Vol. 4] 



Lawson. — Tehachapi Valley System. 



445 



country where no high grade streams had previously existed. It 

 is noteworthy, moreover, that the position of this coarse alluvial 

 material, in the northwest corner of the present Tehachapi Val- 

 ley, establishes the fact that its source was in the mountains to 

 the south. In other words, it is clear that at the time of the 

 accumulation of this great alluvial cone the drainage was from 

 the north, and was approximately, in part, along the line of the 

 present deep canon of Tehachapi Creek which flows from south 

 to north. The present drainage then, to the Great Valley of 

 California has a direction which is the reverse of that which 

 formerly obtained along the same general course. This fact is 

 one of prime significance in any attempt to explain the present 

 dual outlet of Tehachapi Valley. 



But while it is clear that orogenic movements inaugurated 

 the accumulation of the great cone, it is no less clear that 

 orogenic movements subsequent to its upbuilding have deformed 

 it. What is left to-day of the great cone is but a remnant of 

 its original mass and extent. It now lies in a synclinal trough. 

 Whenever its base is exposed it reposes upon the Cable lake 

 beds and the rude stratification of the lower part of the forma- 

 tion where exposed above Cable Station is parallel to that of 

 the lake beds. It probably nowhere extends at present beyond 

 the rim of the synclinal trough formed by the lake beds. It 

 certainly does not in the numerous and often persistent expos- 

 ures where the two are seen in juxtaposition. The lake beds are 

 nowhere horizontal but dip in all observed cases for several 

 miles of outcrop on different sides of the trough under the 

 alluvium, and on the west side of the trough they are well ex- 

 posed in one locality in a perfectly vertical attitude. It is evi- 

 dent then that the whole body of the alluvium has been subjected 

 to the same measure of deformation as that which can be made 

 out clearly from the attitude of the underlying regularly strati- 

 fied lake beds. 



Planatiou. — Since its deformation the Tehachapi alluvium 

 has been broadly terraced by stream action, the terrace has since 

 been deeply dissected and the mass has otherwise been degraded 

 by the forces of erosion. The broad terrace which truncates a 

 large proportion of the total area of the formation is a most 



