Vol. 4] 



Lawson. — Tehachapi Valley System. 



441 



on the railway grade there is exposed an area of 20 or 30 acres 

 of andesitie lava which probably overlies the decomposed allu- 

 vium. The entire absence of fragments of lava in the alluvium, 

 although carefully looked for, is in accord with this interpreta- 

 tion which is, however, based on independent structural evidence. 



Tank Volcanics. — These rocks are best exposed in the vicinity 

 of the railway tank which is situated about 2 miles below 

 Tehachapi station on Tehachapi Creek. The lava is exposed 

 over an area of 20 or 30 acres with a slope of 5° to the west and 

 a vertical range of about 150 feet. Its relations here are not 

 as well revealed as in other localities, but it appears to rest 

 in part upon the Atlas Alluvium mentioned above, and is cer- 

 tainly below the Tehachapi formation. The Cable formation is 

 not here exposed. 



Another occurrence of the lava is on the west side of 

 Tehachapi Creek to the west of the high ridge, composed of the 

 Cable and Tehachapi formations, which is situated southwest of 

 Cable station. Here the lava rests upon an old surface of the 

 Bed-rock Complex composed of granitic rocks, schists and 

 crystalline limestone and is clearly stratigraphically below the 

 easterly dipping beds of the Cable and Tehachapi formations. A 

 third occurrence has already been mentioned in speaking of the 

 exposure of the Atlas Alluvium below Cable. Here it was stated 

 that the Atlas Alluvium was overlain by a bed of yellow tuft' 

 and a thick sheet of andesitie lava. The same section shows very 

 clearly the superposition of the Cable lake beds upon the sheet 

 of andesite. 



The tuffs and agglomerates which lie upon the Atlas Allu- 

 vium in the country between Cable and Tehachapi station are 

 without question to be correlated with the lava as part of the 

 same volcanic extravasation. These volcanics as has been shown 

 are clearly above the' Atlas Alluvium; but they are no less clearly 

 below the Cable lake beds which are well exposed by the same 

 dissection as that which has revealed the underlying beds. 



Cable Formation, — The rocks of this formation are best ex- 

 posed in the vicinity of Cable station on both sides of the canon 

 of Tehachapi Creek. They comprise limestones, cherts, gravels,, 

 clays, and fine light colored volcanic tuff. These rocks are for 



