66 GEOLOGICAL SURVEY OF THE TERRITORIES. 



clear, well-marked exhibitions of the trap protrusions, and they deserved 

 a much longer study than I could give them. I believe that this igne- 

 ous material was protruded among the quartz beds prior to their up- 

 heaval. At the entrance of Bed Canon Creek from Brown's Hole the 

 elevation is 5,897 feet, and very nearly the highest point of the range was 

 8,073 feet, and the bottom of Green Biver, about ten miles below, was 

 5,175 feet; so that by these elevations we may estimate approximately 

 the heights of these mountains above the surrounding country. 



As we emerged from the Bed Creek Canon, we came out into a sort 

 of semicircular area, occupied by yellow-brown clays, the same as those 

 occurring in a similar locality at the mouth of Henry's Fork. The north- 

 east side of this quartz range is very abrupt, and no rocks appear to be 

 exposed between the quartz rocks and the cretaceous. Bed Creek runs 

 through the widest portion of this semicircular area, about two miles on 

 the south side. The ridges of cretaceous and tertiary soon close up 

 against the sides of the mountains, and about four miles up a little 

 branch of Bed Creek, which flows parallel with the range between the 

 ridges, the same beds jut up against the range in the same manner. The 

 southeast wall of this semicircle is formed by a massive bed of tertiary 

 (lower) sandstones, one hundred to one hundred and fifty feet thick, 

 south of the Bed Creek, dipping about 10°. The soft clays are shown 

 under the sandstones for thirty to fifty feet in thickness. 



As far as the eye could reach from the summit of the highest moun- 

 tains these ridges of tertiary extend off ridge after ridge, each one 

 inclining at a moderate angle, and having an open valley or space 

 between, which seems to be composed of soft beds. We have, therefore, 

 the cretaceous clays occupying the first open semicircular space; this is 

 walled in by a ridge of lower tertiary sandstone one hundred aud fifty 

 to two hundred feet, inclining northeast 10° to 15°; then an interval of 

 a quarter of a mile, which is occupied by variegated clays, with thin 

 layers of soft sandstone. The whole weathers smoothly and is covered 

 with grass. The next ridge is composed of sandstones, pudding-stones, 

 and conglomerates, rising two hundred to two hundred and fifty feet, 

 inclining 10°. The rocks of this ridge have a reddish tinge and remind 

 one of the conglomerates and sandstones of Echo Caiion. 



I find it difficult to account for this tremendous development of quartz 

 with gneiss at the eastern end of the Uinta range. The white quartz 

 beds rise abruptly from beneath the red quartzites, occupying a belt five 

 to nine miles in width, and end as abruptly as they commence. I do 

 not know why they should appear at this locality, when further to the 

 west, at the sources of Black's Fork and Bear Biver, where the rocks 

 rise to an elevation of over 13,000 feet, no trace of them can be seen. 

 Here the red quartzites and the white quartz beds seem to conform, and 

 on the side fronting Brown's Hole the red quartzites present an enorm- 

 ous thickness. On the summit, toward the outer portion of the white 

 quartz belt, there is only a thin remnant remaining. I could not spare 

 the time to study this portion of the range to my satisfaction, but I am 

 inclined to believe that the immense thickness of quartz was thrust up 

 beneath the red quartzites, carrying the latter so high up that they 

 have been swept away by erosion, except the remnant now remaining. 



When we passed over the high ridges on our way to Brown's Hole 

 from Henry's Fork we spoke of a high carboniferous limestone ridge on 

 our left or north side. This extends down the river about five miles 

 and juts up against the quartz ridges and disappears. Below this 

 point there is a space of ten miles or more, where all the formations from 

 the cretaceous to the quartzites, inclusive, seem to have been swept 



