This paper describes the geology of an area of approximately 430 square miles in northwestern Wyoming and includes the southern margin of the Absaroka Range, the western end of the Owl Creek Mountains, and the northwestern part of the Wind River Basin. Most of the area lies within the southern half of the Kirwin quadrangle and the southeastern part of the Younts Peak quadrangle and extends from 25 to 55 miles southeast of Yellowstone National Park. Except for a few square miles in Hot Springs County, the entire region is in Fremont County, the northern part being in the Washakie National Forest and the southern part in the Shoshone Indian Reservation.

RESULTS OF INVESTIGATION

A geologic map including 430 square miles was made (Pl. 17). The stratigraphy, structure, lithology, and paleontology of the 15,500 feet of post-pre-Cambrian rocks were studied. Every system except the Silurian is represented. Uppermost Cretaceous and Paleocene rocks are absent. A remarkably complete section of Lower Tertiary rocks is preserved on the crest of the folded and faulted Washakie Range, in the central part of the area.

Eight localized pulsations of the Laramide Revolution are believed to have affected the rocks of the region: (1) At the close of Lance time; (2) at the close of the Paleocene; (3) during early Early Eocene time; (4) at the close of early Early Eocene time; (5) at the close of late Early Eocene time; (6) at the close of Middle Eocene time; (7) at the close of Late . . .