196 0. a Marsh— Geology of the Uintah Mountains. 



we crossed a second great depression leading into tlie Green 

 River Yalley. _ This had been washed out, to a depth of 300 

 feet or more, in a series of nearly horizontal strata, composed 

 of red shales, sandstones, and conglomerates. In some of the 

 beds there were layers of ash-colored clays, and in these a few 

 mammalian and tortoise bones were found, which indicated 

 clearly the Tertiary age of the deposit. The same beds were 

 seen the next day, near one of the branches of the North Uintah 

 River, dipping about 5° to the N.W., and having beneath them 

 a series of chocolate and ash-colored clays, which, rising gradu- 

 ally, attain a great development farther to the S.E., and form 

 the remarkable Tertiary bluffs along the the Green and White 

 Rivers, which it was our special object to investigate. 



Crossing the Green River a few miles above the mouth of the 

 Uintab, we passed eastward to the White River, over an elevated 

 plateau, which was washed out along its sides into the true 

 "Mauvaises Terres" form of conical buttes, beautifully vane- 

 gated with alternating chocolate, green, and ash-colored layer?. 

 An examination of these deposits soon showed that they con- 

 tained many vertebrate fossils, which were weathering out of the 

 cliffs on every side. Farther up the White River, these remains 

 were more numerous, and large collections were o^t^^,"f '/^' 

 cludmg many species of Tertiary mammals, reptiles, and iishfc. 

 some of which were undescribed. Tortoises were especially 

 abundant, and at one locality no less than eleven of them ver« 

 seen from one point of view. These various remains proved to d 

 almost all identical with those we had found north of the Uin- 

 tah Mountains, near Fort Bridger, and hence indicated plainly 

 the synchronism of the two deposits. The great difference m eie 

 vation, however, and the character of the intervening regio"' 

 render it more than probable that they belong to distinct ia^^ 

 basins, connected in the same system of drainage, fo ^b ^ 



guish this ancient lake-reo-ion from the Green River lertia 

 basin north of the mountains, the former may appropriately 

 called the Uintah basin. The stream which connected tbe ^ _ 

 however, did not flow through the present Green River Vai^^^^^ 

 although the tongue of Tertiarv strata extending up 

 "Brown's Hole" would seem to point to that depression i" 

 probable inlet from the north. , ^,,ntT 



^ After exploring the region near the White River ^^""^H^ 

 nd finding the variegated Teri;iary clays re^ ^^^ 





-J — .V.I oaiiiasMmes ana gnts oi a lower norizou, w^ -— „|^gr 

 and proceeded by a nearly N.W. course across the ^^^^^\x^ 

 to Fort Uintak Here we procured an Indian guide, wno 

 lis neariy N.E. over the mountains by an extremely, dim 

 route. On +V.^a \^. n.... ] „„„„ on pvtensive sei. 



of shales and sandstoi 



journey we first passed 



