112 



ELIOT BLACKWELDER 



both ends of the Wind River and Owl Creek anticlines and have 

 evidently been eroded from large areas which they once covered. 

 On the other hand, there seems to be no good reason to suppose that 

 some of the principal mountain ranges did not rise above the 

 aggraded plains somewhat as they now do in the Bonneville Lake 

 basin of Utah (Fig. 7). 



Fig. 7 



Mid-Tertiary deformation. — The early Tertiary sediments no 

 longer lie in their original almost horizontal attitude. Nearly 

 everywhere they have been tilted gently, and in a few places bent 

 into folds and broken by faults of large displacement. In Jackson 

 Hole the beds of travertine or freshwater limestone with lava flows 

 dip 10-15° toward the west. Near the forks of the Gros Ventre 

 River the alternating sandstones and clays dip 12-14° northeast- 

 ward. Near Dubois in the Wind River basin, the finely laminated 

 Eocene clays dip 5-8° away from the Wind River Range. In the 

 southwest part of the Bighorn basin, Sinclair and Granger observed 



