UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 4, No. 19, pp. 431-462, Pis. 42-51 Andrew c. lawson, Editor 



THE GEOMORPHOGENY 



OF THE 



TEHACHAPI VALLEY SYSTEM. 



BY 



Andrew C. Lawson. 



contents. 



Introduction 431 



Tehachapi Valley 432 



General Features 432 



Streams 432 



Alluviation 433 



Isolated Hills 435 



Eemains of Mammoth 436 



Rocks of Surrounding Mountains 437 



Outlets of Tehachapi Valley 438 



Atlas Formation 440 



Tank Volcanics .". 441 



Cable Formation 441 



Tehachapi Formation 443 



Planation 445 



Dissection and Reversal of Drainage 447 



Mature Geomorphy - 449 



Western Boundary of Valley 450 



Geological History 451 



Brites Valley _ 454 



Cummings Valley 45g 



Bear Valley _ 460 



INTRODUCTION. 



At the southern end of the Sierra Nevada there are certain 

 high valleys, situated about 4000 feet above sea level, which, by 

 reason of their abnormal position, their peculiar drainage, their 

 large dimensions, and their discordant relation to their geomor- 

 phie environment, invite geological inquiry as to their genesis. 



