Vol. 6] Eekl: The Geomorphogeny of the Sierra Nevada. 



91 



the most important. A geological inquiry into its genesis became 

 the stepping stone to the study of the geomorphogeny of the sur- 

 rounding part of the Sierra. The work is yet necessarily incom- 

 plete, for the subject is one of vast complexity and almost in- 

 finite detail, yet sufficient has been accomplished to establish a 

 few fundamental relations between the various geomorphic and 

 physiographic elements. It is believed that a definite basis has 

 been constructed for future work in deciphering the history of 

 the Sierra Nevada in Professor Lawson's recent papers, 1 and the 

 facts presented in this paper are offered as a small contribution 

 to extend our knowledge of the Snowy Range. 2 



This paper aims primarily to present the larger details of 

 the geomorphogeny of the area examined. The study has led 

 naturally and unavoidably into the consideration of other details 

 of the history of the Sierra Nevada, and outlines of these will 

 be sketched as completely as possible, in order to facilitate fu- 

 ture work. The petrographic investigation of the rocks of the 

 roof of the Great Sierran batholith is a most important subject 

 for study. The correlation of the various Tertiary extrusives 

 with one another, and with the different orogenic movements of 

 the range is likewise a most fascinating and important field for 

 research. Further than these there is the history of the Carson 

 River, with that of the Truckee further north ; the study of the 

 evolution of the Tahoe moat and the history of the lake basin 

 proper ; the glaeiation of this portion of the range ; and smaller 

 details too numerous to mention. 



The area covered, in part carefully and in part by hurried 

 reconnaissance, constitutes the southwest portion of the Carson 

 quadrangle of the United States Geological Survey lying be- 

 tween longitudes 119°-i0' and 120°, and between latitudes 39° 

 and 39°20' (see map, plate 28). There is thus embraced a por- 



1 Andrew C. Lawson, ' ' The Geomorphogeny of the Upper Kern Basin, ' ' 

 Univ. Calif. Publ. Bull. Dept. Geol., 3, 1904, no. 15; and "The Geomorpho- 

 geny of the Tehachapi Valley System," ibid., 4, 1906, no. 19. 



2 The writer's first visit to Little Valley was made in September, 1904. 

 A complete geologic survey of the whole area was planned, but had to be 

 abandoned. The first notes on the subject were presented to the Cordilleran 

 Section of the Geological Society of America in December, 1904. Since 

 then further work has been done, and the present paper is the result. The 

 writer desires to express his sincere obligation to Professor A. C. Lawson 

 for his critical reading of the first notes. 



