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Show 76 RECONNAISSANCE IN THE UTE COUNTRY. conglomerate, and a little lower down the stream a ledge of volcanic trachyte. One mile below this occurs a ledge of feldspathic granite 50 feet thick, succeeded by 150 feet of quartzose strata, granular at the base and shading upward into a quartzose sandstone of different colors, this again succeeded by red porphyry 80 feet thick and capped by trachy- doleiite. The two latter are much like those formations in the eastern approach to the pass, and the trachyte identical with that vast volcanic deposit on the Atlantic slope, along the Ute trail, between Camps 52 and 53. Farther down Tumitchi Creek the granite forms the walls of a canon? is 150 feet thick, is often quartzose, in several instances penetrated by-trap dikes. Between Camps 9 and 10 the granite disappears. The sandstone and trachyte were observed to the close of the day's march. In the bluffs on the right, on entering Cochetopa Valley, is a ledge of hornblende slate. From Camp 10 the slopes on the right side are of the quartzose sandstone observed in Tumitchi Valley. On the left are frequent protrusions of trappean deposits. Coarse conglomerates also occur at intervals. From Camp 11, except in the distance, the mountains dwindle into foot- hills, regular in contour, with a few outcrops of quartzose sandstone and protrusions of trap in the earlier part of the march. At the base of the former occur 25 feet of fine conglomerate of small silicious gravel and rounded water- worn pebbles. These were cemented by a white paste, and formed one solid mass. The finest would take a fine polish and might be worked into ornaments. These were probably the result of the earlist fluviatile development. In the same vicinity, but lower down in the valley, is another species of conglomerate in high ledges, coarse and of recent date. Four miles above the head of Gunnison River they form escarpments several hundred feet in height. During the greater part of the day a distinct shore or water line was observed on the lett of the stream, 800 feet above the bottom of the valleys. • Three miles above Camp 12, on the right of Ohio Creek, elevated 7,647 feet, I found a bank of marly shale, in thin and horizontal laminae, containing Ostrea congesta, and many fragments of what was once a large and fragile Inoceramus. The formation is 75 feet thick, and outcrops were frequently observed during the day higher up along the valley. This is one of the earlier formations of the cretaceous system, and is the equivalent of No. 3 of Meek and Hayden's Nebraska sections, 1857. Thick beds of coarse conglomerates were frequently observed above this formation. Immediately above Camp 13 is a high table, with terraces of light brown, hard, compact, amorphous sandstone, dipping toward the southwest. It lies against Mount Umbraculum, and reaches high up in the approach to the pass leading across to the head of Nigger Creek and Anthracite Creek. Mount Umbraculum, a spur, is of volcanic origin, mostly a porphyritic trachyte. The herbage luxuriant, rich, and abundant. Not that the soil is any different from that of the valleys below, but here the surface receives the diurnal rains that prevail in the mountains from July to September, but rarely reach half a mile below lower timber- line. Yesterday I observed the full effects of these conditions. In travel- |