294 



University of California. 



[Vol. 3. 



The rocks which underlie the hydrographic basin of the Upper 

 Kern are almost wholly granitic in character. This is a fact of 

 prime importance for the study of the geomorphic evolution of 

 the region. The relief as determined by general atmospheric, 

 stream, and glacial erosion has been controlled by the uniformity 

 of the materials subject to sculpture by these agencies. It has 

 been uninfluenced by that marked differentiation of structure 

 and of resistance to erosion which characterizes the stratified 

 rocks whether they be detrital or volcanic, unaltered or meta- 

 morphic, horizontal or folded. There are no belts of soft rocks 

 which might have been sought out by enterprising head-water 

 streams, and by these exploited till they became the dominant 

 drainage lines of the region; no belts of hard rocks which might 

 have been left as dominant ridges; no superposition of hard 

 rocks upon soft which might have yielded mesas and serried 

 escarpments. Yet the region is one of the boldest possible 

 relief. The altitudes within the basin have a range of over 8000 

 feet. There are very striking contrasts in the slopes of the 

 basin. There is a pronounced system in the drainage lines; and 

 the master stream of the basin, the Kern itself, has a course as 

 straight as an arrow for nearly its entire length. These facts 

 indicate clearly that, notwithstanding the nearly uniformly 

 granitic character of the region, there has been a certain direc- 

 tive control of its sculpture due in part to the character of the 

 rocks . 



If, with this conclusion in mind, we turn again to the rocky 

 floor of the basin and attempt to characterize it more precisely 

 we find facts which to some extent, at least, justify it. 



Granitic Roclis. — In the first place it may be stated that even 

 where the rocks are granitic, even in the strict sense of the 

 term, this granite presents considerable variation in character. 

 In the middle of the basin, along the eaiion of the Kern, the 

 rock is prevailingly a light-colored, coarse, very quartzose biotite- 

 grauite. This rock has frequently a porphyrinic appearance 

 owing to the exceptional size of the orthoclase crystals, but the 

 latter are as a rule imperfectly formed and the stracture would 

 on the whole be classed as hypidiomorphic granular. This granite 

 grades through varieties, in which hornblende replaces part of 



