USA > Wyoming > History of Wyoming, Volume I > Part 42
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Algonkian-The name Algonkian has been given to the great series of sedi- mentary and metamorphic rocks which lie between the basal Archaean complex and the oldest Palaeozoic strata. The Algonkian rocks seem to represent the first series of deposits made under water and the first chapters in the history of life. Fossils have been found in the less changed sediments, but they are too few to tell much of the life of the times. It is believed, however, that both animal and vegetable life had their beginnings in this period. The Algonkian rocks are especially notable in the Black Hills region in Northeastern Wyoming, and also in the Hartville region where immense deposits of high grade iron ore occur. The most important gold bearing deposits in the state near Atlantic City and South Pass also belong to the Algonkian.
Metallic Minerals-Practically all of the precious and base metals of the
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HISTORY OF WYOMING
state are found in the rocks of the pre-Cambrian complex, which is exposed over an area of approximately 10,000 square miles, or one tenth of the area of the state. The principal exposures are the Laramie Range, extending from Casper Mountain east and south to the Colorado line, containing gold, copper, lead, zinc, titanium, iron, asbestos, graphites, mica, chromium. The Medicine Bow Range, a mountainous area of nearly two thousand square miles, lying west of Laramie and south of Rawlins is rich in minerals, having produced platinum, gold, silver, copper, in large quantities, in addition to other metals. The Fremont or Wind River Range is the largest exposure of pre-Cambrian rocks in the state, covering about two thousand four hundred square miles near the center of the western half of the state. It is also the highest and most inaccessible mountainous area, some of its peaks rising more than fourteen thousand feet above sea level. The southeastern end of this exposure is the Atlantic City-South Pass District, the most important gold bearing area in Wyoming. Other metallic minerals undoubtedly occur in this great area, and offer an attractive field for the prospector. The Big Horn Mountains covering probably one thousand square miles south of Sheridan, also contain extensive deposits of gold and copper bearing minerals.
The occurrence of metallic minerals is limited to the pre-Cambrian rocks, but practically every exposure of these rocks has associated with it metalliferous veins or other deposits, copper and gold being the most common. The attention of prospectors is therefore invited to these rocks.
Palaeozoic-The strata following the Algonkian are fossiliferous, and are divided into three main groups, the Palaeozoic, Mesozoic, and Cenozoic Eras. The Palaeozoic is composed of conglomerates, sandstones, shales, and limestones, attaining great thickness, though relatively less in Wyoming than in the eastern part of the United States. The rocks are in a majority of cases of marine origin. The first subdivision of organic and geographical development of the Palaeozoic is the Cambrian, containing the first known and recognizable fossils, those of the simplest marine fauna, no plant remains having been identified.
Cambrian-In Wyoming the Cambrian is entirely missing in the southern half of the state, and not of great importance in the northern half, its main outcrops being in the Big Horn Mountains, and west of Big Horn Basin, attaining a thickness of seven hundred to nine hundred feet at the latter location. The rocks are mainly a red, basal conglomerate resting unconformably upon the Algonkian, also shale, limestone, and red sandstones. In the northeastern corner of the state, the Cambrian is very thin. So far as is known, the Cambrian contains no economic minerals.
Ordovician-The next succeeding subdivision of the Palaeozoic is the Ordo- vician, which has a geographical distribution similar to the Cambrian, upon which it lies. Its greatest thickness, in the vicinity of Big Horn Basin, is only about three hundred feet. the rocks being siliceous, grey limestone, very hard and massive. not known to contain any valuable minerals.
Silurian & Devonian-During the Silurian and Devonian Periods the entire area of Wyoming remained above water level, consequently there are no repre- sentatives of these rock systems, and sufficient time elapsed to allow the land surface to be reduced almost to a peneplain, upon which the Carboniferous sedi- ments were laid down, almost conformably.
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HISTORY OF WYOMING
Carboniferous-The name Carboniferous was given to the next system of rocks because of the importance of the coal seams present in it in other parts of the world, though in Wyoming it contains no coal as the Carboniferous sedi- ments were laid down in the deep sea and in salt lakes, resulting in massive limestones of great thickness in the Lower Carboniferous, and red sandstones, shales, and occasional gypsum deposits in the Upper. The thickness of the Car- boniferous is about one thousand feet in the southeastern part of the state, about two thousand in the northeastern, increasing to approximately five thousand feet in the western part. In the southwestern part the lower member is a quartzitic sandstone over one thousand feet thick, overlain by more than seven hundred feet of sandy limestone.
Economically the Carboniferous is important as it contains immense deposits of pure limestone which occur in thick beds in the lower part of the system, which furnish excellent quarries wherever they outcrop under favorable con- ditions. The principal limestone quarries are at Hartville, while others are being worked at Laramie and Rawlins, and in the Big Horn Basin, the stone being used by the sugar refineries. Copper also occurs in the Carboniferous in the Hartville Uplift, also in the southwestern part of the state, among other localities, and warrants further prospecting. The Embar sandstone, in the Upper Carboniferous, is an important oil sand near Lander in the central part of the state, and north of Powder River Station. Some geologists assign this to the Permian subdivision.
Permian-The Permian is the latest subdivision of the Palaeozoic Era. It is of little importance in Wyoming, there being a thickness of only 80 to 100 feet in the Hartville and Black Hills regions, the rocks being thin, bedded, sandy lime- stones, sandstones, and thin red shales.
Mesozoic-The Mesozoic Era is distinguished by marked changes in plant and animal life, many new insects having appeared, fishes became modernized, birds and mammals made their first appearance, but the most characteristic feature was the reptiles, which attained an extraordinary state of development, being the dominant form of life. The Mesozoic Era comprises three periods, the Triassic, Jurassic and Cretaceous.
Triassic-The Triassic of Wyoming is of fresh water origin, in some localities resting upon pre-Cambrian crystalline rocks, but in general upon Permian or Carboniferous beds usually in apparent conformity. The rocks consist of bright, red sandstones and red, sandy shales, being well known as the Chugwater Red Beds, their thickness in the northeastern part of the state and the Hartville region being about 500 feet, in the Big Horn Basin, central part of the state, and south- eastern part being about one thousand feet increasing to two thousand feet in the southwestern part.
An important characteristic of the red beds is gypsum, which occurs in beds of considerable thickness in many localities. Several plaster mills are located at Laramie where gypsum is mined. It is also mined near Sheridan. Thick gypsum beds of pure variety occur near Cody and will undoubtedly be mined when rail- . road facilities become available. Gypsum can be found in the red beds almost anywhere they outcrop. Fossils however are exceedingly rare.
Jurassic-The Jurassic in Wyoming was laid down in a great inland sea and thins out toward the east, the formations being buff sandstones at the base, above which are variegated shales and clays with occasional sandstones and limestones.
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In the southeast part of the state its thickness is only 150 feet increasing to 350 feet in the northeast part, to 1,100 feet in the Big Horn Basin, and attaining its greatest thickness of 3,800 in the southwest. The name Twin Creek has been applied to the formation in the southwestern part of the state, and Sundance over the remainder of Wyoming.
Cretaceous-The Cretaceous is of great importance in Wyoming, as it con- tains most of the oil and gas bearing strata, and workable coal beds, and is displayed on a vast scale. At the end of Jurassic time Wyoming was a broad flat plain which slowly subsided causing the Cretaceous seas to invade gradually resulting in the deposition of the Lower Cretaceous in practical parallelism with the older formations. The formations first laid down were the Beckwith and Bear River formations in the southwestern part of the state, and the Morrison, Dakota, and Fuson over the rest of the state. The sediments deposited in the Cretaceous sea were mainly derived from a great land mass on the west, as the deposition is much heavier in the western part of the state. The Beckwith formation consists of yellow shales and sandstones with occasional conglomerate beds, and attains a thickness of 5.500 feet. The Bear River is composed of dark shales and thin bedded sandstones, and is about 5,000 feet thick in places. The Lower Cretaceous over the remainder of the state is only 300 to 600 feet thick, the lowest member being the Morrison composed of purplish and greenish grey shales with interbedded sandstone ; resting on this is the lakota, massive buff sandstones, with local coal beds in the northeastern part of the state, followed by the Fuson composed of thin shales and sandstones.
The Dakota is the basal member of the Upper Cretaceous, and is of very uniform character over nearly the entire state. It is a coarse conglomeratic sand- stone, the formation being from 50 to 300 feet thick, in places there are two sandstone beds separated by shale. The name Cloverly is also applied to it in the Big Horn Basin, where it is of great importance as the carrier of large quantities of oil and gas.
Colorado Group-Upon the Dakota rests a great thickness of shale, with beds of sandstone, the lower part being of the Colorado group of marine origin, and the upper. the Montana, of fresh water origin, with coal beds and a greater proportion of sandstones. The Colorado contains near its base the Mowry shale member, with an intermittent sandstone often productive of oil and gas, also a bed of bentonite. The principal shale beds, however, are the Benton in the eastern and central part of the state, and the Frontier in the west and south, containing the famous Frontier or Wall Creek sands which are the most important oil pro- ducing formations in this part of the United States. The Frontier sandstones are greater in number and thickness in the western part of the state where there are eleven beds, thinning out toward the east, seven at Pilot Butte near Lander, three in the vicinity of Casper, and only one as far east as Lusk, while in the Newcastle district, there is no sandstone member in this part of the Colorado group distinguishable. The Upper member of the Colorado, is the Niobrara. The Colorado varies greatly in thickness in different parts of the state, ap- proximately fifteen hundred feet thick in the southeast, central and northwestern parts. two thousand feet in the northeast, and possibly ten thousand in the southwest.
Montana Group-The Montana group is composed of interbedded shales and
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sandstones of great extent and thickness, containing many veins of coal. The thickness of this group varies from about two thousand feet in the northeastern part of the state to six thousand feet in other parts.
Fully half the area of Wyoming has the Cretaceous outcropping on the surface or covered by other formations, and as it is the great source of oil, gas, and coal, it can be readily understood why this state boasts of such great resources in these minerals.
Mountain Building-Though laid down over the entire state, the Cretaceous has been removed from nearly half the area by erosion, as the end of Cretaceous time was accompanied by tremendous mountain building. All of the main mountain ranges of the state and probably most of the minor folds were made at this time and remain today the most important topographic features. These folds were so great that in most cases the pre-Cambrian crystalline rocks have now been exposed where the overlying rocks have been eroded away.
Cenozoic-This brings us to the Cenozoic Era, which by gradual steps leads to the present order of things. The rocks of the Cenozoic are loose and uncompacted and are locally restricted in their range. While rich in animal fossils, they are not important for economic minerals, and space does not permit of great con- sideration of them. During Cenozoic time great lava flows occurred from the region of Yellowstone Park and covered about one-twelfth of the state with several thousand feet of andesite tuffs and lavas, which are of no importance in a mineral way. The Cenozoic sediments are characterized by red and drab clays forming bad lands, also terraces of gravel and conglomerate, and chalky sandstones. These overlie the Cretaceous in the great synclinal troughs between the mountain ranges usually unconformably with the Cretaceous.
WYOMING OIL GEOLOGY
No discussion of the theories advanced to explain the synthesis of oil in rocks will be attempted here. It is sufficient to state that oil and gas are known to occur in shales, sandstones and sometimes limestones. Where a porous formation such as sandstone occurs between shales the oil migrates into the sandstone, and where the sandstones are not level the oil will travel down the slope unless the sandstone is saturated with water, in which case the oil will advance up the incline. If water saturated sandstones outcrop on the surface without an inter- vening reverse dip, the oil will escape at the outcrop. If, however, the sandstones are closed by a dome structure, and sealed in by several hundred feet of impervious rock, the rising oil is unable to escape and is trapped in the dome. Gas, if present, will rise above the oil, thus if the structure contains gas it will be found at the apex. the oil further down, and the water below the oil, all confined in the sandstone. The dome structure is the simplest and most general trap for oil in Wyoming, in fact there is only one field not a dome in which oil has been discovered in commercial quantities. All domes are not productive of oil, the oil bearing formations may have been eroded away or may lie at a great depth. Also there should be a considerable area of properly inclined strata to furnish a gathering ground, otherwise the dome may contain only small amounts of oil or gas. Drilling into the oil sands in localities not structurally favorable would be almost useless, as the oil would have migrated to points geologically higher, and water would be found in its place.
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HISTORY OF WYOMING
In addition to domes, other structural conditions which merit investigation in Wyoming are structural terraces, faults with sufficient throw to seal the ends of the sandstone beds against impervious shales, inclined lenticular bodies of sandstone in shales, inclined sandstones sealed in by unconformities with more recent formations, and inclined sandstones outcropping at the surface but con- taining an asphaltic oil which upon evaporation leaves asphalt in the rock, which clogs the pores and prevents the escape of the remaining oil.
The Lower Cretaceous contains nearly all of the productive oil formations, including the Dakota, Frontier, and Shannon series, the oil being a green paraffine oil of very high grade. Below the Dakota the oil is black, of an asphalt base, occurring in the Sundance, Chugwater, and Embar. Many of these formations contain gas pools under proper geological conditions. Practically the entire area of the state has been examined for oil, and it is estimated that the number of structures which have oil possibilities is not less than one hundred to one hundred and fifty. In a majority of cases the geological conditions are easy of interpreta- tion, hence it is possible to direct drilling operations with intelligence and with greater possibilities of success than in other states. With about five hundred producing wells, the number of important dry holes is comparatively small, probably fifty.
Wyoming first became mentioned in petroleum history in 1894, when the Shannon field, now a part of Salt Creek, contributed 2.369 barrels production, hauled to Casper, in trail wagons, and treated for its lubrication content, used largely by railroads. With slight variations the production increased to 8,960 barrels in 1903, and 11.542 barrels in 1904. There was a decrease then until 1908, when the total was 17,775 barrels. In 1910 the production was 115,430 barrels; in 1911, 186,695; in 1912, it had reached 1,527.306 barrels ; in 1913, 2,406,522 ; in 1914, 3.500,373 ; in 1915, 4,245,525 ; in 1916, 6,234,137 barrels ; while the estimate for 1917 is 9,000,000 barrels.
The present year promises to be one of extensive development, and if the 700,000 acres of land which have been withdrawn by the government, which is reckoned to be some of the best land in the state, is released this year, and it now seems almost certain it will, the development of the state will far exceed expecta- tions. There are sixteen producing fields now, of which the eleven most important have a daily production as follows :
Field
Run
Shut In
Salt Creek
11,000
9,000
Grass Creek
5,000
1,000
Elk Basin
5,500
.....
Big Muddy
4,500
Lander
800
400
Park County
600
Lost Soldier
2,000
Pilot Butte
500
Thornton, etc
150
Thermopolis
150
Totals
27.400
13,300
Copyright by Doubleday
MIDWEST REFINERY, CASPER
Copyright by Doubleday
STANDARD REFINERY. CASPER
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HISTORY OF WYOMING
There are also four important gas fields with individual wells making from two million cubic feet per day to twenty million, each.
It will be noted that the fields are not confined to any part of the state, but occur in all parts, with the central area and Big Horn Basin being most favored. There are thousands of square miles of possible territory so covered with shales that the structure formations are difficult and in many places impossible to read. Such formations as those which produced the Glen Pool in Oklahoma could exist in a hundred places without surface indications. Even in the producing fields deeper drilling may have unusual results. Salt Creek has punctured only three of the Wall Creek sands. A well 3,500 feet deep on top of the Salt Creek structure would be a fascinating speculation.
There are ten pipe lines already constructed, aggregating over three hundred and fifty miles of line. In addition to these about one hundred miles of ad- ditional line is proposed, some of which will probably be constructed during the present summer. Four large refineries, two at Casper and two at Greybull, one small refinery at Cowley and a carbon plant near that place, are now in operation. Several small refineries are now anticipated, and some are actually being built.
In addition to the well fields mentioned an important source of oil for the future will be the oil shales which occur at or near the surface over several thousand square miles in the southwestern part of the state in the Tertiary strata. These shales contain two to twenty barrels of oil per ton, in addition to valuable ammonium sales. The extraction of oil from shale is being done profitably in other states and countries, and will surely be undertaken in Wyoming soon, as it offers an unlimited field for the investor.
GEOLOGY OF COAL
According to the United States Geological Survey Wyoming contains 424,- 000,000,000 tons of coal in beds of workable depth and thickness, or enough to supply the entire United States for one thousand years at the present rate of con- sumption. In addition to the coal thus estimated, there are billions of tons at depths not now considered workable, but which in future years will be available.
Most of the coal occurs in the Cretaceous, in the fresh water deposits in the upper part of this series, and also in the Tertiary, the former being bituminous, the latter lignite. Coal also occurs in the Lower Cretaceous at some points, notably at Cambrai in the northeastern part of the state, where a deposit of some thirty million tons occur in the lower part of the Dakota, this being the only coking coal in the state.
Approximately thirty-five per cent of the area of the state, or about thirty-five thousand square miles, is underlain by coal veins, varying from three to eighty feet in thickness, most of them ranging between four and twelve feet thick. The geology of coal is generally well understood. It was formed from vegetation which accumulated in great thickness in fresh water, and occasionally salt marshes, and was later covered by sedimentary formations of sufficient thickness to compress it into the form of coal. It is estimated that one foot of coal represents fourteen feet of solid vegetation, from which one can attempt to imagine the luxuriance of the growth, and the time involved in the growth of sufficient vegetation to result in a workable coal bed.
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HISTORY OF WYOMING
The coal beds occur in nearly all parts of the state not occupied by mountain ranges, and their location has been worked out by the United States Geological Survey. Under former land laws it was possible to secure title to coal land at a cost of ten dollars to twenty dollars per acre. Some years age, however, when the so-called movement of Conservation of Resources swept the country, the coal land to which the Government still retained title was classified at prices ranging up to five hundred dollars per acre. This had the effect of at once stopping the opening of new mines, as prospective operators could not pay for the land in ad- dition to the necessary plant of machinery required for proper development. That this policy was a grave mistake is apparent from the present coal shortage in time of war. Congress now has a leasing bill under consideration.
GEOLOGY OF WYOMING IRON
Wyoming has four important deposits of iron ore, the locating places being at Sunrise, Rawlins, Seminoe and Iron Mountain, with other less notable deposits in other parts of the state.
The deposit at Sunrise is the only one from which shipments are being made, this camp having been producing about two thousand tons a day for a number of years. The ore is a very pure hematite known as a Bessemer ore, running about sixty-two per cent to sixty-six per cent metallic iron, and from one per cent to two per cent silica, being free from phosphorous and sulphur. Geologically it occurs mainly in the schist and also in the dolomite and along the contact of the two, in the Algonkian rocks; evidence, demonstrating that mineralization took place before the deposition of the Guernsey formation, is abundant. The ore occurs in long lenses of variable size, some of them five hundred feet or more in thickness and extending for considerable distances. An area of several square miles is underlain by this ore body, but the full extent of it is not known because of the overlying sediments, but it is certain that many million tons of ore are available.
The geological occurrence of the ore at Seminoe and Rawlins is similar to that at Sunrise, the former probably being nearly equal in size and quality of ore. Some ore has been shipped from Rawlins. The Seminoe deposit has been handicapped by its distance from the railroad.
The Iron Mountain deposit is very unique, the ore being a titaniferous mag- netite of great purity, assaying about eighty-two per cent oxide of iron and about seventeen per cent titanic acid. The ore appears as a lens outcropping for about two miles on the surface, with a width of one hundred to two hundred feet. It occurs in basic granites of the archean series, probably having been formed by magnetic segregation while these rocks were in a molten condition. Smaller lenses of the same ore occur in other places in the vicinity.
While various attempts have been made to utilize this iron, it is doubtful if they have been prosecuted with sufficient effort, as it is the writer's opinion that this is capable of making one of the most valuable sources of hard steel in the world. Owing to the high content of titanic acid the ore smelts at such a high temperature that in ordinary blast furnace practice it freezes in the furnace. Necessity, how- ever, will soon stimulate further endeavor as the pig iron obtained from previous experiments is said to be harder than ordinary tool steel, and there is no doubt that this ore can be smelted with other ore for the purpose of producing a titanium Vol. 1-25
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