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University of California Publicatio-ns in Geology [Vol. 13 



There is very little true soil on these hills in spite of their flatness ; 

 although basalt is a rock usually yielding readily to decay. Since the 

 climate of the region is arid, the bareness is probably due to deflation. 

 Another peculiarity is the presence of several inclosed basins; these 

 may also be the work of deflation, although, being on a lava surface, 

 there is the possibility, of collapse. 



The rather flat but hummocky surface on the granite west of The 

 Pipes is probably a slightly modified portion of the pre-basalt surface 

 which has been stripped of its covering. Remnants of the basalt are 

 still present on some of the ridges to the southwest and present an 

 appearance somewhat similar to the basalt-capped hills to the west 

 (pi. 18, A and B). That all are part of a once continuous surface is 

 evident. Remnants of a basalt flow are found on the ridges on each 

 side of Antelope Creek, which indicate the pre-basalt surface. These 

 remnants of basalt sloping up to the west suggest that either the sur- 

 face on which the basalt rests or that carved in the basalt is corre- 

 lative with the old summit ridge between San Gorgonio and San 

 Bernardino peaks. 



Looking eastward from Kitching Peak the whole country has the 

 appearance of sloping in that direction and in some cases the crests 

 of the ridges are smooth and even. Although it is not known 

 whether these crests represent the first or second cycle, the general 

 slope strengthens the argument that the flat ridge between San Gor- 

 gonio and San Bernardino peaks was once continuous with the old 

 surface in the vicinity of The Pipes. 



Baker 2 has described a post-Miocene surface in the locality north 

 of Bar-stow, in the Calico Hills, and at Black Mountain. He says: 

 "This old surface can be traced on the crests of the Sierra Nevada 

 and Tehachapi mountains in the vicinity of Tehachapi Pass and on 



the summits of the latter range northeast of Tejon Pass There 



is a disposition to correlate the surface developed during the first cycle 

 of post-Miocene erosion with the surface of the summit ridge of the 

 San Bernardino Mountains." This conclusion is based entirely upon 

 the flat surface developed in each case. 



The question arises as to whether this old surface was developed 

 under humid or arid conditions. San Gorgonio itself is flat except 

 for the knobs of granite. The boulders have peculiar forms ; some 

 are rounded but others have fantastic shapes and are pitted as if by 

 wind-driven sand. There are also a few pinnacles consisting of granite 



- Baker, C. L., Cenozoie history of the Mojave Desert, Univ. Calif. Publ. Bull., 

 Dept. Geol., vol. 6, pp. 361, 365. 



