406 



University of California Publications. 



[Geology 



lateral branches of the affluents of the Kern if we suppose the 

 existence of a zone of exceptional weakness paralleling the main 

 canon wall. Such a zone of exceptional susceptibility to stream 

 erosion might inhere in the character of the rocks themselves or 

 it might be purely a structural feature such as a rift, which, it 

 may be recalled, was found to exist along the canon of the Upper 

 Kern in what is practically the projection of the line we are 

 now considering. As regards the possibility of a zone of weak- 

 ness in the rocks themselves, it is to be noted that for several 

 miles along the canon of the Kern there is a belt of crystalline 

 schists which is sunk down into the granitic rocks of the region 

 in much the same way as is the similar belt of schists at Mineral 

 King described by Knopf and Thelen.* These schists are, however, 

 common to both sides of the canon, whereas the peculiar features 

 noted are confined to the east side. In several eases, noted only 

 from the trail on the west side of the canon, the ridges and buttes 

 are composed chiefly of crystalline schists, in other cases of a 

 mixture of crystalline schists and granitic rocks, and in other 

 eases toward the upper end of the canon they appear to be com- 

 posed chiefly of granitic rocks. It would appear, therefore, that 

 there is no good warrant for assuming a zone of weak roclcs 

 which might be easily removed by subsequent erosion so as to 

 produce in straight alignment the series of defiles which separate 

 these ridges and buttes from the main canon wall. Moreover, if 

 such a zone of weak rocks existed, it would undoubtedly have 

 been discovered by the Kern in the course of its downward corra- 

 sion and have become the main line of canon cutting. But the 

 main course of the canon crosses granite and schists indifferently 

 and has evidently not been greatly influenced in its course by 

 peculiarities of these rocks-. 



We are forced, then, still under the assumption that the series 

 of defiles is due to subsequent corrasion along a line of weakness, 

 to the view that the weakness postulated must be structural, a 

 line which is common to both granite and schists. Such a struc- 

 tural line might have existed prior to the development of the 

 Kern Canon, or it may have come into existence after the canon 

 trench in its main features had been established. If the first 



* Bull. Dept. Geol. Univ. Cal. Vol. 4, No. 12. 



