POST-CRETACEOUS HISTORY OF WESTERN WYOMING 113 



an anticline in the Wasatch deposits, the dips being 5-7° on either 

 limb. In the slope just east of the E. A. ranch, north of Dubois, 

 there is a fold the southern limb of which dips at an angle of about 

 35°. The strongest folding I have yet seen in the Wind River beds 

 was found on the north fork of Wind River in the southwest corner 

 of the Kirwin quadrangle (see Fig. 8). There a relatively sharp 

 anticline between two broad flattish synclines exhibits dips of from 

 5° to over 50°. Although in a few cases the dips may be initial, 

 it is improbable that the fine clays were deposited at angles of 

 even 5-10°. 



Faulting is more common than folding in the Eocene strata. 

 Near the mouth of Dinwoody Creek on the north side of the upper 



Fig. 8 



course of Wind River, a fault of several hundred feet displacement 

 interrupts the nearly horizontal Wind River beds (Fig. 9). On 

 the northwest side of the Teton Range a normal fault of at least 

 1,500 feet displacement drops the Tertiary volcanic breccias and 

 rhyolitic flows down against Paleozoic strata. At Granite Falls, 

 and again along Jack Creek, both on the south side of the Gros 

 Ventre Range, a coarse conglomerate, apparently the same as the 

 Pinyon formation farther north, has been faulted down against the 

 Paleozoic rocks (Fig. 10). In the southern part of Jackson Hole 

 the freshwater Eocene limestone, with its interbedded lava flows, 

 is several times repeated in successive buttes rising above the 

 alluvial floor of the valley. The structure is readily explained by 

 assuming several normal faults with a downthrow on the east, but 

 if the faults exist they are concealed by the alluvial deposits. On 

 the west front of the Hoback Range the Tertiary beds have been 

 faulted down against the Carboniferous. There is abundant cir- 

 cumstantial evidence to indicate that a great fault marks the east 

 base of the Teton Range, cutting off the Paleozoic and Mesozoic 



