THE AGE OF THE DOMES AND ANTICLINES 309 



T. 28 N., Rs. 89 to 95 W/ This greater altitude of the nearly 

 flat-lying Tertiary beds south of the Sweetwater uplift and the 

 possibility that the White River and Wind River formations lie 

 only on the uplift itself are indicative of a readjustment movement 

 here in post- Wasatch time and possibly as late as White River 

 time. BalP mentions the fact that the Hanna formation (Wasatch ?) 

 is vertical and overturned in the Freezeout Hills. 



There has even been some post-Pleistocene movement in the 

 region, for gravel-covered terraces in some places are reported to 

 have slopes opposite to those of the present drainage.^ These 

 compa ratively recent movements were probably of small magnitude 

 and are cited principally to indicate that deformation did not 

 necessarily cease here in the Tertiary period, but that warping has 

 occurred in the Quaternary. It is possible that deformation has 

 taken place even within recent times. 



Inasmuch, therefore, as mountain-forming deformation has 

 occurred here in post- Wasatch time and possibly as late as White 

 River (Oligocene) time, or even later, it would seem that the 

 Ferris and Seminoe mountains should be regarded as the local 

 results of this late movement of readjustment along the south 

 margin of the Sweetwater uplift. Although the exact time when 

 these mountains were formed has not been ascertained, it seems 

 nevertheless that they must be considerably younger than the 

 main deformative movements which produced the Sweetwater and 

 Rawlins upHfts. If it is regarded as established that the Ferris 

 and Seminoe mountains are due to a late and possibly final spasm 

 of mountain-forming movements in this general region, it should 

 probably be conceded that the minor domes and anticlines of the 

 Lost Soldier-Ferris district are also due to the same movements. 

 Credit must be given to BalP for his recognition of a marked 

 difference between the deformation features of the Ferris and 

 Seminoe mountains and those of the Wyoming mountains of the 



^ No positive statement to this effect can be made, for the relation was noted 

 over only a small area by the writer, and the evidence gleaned from the unpublished 

 work of Hares and Smith above cited, though apparently supporting the inference, 

 does not fully confirm it. 



^ Op. cit., p. 55. 



3 K. C. Heald, personal communication. t Op. cit., p. 59. 



