ALASKA GEOLOGY 



The curious tuff at Indian River, near Sitka, shows only 

 andesite and basalt. 



The very interesting radiolarian chert of Halibut Cove, 

 on Cook Inlet, which we compare with the Franciscan 

 Series of California, of Jurassic or early Cretaceous age, 

 has its own peculiar igneous rocks, crushed and altered 

 spheroidal diabases and dacite-porphyries. 



At Dutch Harbor we studied the older beds of the 

 newest series of volcanic rocks highly altered augite- 

 andesites and through the Shumagin and Sannak islands 

 and in the sea cliff sections on Hall and St. Matthew 

 islands we were able to examine the whole series of these 

 andesitic, trachytic, and basaltic rocks. We saw the 

 newest of the series in the basaltic tuff cone at Black 

 Bluff, on St. George Island, and in the wall of pearl-grey 

 andesite on Bogoslof. 



