250 Tertiary. 



between Green River station and Bryan and in the escarpments on 

 either side of Henry's Fork at man}- places. The Tower sandstone is 

 well shown in the cliffs at Gi-een River station, and in that vicinity and 

 below the mouth of Currant creek. The Tower sandstone is laid down 

 unconformably on the Lower Green River Group, the unconformity 

 being represented by gentle vallej's of erosion. 



The Bridger Group consists of Bad Land sandstones (chiefly green 

 sands) limestones, shells, marls, and concretionary and stratified flints. 

 Thickness, 2,000 feet. 



It is well exposed in the vicinity of Fort Bridger, at Church Buttes, 

 at Haystack mountain and in the Cameo mountains. An outlying- 

 patch is found north of the Dry mountains between Vermilion creek 

 and Snake river. Unconformity with the beds of the Lower Green 

 River Group may be seen in the vicinity of Carter station, but uncon- 

 formity with the Upper Green River Group has not been observed. 

 The two are separated, however, upon lithological grounds, though the 

 plane of demarkation is obscure. The moss agates for which the re- 

 gion about Fort Bridger has been noted are from irregular beds and 

 aggregations of chalcedonjMU this Group. 



The Brown's Park Group consists of sandstones, gravels, limestones, 

 concretionary^ and stratified flints. Unconformable with all under- 

 lying rocks. Thickness, 1,800 feet. 



It is well represented at Brown's Park, in northeastern Utah, and in 

 northwestern Colorado. About five miles above the confluence of Snake 

 river with the Yampa, the beds may be seen resting u neon form abl}' 

 against Carboniferous strata, and on going north they may be observed 

 to rest unconformably with the Bridger Group. 



In Brown's Park, it lies in a deep basin of erosion, the bottom and 

 sides of which ai'e composed of Uinta sandstone. This basin is in the 

 very axis of the Uinta uplift. Its sandstones are Bad Land rocks of 

 exceedingly fine texture. In some places there are extensive and ir- 

 regular aggregations of chalcedony. 



The Bishop's Mt. Conglomerate, which is unconformable by plica- 

 tion and erosion with underlying rocks. Tliickness, 300 feet. It is 

 found on the summits of Bishoj) and Quien Hornet mountains, and up 

 on various tables in the Uinta mountains. On the north side of Con- 

 nor basin, at the head of Sheep creek, this conglomerate has a thickness 

 of more than 1,000 feet. It is neither a marine nor lacustrine deposit, 

 but a subaerial one. 



Prof. Powell says, witnessing on every hand the accumulation of such 



