194 0. C. Marsh — Geology of the Uintah Mountains. 



On reacliing " Brown's Hole," a narrow valley about thirty 

 miles in length, through which the river flows, a series of more 

 recent beds was met with, that are well developed to the south- 

 ward, where they have played an important part in shaping the 

 present topography of the country. These strata, which are 

 several hundred feet in thickness, lie nearly horizontal, and are 

 mainly composed of conglomerates, and very soft, white, friaWe 

 sandstones, which at some localities pass into thinly laminated, 

 calcareous shales. At one point on the right bank of the river, 

 a thin seam of lignite was observed in the white sandstone, and 

 about ten miles below, in a high bluif on the opposite side, some 

 of the calcareous layers had all the physical characters of white 

 chalk, although apparently without the same organic structure. 

 As no fossils were detected in these beds, except some obscure 

 remains of plants, their exact age is a matter of some doubt. 

 That they are Tertiary, however, is rendered probable by the 

 fact that, farther down the river, they are seen to rest uncon- 

 formably on the upturned edges of Cretaceous rocks. 



Finding it impossible to proceed with our pack-animals down 

 the river on the east side, we crossed just above the mouth oi 

 the Vermilion, and proceeded in a southwesterly course, by a 

 difficult pass, over the eastern extension of the Uintahs. iQ as- 

 cending the mountains from the river we first found a great de- 

 velopment of red and purple ffrits and sandstones, apparently 

 the same as those seen on the eastern side above, but here dip- 

 ping about 15° to the S.W. Above these strata, and pertiap* 

 ten miles to the south, we passed over a series of ^"giit rei. 

 thickly bedded sandstones, having the same general inclinatw ■ 

 and at least 1000 feet in thickness. In these beds, also, no ^^ 

 sils were detected during the hasty examination we were oW^^^ 

 to make. Resting conformably on this sandstone, was a oe^ 

 gray, siliceous limestone, at least 100 feet in thickness, ^d^^ 

 formed the summits of several of the smaller elevations betw 

 the main Uintah range and the Green River, and by its aen ^.,, 

 tion had strewn the region to the southward with its ^vaten^ ■ 

 fragments. This rock, fortunately, contained a few fo?^''^ 

 most characteristic of which were specimens of Producm- 

 ifer cameratns Morton, Athyris suhtUita Hall, Hemlpronn'- 

 SW5 M. and H., a species of Zaphrentis, apparently^- ^^^^ , 

 Hall, with fragments of Fenestella and PhUlipsm. These reu ^ .^ 

 cleariy mdicate the Carboniferous age of the limestone, ^^ - 

 directly, throw considerable light on the strata beneatD i^- 



Continuing our journey southward, for fifteen miles or;^ 

 across an elevated plutoau wp cum- snd<lenlv to the overnj . 

 mg edge of a oroat Ir,.!,, n-i.irl, ■.lloi^l.-d a ino.^t stnk'iDg i' , 

 tration of the va^t •m'lonnt of .•rn'.ion to wliidi this region ^ 

 been subjected sine- the raouiit'uns 'ittaiucd their present eie ' 



