52 GEOLOGICAL SURVEY OF THE TERRITORIES. 



but downward in a geological sense, we observe a series of purplish sand- 

 stones and slates, perfectly conformable to the limestones, and appa- 

 rently unchanged. These sandstones gradually pass to thick beds of 

 gray and purplish quartzites, which are exceedingly brittle in fracture, 

 and plainly metamorphosed by heat. Intercalated among the beds of 

 quartzite are thin layers of quartzitic sandstone and clay slate. As we 

 proceed toward the crest of the mountains, where the rocks have been 

 elevated from a great depth, the slates and sandstones become thinner 

 until they disappear. I am therefore inclined to regard this as a re- 

 markable example of the gradual transition of Unaltered into meta- 

 morphic rocks. It would seem also that the finer the texture of the 

 rock the more readily is it affected by metamorphic action. 



On the morning of the 27th we descended from the high plateau into 

 the valley of the small side branches of the east fork of Bear River, with 

 the high, steeply inclined limestone ridge on the left, and the gray sand- 

 stone, and red argillaceous sandy clays on our left. The surface is so 

 covered with fragments of rocks that the traveling is difficult. Our 

 course was nearly due west for about three miles, when the valley flexes to 

 the northwest. When we left our camp in the morning we were about 

 two miles above the source of this branch. At our noon camp the little 

 stream was two feet wide. For about ten or fifteen miles the stream 

 flows between ridges twelve hundred to fifteen hundred feet above the 

 valley, covered with pines and aspens, with no exposures of the under- 

 lying rocks. The same vast deposit of drift covers the valley and ridges 

 ail over the drainage of Bear Biver. As soon as we come out into the 

 plains the valley expands to a width of several miles, and the tertiary 

 beds jut against the foot-hills with a slight inclination from the range. 

 Sulphur Creek is the most eastern part of Bear Biver, and rises in 

 Spruce Bidge, flows northwest, and empties into Bear Biver near Bear 

 Biver City. On the east side of Sulphur Creek, about two miles north 

 of the railroad, there is a high ridge of sandstone one hundred to one 

 hundred and fifty feet high, with an inclination of 20° to 25° west to 

 northwest. It extends across the railroad a little east of north, and 

 joins on to a range of hills, of which Medicine Butte forms a part. On 

 the summit of this ridge is a layer of rusty brown arenaceous limestone, 

 composed largely of a species of Ostrea. This ridge is the first indica- 

 tion of cretaceous rocks I have seen in the vicinity of the Uinta range. 



From Sulphur Creek to the " rim of the basin," a series of modern 

 tertiary beds are deposited unconformably upon the lower tertiary and 

 cretaceous, filling up all the inequalities of the surface, and jutting up 

 against the foot-hills of the Uintas. They are mostly horizontal in posi- 

 tion, but sometimes dip 5°. This most characteristic feature is the 

 light pinkish hue by which they are detected as far as the eye can reach. 



In completing our section of the Uinta range and connecting it with 

 the formations of the plains, the only period wanting is the Jurassic, 

 no indication of which has been observed. The geologieal features of 

 this region will be discussed more fully in a succeeding chapter, in. con- 

 nection with the belt of country along the line of, and contiguous to, the 

 Union Pacific Bailroad. The study of the Uinta range has been full of 

 interest. It has been sometimes called the Alpine Mountain of America, 

 though we miss the vast masses of snow and the glaciers ; but in an artistic 

 sense, no range that I have ever seen on this continent can compare 

 with it in beauty. There is a far more rugged grandeur about the Wind 

 Biver, the Sierra Nevada, or the Coast ranges ; but in none of them is 

 there such simplicity of structure, nor the contrasts so pleasing to the 

 eye. 



