Lawson.] 



The Upper Kern Basin. 



is strongly developed; the pleochroism is in tones of green; the 

 central areas are usually light, colored, suggestive of its derivation 

 from pyroxene, but no remnants of the original pyroxene can be 

 discovered. The hornblende is often finely fibrous and gives but 

 small extinction angles. It is in places replaced by chlorite. 



Inclusions in Granitic Rocks. — Of the inclusions contained in 

 the granitic rocks which are referred to in the general description 

 of the rocks of the Upper Kern Basin (p. 295) three were studied 

 in this section. The first of these to be noted is contained in a 

 grano-diorite similar to that last described. It has an angular 

 outline with a rather sharp but irregular boundary against the 

 containing rock. It is much darker and much finer grained than 

 the grano-diorite. A shear zone running through the grano- 

 diorite forms one boundary of the inclusion. The longest diameter 

 of the inclusion is about four inches. 



Microscopically it is a hypidiomorphic aggregate of horn- 

 blende, biotite, feldspar and accessory apatite and magnetite. The 

 rock is not very fresh and the feldspars are usually turbid. The 

 plagioclase occurs in shapeless patches and in broad plates show- 

 ing closely crowded albite lamella 1 . The extinction angle of 1-4° 

 indicates that they are oligoclase-andesine. Numerous large 

 Carlsbad twins occur. The feldspars are often bent and even 

 faulted, the fault zones being filled with a mosaic of feldspar 

 grains. This internal deformation is doubtless connected with 

 a small shear zone which appears in the hand specimen and is 

 common to both inclusion and the containing grano-diorite. 



The ferro-magnesian minerals form nearly one-third of the 

 bulk of the rock; biotite predominates, with hornblende in sub- 

 ordinate amount. The biotite does not occur in well developed 

 plates, but in small irregularly oriented laths which are often 

 aggregated in nests. 



The second inclusion to be noted is contained in a coarse 

 biotite- granite in which orthoclase crystals, ranging up to half an 

 inch in diameter, are abundant in rude porphyritic development. 

 The inclusion is of the nature of a stout lens with maximum 

 diameter of about four inches, having no pronounced angularity 

 of outline. The coutact with the enclosing rock is irregular and 

 interlocking in detail. The inclusion is much finer grained and 



