64 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



tearing out such gorges in the alluvial bottoms as to make travel almost 

 impossible. The continuation of this sliding process from year to year 

 keeps large portions of the mountain-sides swept clear of all movable 

 material, leaving only the bare rock. 1 All along these deep valleys such 

 avalanche-pathways may be noticed. 



The vegetable growth is quite profuse in this region. Dense groves 

 of aspens occupy the more fertile spots, pines and cedars cling to the 

 rocky slopes, while Scrub-oaks and a great variety of smaller bushes 

 abound. There is but little room for agriculture or grazing. 



At the upper end of the canon the granite disappears and the yellow 

 quartzites descend into the valley and also disappear, dipping 30° S. 

 The Carboniferous maroon beds follow, but soon assume a horizontal 

 position, so that there is nothing else exposed in the walls, for a distance 

 of five or six miles. Then, by an abrupt monoclinal fold, the whole 

 series pitches into the valley, leaving nothing exposed but the massive 

 sandstones of the Upper Cretaceous. These beds in turn assume a hori- 

 zontal position, forming shelved slopes to the height of 1,200 to 1,500 

 feet on either side of the creek. The creek cuts obliquely through this 

 fold, and the section exposed consists of the Upper Carboniferous, 

 Jurassic, and Lower Cretaceous strata. On the left hand the hard layers 

 of the Dakota group, standing almost on edge, form a high ridge that 

 extends to the southward up the western slope of the Snow Mass group. 

 On the opposite side, the trend of the same beds is to the northwest, 

 passing up the face of a high mountainous ridge which culminates in 

 Ganuett's station 28, ten miles west of Sopris. Section C of the large 

 sheets cuts this fold near the creek-crossing, and also gives a transverse 

 -section of the great red arch which lies between Sopris and Capitol peaks. 



The facilities for measuring the strata in this locality are very poor. 

 The yellow quartzites, supposed to belong to the Silurian age, do not 

 measure more than 500 feet, while the Carboniferous series will hardly 

 fell short of 4,500. The Triassic (?), Jurassic, and Cretaceous beds will 

 add about 5,500 more, so that the exposed strata will include a thickness 

 of some 10,000 feet. 



Ever since entering the valley a handsome group of mountains had 

 been in sight, apparently standing in the valley-course, and quite cut- 

 ting off the view. From the crossing of the monoclinal fold, the first of 

 these mountains appeared three or four miles farther up, standing on 

 the west side of the valley, and rising abruptly from the creek. We 

 determined to climb this in order to get good views of the Elk Mount- 

 ains, which lie mostly to the east, and of the unknown area to the west. 



In the first place, we ascended the steep Cretaceous slope to the right, 

 at its lowest point, and found ourselves on a level with the undulating 

 country to the west. Gannett's station 26, was on our right, some ten 

 miles to the north, and the mountain which we desired to climb on the 

 left, three miles away, and rising nearly three thousand feet above us. 

 Following the summit, or back of the ridge which leads up toward it, I 

 observed that the Cretaceous strata were rising with the slope, and at 

 the base of the steeper face were turned sharply up against it at an 

 angle of 45°. In crossing these upturned edges, I observed that they 

 comprised no great thickness; that the bulk of the sedimentary beds 

 seemed not to change from their horizontal position, and that this up- 

 turned portion had been separated from the rest and forced upward by 

 a wedge-like mass of intrusive rock which belonged to the central mass 

 of the group. (See Figure 5.) These strata seem to belong to the Cre- 

 taceous Coal Measures, as there were outcrops of coal and carbonaceous 

 shale. The horizon would hardly be less than 3,000 feet above No. 1. 



