WASHAKIE BASIN. 207 



SECTION III. 



DESCRIPTIVE GEOLOGY OF THE BASIN EEGION. 



Washakie Basin. — In pursuance of the general plan followed in 

 Chapter I, the detailed description of localities will follow the general idea 

 of proceeding from east to west, and, in this case, commence with the broad 

 area of Tertiary occupying the northeastern portion of Map II, which is 

 included under the general name of the Washakie Basin, as distinguished 

 from the Bridger Basin, to the west of Green River. 



Over the greater portion of this region, only the comparatively undis- 

 turbed beds of the Eocene Tertiaries are exposed. Owing to the soft, friable 

 character of the material of these beds, and the approximately horizontal 

 position that they occupy, it were almost impossible, even with a much 

 more careful. study than our time permitted us to give, to define accurately 

 the outlines of the different divisions of these formations. Those given on 

 the map, therefore, are to be considered only as approximately correct. 

 The northeast corner of the map represents a portion of an almost level 

 desert country, extending from Rawlings Peak to the Bitter Creek ridges, 

 bare of vegetation, and even without the dry water-courses, which are gen- 

 erally found on these plains. To the west of Rawlings Peak, as we have 

 seen, the Cretaceous strata fall off with an ever-decreasing angle of dip, 

 assuming to the north of the railroad, between Separation and Washakie, 

 an almost horizontal position, and are gradually succeeded by the overlying 

 and, in this region, conformable beds of the Vermillion Creek Tertiary. 



It is probable that the latter beds extended much farther east than 

 has been indicated on the map, and that remnants may still exist in the 

 region included in the color of the Laramie Cretaceous, Mdiich, owing 

 to the similarity of the lithological character of the two formations, and 

 the absence of palseontological evidence, it has been impossible to dis- 

 tinguish. The line of division, as drawn between these two foraiations, 

 indicates the Avestern limit of well-defined exposures of the Laramie Cre- 

 taceous. On the line of the railroad, about six miles east of Washakie 



