VOLCANIC EOCKS OF SEPULCHKE MOUNTAIN. 



123 



feldspar. The tipper portion of this breccia is more hornblendic, and 

 hornblende-pyroxene-andesites predominate. The transition from the 

 pyroxene-andesite portion to the hornblende-pyroxene-andesite portion 

 appears to be gradual. The later breccia is accompanied by vesicular 

 flows of similar andesite, often quite porous. It is lighter colored in gen- 

 eral, but parts are quite dark, with prominent hornblendes, the habit being 

 andesitic, not basaltic. There are no evidences of any considerable break 

 or interruption between the higher and the lower parts of this breccia. 

 They appear as a continuous geological body, composed of fragments and 

 flows of andesite which were ejected from one center of eruption during a 

 considerable period of time. 



The andesitic material composing this breccia varies somewhat in min- 

 eral composition and in megascopical habit, as will be seen frpm the following 

 descriptions. The variation in the phenocrysts present other than feldspar 

 in the specimens examined is indicated in Table XL They are andesites 

 with glassy groundmass and phenocrysts of plagioclase, hypersthene, and 

 augite in some cases, and with these minerals and hornblende in others. 



Table XI: — Mineral variation in the upper breccias of Sepulchre Mountain. 



Mineral 

 groux>s. 



Specimen 

 number. 





Phenocrysts other than feldspar. 





Pyroxene. 



Hornblende. 



Biotite. 



Quartz. 



B, .... 



B, .... 

 B 3 .... 



385 

 386 

 387 

 388 

 390 

 391 

 392 

 393 

 394 

 396 

 397 

 398 

 400 

 401 

 402 

 403 

 404 

















Much 









Much 





























Much I 







Much 



Much 



Much 



Much 



Much 



Much 



Much 



Much 



Much 



Little 







Little 







Little 







Little 



Little 



Little. ..• 







































