GEOLOGICAL SURVEY OF THE TERRITORIES. 55 



tributaries. We had obtained a pretty clear idea of the geology of the 

 north slope of the Uintas and a part of the shore line of the Bridger 

 basin and this gave us an earnest desire to trace it to Green River, to 

 ascertain its connection with the " Green River beds," and the lignite or 

 lower tertiaries. 1 take great pleasure in acknowledging here my great 

 obligations to Lieutenant Shepard, the quartermaster of Fort Bridger, 

 for numerous courtesies and favors which were indispensable to us, and 

 which, in a country like this, money will not purchase. From Captain 

 Olift, the commanding officer, and Dr. J. K. Corson, the surgeon of the 

 post, myself and party were the recipients of many kindnesses. J have 

 already spoken of my obligations to Judge Carter, to whom I was indebted 

 for many favors and much valuable information. To him this portion of 

 the West has been in the past, and will be in the future, more indebted 

 for its prosperity and development than to all others. I take pleasure 

 here in adding my testimony to the fidelity and truthfulness of his state- 

 ments in regard to its resources. 



Fort Bridger is quite pleasantly located in what appears to the eye a 

 sort of basin inclosed by high, arid table lands, but really in a central 

 portion of the drainage of Black's Fork. These beautiful valleys, Smith's, 

 Black's, and Muddy, have been carved out the horizontal strata, and be- 

 tween the streams are terraces and flat table lands which give a singular 

 as well as instructive outline to the surface of the country. No forces 

 now in operation in this vicinity could have given the existing features to 

 the surface of the country, and the cause must have been local, proceed- 

 ing from the northern slope of the Uintas. The beautiful table-top 

 divides between the valleys and streams are extensions into the plains of 

 the radiating ridges of the mountain slope, and are literally paved, in 

 many places, with the water- worn boulders of the purplish sandstones and 

 quartzites, and with the carboniferous limestones that compose the nucleus 

 of the Uinta range. Here and there we can see a flat-topped butte cut 

 off by erosion from some of the intervening ridges and rising above the 

 surrounding country as a partial witness to the extent of the denuda- 

 tion. A little south of west of Fort Bridger is an isolated butte called 

 Bridger's Butte, which forms a prominent landmark to the traveler, 

 and according to the barometer, rises seven hundred and fifty feet 

 above the valley of Black's Fork at the fort. The summit appears per- 

 fectly level, and was estimated to be about two miles in length from 

 north to south, and about a fourth of a mile in width from east to west. 

 The upper portion of the butte is composed of the somber brown in- 

 durated arenaceous clays, grey and rusty brown sandstones of the 

 Bridger group, passing down into limestones and marls of the Green 

 River beds. In the brown clays are abundant remains of turtles, with a 

 few fragments of other vertebrate remains. The terraces along the 

 valley of Black's Fork are composed of yellowistfand whitish-gray marls 

 and chalky limestones, some of the layers mostly formed of Unios and 

 other fresh-water shells. A few plants were found in the valley of 

 Smith's Fork, in thin, black flinty layers, mostly ferns and leaves of 

 deciduous trees. Between Fort Bridger and Henry's Fork the indurated 

 arenaceous clays of the Bridger group are weathered into remarkably 

 unique forms. The absence of harder layers of sandstone did not admit of 

 the weathering into pinnacles, turrets, steeples, domes, &c, as we observe 

 near Church Buttes. The surface, though very rugged and almost im- 

 passable except along the valleys of the streams, is much more rounded ; 

 the hills are more dome or rjyramid shaped, and entirely destitute ot 

 vegetation, except the sage and several varieties of chenopodiaceous 

 shrubs. As we passed up the Cottonwood Fork the marls and limestones 



