POST-CRETACEOUS HISTORY OF WESTERN WYOMING 335 



been formed. On the northeast side of Sheep Moimtain at the 

 northwest end of the Wind River Range there is a good example 

 showing the tongue-Hke form and surface corrugations (Fig. 48). 

 Rock-falls have been observed where outcrops of the massive Big- 

 horn dolomite have given way suddenly, perhaps because of the re- 

 moval of the support previously given by the mass of glacial ice in 

 the valley. Figs. 49 and 50 show two rock-falls of this kind in the 

 Teton and Gros Ventre ranges. More numerous landslides of the 

 commoner type, developing in soft or unconsolidated rocks, are 

 observable here and there along the slopes of the canyons in the 



Fig. 49. — A rock fall in Paleozoic dolomilc near Uie head of the ( Jros Venire River 



district. There is a particularly large and fresh slide near the head 

 of Dell Creek on the south side of the (iros Ventre Range. Perhaps 

 the most novel of the many landslides in this region are the earth- 

 flows which are especially characteristic of the (iros Ventre valley 

 (Fig. 51). They depend upon steep slopes in soft argillaceous 

 material such as constitutes the Jurassic, Cretaceous, and Tertiary 

 systems. The most recent of these flows I have described in 

 another paper,' and for this reason further mention of them may 

 be omitted here. 



The landslides and talus deposits are clearly of various ages. 

 A few have been made within recent years. Many others are 



' Bull. Geol. Soc. Am., XXIII (1912), 487-92. 



