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University of California Publications. [Geology 



interesting feature of the geomorphy of the region. The terrace 

 is not confined to the alluvial formation, but extends, as a broad 

 even plain, indifferently across the alluvium, the soft beds and 

 hard cherts of the Cable formation, and the schists, limestones 

 and granite of the Bed-rock Complex. The terrace slopes down 

 to the south at a low angle. Its expanse increases also in this 

 direction and it eventually passes beneath the present floor of 

 Tehachapi Valley where it meets the opposite slope of the China 

 Hill alluvial fan. The terrace becomes constricted to the north, 

 and leaving the valley it passes into the mountains, which lie on 

 this side of the valley, in the form of bench-like remnants high 

 up on the eastern slope of Tehachapi canon. Just before passing 

 into the mountains north of Cable, it is bounded on the west for 

 a short distance by a sharp residual ridge of the Tehachapi 

 alluvium. Beyond the south end of this ridge, however, the ter- 

 race extends over to the steep, rocky mountain slope which forms 

 the western boundary of the valley. On the east side of the 

 railway above Cable, the stream which carved the terrace, in 

 the course of its meandering and lateral corrasion, cut an embay- 

 ment over a mile in breadth out of the main mass of the 

 Tehachapi Alluvium. This embayment is bounded on the east 

 and south by a relatively high semicircular residual ridge of the 

 alluvium. This semicircular ridge, together with the similar 

 residual ridge on the west side of the railway nearer Cable, are 

 so disposed as to give these prominent residuals of the Tehachapi 

 alluvium the configuration of a terminal moraine. This super- 

 ficial resemblance to a moraine is enhanced by the numerous 

 spauls of rock of considerable size which weather out of the allu- 

 vium and lie strewn over its surface. The facts above cited 

 prove, however, that the resemblance to a moraine is quite super- 

 ficial and accidental as regards at least its form.* 



It has been pointed out that the source of the materials for 

 the Tehachapi Alluvium was probably in the mountains to the 



* It is to be observed that on the basis of its composition alone there 

 might be considerable doubt as to whether the Tehachapi formation were 

 fluviatile or glacial in origin. But as the mountains of the region do not 

 exceed 7000 feet in altitude, and present no traces of glacial sculpture, 

 and as the material rests on a non-glaciated surface and is in part stratified, 

 the writer was forced to reject the glacial hypothesis and interpret the 

 accumulation as an alluvial cone. 



