Lawson.] 



The Upper Kern Basin 



369 



APPKXPIX. 



PETROGRAPHIC NOTES ON SOME ROCKS FROM THE 

 UPPER KERN BASIN. 



No systematic attempt was made by the writer to collect 

 materials for a petrographic study of the rocks of the Upper 

 Kern Basin, but where opportunity offered occasional hand 

 specimens were taken as representative of the more important 

 rock masses. The examination of these specimens has been 

 kindly undertaken by Mr. A. Knopf, a student in the depart- 

 ment of geology in the University of California; and the results 

 of that examination are herewith appended as a contribution to 

 the geology of the region which could not be conveniently incor- 

 porated in the general discussion. The specimens comprise 

 fragments of different facies of the granitic rocks, the inclu- 

 sions contained in these rocks, and the lamprophyrie dykes 

 which cut them, all taken from Kern Canon in the vicinity 

 of the main cam}) at the mouth of Coyote Creek. Besides these 

 there are a few specimens of the Quaternary lavas from the 

 Little Kern Plateau and from Volcano Creek. 



The Common Facies of the Granite in Kern Canon. — This rock 

 is a coarse grained, light colored granite, showing numerous large 

 phenocrysts of orthoclase. This structure is best seen in the 

 hand specimen. In thin section it is not so apparent, the rock 

 resolviug into a hypidiomorphic granular assemblage of ortho- 

 clase, quartz and biotite, with accessory magnetite. 



The orthoclase is the dominant feldspar occurring both in 

 Carlsbad twins and large allotriomorphic patches. A lesser 

 amount of finely striated plagioclase also occurs. This is an 

 oligoclase corresponding to an extinction angle of 6? The feld- 

 spar comprises 75% of the entire rock. Quartz occurs in great 

 abundance. The rock is very poor in ferro-maguesian consti- 

 tuents, the latter being represented sparingly by biotite. 



