152 University of California Publications. [Geology 



ably upward movement in the Pine Nut Range. Had the latter 

 block alone been raised, the valley floor would have suffered some 

 tilting to the west. Such tilting has not been recognized directly, 

 though careful surveys may show it. On the other hand, the old 

 channel of the Carson River may indicate that the river was 

 forced to the west side by an elevation of Prison Hill. Further, 

 the very evident fault-line on Prison Hill prolonged westward 

 across the valley joins another evident fault north of Clear Creek, 

 along which the north side has moved relatively eastward. This 

 would require merely a greater elevation of the east than the 

 west side, and not necessarily an absence of elevation on the west. 

 From what facts are now known there appear to have been two 

 uplifts of Prison Hill and the block east of Kings Canon. The 

 first caused in part the projection eastward of the hills southwest 

 of Carson, between Kings and Clear Creek canons, and moved 

 the Prison Hill block as a unit. The second caused the further 

 eastward projection of the hills south of Carson to within a mile 

 of Clear Creek, and the slight projection westward of the south 

 half of Prison Hill. This latter movement dammed the old chan- 

 nel of the Carson River and turned it to the east, as already 

 noted. The complete history of the Carson River is a very fas- 

 cinating problem yet to be solved. 



All these many facts centering about the Carson topographic 

 area form a basis for the belief that the important east-west fault 

 line was established very early in the history of the orogenic 

 movements of the region, probably at about the time of the first 

 north-south faulting that can be discerned. For the effects of 

 the east-west movements exist near Lakeview associated with the 

 lower and older north-south scarp, while the upper scarp is 

 broken only by the distinctly later east-west motion. Further, 

 the faulting west of Lake Tahoe has been recognized by Lind- 

 gren as entirely pre-andesitic. The scarps on the east side of 

 Lake Tahoe are later than the rhyolite and some andesite flows. 

 It is not impossible, then, that the eastern north-south faulting 

 was contemporary with the main faulting to the west, and that 

 the later movements, entirely confined to the east slope of the 

 Sierra, were begun with the second period of the north-south 

 faulting best represented by the scarps on the ridge crest between 



