OCR Text |
Show BECONNAISSANCE IN THE UTE COUNTRY. 83 ing up into a siliceous sandstone of various colors. This formation was observed in the valleys below as far as Taylor Eiver. The igneous rocks are divided between the trappean and the volcanic deposits; the former more often occupies the lower slopes, while the latter often overlaps the former, and occupies the high peaks. Some of the volcanoes were in active operation long after the other deposits had become consolidated. On the Ute trail, over the Central Eange, the slope of the Saguache Valley was deluged with volcanic flux from near the summit to the base. Fragments of beds of this flux were found in depressions of Co-chetopa Valley, indicating it to have been of recent origin, or since the surface had assumed its present form. The thickest beds, however, are found in the Central Range, toward the west, and probably in the direction of the center of dispersion. There are other formations more definite in their characteristics, more recent, and limited to the valleys, but, nevertheless, intricate in their positions. Between Hamilton and Animas Parks, the right slope of the valley of Las Animas and mountain is covered in large areas by carboniferous formations of the Coal- Measure period. These were classified into a section by Assistant L. Hawn, and embrace over one thousand feet in the aggregate. At the head of Anthracite Creek occurs a bed of anthracite coal in connection with and in the vicinity of thick and massive formations of sandstone, shale, and conglomerates, at an elevation of about nine thousand feet above the Gulf of California. These, like those formations in Las Animas Valley, dip at considerable angles. A preponderance of coal- measure formations exist also along the line of I march of the 13th of September, between Camps 21 and 22. I might also refer to the lesser formations of this period, on the Atlantic slope, in the valley of Sangre de Cristo, but they are fully explained in my journal. The relative position of these carboniferous formations is readily defined, when it is known that the mountains were forced up into their position at the close of the Carboniferous age, and in many cases carried up with them fragments of that system. The other, or more recent formations, to which reference has been made, are not so easily defined or comprehended. In illustrating, I will endeavor to read the history of the mutations of a park through which Oocbetopa Creek, Taylor River, and Ohio Creek run, and their junction at the lower end of the park form Gunnison River. The original condition of the park, with the valleys, were probably mere clefts in the mountain, but the manipulating forces of the elements during five successive ages, including millions of cycles, wore away and formed the outlines much as we now find them. Early in the fifth age and the second condition of the park, it became an estuary of the sea, as the marine deposits prove. The remnants of these deposits were found on the right side of Ohio Creek, 9 three miles above its mouth, consisting of marly clay and slate of the same. The thickest measures about 90 feet, but the indications are that the formation will reach 200 feet, and an altitude of 7,600 feet above the Gulf of California. In the several outcrops I found Ostea oongesta^ aud numerous fragments of a fragile inoceramus. These are referable to the earlier productions of the Cretaceous, age, and the undoubted equivalent of No. 4 of Messrs. Meek aud Hayden's Nebraska section of 1857. It is the next formation in the series above the section classified during the reconnaissances, the formations of which extend in the valley of the Arkansas from Canon City to Pueblo> thence along the base of the mountains to Huerfano Canon. |