3i6 • ELIOT BLACKWELDER 



appear not to have left notable marks in any but the softest strata. 

 For the present, therefore, they must be neglected. 



Circle cycle: Benches cut across folded rocks along the sides 

 of the mountain valleys and much wider terraces and mesas 

 cut in the Tertiary basin are relics of a surface carved out of 

 the Black Rock peneplain. Near the mouth of Fish Creek, 

 the principal northern tributary of the Gros Ventre River, a 

 broad terrace (Fig. 33) 100-200 feet above the stream is very 

 conspicuous.^ 



Fig. 33. — Rock-cut terrace on Fish Creek, correlated with the benches at Circle. 

 The Cretaceous strata are nearly vertical. 



To the east, in the upper part of the Wind River basin, there is 

 a prominent terrace cut on inclined strata and again standing about 

 150 feet above the stream (Figs. 34 and 35). A fine remnant of it 

 stands out just east of Circle post-office on Wind River. In each 

 case the surface is strewn with coarse, river-deposited gravel, but 

 the layer is only a few feet in depth. As the terrace blends into the 

 earlier moraines of the Dinwoody and Torrey glaciers, the gravels 

 may well consist largely of the outwash deposits of the Bull Lake 

 stage. Again, in the vicinity of Bull Lake and Fort Washakie, 

 a nearly smooth upland surface has been planed across tilted 



^ U.S. Geol. Survey, Mount Leidy, Wyoming, topographic sheet. 



