyrssent in all samples. The endothermic peak at 450 C on the curve for sample BL-19A (18-21 1/2) (8) may indicate the presence of siderite. As X-ray analysis is the most dependable method for identifying minerals in clay, seven selected saz,plcs were analyzed by tIlat method. The results are shown in Table 1. In all there sa7p1es the most abundant mineral is kaolinite, followed by a arr a trace amounts of gibbsite, montmorillonite, and illite. Trace amounts of K-feldspar wore found in all but one of the samples. Trace amounts of gccnite were found in three samples, all of which were from the upper Dalt of the deposit in the zone of oxidation or weathering. Trace amounts of organic mz.tte.,.wsro fo—ld in three samples below the zone of oxidation; two of them cc7Ita'..n--1. -L.-ace amounts of pyrite and one of these contained a trace amount of s:_cicoo One sa7inle contained a trace amount of amorphous silica or all7rin, From these data it is a— ::ent tha c2ay is a mixture of minerals but that the dominant mineral f.s :aoljnj.tce Koolite-rich clays are usually the ceramic clays of industry but more information is needed to determine the suitability of a specific clay. P=t of this information can be obtained from chemical analyses of the cDc.y. As prc-coully shown, the color banding in the deposit changes with depth; three samples were analyzed from each of the units for a total of 27 samples. The results are shown in Table 2. A brief discussion of the oxides Is given "b_low,

, tlf 1000° (' 100(10 ('

(0-11(1) light brown 131.-11A (0-1)(1) (5 YU 5i6) Moderate bro,,n (1-3 ('21(I) Moderate reddish (1-')1:21(3) orange (10(4 6:6) Moderate reddish orange (1014 (4'6) 131,-14.5 (3 1:2-6)(5) Grayish orange ' Pink ((014 8'2) 131.-HV 1 ,'2-8)(4) Moderate reddish orange (IOU 6:6) J .Ii1.-11A (8-90(6) Very pale orange (10YR 8 . 2) III -145 (6.41(8) 111.-11A (9-12 I 21(7) J Very pale orange (10YR 8:2) HI.-14A (7-12 1;2)0) Medium light gray (5-61 131.-11A (12 1/2-15 1/2) (.9 Grayish black (N-2) DRILL HOLE BL-11A DRILL HOLE BL-14A (0-0-DEPTI1 1..1.1:1 01-11- 01 1'111 i (0-UNIT M.:V1I4EH. Figure 4a. - Differential thermal analysis curves of samples

-10,1;() i 3- 1 1 2) fight brov.n (5 VII 5, 61 1)1.-1611 (4 1 light reddish brown ((OR 5.,6) 1-11.-16It (7,7)(7, ) light reddish orange (MR 7 , 6) 111.-161) (7-8 1 - 2)(6) gray (5 Yli II 1) 131.-1613 (8 1'2 -16)(8) Very pale orange 110 YR 8'2) 1(1.-11C (0-3)(2) Pinkish gr, (5 NA( 11 1) '0 0 1)011 '001 1 111111, (0-11 Light bro,r, (5 Nit IS 6) (1-2 1:2); 114\111(t 1,61:4t; III -(65 (. 1 ..-4 1121' light brov,It 1.11.-16A (4 li2-5 1 Pale re(h(tsh orange (10)1 7 6) 1t1.-16A (5 I 2 -8 1:2)(5) Moderate 0 rarlg, )(nk (10)1 7 4) 1 2-11)(7) Vol, pale orange (1).> V12 8'2) Ill.-16 1 (14-15) CO 11:)1.6 gr;)y DRILL HOLES BL-16B AND BL-11C DRILL HOLE BL-16A i00-1)1:1'111N '1:)-1 (0-1)-1)1.11H IN ) 1,1 NI 51111111 (1)-1 NI'l N1 31,1 II Figure 4b.- Differential thermal analysis curves of samples

"

' nm" o" It , .. / / ! ! DRILL BC]T.E BL-17A DRILL HOLE BT.-13A '0-1) M;' I P 1% ,o. ,n`..vm., ,x.`n .,axx Figure 4c.- Differential thermal analysis curves of samples

Table 1. --X-ray mineralogical analyses of clay from the Bushrod Island-New Georgia deposit. by Analyst, Paul D. Blackman. USGS Laboratory Report No. DEG.140 The following information is quoted from the report: "Each sample was treated as follows: An appropriate portion was ground, packed in an aluminum holder, and an X-ray diffraction pattern prepared of the total sample. Then a portion was dispersed in water, utilizing an ultrasonic trans­ ducer, and the fine fraction was removed and deposited on tiles for X-ray dif­ fraction examination. A series of treatments were performed, including heating, glycolation and cation saturation to determine the clay type mineralogy. "The mineralogical content of the samples is listed below as parts in ten. As these estimates are derived from the relative intend ities of the diffracted lines, and other factors in addition to quantity of a mineral affect diffraction intensity, these estimates are not intended to give more than an indication of 1t the relative amounts of the various minerals present. Estimated amount Samples Minerals present (parts in ten) Field No. BL-14A Kaolinite Depth - 0-1' Gibbsite tr* Unit No. 1 Montmorillonite (aluminum interlayered) tr Illinte tr Goethite tr Quartz K-feldspar tr Field No. BL-14A Kaolinite 6+ Depth - 1-3 1/2' Gibbsite tr Unit No. 4 Montmorillonite (aluminum interlayered) tr Illite tr Goethite tr Quartz 1+ K-feldspar tr Field No. BL-14A Kaolinite Depth - 3 1/2-6' Gibbsite tr Unit No. 5 Montmorillonite (aluminum interlayered) tr Illite tr Quartz K-feldspar tr Amorphous silica or alumina? tr Field No. BL-14A Organic matter tr Depth - 6-7' Kaolinite Unit No. 8 Gibbsite tr Montmorillonite (aluminum interlayered) tr Mite tr Quartz K-feldspar tr *tr - less than 9%

Table luineralogtal—analysee—e—clay froarthe—Aushrocl Island-New Georgia deposits (cont.) Samples Minerals _present Field No. BL-14A Organic matter Depth - 7-12 1/2' Krolinite Unit No. 9

Gibbsite Montmorillonite (aluminum_interlayered Illite Quartz K-feldspar Pyrite Field No. BL-19A Kaolinite Depth - 2-3 1/2' Gibbsite Unit No. 4 Montmorillonite (aluminum interlayered) Illite Quartz Goethite Field No. BL-19A Organic matter Depth - 18-21 1/2' Kaolinite Unit No. 8 Gibbsite Montmorillonite (aluminum interlayered) Illite Ouartz K-feldspar Siderite Pyrite *tr - less than 5% 'Estimated amount (parts in ten) tr tr tr tr 1+ tr tr 7+ tr tr tr 1+ tr tr 6+ tr tr tr 2+ tr tr tr

Table 2.--Chemical analyses of clay samples from the Bushrod Island-New Georgia depositgLi (In percent) Lab. No. 14170 -349 Field No. BL-4B BL-GA BL-11A BL-11A BL-11A BL-11A BL-11A BL-11A BL-14A BL-14A BL-14A BL-14A BL-14A Depth 10-12' 2-3' 0-1' 1-5 i.' 4-8' 8-9' 9-124' 123-1* 0-1' 1-3i, o-7' 7-12,1 Unit No. Oxides: S102 4').7 A1203 Fe203 FeO 2/ Mg0 Ca0 Na20 1(20 .8; $ % H904. T102 P205 Mn0 co, .o8 Volatiles other than 1120 and CO2 Sum Total iron as Fe203 s.3 1/ Analysis performed in the Rapid Rock Analysis Laboratory under Leonard Shapiro, U.S. Geological Survey laboratory, Report No. 68 WRC 99. 2/ Color prevents determination.

Table 2.--Chemical analyv,s of clay zamples from 2ro5 Island-New l;eorrj: 'Toit (continued) :6 Lab. No. W170 ..", -37, -57' Fiel1 No. 31,-16A 31-17A BL-17A BL-18A BL-19A 2L-19A PL-19A 31-19A 31-19A 95-19A 3I,-19A Depth 14-3Y 14-,' Unit No. Oxides: SIO2 (2.0 4,:,.4 4,4 ,4.8 A120 23.) ,2.6 ;0.8 22.? Fe° .:It .so MgO Ca0 . ;5 Na20 .6, K20 H20_.t, I.j 1mi H20+ 9., 1 .Q 9.; Cra TiO2 .9" P205 Mn0 .01, CO2 <.0 Volatiles other than <.0 2.; 320 and CO2 Sum Total iron as Fe203

SiO2 ranges from 24.7 to 64.o percent and shows no systematic variation. The distribution appears to be the result of original deposition. In general, there is a positive correlation with the amount of quartz. A1203 ranges from 16.3 to 33.4 percent, generally increasing with depth within the zone of oxidation, then decreasing below. The distribution appears to be the result of original deposition slightly modified by weathering. Fe203 ranges from 0.17 to 8.9 percent and is generally high at the surface, increasing ,ith depth to a point above the base of the zone of oxidation, then decreasing sharply and varying in amount with further increase in depth. The distribution appears to be the result of original deposition and diagenesis strongly modified by weathering in the upper part of the deposit. Fe0 ranges from 0.19 to 4.8 percent and is relatively high in the upper foot or so, generally, decreasing with depth aithin the zone of oxidation then, generally, increasing with depth. The distribution appears to be the result of original deposition and diagenesis strongly modified by weathering in the upper part of the deposit. The apparently anomalous high near the surface may be explained as the result of a temporary reducing environment caused by the presence of humus and charcoal. P2°5, Each of the oxides Mg0, Ca°, K20, Ti02,/and CO2 is present in quantities of less than 2 percent and shows no systematic variation. The distribution appears to be the result of original deposition and diagenesis. Na20 ranges from 0.02 to 0.95 percent and shows no systematic variation. However, the upper 3 1/2 feet of the deposit at location BL-19A anomalously high in Na20 and the normal K20/Na20 ratio of greater than 1 in sedimentary rocks is reversed here. This may be due to the activity of man; elsewhere the distribution appears to be the result of original deposition and diagenesis. H20+ ranges from 8.1 to 13.7 percent and varies with A1,01. The A120/H20+ ratio ranges from 1.6 to 2.8, averages 2.3 with a mode of 2.4 gnd shows Eh abundance of kaolinite, in which this ratio is 2.8 to 2.9. Mn0 ranges from 0.00 to 0.10 percent; it is slightly higher at the surface than at depth but otheraise shows no systematic variation. The distribution except for the concentration at the surface appears to be the result of original deposition. The concentration at the surface may come from decaying vegetation. Volatiles other than H20 and CO2 range from 0 to 33.7 percent and show in part the amount of sulfide presen, but mostly they indicate the amount of organic material present, as there is a direct correlation between the amounts of these volatiles and the abundance of plant remains. From these data it is apparent that the color banding varies with the amount of Fe2O3 and organic material but that the amount of Fe0 cannot be estimated. However, there is a rude, direct correlation between total iron content and the amount of plant remains or organic material in the unweathered parts of the deposit.

Bccauso of the preceding correlations and for convenience in tonnage estimates and further discussion, the units may be combined so that the clay deposit is divided into three groups: Group A, high in iron; Group B, relatively low in iron; and Group C, high in both organic material and iron. Group A is formed from the combination of units 1, 3 and 4; Group B from units 2, 5, 6, 7, and 8; and Group C is unit 9. The unweighted averages and ranges of the oxides and volatiles are given in Table 3. P0S-7121AL RESERVES As there is no commercial production of ceramics in this area at the present time, the reserves estimated below must be considered as potential reserves. The potential indicatod reserves for each of the three groups of clay (Table 3) were estimated for that portion of the deposit south of the St. Paul River, east of Stockton Creek, and north of the short road from New Georgia to Stockton Creek (fig. 1). For each of the groups an isopach map was compiled (figs. 5, 6, and 7); the areas were measured by planimeter and the volumes computed by means of the prismoidal formula. The volumes obtained were generally reduced for geologic reasons and were then converted to tons of clay. From the geology of the deposit it seems reasonable to infer an amount of clay for each of the three groups in the remaining portion of the deposit equal to that estimated for the potential indicated reserves. The volume of clay in the group (A) formed from combined units 1,31 and 4 is 76,000,000 cu. ft. This was reduced by 50 percent for thinness along the edges of the area and irregularities of the surface to a volume 38,000,000 Cu. ft. This was reduced by 30 percent for air shrinkage; 2.2 was assumed to be the specific gravity of the dry clay; and the computed result is a potential indicated reserve of 1,800,000 short tons of clay. The volume of clay in the group (B) formed from the combined units 2, 5, 6, 7, and 8 is 110,000,000 cu. ft. This was reduced by 30 percent allowing for possible sand lenses (the drilling is too widely spaced for development drilling) to a volume of 77,000,000 cu. ft. This was reduced by 30 percent for air shrinkage; 2.2 was assumed to be the specific gravity of the dry clay; and the computed result is a potential indicated reserve of 5,300,000 short tons of clay. The volume of clay in unit 9 (C) is 14,000,000 Cu. ft. This was reduced by 30 percent for air shrinkage; 1.5 was assumed to be the specific gravity of the dry clay (the specific gravity was reduced because of the abundant plant remains in the clay); and the computed result is a potential indicated reserve of 470,000 short tons of clay. The amount of reserves depends on what can be mined economically, and the problem in this deposit will be one of high water part of the year in the upper part of the deposit and water all year in the lower part of the deposit. Horever, the water problem has been solved successfully in other places and presumably will be solved here.

Table 3.--Averages and ranges of the oxides and volatiles in the three sub­ divisions of the clay in the Bushrod Island-New Georgia deposit. (In percent) Combined units Combined units Oxides 1,3 and 4 2, 5, 6, 7, and 8 Unit 9 Average Rut Average ' A'ange Average unge Si02 49.8 43.4-60.5 49.6 44.o-64.o 24.7-41.7 A1203 26.0 18.6-30.8 28.5 20.2-33.4 19.6 16.3-21.5 Fe203 FeO Total iron as Fe2O3 Mg° Ca0 .0o- .96 Rae .04-.85 K2o .48- ,69 H20 H20+ 7.7-13.7 10.4 9.5-11.1 TiO2 P205 .03- .27 .03 MnO CO2 .06 ‹.05- .11 <05-2.3 <.05- .08 Volatiles other than H20 and CO2 18.7-33.7 ,41106

2 KILOMETEF1S MILE 130:Nriproic. Declination 1969 CONTOUR INTERVAL 5 METERS ISOPACII INTERVAL 5 FEET Southern boundary of block for which indicated reserves of clay were estimated Figure 5. - Isopach map showing thickness of combined units I, 3, and 4

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1 MILE 13°Approx. Declination 1969 CONTOUR INTERVAL 5 METERS ISOPACIli INTERVAL 5 FEET Southern boundary of block for which indicated reserves of clay were estimated Figure 6. - Isopach map showing thickness of combined units 2, 5, 6, 7, and 8

C, 0., St. '7 New Krutown Bushrod Island Logan Town k

2 KILOMETERS I MILE PApprox. Declination 1969 CONTOUR INTERVAL 5 METERS ISOPACH INTERVAL S FEET Figure 7. - Isopach map showing thickness of unit 9

In summary, it is estimated that the potential indicated reserves of clay for each of the three groups is as follows: (A) clay high in iron --1,800,000 short tons; (B) clay relatively low in iron--5,300,000 short tons; and (C) clay high in both organic material and iron-470,000 short tons. Because of geologic similarity it seems reasonable to infer an amount of clay for each of the three groups in the remaining portion of the deposit equal to that estimated for the potential indicated reserves. COMMERCIAL USES From the foregoing discussion it is apparent that the clay in this deposit is a mixed clay composed dominantly of kaolinite, with generally abundant vartz, trace amounts of illite, montmorillonite, gibbsite, and K-feldspar, caring amounts of iron-bearing minerals, and varying amounts of organic material in the form of plant remains. The main commercial use of this type of clay is in the ceramics industry. Manufactured clay products of the ceramics industry may be divided into the following categories: structural clay products, which includes brick, drain tile, sewer pipe, conduit tile, glazed tile, and terra cotta; pottery or stone­ ware; refractories; whiteJare; and porcelain. Specific commercial uses depend upon physical properties of the raw and fired clay which include: plasticity, drying shrinkage, drying strength, fired color, firing shrinkage, absorption, modulus of rupture, and pyrometric cone equivalent. In order to determine the specific commercial uses for which the clay of the Bushrod Island-Nei Georgia deposit might be suitable, representative samples from the three groups previously described were submitted to the Refractories Industry Research Center, Department of Ceramic Engineering, Ohio State University, for testing and evaluation. For these tests a representative sample of the combined units 1,3,and 4 (Group A) was designated A; a repre­ sentative sample of the combined units 2,5,6,7, and 8 (Group B) was designated B; and a representative sample of unit 9 (Group C) was designated C. The results of the tests are shown in table 4.

Table 4.-- Physical properties of the raw and fired clay as determined in the laboratories of the Refractories Industry Research Center, Department of Ceramic Engineering, Ohio State University. Physical properties Sample A Sample B Sample C Plasticity and extrusion properties Water of plasticity (percent) gpca. good good Drying shrinkage (linear in percent) Drying strength (lbs. per sq. in.) 515 Pyrometric cone equivalent (in cones) Fired color red to darkbuff to dark buff to grayred buff-gray buff Firing shrinkage (linear in percent) 1800°F 2.4o 1900()F 2000 F 2100°F 2200°F 2300()F 2400°F Absorption (in percent) 1800°F 1900°F 2000°F 210100F 2200°F 2300°F 2)+00°F Modups of rupture (ibs. per sq. in.) 1800 F 1900°F 2000°F 2100°F 2200°F 2300°F 2400°F The values of the physical properties dependent upon firing were obtain­ ed on specimens fired in electrically heated laboratory kilns. It is the opinion of Metzgar (written commun., 1969) that in commercial kilns these values will be developed at temperatures approximately 200°F lower than those given in this table.

A. J. Metzger (written commun., 1969) Director of the Refractories Industry Research Center, evaluated the clays for specific commercial uses. The results of this evaluation for the three groups of clay are: A. The clay designated A is suitable for making building brick, hollow tile, drain tile, roofing tile, quarry tile, flower pots, and porous earthen­ ware pots such as those used for water coolers. B. The clay designated B is suitable for making the items listed above and probably for stoneware and small diameter sewer pipe. C. The clay designated C is suitable for making the items previously listed, low-to intermediate-duty refractory products, and possibly an insulating refractory if a ready source of sawdust or other inexpensive combustible is available. It was also recommended that precalcined clay of minus 1/4 inch particle size be added to the raw clays B and C in making the more refractory products. The addition of precalcined clay would improve the firing properties of the clays and make the finished products more resista::t to thermal shock. In the past, Munariz S. A. located on Bushrod Island has made bricks from the clay of the Bushrod Island-New Georgia deposit (the inactive pit in the New Georgia area is shown on Figure 1). The Firestone Company makes bricks for its awn use from alluvial sandy clay found in its "arbel concession area. REFERENCES Battelle Institute, 1963, Clay and Kaolin, in City and regional planning, Monrovia, Liberia, Part I: Frankfurt, Battelle Institute, v. 6, p. 219-224. Geological Society of America, 1963, Rock-color chart: distributed by the Geological Society of America, New York, N. Y. Worrall, G. A., and Dinkins, E. L., 1965, Soils of the Monrovia district: Liberia UnivO, College of Agriculture, unpub. rept., 17p.

LPITNDIKI: Logs of hand-auger holes drilled during the investigation of the Bushrod Island-New Georgia clay deposit. All holes were logged by L. V. Blade. All the samples were moist or wet and the colors recorded are those of the wet samples. The approximate altitudes were taken from the Hansa Luftbild 1963 topographic map. ifole number, date, and altitude Depth (feet) Descriqion Hole PL-1LIREHL2L1912LL.212mximate altitude 16 feet. 0 - 1 Dark gray, silty, coarse-grained quartz sand with humus. 1 - 14 Light gray, slightly silty, medium- to coarse-grained quartz sand. 3 Reddish-brown, slightly silty, medium-- to coarse-grained quartz sand. 10 Light brown, silty, medium- to coarse-grained quartz sand. Grains are angular to subrounded. Water table was 9 feet below surface. 154 Light reddish-brown, silty, medium- to coarse-grained quartz sand. Grains are angular to subrounded. 154 - 24 Reddish-brown slightly silty medium- to coarse-grained quartz sand with sparse quartz granules. Grains are angular to subrounded. Thin cemented zones occur from 22 to 24 feet. Ent2k21LImIEL1222.2267timE2ximate altitude 15 feet. O1 - 2 Brownish-gray plastic clay with humus. Unit 1. 1 Brown plastic clay. 3 Brown and reddish-brown plastic clay. unit 4. 3 - 61 Light brown and light gray mottled plastic clay. Water table was 34 feet blow surface. Unit 5. K.1 '-'2 ". 19 Gray to dark gray plastic clay with plant remains below 84 feet. Units 7 and 8. Hle BL-2B, August 15, 1967, approximate altitude 1 feet. O - , Road fill. y ., - 3 Brown to light brawn plastic clay. unit 3. Light brown, brown, and light gray mottled plastic clay. Water table was 7 feet below surface. Unit 4 10 . 13 Light gray and light brown mottled, slightly sandy, plastic clay. unit 13 - 231 Gray to dark gray plastic clay with plant remains below 19 feet. Upper 1 foot unit 7, remainder unit 8. lio.1e kr.., zal,Atrist 16, 196/1.j-0-proximate altitude 15 feet. O - 2 Road fill. 2 "" 4 Light brown and reddish brawn mottled plastic Clay. tipper 1 Toot gray with humus. Units 1 and 4. 4 - 7 Light gray and light brown mottled plastic clay. Water table was 1.4.4 feet below surface. unit 5. 7 - 10 Dark gray, clayey, very fine-grained quartz sand with plant remains below 8 feet. 10 - 13 Dark to light gray, medium- to coarse-grained quartz sand with scarce granules. Grains are angular to subrounded.

Hole number? date, and altitude Depth (feet) Description Hole ,BL-3B, August 16, 1967, approximate altitude 15 feet. O - Dark gray, silty, medium- to coarse-grained quartz sand with humus. 21 Yellowish-gray, silty, medium- to coarse-grained quartz sand. Grains angular to subrounded. Yellowish-brown, silty, medium- to coarse-grained quartz sand. Grains are angular to subrounded. Water table was 3 feet below surface. pole BL-3C, August 17, 1967A, approximate altitude 15 feet. Unit 1. O - 1 Grayish-brown, sandy, plastic clay./ Quartz sand is very fine grained. Brown, sandy, plastic clay. Quartz sand is very fine grained. Below IL- feet the clay is mottled brown and reddish-brown. units 3 and 4. a Light and moderate brawn mottled, clayey, very fine-grained quartz sand with light gray mottling below 5 feet. Water table was 0 feet below surface. Light gray and light brown mottled, clayey, very fine.. to fine-grained quartz sand. Gray, clayey, very fine- to fine-grained quartz sand with plant remains below- 11 feet. Hole BL..44 Autust 1 1 appoximate altitude 3.5 feet. Road fill. Unit 3 Dark brown, sandy, plastic clay. es 1-2- - 6-2floderate to light brown, slightly sandy, plastic clay with gray and brawn mottling below 6 feet. Units 3 and 5. Light gray and light brown mottled, clayey, veryfine- to fine-grained quartz sand. Water table was 8 feet below surface. 10 - 13-LDark gray, clayey, very fine- to fine-grained quartz sand thinly interbedded with dark gray clay. Plant remains below 12 feet. 131- - 15 Light gray, medium- to coarse-grained quartz sand with sparse granules and pebbles. Grains are angular to sUbrounded. August 18, 1967, approximate altitude 15 feet. Dark gray and brown mottled plastic clay with humus. unit 1. Brown plastic clay. Water table was 4 feet below surface. unit 3. Light gray and reddish-brown mottled plastic clay. unit 5. Gray plastic clay. unit 6. Dark gray, clayey, very fine- to fine-grained quartz sand. The color is a lighter gray below 14 feet. 111024231n241,August 18, 1967, auroximate altitude 15 feet. O . 1 flaterial washed in from railroad fill. Bram plastic clay with humus in upper L'- foot. The color is mottled brown and reddish-brown below 2 feet. Water table was 3 feet below surface. Units 1 3, and 4. Light gray and reddish-bratm mottled plastic clay. unit 5. 7 - 13L- Grayish-brawn plastic clay with plant remains at 7 - feet. unit 7. 13L% ii. 1.14. Dark gray, clayey, very fine- to fine-grained quartz sand above light gray, medium- to coarse-grained quartz sand.

Hole number date, and altitude De th feet Hole BL-5B, August 221267x_apyroximate altitude 15 feet,. 0 - 11 Material washed in from railroad fill. Grayish-brawn sandy plastic clay. Unit 3. 2 - 41 Light brown and moderate brown mottled, slightly sandy, plastic clay. The lowest -1- foot is gray in color. Water table was 4 feet below surface. Units 4 and 6. 5-1- Light gray, slightly silty, medium- to coarse-grained quartz sand. Hole BL-5C, August 22, 1967J approximate altitude 15 feet. O - 1 -2' Material washed in from railroad fill. Light brawn and reddish-brown mottled plastic clay with additional light gray mottling below 3 feet. Water table was 3i feet below surface. Unit 4. Gray, clayey, very fine-grained quartz sand. Dark gray, silty, very fine- to fine-grained quartz sand. 10 - 10i Gray to light gray, silty, medium- to coarse-grained quartz sand. Hole BL-6A, August 22, 1967, approximate altitude 16 feet. O . .1 Material washed in from railroad fill. Grayish-brown, sandy, plastic clay. Unit 1, Light brown plastic clay. Water table was 4 feet below surface. Unit Light gray and light brawn mottled plastic clay with light gray color predominant below 9 feet. Units 5 and 6. Gray plastic clay with abundant plant remains. Unit 8. Hole BL-6B, August 231 1967, approximate altitude 15 feet. O - 2 Material washed in from railroad fill. 2 - 2.--'. Grayish-brown plastic clay. Unit 1. 2.A.- - 4i Light brown and reddish-brawn mottled plastic clay, slightly sandy in upper -1- foot. Light gray was added to the brawn mottling below 3 feet. Water table was 3 feet below surface. Unit 4. 4.i - 71 Light gray and reddish-brown mottled plastic clay with light gray color predominant below 5 feet. unit 5. Dark gray plastic clay with plant remains. Unit 8. 16 - 171 Light gray, silty, very fine- to fine-grained quartz sand. Hole BL-7A, August 21967 .1._approximate altitude 11 feet. Unit 3. Light brawn plastic clay? (This hole was drilltd in a cut and the collar is probably about 4 feet below the original ground level.) 3 - 41 Light brown and reddish-brown mottled plastic clay. Unit 4. Light gray, very fine- to fine-grained quartz sand. Water table was 5 feet below surface. 5 - 9i Dark gray, silty, very fine-grained quartz sand.

Hole number, date, and altitude Depth (feet) Description Hole BL-7B, August 25, 1967, approximate altitude 15 feet. o Material washed into ditch. Light brawn and reddish-brawn mottled plastic clay. Unit 3. 5i Light gray, light brown, and reddish-brown mottled plastic clay. Water table was 3- feet below surface. Unit 5. Units 6 and 7. Light gray plastic clay with a darker gray color the lowest t foot. Moderate brawn plastic clay with abundant plant remains turned grayish black on exposure to the air. unit 9. Dark gray plastic clay with plant remains. Unit 8. Gray, medium- to coarse-grained quartz sand. Hole BL-7C. August 2, 19672 approximate altitude 15 feet. 0 - 1 Road fill. 3fI Brown plastic clay. i '" unit 3. .-ff - 5 Light brown, light gray, and reddish-brawn mottled plastic clay. Water table was 41 feet below surface. unit 4. Units 6 and Light gray plastic clay with the lower foot brownish-gray in color/ 7. Dark brown plastic clay with abundant plant remains that turn grayish. black when el:posed to the air. unit 9. 10 -.1271 Dark gray plastic clay with plant remains. Unit 8 Gray, silty, very fine- to fine-grained quartz sand with plant remains locally abundant. B .8ut29, l67, apprx3,nate]4itude ).5 feet. naterial washed in from road. Brown, slightly sandy, plastic clay. Unit 3. 3 - 3i Light brawn, light gray, and reddish-brown mottled sandy olaY. Unit 4, Light brawn, slightly silty, medium- to coarse...grained quartz sand. Grains are angular to subrounded. Water table was 41 feet below surface. Hole 1114-8B, August 29, 1967, approximate altitude 15 feqt. AIMPRIMIONIMINED 1 Road metal. 2 " 1 Dark gray, silty, medium- to coarse-grained quartz sand with humus. Grains are angular to subrounded. 1 . 11 Gray and reddish-brawn mottled, clayey, mediums, to coarsewgrained quartz sand. 11 - 31 Gray plastic clay slightly sandy upper --1. - foot. Water table was 3 feet below surface. Unit 2 Light gray, light brown, and reddish-brawn mottled plastic clay. Unit 5. Dark gray plastic clay with plant remains. Unit 8 7 - 81 Gray to light gray, medium- to coarse-grained quartz sand.

Hole number, date, and altitude Depth (feet) Description Hole BL-9A,_ August 29, 1967, approximate altitude 15 feet. Road fill. Gray, clayey, medium- to coarse-grained quartz sand. Unit 2. Gray to light gray plastic clay. Water table was feet below surface./ Light gray and light brown mottled plastic clay. Unit 5. 6 - 81 Light gray plastic clay with dark gray color and plant remains in lower foot. Units 6 and 7. Brown plastic clay with plant remains that are locally abundant. Color changes to dark gray on exposure to the air. Unit 8. Hole 1Z . Zu aoxirnate altitude 18 feet. Dark gray, silty, medium- to coarse-grained quartz sand with humus. Grayish-brown to light brown, silty, medium- to coarse-grained quartz sand. Water table was 61 feet below surface. 8 -l2* Pinkish-brown, silty, medium- to coarse-grained quartz sand. Hole BL-9C, August 30, 1967, approximate altitude 15 feet. Road fill. Brown plastic clay. slightly sandy in upper I foot. Light brown and reddish-brown mottled below 2-12- feet. Water table :was 2i feet below surface. Units 3 and 4. 3 - 3t Light gray and reddish-brown mottled plastic clay. Light gray, silty, medium- to coarse-grained .quartz sand. Hole BL-10A Al4gust 30, 1967, approximate altitude 15 feet. Light brown, light gray, and reddish-brown mottled plastic clay. Unit 4. Light gray and light brown mottled plastic clay. Water table was 4 feet below surface. Unit 5. Gray to dark gray plastic clay with plant remains. Unit 7. Hole BL-10B, August 31, 1967, approximate 2.1ILtude 15 feet. Grayish-brown, slightly sandy, plastic clay with humus. unit 1. Brawn plastic clay. Water table was 34 feet below surface. unit 3. 4 - 71 Light brown, light gray, and reddish-brown mottled, very clayey, very fine- to fine-grained quartz sand. Light gray, very clayey, very fine- to fine-grained quarts sand. Unit 7 106-f 15 Gray plastic clay with plant remains; slightly sandy in upper 2 feet, / " 15 - 151Dark brown plastic clay with abundant plant remains. The color changes to dark gray on exposure to the air. unit 9 Hole BL-10C, August 31, 1967, approximate altitude 13 feet. Dark gray, slightly sandy, plastic clay with humus. Unit 1 Light brownish-gray, slightly sandy, plastic clay. Unit 3. Light gray, silty, medium- to coarse-grained quartz sand. Water table was ai feet below surface.

Eole number, dave, ''"

:1T2). (feet) Description pole 131,-11, September 1 1967, approximate altitude 15 feet. O - 1 Dark gray, slightly sandy, plastic clay with humus. Unit 1. 1 - 51 Brawn to light brown, slightly sandy, plastic clay. Water table was 51 feet below surface. unit 3 Light brown, light gray, and reddish-brown mottled plastic clay. it

8 - 124 Light to dark gray plastic clay; plant remains in lower portion. tUjrnI 4 8,7 12f - 15-f Brown plastic clay with abundant plant remains. The color changes to grayish-black on exposure to the air. Unit 9. -01e BL-11131._Septmbpr 6, 1967, aPEroximate altitude_1,5 feet. O - .1 Grayl_si-.-brown, slIghtly sandy, Plastic clay with humus. Unit 1. Grayish-brown to light brown plastic clay that is slightly sandy in upper foot. Unit 3. Light bro,m, reddish-brown, and light gray mottled plastic clay. Water table was 6- feet below surface. Unit 4. L5ght gray to dark gray plastic clay with plant remains locally abundant. units 6 and 7. Brown plastic clay with abundant plant remains. The color changes to grayish-black on exposure to the air. Unit 9. Pole BL-11C September 6 1967, approximate altitude 11 feet. O - 4 Light gray plastic clay with roots. Water table was at the surface. Brownish-gray plastic clay with plant remains. unit 8. Dusky brown plastic clay with abundant plant reamins. unit 9. 131 - 15i- Gray, silty, medium- to coarse-grained quartz sand. 707,e_B1-12A, SeEt_Pmbcr 14, 1967, approximate altitude 15 feet. Grayish-brown plastic clay with humus. unit 1. Grayish-brown to brown plastic clay with iron oxide nodules at 2 feet. .and mottled with reddish-brown color below 2 feet. Water table was 3 feet below the surface. Units 3 and 4. Unit 5. Light gray, light brown, and lesser reddish-brown mottled plastic clay./ 1.7rr.y to dark gray plastic clay with plant remains abundant in lower foot. Unit 7. Brown plastic clay with plant remains; changes color to dark gray on exposure to the air. The lower foot is slightly sandy. unit 8. Gray to light gray, slightly silty, medium- to coarse-grained quartz sand. BL712B.., S?„ptem'?er 15, 1967, auroximate allIII4c12_13 feet. O - 1 Grayish-:own, slightly sarAy, plastic clay with humus and snA11 fragmc of charcoal. Prown to 1:-.7:1t brown, slightly sandy, plastic clay. Water table was 3 feet below surface. Lf.ght gray, silty, fine- to coarse-grained quartz sand. - 4i 12,Cat gray, coarse- to medium-grained quartz sand.

Hole number, date, and altitude Dezth cfeet) Descriptton ple BL-12C, September 1Y7) EL,arcximat; altitude 13 feet. .1 Gray, slightly sandy, plastic clay with humus and fragments of charcoal.

Light gray, sandy, plastic clay. Water table was 1 foot below surface. Light gray, clayey, coarse- to medium-grained quartz sand.

Light gray, sandy, plastic clay. 42 Light gray, coarse- to medium-grained quartz sand. Ptle,BL-13A, September 15, 1567, approximate altitude 16 feet. Grayish-brown, slightly sandy, plastic clay with humus and fragments or charcoal. Unit 1. 2 '" 5 Brown to light brown, slightly and plastic clay. unit 3. Brown and reddish-brown mottled, clayey, very fine- to fine-grained quartz sand. Light gray, clayey, very fine- to fine-grained quartz sand. Water table was 7i feet below surface. Light brown, coarse- to medium-grained quartz sand with sparse granules. A thin clayey sand lens occurs at 8 feet. lioleBil soximate altitude 13 feet.. Unit 1. 1-Sete -al Cray and brown mottled plastic clay with humus and fragments of charcoal. / 1 5 Light gray and light brown mottled plastic clay. Water table was 1-1. feet below surface. Unit 5. Light gray plastic clay. Unit 6. Gray plastic clay with plant remains locally abundant. Unit 7. Gray, clayey, very fine- to fine-grained quartz sand with plant remains locioly abundant. Gray to light gray, medium- to coarse-grained quartz sand. S_ektember 19„ 067 apkroxirnate altitude 13 feet. Unit 1. 1 Gray and brown mottled plastic clay with humus and fragments of charcoal./ 1 Light brown, light gray, and reddish-brown mottled plastic clay with a larger proportion of gray in the lower part. Water table was 2 feet below surface. Units 4 and 5. Gray plastic clay with a small amount of plant remains. Unit 7. Light gray, slightly clayey, medium- to coarse-grained quartz sand. E°14.21T14A1 September 21,19671 app3"oximate altitude 16 feet. - Gray to brown plastic clay with humus and fragments of charcoal. Unit 1. Light brown and reddish-brown mottled plastic clay. Water table was feet below surface. Unit 5. Light gray and light brown mottled plastic clay. Unit 5. Brownish-gray plastic clay with plant remains abundant in last i fort. The color changes to gray on exposure to the air. Unit 8. Moderate brwn plastic clay with abundant plant remains. The clay is slightly sandy in the lower foot. Unit 9. Gray to light gray, silty, fine- to Laarae-grained quartz seind with plant remains in the upper 1 foot.

:ole number date, and altitude re th feet Description Hole BL-14B, September 21, 1X7, approximate altitude l feet. Road fill. 1 - 1-21- Gray plastic clay with humus and fragments of charcoal. Unit 1. - 2i Brwn plastic clay with sparse sand grains. Unit 3. Light to dark gray, slightly sandy, plastic clay. Water table WAS 3 feet below surface. Unit 7. Gray to light gray, silty, very coarse- to medium-grained quartz sand with wood fragments in upper foot. Hole BL-145A, September 21, 1967, approximate altitude 15 feet. 0 - li Grayish-brown to light brown, sandy, plastic clay with humus. Unit 1. Brown, light brown, and reddish-brown mottled, sandy, plastic clay.Unit 4. Light brown and light gray mottled clayey, very fine- to fine-grained quartz sand. Water table was 3i feet below surface. Light gray and light brown mottled, sandy, plastic clay. Unit 5. Light gray and light brawn mottled, clayey, very fine- to fine-grained quartz sand. Light gray to light brown, very coarse- to medium-grained quartz sand. Gray, clayey, very fine- to fine-grained quartz sand. Hole BL-15B, September 22, 1967)approximate altitude 13 feet. Grayish-brown plastic clay with humus, fragments of charcoal, and sparse grains of sand. Unit 1. Brown, light brown, and reddish-brown mottled plastic clay. Water table was 2-1-- feet below surface. unit 4. Light gray and light brown mottled plastic clay. Unit 5. 8 - 131 Light gray to gray plastic clay. units 6 and 7. Brownish-gray, clayey, very fine- to fine-grained quartz sand that changes to dark gray on exposure to the air. Brownish-gray, sandy, plastic clay that turns dark gray on exposure to air. Unit 8. 1111e BL-16A, September 26_, 1967, approximate altitude 15 feet.

Dark gray to brownish-gray, clayey, very fine- to fine-grained quartz sand with humus and fragments of charcoal. 1 - 21 Brown to light brown, clayey, very fine- to fine-grained quartz sand with nodules up to -1' inch in diameter of iron oxide. 3 : 4 Light brown, clayey, very fine- to fine-grained quartz sand. Light brown and light gray mottled, sandy, plastic clay. Water table( was 51 feet below surface. Unit 5. 5t - 8i Light gray and light brown mottled plastic clay. Unit 5. Dark gray plastic clay. Unit 7. Brown plastic clay with abundant plant remains. The color changes to dark gray on exposure to the air. Unit 9. Light bluish-gray, sandy, Plastic clay. Sand grains are medium-cto very coarsevgrained. Light gray, clayey, sandy, pebble gravel. Pebbles are of quartz and are well:rdunded.

Hole number date, and altitude DePt.h (fee.t. Description

Hole BL-16B, September 26, 1967, uproximate altitude 1A5 feet. O -l.. Washed-in fill material. Light brown, clayey, very fine- to fine-grained quartz sand. Water table was 21 feet below surface.tnit 3. Light brown, sandy, plastic clay./°Sand is very fine- to fine-grained. Light gray and light brown mottled plastic clay. Unit 5. 7 - 81 Light gray plastic clay. u4j_t 6 Brownish-gray plastic clay at turns dark gray on exposure to the air.' Plant remains are locally abundant. unit 8. . Ilgia,BL01VL.) Ssotember 27)1967, . approximate altitude 18 feet.

O - lloae 31 - 41 Dark gray plastic clay with humus and fragments of charcoal. Unit 1. 4-ff Brown, light brown, and reddish-brown mottled plastic clay. Water table was 5 feet below surface. Unit 4. 7t gi Light gray and light brown mottled plastic clay. Unit 5. 9f - 13 Brownish-gray plastic clay that turns gray on exposure te the air and contains plant remains. Unit 7. Brownish-gray plastic clay with plant remains loca1.34. abundant. The color of the clay changes to dark. gray on exposure to the air. Unit Hole BL-17B,SepteMber 27, l967i approximate altitude 18 feet. A .. li Dark gray to brown, clayey, medium- to coarse-grained luartz sand with humus and fragments of charcoal. 11 - 6Brown to light brown, clayey, medium- to coarse-graine4 quartt sand. . Water table WAS 4i feet below surface.- Hole 2.4..2eztenter 28 1 te altitude ide 12 feet

Brown, slightly sandy, plastic clay with humus. Unit 1. 2 s' 2 Light brown plastic clay with plant roots. Water table was 2 fite below surface. Unit 3. Brownish-gray plastic clay with plant remains. Unit 7. Dark gray, clayey, very fine- to fine-grained quartz sand with plant remains. 4 - 6i Gray, very coarse- to medium-grained quartz sand with granules nf quartz. Hole BIT.g September_2j967, approximate altitude 1.3 feet. O - t Brownish-gray plastic clay with humus. Unit 1. - 4 Light gray plastic clay. Water table WAS It ta - feet below sfsce. Unit -

. Light gray to gray, silty, medium- to coarse-grained quartz sand.

Hole number:date, and altitude Depth (feet) Description dole BL-18B, September 28, 196Zx approximate altitude l feet. Dark gray to brownish-gray, clayey, medium- to coarse-grained quartz sand with humus. Brown, clayey, medium- to coarse-grained quartz sand. Grayish-brown to mottled brown and reddish-brown, clayey, medium- to coarse-grained quartz sand with angular granules and pebbles of quartz and thoroughly weathered quartz-mica(?) schist. Hole BL.-18C, Stember 2 l967 approximate altitude 12 feet. 0, - Washed in fill from the road. Water table was foot below surface. Dark gray plastic clay with humus. unit 1. 1 - 2i Gray, light gray, and brown mottled plastic clay. Unit 5. Light gray plastic clay. Unit 6. ,i. 3 - ..)2 Brawn plastic clay. Unit 7. Dusky brown plastic clay with plant remains. The clay changes color to a dark gray on exposure to the air. Unit 8. Dark gray to gray, clayey, fine- to coarse-grained quartz sand. Hole BL-18D1.)_September 23., 1967)approximate altitude 10 feet. 'rayish-brown, slightly sandy, plastic clay with humus and fragments of charcoal. Unit 1. Brawn, light brown, and reddish-brown mottled plastic clay. Water me' 21 table was 2-i feet below surface. Unit 4 Light gray and brown mottled, very sandy, plastic clay. Sand is coarse-grained. Very light brown, coarse- to medium-grained quartz sand.. Hole BL-15k, Seztember 29, 1567, approximate altitude 12 feet. Grayish-brown plastic clay with humus. Unit 1. Brawn to light brown plastic clay. Unit 3. 2 - 31 Light brown and reddish-brown mottled plastic clay. Water table- was 2i feet below surface.. Unit 4. 3t - 6Light gray and light brown mottled plastic clay. Unit 5. 6f - 9. Gray to dark gray plastic clay. Unit 7. 9 - 211 Brown plastic clay with plant remains dispersed through the clay. The color changes to dark gray on exposure to the air. Unit 8.

sor.do

Plates & figures from the original