Preliminary Field Report of the United States Geological Survey of Colorado and New Mexico

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1869. Not illustrated. Excerpt: ... not tell. This narrow belt, about ten or fifteen miles wide, extending up to the granite rocks, and for the most part concealing all the intermediate rocks, forms a sort of bench, with a gently ascending grade for the Union Pacific railroad. Either above or below this bench the ascent to the mountains would have been very difficult, expensive, and perhaps impossible. About twenty miles south of Cheyenne a bed of coal has been opened and wrought to some extent. The outcropping revealed a bed of impure coal four feet eight inches thick, with an inclination 12 east. The coal became more valuable as it was worked further into the earth; and by following the direction of the dip, the coal was found to be five feet four inches thick. In nearly all instances coal beds increase in thickness, rather than diminish, the further they are explored. The whole plain country is covered with such a thickness of superficial drift that it is next to impossible to obtain a connected section of the underlying rocks. Sometimes a stream will cut so deep that a portion of them is exposed, and by following it a great distance, the order of superposition may be obtained with some degree of correctness. A section across the upturned edges of the strata, from the direction of the mountains eastward, is as follows: 7. Drab clay passing up into areno-calcareous grits composed of an aggregation of oyster-shells, Ostrea subtrigonaUs. 6. Lignite--5 to 6 feet. 5. Drab clay--4 to 6 feet. 4. Reddish, rusty sandstone, in thin laminae--20 feet. 3. Drab arenaceous clay, indurated--25 feet. 2. Massive sandstone--50 feet. 1. No. 5, cretaceous apparently passing up into a yellowish sandstone. The summits of the hills near this bed of coal are covered with loose oyster shells, and a stratum four feet thi...