USA > Colorado > Arapahoe County > History of the city of Denver, Arapahoe County, and Colorado > Part 12
USA > Colorado > Denver County > Denver > History of the city of Denver, Arapahoe County, and Colorado > Part 12
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The Glacial or Drift period followed, in due course of time, the Tertiary period. But there are little, if any, evidences of drift action upon the plains proper, and it is rare that unequivocal evi- dences are met with even along the base of the mountains, on the eastern side. It is when we find ourselves far up among the majestic gorges that we begin to perceive abundant proofs all about
us of "glacial action." On the Fontain qui Bouille, eight miles above Colorado Springs, and at the foot of Pike's Peak, at what is now known all over the country as Manitou, are immense granite bowlders, lying near soda, sulphur and iron springs, whose healing qualities attract thousands to them every year. Below there are to be found some lateral moraines, principally composed of large bowlders, left by some glaciers that once passed down a small valley and joined, near that point, a larger one which traversed the valley of the Fontain qui Bouille. In this latitude, the highest peaks of the Rocky Mountains are barren of snow during the months of July and August.
There are bowlder-beds of large extent, and from thirty to forty feet high, in a beautiful park on South Boulder Creek, in the northern part of the State. They lie about six miles below the snowy peaks, cut through and exposed on each side of the stream which takes its name from them. The bed is full of them, running quite down into the val- ley. On South Clear Creek, not many miles above the city of Georgetown, many rocks were exposed at the time the road over the Berthoud Pass was being constructed. On the surfaces of some of these, glacial striæe are distinctly visible; this is the only place in the State east of the snowy range where they have been seen, and their general ab- sence is remarkable. Evidences of glacial action increases as one ascends to the higher altitudes. No longer are the valleys bordered by rocks that are rough and craggy, as they are in the lower portions; but they are nearly as rounded and smooth in their outlines as are the chalk downs of England or the glacier-planed hills of the old Bay State.
West of the Middle Park, on the flat summit of the Gore Range, can be found rocks plaued and plowed into deep furrows with a due westerly direction. These can be found continuing down the mountain-side until they reach the valley of the White River, wherein are to be found numer- ous terminal moraines, brought by contributary glaciers proceeding from the highlands on both
RESIDENCE OF J. W. HORNER.
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sides, but principally on the south. These moraines are also abundantly visible at the mouths of the various small streams that flow into White River, for a distance of nearly one hundred miles from the top of the range.
It would seem to be a fact established beyond question that, during the Drift period, the vast ex- panse of the Rocky Mountains was not only cov- ered with snow on its highest summits, but that the valleys were filled with ice and snow which did not melt, but kept continually pressing down the mountain gorges toward the plain. These were thickest and most glacial in their character as they neared the mountains and upon the western slopes ; they became thinner and occupied but the bottoms of the valleys as the glaciers descended, melting, at last, into numerous streams laden with debris that finally found a resting-place upon the plains below.
But since that icy era, wonderful changes have been evoked. The climate has been remarkably modified, especially on the western range has it changed. Once possessing a most rigorous climate, now pines grow on it two thousand feet higher up than they do upon the eastern side. The glaciers are gone from the valleys and only the snowy patches upon the highest points remain in witness of the immense ice-fields of the far-away ages of the past.
Passing now from the geological history of the State to its more positive geology, we begin with the Granitic formation, which is the oldest forma- tion of all, resulting from the cooling of the primi- tive mass of fiery liquid composing the globe. This formation may be seen upon and beyond the snowy range of the Rocky Mountains in various parts of the State, but more abundantly upon the western slope than upon the eastern. In masses of true granite, syenite, or porphyry it makes its appearance, notably on McClellan Mountain, in the Argentine Silver District, where it is seen to have been thrust through younger formations to the prominent position that it now occupies ; it is found also on the west side of Boulder Pass,
where massive granitic ranges form the buttresses of the snowy Sierra, as we descend to the Middle Park, and also on the western side of the park, where it forms the grand mountain that encom- passes it.
Of metamorphic rocks, gneiss is by far the most abundant, and most of the gold-bearing veins are formed in gneissoid rocks, though among the mining people they are generally termed granite. Fine exposures are to be seen near Black Hawk, the lines of stratification marking the mountain- side as stripes mark the body of a zebra.
Resting upon the granite in the Middle Park, on the banks of the Grand River, are exposures of conglomerate, probably of Silurian age, overlaid by sandstones and limestones, probably of Devonian age, and above this are found the coal measures of the carboniferous formation. Near the Sangre de Christo Pass, the granite is overlaid by slates and limestones, probably of Silurian age, the lime- stones containing crinoidal fragments, but too small for the identification of the species. Farther to the north are to be found mountains composed of conglomerates, formed of pebbles, bowlders, and large masses of gneiss, granite, mica-schist and hornblend-schist, with gneissoid rocks, slate and limestone, on their flanks. Rocks of the Permean age have been discovered on the plains in the eastern part of Colorado, consisting principally of limestones, some of which abound with the characteristic fossils of this period.
The Cretaceous formation is well represented, especially along the base of the mountains on the eastern side. The shells of the inoceramus are found in a limestone at Boulder, baculites of large size and great abundance on the Platte, a few miles from Denver, while the limestones lying between Colorado Springs and Pueblo contain the inocera- mus, scaphites, baculites, ammonites and other characteristic cretaceous fossils. These beds extend for a considerable distance to the eastward, and in wearing down under the action of atmospheric agencies, masses have been left in conical hills, looking like gigantic ant-hills; on these fossils can
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be picked up in great abundance. Between Pueblo and the Sangre de Christo Pass, the teeth, spines and bones of fishes, principally of the genera Ptyehodus and Lamna, so common in the cretaceous beds of England, are found in remark- able profusion. There is a ranche on the Green- horn River where is contained the finest deposit of fossils of this description that has yet been dis- covered.
The Cretaceous formation is well represented in the Middle Park by baculite beds and sandstone, abounding with the scales of fishes, and the posi- tion of these beds as they occur on one of the streams in Middle Park, shows as follows: First. Two hundred feet of lava, containing agates and chalecdony. Second. Four hundred feet of white sandstone and quartzose conglomerate, in which are to be found fossil woods in fragments, with some bones of mammals and birds. Third. Four hundred feet of shaly sandstones full of the scales of cycloidal fishes. Fourth. Twenty feet of blue limestone. Fifth. Five hundred feet of shales, marls and sandstones, containing fish teeth, bac- ulites, conchifers and tucoids. Of these numbers, three, four and five are probably cretaceous; the rest tertiary. From the disintegration of the lava come the agates and chaleedonies of the park. Where the lava mingles with the sandstone and other material of the second, agates and fossil lie mixed together on the surface. The slabs of shaly sandstones are covered with the scales of cycloidal fishes, that is, of fishes resembling those of the salmon and the trout. The baculite beds are so denominated because of the great number and large size of the baculites found in them.
The Tertiary formation may be said to have a remarkable development in Colorado. It shows a thickness of over ten thousand feet on the western side of the Rocky Mountains, from the Gore Range, which is composed of tertiary lavas, to the Junc- tion of White and Green Rivers. Here are to be found the coal measures, containing many thin veins of coal, beds of gypsum, thin beds of lime- stone, and, above these, petroleum shales of at
least a thousand feet in thickness, abounding in fossil leaves and insects, the shales containing them occurring at points sixty miles apart, and, above them, brown sandstone and conglomerates having a thickness of from twelve hundred to fifteen hun- dred feet, and containing silicified wood, turtles, and bones and teeth of large mammals. They lie in the following order in the valley of the White River : About two thousand feet of red and white sandstone, followed by twelve hundred feet of brown sandstones, alternating with blue shales and beds of conglomerate ; in these are found bones of mammals and turtles, while, particularly noticeable in the lower shales, deciduous leaves and insects are found. There are also seen perpendicular veins of petroleum. Next succeeds a thousand feet of petroleum shales, varying in color from cream to black, one bed, twenty feet thick, resembling can- nel coal. Here, also, are found insects and the leaves of deciduous trees. The next in the series is eight hundred feet of white and light-brown sandstones, white shales on which are to be found ripple marks, brown shales and shaly sandstones. To these succeed a thousand feet of thick, white sandstones, and brown shales, and thick, brown sandstones weathered into cavities. Then follow the coal measures, fully twenty-seven hundred feet, to wit : Sandstone, limestone containing conchs and small gasteropods, blue, black and brown shales, under-clays, beds of coal or lignite ; brown sandstones and shales, very soft; coal in vari- ous beds, with under-clays; white sandstones, with alternating blue shales. To the soft shales, we are indebted for the two wide expansions in the White River Valley. Seventh in the order follows fourteen hundred feet of compact red sand- stones, white sandstones, red sandstones shaly and micaceous, with thin, fetid limestones containing fragments of shells. To these succeed three hun- dred feet of soft, yellow sandstone, and, finally, about two hundred feet of gypsum. It is to be under- stood that the foregoing are only estimated thick- nesses, they having in no case been measured by the one who examined them. The upper beds are
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formed near the junction of the White and Green Rivers in Utah; the lower ones near the Gore range, where they are covered by immense beds of lava, in some places, especially on the eastern side of the range, alternating with beds of white and friable sandstone lying in a perfectly horizontal position and rising to a height on the top of the Range of about thirteen thousand feet. The groups of gypsum, soft, yellow standstone, and thin fetid limestone make their appearance in valleys upon the eastern side of the range, the lava having been poured out, apparently, during the period of the lower tertiary coal measure.
Mr. Samuel H. Scudder, an eminent member of the Boston Society of Natural History, who has made the study of fossil insects a specialty, had submitted to him a number of specimens taken from the petroleum shales ; the report he returned was as follows :
"This is the fifth discovery of fossil insects in this country, if some tracks and an apparent larva in the Triassic rocks of the Connecticut Valley be correctly referred to insects; but it is the first time that they have been found in the tertiary beds of America. These were obtained by Prof. Denton while on a trip of exploration west of the Rocky Mountain range, not far from the junction of White and Green Rivers in Colo- rado.
" The specimens were brought from two local- ities, called by Prof. Denton Fossil Cañon and Chagrin Valley, lying about sixty miles apart. The rocks in both cases are the same; above are beds of red sandstone, passing occasionally into conglomerate and thin beds of bluish and cream- colored shale alternating with the sandstone, all dipping to the west at an angle of about twenty degrees. These contain fossil wood of deciduous trees, fragments of large bones, most of which are solid, and turtles, some of which are two feet in length and perfect. Prof. Denton considers this sandstone as probably of Miocene age. Beneath these rocks are beds of petroleum shale a thousand feet in thickness, varying in color from a light
eream to inky blackness; these shales are filled with innumerable leaves of deciduous trees, and throughout their extent the remains of insects abound. The specimens brought home are about fifty in number, many of the little slabs contain- ing several different species of inseets upon them. The number of species amounts to about fifty also, although some of the specimens are so fragmentary or imperfectly preserved as to be difficult and often impossible of identification.
" The most abundant forms are Diptera, and they comprise, indeed, two-thirds of the whole number, either in the larval or perfect state; the others are mostly very minute Coleoptera, and besides these are several Homoptera, an ant be- longing to the genus Myrmica, a night-flying moth, and a larva apparently allied to the slug- caterpillars or Limacodes.
" The most perfect insects among the Diptera are mostly small species of Mycetophilida, a fam- ily whose larvæ live mostly in fungoid vegetation, and Tipulida, whose larvæ generally live in stag- nant water. There are, besides, some forms not yet determined, of which some are apparently Muscida, a family to which the common house-fly belongs. The larvæ of Diptera belong to the Muscida, and to another family, the latter of which live during this stage in water only. None of the larvæ, however, belong to the species of which the perfect insects are represented as these stones. The Homoptera belong to genera allied to Issus Gypena, Deephax and some of the Tettigo- nidæ.
" A comparison of the specimens from the two localities shows some differences. They both have Mycetophilida, but Fossil Cañon has a propor- tionately greater abundance and variety of them. Fossil Cañon has other flies also in greater num- ber, though there are some in both ; but Myrmica, the very minute Diptera and the minute Coleopte- ra, are restricted to Fossil Cañon. On the other hand, all the larvæ, both the Diptera and that which appears to be a Limacodes, were brought only from Chagrin Valley.
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" Of course, the number of specimeus is too small to say that the fauna of these two localities are distinct, although the same species has not been found to occur in both, and the strata being 1,000 feet in thickness, there is opportunity for some dif- ference in geological age, for new collections may entirely reverse the present apparent distinction. Neither is it sufficient to base any satisfactory- that is, at all precise-conclusions concerning their age. Enough is before us, however, to enable us to assert with some confidence that they cannot be older than the tertiaries. They do not agree in the aggregation of species with any of the insect beds of Europe, or with the insects of the Amber fauna, and, since they have been found in Europe in considerable numbers only at rather wide inter- vals in the geological record, we should need more facts than are at our command by the known remains of fossil insects, to establish any synchro- nism of deposits between Europe and America. Much more satisfactory results could probably be reached by a comparison of the remains of leaves, etc. Anything more than a very general state- mment is, therefore, at present quite out of the question."
The country in which these are fouud is a very remarkable one. Standing upon the summit of a high ridge on the east, one sees stretched out before him and distinctly visible, a tract of country covering five or six hundred square miles. Over this whole surface one sees nothing but rock, bare rock. Cut up into weird and wild ravines, mys- terious cañons, deep, dark and dangerous gorges, and quiet little valleys, leaving in magnificent relief terrace upon terrace, pyramid beyond pyramid, rising to mountain heights, presenting to the aston- ished beholder amphitheaters that would hold a million spectators, with stately walls and pillars, towers and castles on every haud. An abode fit for the gods of the ancient world, who might well have held solemn conclave in such a temple, stand- ing now bare, blasted and desolate, but still inex- pressibly sublime in its grandeur. Originally-far back in the ages of the past-it was an elevated
country, composed of a number of soft beds of sandstone of varying thickness and softness, under- laid by immense beds of shale. But the run- ning rill and the flowing stream and the meandering creek have worn it down and cut it out, until it has become a strange, weird country, to be the won- der of all generations.
In this region is found a deposit of petroleum coal, scarcely to be distinguished in any way from the Albertite of New Brunswick. In luster, fracture and smell, it appears to be identical, and would yield as much oil as this famous oil-producing coal. It is in a perpendicular vein, three feet wide, and was traced from the bottom of Fossil Cation, near Curtis Grove on White River, to the summit level of the country a thousand feet in height and nearly five miles in length, diminishing in width toward the ends of the vein. An analysis and description of this has been given by Dr. Hayes, of Boston, and we herewith append it:
" Black, with high luster like Albertite, which it resembles physically ; specific gravity 1.055 to 1.075. Electric on friction ; breaks easily and con- tains .33 of one per cent moisture. It affords 39.67 per cent of soluble bitumen when treated with coal naphtha, and, after combustion of all its parts, 1.20 per cent of ash remains ; 100 parts dis- tilled afforded bituminous matter, 77.67; carbon or coke, 20.80; ash left, 1.20; moisture, .33; total, 100. It expands to five or six times its volume, and leaves a porous cake, which burns easily."
The vein is in an enormous bed of sandstone with smooth walls; beneath the sandstone are the petroleum shales, one bed of which, varying from ten to twenty feet in thickness, resembles caunel- lite, and would, it is thought, yield from fifty to sixty gallons to the ton. This bed was traced for twenty-five miles in one direction and was seen at points sixty miles apart in another, and it no doubt extends over the entire distance. If so, in that single bed are twenty million million barrels of oil, or over five hundred times as much as America has produced since petroleum was discovered in
Atrailer
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Pennsylvania. There are few beds of coal that can compare with this in the amount of bituminous matter which it contains, or in the great value that it possesses as an article of fuel. The tertiary beds of Colorado are rich in fuel and gas-making material, though it is more than probable that the petroleum now in the shales aud petroleum coals came originally from the oil-bearing coral beds of some much older formations.
On the eastern side of the mountains, mainly, lie the tertiary coal measures, containing beds of coal and of iron ore of excellent quality. These coal-bearing lands embrace many thousand square miles of the State's area. The bulk of these thus far located extend along the plains, east of the foot-hills, the entire length of the State. Those opened and worked lie principally in the counties of Boulder, Weld and Jefferson. These mines have probably yielded nearly two hundred thousand tons this season. In Fremont and Las Animas Counties, in the southern part of the State, the miues are being developed. The Trinidad coals, in the latter county, coke equal to any in the coking districts of Pennsylvania, and this interest is steadily growing in importance, two companies having each one hundred ovens in active operation.
These companies are named the Southern Colo- rado Coal Company and Riffenburg Coal Company. To show what an advance has been made in the growth of this industry, we have but to state that, four years ago, six ovens, producing ten tons per day, were capable of supplying the market of Utah and Colorado. Now, Utah consumes about fifteen hundred tons per month ; Northern Colorado, five hundred, while Leadville calls for three thousand, and is likely to demand a constantly increasing num- ber. Prof. Hayden, in his report of 1875, relative to the coal deposits in the neighborhood of Trimdad, calls these coals a binding bituminous coal, not considering the term "lignite," as generally used, strictly applicable, from the standpoint of a miner- alogist. The thickness of the seams vary from nine to thirteen feet, nearly horizontal, and are
easily worked by tunneling. An assay of the Riffenburg coal, which lies close to that of the other company, gave the following result :
Loss at 110° C. (water) 0.26 per cent.
Carbon, fixed 65.76 per cent.
Volatile combustible matter 29.66 per cent.
Ash 4.32 per cent.
Total 100.00 per cent. " Its specific gravity varies from 1.28 to 1.53."
The coke made has a bright, silvery color; is hard and strong, and suitable for all smelting pur- poses.
Above these coal beds are beds of sandstone and conglomerate, abounding in fossil palms, firs and various kinds of resinous and gum-bearing trees, together with modern exogens. Trunks of trees of large size have been found lying far out on the plains, where they have been left when the disin- tegrating rock loosened them from their captiv- ity. Between Denver and Golden, many very fine specimens have been found; still more on a low range of sand-hills about twenty miles south of Denver, while some very fine specimens have been brought from South Park.
In the Middle Park, west of the Grand River, is also a coarse sandstone passing into conglomer- ate, and containing silicified wood. Above it are beds of trap; and where this has disintegrated, chalcedonies and agates are found; principally moss agates, as they are called, but which are, in reality, chalcedonies containing oxide of manga- nese iu a deudritic form. The rock originally holding them was a lava poured out of some long extinct volcano; this was full of vesicles or hollow places produced by gas or vapor, and, in process of time, these were filled with extremely thin par- ticles of silica, separated from the surrounding rock, forming the ordinary chalcedonies. In some cases, a small quantity of oxide of manganese has been carried in with the silica, and this, crystalliz- ing in an arborescent or tree-like form, has pro- duced the appearance of moss in the chalcedony, and thus have been formed the beautiful moss agates which abound throughout Colorado.
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We can see in the lava beds of the plains, run- ning northward from Golden, and also to be found in other localities, the witness to terrible volcanic eruptions, that at no very distant period, geologi- cally speaking, devastated the country. These lava beds seem to be the most recent tertiary deposits in Colorado. There are also other wit- nesses to this stormy time in the hot springs that abound at various points. Some of the principal of these may be named as follows: Hot Sulphur Springs, in Middle Park, with a temperature of 121º F .; Hot Springs at Idaho, 110º F .; at Cañon City, 102º F .; Arkansas Hot Springs, 140° F .; at Wagon Wheel Gap, 148º F .; Pagosa Springs, 150° F. This last ranks among the greatest mineral springs of the country.
The Drift period has left its unquestionable rec- ord in the immense accumulation of bowlders and gravel in the valleys of almost every mountain stream, although the ice does not seem to have produced as much effect during that period as the height of the mountains and their latitude would naturally lead us to expect.
The above description of the geology of Colo- rado is necessarily very disconnected and incom- plete. It would be impossible to gather within the scope of a work like this, a thorough and comprehensive analysis of the various formations. We have only endeavored to give to the general reader an idea of the field, so vast in extent, of geological research within the limits of the State, and refer the student, who enters it as a special field of investigation, to the various reports, nota- bly those of Clarence King and Professor Hayden, made of late years, to the Government of the United States.
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