Origin of Gypsum, with Special Reference to the Origin of the Michigan Deposits
"Origin of Gypsum, with Special Reference to the Origin of the Michigan Deposits" is an article from Transactions of the Kansas Academy of Science (1903-),…
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110 Kansas Academy Of Science.
ORIGIN OF GYPSUM, WITH SPECIAL REFERENCE TO THE ORIGIN OF THE MICHIGAN DEPOSITS.'
By Q. p. Geimslbt, Assistant State Geologist, Morgantown, W. Va. Read before the Academy, at Topeka, December 31, 1904.
VARIETY of theories have been advanced at various times to explain the origin of gypsum in various parts of the world. In order to arrive at a satisfactory explanation of the gypsum deposits in the state of Michigan, it may be well to give a resume of these different theories.
DEPOSITION or GYPSUM BY ACTION OP SULPUH SPRINGS.
Gypsum is deposited directly by some thermal springs, as in Ice- land, where the mineral is formed by the decomposition of volcanic tufa by acids dissolved in the water. The sulfurous acids become oxidized to sulfuric acid, and thus convert the carbonates, especially of lime and magnesia, into sulfates. Then, through evaporation, the sulfate of lime is deposited, forming layers of fibrous and selen- itic gypsum.
Small gypsum deposits are found about the fumaroles of craters and lava streams in Hawaii, where sulfurous acid (SO3) is con- verted into sulfuric, and attacks rocks which contain lime. The gypsum concretions in the Harz mountains are regarded as due to action of sulfur vapors on lime. Dana explains the origin of part of the New York gypsum as a secondary mineral, formed by the altera- tion of limestone by action of sulfuric acid; the sulfuric acid coming from sulfur springs by oxidation of the sulfuretted hydro- gen. Such springs are to be found in New York, especially about Salina and Syracuse.
According to the French geologist Lapparent, the large deposits of gypsum and anhydrite at Montiers, Bourg, and Saint Maurice, in the western Alps and Switzerland, are due to a similar transformation of lime. According to Lyell, the thermal waters of Aix, in Savoy, in passing through the strata of Jurassic limestone, turn them into gyp- sum. The springs of Baden, near Vienna, deposit a fine powder composed of a mixture of gypsum, sulfur, and muriate of lime.
Mr. R. S. Sherwin presented a paper before this Academy in 1901 in which he gave a series of arguments for this mode of origin of the Oklahoma gypsum deposits.
1. Published with permission of the director of the Michigan Geological Survey.
2. Annalen der Chem. 1847, Bunsen.
3. Iowa Geological Survey, vol. 12, p. 116, 1902.
GEOLOGICAL PAPERS. Ill
Deposition Of Gypsum Through Volcanic Agencies.
Dawson, following Lyell, explained the origin of the gypsum in Nova Scotia as due to an accumulation of these layers of limestone which were later acted upon by sulfuric acid in solution or in vapor produced by volcanic action. The limestone and calcareous matter were thus changed to the sulfate, and gypsum of good quality ac- cumulated in considerable thickness.
hunt's CHEMICAL THEORY OF GYPSUM FORMATION,
T. Sterry Hunt many years ago proposed a very complex theory of chemical interactions whereby gypsum was formed. The bicarbon- ate of soda acting upon sea-water separated the lime in the form of carbonate, which gave rise to a solution of bicarbonate of magnesia. The action of this solution on the sulfates of soda and magnesia formed bicarbonates of these bases and sulfate of lime (gypsum).
This theory was applied by Logan, in 1863, to explain the origin of the Canadian gypsum by the reaction between solutions of bicar- bonate of lime and water containing sulfate of magnesia, forming the sulfate of lime, or gypsum.
Gypsum Deposited In Rivers.
Rivers may in some instances carry high percentages of sulfate of lime, and so deposit gypsum at their mouths or in the basins into which they empty. Lyell cites the river in Sicily known as the La Frume Salso as an example of a river forming such gypsum deposits.
Secretion Of Gypsum By Animals.
In the cruise of the "Challenger," M. Buchanan found that the bathybius formed a sulfate of lime deposit. This form is an uni- cellular animal belonging to the lowest group of animal life, the Pro- tozoa, and it forms slimy masses on the floor of the ocean. Many scientists maintain that it is not an animal, but merely a deposition of lime salts in the depths of the ocean.
Gypsum Formed From Anhydrite.
Anhydrite, which is the sulfate of lime without water, on taking up two molecules of water becomes gypsum. In this process there is an increase in volume of thirty-three per cent. According to Lap- parent, the force exerted by this .change is four times as great as that of water in process of freezing. Such a change on a small scale is found in many places, but in the Harz mountains, according to Gary, the large gypsum deposits are formed from anhydrite through the entrance of water. Near Ellrich this change has formed mounds of gypsum in concentric shells fifty-two feet high, often hollow at the interior. The force of the resulting expansion has been sufficient to break crystals of quartz and the dolomite in the layers above.
112 Kansas Academy Of Science.
DEPOSITION or GYPSUM PROM BODIES OF SALT WATER.
The most generally accepted theory of origin of the large deposits of gypsum and salt has been the evaporation of salt-water lakes, bays, and seas, cut off from the main ocean. This theory has been given for the Iowa, New York and Kansas deposits in the reports on salt and gypsum in those states. In the Kansas report the writer en- deavored to picture the history of the changes resulting in the de- position of gypsum in a bay whose waters retreated to the southwest in Permian time.
Examples of these changes can be found in the salt lakes, ocean gulfs and bordering seas at the present day. In southern Europe are excellent examples of the evaporation of salt lakes ; and in this country the best examples are to be seen in the Great Salt Lake and neighbor- ing salt lakes of Utah and Nevada.
Lake Bonneville, in the Quaternary geological time, covered an area of 19,750 square miles, with a depth of 1050 feet, and its waters were fresh. Through evaporation, its level was lowered below the place of outlet at the north, and its waters in course of time became more and more saline. This evaporation has continued until the present remnant, Salt Lake, has less than 2400 square miles of area, with an extreme depth of fifty feet, and its waters almost a concen- trated brine, with specific gravity of 1.1. The total amount of salts in this lake water is 15 per cent., of which 11.8 per cent, is common salt (sodium chloride).
The waters of the Dead Sea afford another example of concentrated brine due to evaporation. In this water there is 26 per cent, of salts, but differing in composition from the American lake. There is only 3.6 per cent, of common salt and over 15 per cent, of magnesium chloride, as compared with 1.5 per cent, in Great Salt Lake. The amount of gypsum (lime sulfate) in the two basins is nearly the same, 0.086 per cent. Geikie, in his text-book (page 383), gives the chemical composition of these waters as follows :
Great Salt Lake. Dead Sea,
Chloride of sodium (common salt) 11.8628 3.6372
Chloride of magnesium 1.4908 15.9774
Chloride of calcium 4.7197
Chloride of potassium 0.0862 0.8379
Bromide of magnesium 0.8157
Sulfate of lime (gypsum) 0.0858 0.0889
Sulfate of potassium 5363
Sulfate of magnesium 0.9321
Water 85.0060 73.9232
100. 100.
Ocean water, according to the analyses of the "Challenger" reports, contains 3.5 per cent, of mineral salts, of which three-fourths is com-
Plate X.— Bluffs of Rio Gallegos, Patagonia, at Low Tide — University of Kansas Expedition.
Plate XI.— Bluffs of Rio Gallegos, Patagonia, at High Tide — University of Kansas Expedition.
Geological Papers. 113
mon salt. The waters of the Atlantic show the following varieti 38 and proportion of salts :
Chloride of sodium (common salt) 77.758
Chloride of magnesium 10.878
Sulfate of magnesia 4.737
Sulfate of lime (gypsum) 3.600
Sulfate of potassium 2.465
Carbonate of lime 0.345
Bromide of magnesium 0.217
loo
When such a body of water is cut off and evaporated, the gypsum is deposited after 37 per cent, of water is removed, and common salt only after the removal of 93 per cent. The normal order of thsse formations would be a deposit of gypsum, and then a much heavier deposit of salt. But since 93 per cent, of the water must be evapo- rated before the salt would be thrown down, the evaporation might go far enough for the deposition of gypsum, but not far enough for salt ; or the salt might be deposited and subsequently removed by solut.on. The first condition apparently took place in the Kansas gypsum area, and both conditions probably occurred in Michigan. Q-ypsum de- posits are more wide-spread in nature than salt, but they usually oc- cur in thinner beds.
In most areas, the amount of gypsum found is far greater than the amount that would be found in a body of ocean water suflScier t to cover the gypsum area at reasonable depths. The present conditions in the Mediterranean sea seem to aid in explaining the formation of such deposits, and it has been cited for this purpose in the discussion of the Kansas and Iowa deposits, and also in the older reports of the Michigan gypsum.
The most complete study of the composition and currents oi: the Mediterranean sea has been made by Captain Nares and Doctor Car- penter, in charge of H. M. S. Shearwater" in 1871. They found the basin of this sea to be 6000 feet in depth, separated from the ocean at the Straits of Gibraltar by a ridge 1200 feet high. The water of the Atlantic outside this ridge had a specific gravity of 1.026; fit the western end of the basin the gravity was 1.027, and at the eastern end, 1.03. The proportion of salts in the ocean was 3.6 per cent., a:ad in the Mediterranean it was 3.9. Passing over the dividing ridge were two currents, one over the other. The upper was inflowing and the lower outflowing. The water of the basin is not concentrated enough to deposit salt and gypsum, but it is gaining in quantity of sal: held in solution.
1. Published in Proc. Royal Soc, XX, pp. 97, 414, 1872; quoted also in Encycl. Britannica, vol. XV, p. 821.
1*14 Kansas Academy Of Science.
So it is thought the water in the old seas and gulfs of Kansas and Iowa received additions of salt and gypsum by inflowing waters, thus increasing the thickness of the deposits. The same theory is used to explain the great thickness of salt at Stassfurt (1000 feet) and at Sperenberg (3000 feet), in Germany.
QUANTITY OF GYPSUM IN THE ANCIENT MICHIGAN SEA COMPARED WITH THE PRESENT SUPPLY.
The area of rocks in Michigan after the Marshall or Kinderhook series is approximately circular in outline, with a radius of eighty -five miles, giving an area of 22,686 square miles. As will be shown later, the sea covering this area in Osage times was approximately 700 feet in depth, and assuming an average depth of 326 feet, based on well records, there would have been about 1,280,000 billion gallons of water.
The analysis of Atlantic ocean water given above shows 93.3 grains of gypsum to the gallon. If this Michigan sea had this same propor- tion, it would have yielded 8,500,000,000 tons of gypsum.
The thickness of gypsum at Grand Rapids is eighteen feet and at Alabaster twenty feet. The gypsum in the Grand Rapids quarries is shown in plates XIII and XIV. The approximate area at Grand Rapids is twenty-four square miles and at Alabaster ten square miles ; and while the gypsum does not by any means keep the thickness given over the entire area, and is even absent in places, it has probably been removed by solution since its deposition.
These figures would give a total quantity of 1,237,764,000 tons of gypsum. Where gypsum is found in the deep wells it is usually in thin beds, and in many of them it is entirely absent. It is thus evi- dent that the quantity of gypsum held in this old Michigan salt sea is sufficient to explain the quantity of gypsum actually in existence to- day in its basin.
If the assumption is made, and there is no basis for it, that the gypsum covered all the interior sea area with a thickness of twenty feet, then it would require 917 billion tons of lime sulfate in the sea, more than a hundred times the quantity probably in the basin.
Caspian Sea As An Illustration Of The Michigan Sea.
The gypsum deposits in Michigan do not occur uniformly dis- tributed through all parts of this old sea basin, but they appear con- centrated in certain areas of comparatively small size. For the cause of this localization of the deposits we may look for a modern illustra- tion of the conditions in the Caspian sea.
Into the northern part of the Caspian sea empty the Volga, Ural and Terek rivers, bringing in a large quantity of fresh water, so that in this portion of the sea the water is nearly pure, with a specific gravity of 1.009. This small percentage of salt is, according to Van
Geological Papers. 115
Baer, due to the number of shallow lagoons surrounding the basin, each being a sort of natural salt pan. At Novo Petrovsk, a former bay of the main sea is now divided into a number of basins, showing all degrees of saline concentration. One of these has deposited on its banks only a thin layer of salt, a second is a compact mass of salt, and a third has lost all the water and is a mass of salt covered with sand.
The concentration is seen on the greatest scale in the Karaboghay (Black Grulf) of the Caspian, where the nearly circular shallow basin is about ninety miles across and almost entirely cut off from the sea by a long, narrow spit of land, so that the gulf and sea ate only con- nected by a channel not over 150 yards broad and five feet deep. Through this channel there passes into the gulf a current with an average velocity of three miles an hour, but which is accelerated by the western winds.
This current is due to the indraught produced by excessive evapo- ration from the surface of the basin, due to the heat and winds. The shallow depth of the bar prevents a counter-current of highly saline water into the Caspian. This current carries into the Black Gulf, ac- cording to Van Baer, 350,000 tons of salt daily. If this dividing bar of land should be elevated and cut off the basin from the sea, the gulf would rapidly diminish and become a salt marsh, which, later, drying up, would leave a large salt deposit.
With a greater depth of water over the dividing ridge, the counter- current would come in as at the straits of Gibraltar, and the evapora- tion could go far enough for the deposition of gypsum, while the concentrated salt brine would pass back into the larger sea. This was more probably the condition in the Michigan gypsum basins, as will now be shown from a study of geological conditions and well records.
Michigan Interior Salt Sea.
The Kinderhook sea of the American continent was an interior sea with a bay extending northeast into Michigan. In this bay were de- posited the Marshall sandstones. The close of the period was marked by uplift in this area, causing a retreat of the sea southwestward, finally exposing a wide area of land in southern Michigan and north- ern Indiana. At Lafayette, Ind., the floor of this sea was at least 563 feet above sea-level. North of this barrier was a large interior sea, with its floor 375 feet above sea-level near Grand Rapids, lower by nearly 200 feet than the ocean to the southwest. This sea was sur- rounded by the Marshall series, at this time dry land, 777 ( Kalama- zoo), 983 (Ooldwater) and 1000 (Hillsdale) feet above sea-level on the south ; 700 ( Huron county) feet on the east; and 755 (Grayling)
116 Kansas Academy Of Science.
feet at the north — a sea like the Caspian, with a depth at first of probably 700 feet or more and an area of 22,686 square miles.
In this sea were elevations and depressions ; a ridge at Lansing 500 feet above sea-level and a depression east of Saginaw 380 feet below sea-level, separated from the main basin by a ridge 187 feet above the sea floor.
This sea probably had its tributary streams coming from the high land at the north and northeast, flowing down across the recently emerged flats of the Waverly and Marshall land, bringing a supply of sediment and doubtless salt from the Salina beds at the north. The lake basins of Michigan and Huron were not in existence at this time, but belong to a much later chapter in the geological history of our continent. The irregular clay seams and the clay-dividing planes in the gypsum represent an influx of sediment, wind-blown material, or tidal currents.
As the evaporation of these waters went on, the first deposit would be carbonate of lime, thrown down when the specific gravity was raised to between 1.0506 and 1.1304. By further concentration the gravity would reach 1.22, and in this interval the gypsum would be deposited. At this period 37 per cent, of the water must have been evaporated. If the sea was 700 feet in depth, it would now be 440 feet, still covering the Saginaw ridge but exposing the Lansing ridge. Further well records might give a clue to other basins sepa- rated by ridges of land. The sea would gradually become like the Caspian, with smaller basins around it, in which all degrees of con- centration would be found.
In the deep basin near Saginaw the dividing ridge would be ex- posed before salt was deposited. In such an evaporating basin the deposit of salts would occur around the borders of the basin first, and by the influx of water across the Saginaw ridge the water in the concentrating basin was probably renewed, resulting in the twenty to twenty-five feet of gypsum now found in that area.
The normal order of deposits should be lime carbonate, on which would be a deposit of gypsum, covered by layers of salt. In the present developed areas the gypsum rests on a limestone floor, but with no traces of salt over it. The rock-6alt deposits are below the gypsum series, in the Monroe or Salina series. Further, in the salt series of Saginaw, Grand Kapids and other places there are no traces of rock salt, but the salt-wells secure the salt from natural brines.
If the Michigan interior sea evaporated completely, there would have been, on the assumption its waters were like those of the presen Atlantic, 17.9 times as much salt as gypsum, and the salt over the
Geological Papers. 117
gypsum, or in the lower part of the basins toward the interior, where the waters, deprived of their gypsum content, had retreated.
If these conditions were true, the salt might later have been re- moved by solution in downward percolating waters which dissolved the more soluble sodium chloride. The gypsum now remaining does show marked effects of solution, the surface being rounded and fur- rowed by solution, and in places it is entirely removed. These ef- fects would have been far greater in the common salt. The salt-laden waters or brines would flow downward along the slope of the rocks and through them, finally remaining at rest in the lower porous for- mations, where it is now found. Further, the salt seems to be found in greater amounts toward the interior of the basin than near the edges; more at Saginaw, Ann Arbor, Lansing, etc., than at Tawas and Grand Rapids, though it is found in all these places.
Another possible explanation of the final history of this sea is to be found in the great extension of the sea in the next epoch, when the St. Louis limestone was found. The sea in the St. Louis epoch extended its borders north and south, and passed across the interior basin of Michigan to Grand Rapids on the west and to Huron county on the east. Possibly this renewal of the waters took place before the Michigan sea had disappeared by evaporation, or before it had evaporated enough to deposit a large quantity of salt, except in cer- tain smaller basins separated by the dividing ridges.
From the evidence of sandstones and shales of the Michigan series found in the well borings of the interior, it would seem that the ocean flowed over the southern barrier into the interior basin a number of times before the greater St. Louis inundation, and at these times de- posited the sediments which are lacking in gypsum and salt contents. At these times the water would be diluted, its specific gravity lowered, so that precipitation of the salts would not take place. These over- flowing waters, local in their occurrence, cannot be correlated with other sections, unless with those of the Logan series of Ohio, whose origin may be similar.
In the deeper Michigan borings, gypsum appears to be replaced by anhydrite ; but where the depth of concentrated waters is 325 feet, giving a pressure of ten atmospheres, anhydrite is formed instead of gypsum.
This theory, as outlined for the Michigan gypsum deposits, is based on the study of a few well borings and a comparative study of the conditions in the Caspian sea of to-day and those of the Michigan area as far as they can be determined. There is a wide range of probability involved, and while the theory is advanced as a theory rest- ing on limited data, it may be taken as representing approximately the conditions of origin of these deposits.