304 A. E. PATH 



the major uplifts in Wyoming on account of its size, but the fact 

 that its central axis is elevated so high that the pre-Cambrian 

 rocks are now exposed at the surface is sufficient, as pointed out 

 by Ball/ to justify ranking it as a major uplift. Its alignment 

 makes it a part of that series of Rocky Mountain flexures char- 

 acterized by northerly lines of folding and faulting. It is to be 

 noted especially that the Rawlins uplift is one of a group that forms 

 the northernmost member of this northerly series, beyond which 

 the Rocky Mountain folds abruptly change in direction to a 

 transverse series with east-west trend, of which the Sweetwater 

 uplift, described below, is one. 



From the general horizontal position of the Wasatch beds on 

 the west flank of the Rawlins uplift, it seems certain that the 

 development of this uplift was complete, or practically complete, 

 by the beginning of Wasatch time. 



The central pre-Cambrian granite core of the Rawlins uplift 

 is faulted along its west side, and toward the north this fault zone 

 turns northeastward and crosses the axis of the fold. The portion 

 of the uplift north of this fault is on the down-dropped side, and 

 this lower-lying north end of the uplift is occupied by the oil and 

 gas fields of the Lost Soldier-Ferris district. The oil and gas 

 accumulations of this district are controlled by minor folds, and 

 it is these minor folds that constitute the subject of this paper. 



North of the Rawlins upHft is the Sweetwater uplift, a major 

 fold about one hundred miles long and forty miles wide that trends 

 nearly due east. The Granite Mountains, which occupy the 

 central part of this uplift, represent the higher peaks of the much 

 dissected pre-Cambrian crystalline rock core, whose valleys and 

 lower-lying parts are now filled and covered by nearly horizontal 

 Tertiary sediments. These sediments form a nearly flat plain, 

 above which the Granite Mountains rise like islands in a sea. On 

 the south margin of the Sweetwater uplift, immediately adjacent 

 to the Lost Soldier-Ferris district, are the Ferris and Seminoe 

 mountains. The north side of the Ferris Mountains consists of 

 pre-Cambrian crystalline rocks, adjacent to which, in a sharply 

 upturned attitude, lie the Paleozoic and Mesozoic sediments that 



' Max W. Ball, op. ciL, p. 51. 



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