266 



CALIFORNIA ACADEMY OF SCIENCES. [P roc. 3D Ser. 



lake beds were deposited before the fault formed, they must 

 have undergone a subsidence of 2,000 feet without being 

 tilted or dislocated, except along the immediate line of 

 faulting, which erosion has no doubt long since removed. 



Owen's Valley has been said to be a post-Tertiary fault 

 valley, but to the south of Owen's Lake there are beds 

 which dip west at a gentle angle, and through these beds 

 the stream which formed the outlet of Owen's Lake at an 



1 



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9 



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Fig. I. -Sketch map of the south-central Sierra Nevada. 



earlier period has cut a channel. These beds in their upper 

 portions are largely made up of rhyolite tuffs, but at their 

 base are seen shales and conglomerates composed of ordi- 

 nary sediments, the series strongly resembling Tertiary beds 

 as seen at other points. There then appears to have been 

 a basin here in Tertiary time. The west border of this 

 basin is presumed to have been the Jurassic Sierra Nevada, 



