314 ELIOT BLACKW ELDER 



patches of gravel near Lander are remnants of torrential fans agrees 

 with the evidence so far as I have seen it. 



In the Owl Creek Range also features indicating the Black Rock 

 cycle have been observed although but sparingly. South of Anchor 

 certain shoulders 600-800 feet above the valley bottoms are strewn 

 with coarse, deeply weathered gravel and bowlders, which were once 

 water-worn. There is considerable resemblance between condi- 

 tions here and near Lander. In the upper course of Green River 



Fig. 31. — Tabular divide about twenty miles south of Lander. Probably repre- 

 sents the Black Rock cycle. Hogbacks of Permo-Mesozoic strata in the foreground. 

 (Photograph by D. D. Condit, U.S. Geological Survey.) 



similar high buttes and mesas, such as Flat Top Mountain near 

 Kendall, suggest the same cycle. 



In the type locality, the Buffalo old drift seems to lie always 

 upon the remnants of Black Rock valley floors, and in the Teton 

 Range the relations are similar. From these facts I infer that these 

 shallow older valleys were completed about the time of the first 

 well-recognized stage of glaciation in western Wyoming. It is a 

 persistent and distinctive characteristic of the Black Rock surface 

 that it is floored with thick and very coarse gravel deposits. None 

 of the earlier or later partial plains of the region carry more than 

 a thin veneer of such material. It has been suggested that the 



