MIDDLE JURASSIC 



327 



These strata of Middle Jurassic age are divided into two series, sepa- 

 rated by a pronounced unconformity. The lower series will be described 

 first. 



20 miles 



^^ 





Tertiary sandstones, Jurassic volcanics. State-schist series GranitFc rocks with 

 shales,and conglomerate sandstones, shales, with intrusive granite areas of volcanics 

 locally carrying coal and conglomerate, 



loca'ty carrying coal 



Figure 1. — Geologic Hup of Region Xoi-thcast of Cook Inlet, Alaska. 



Greenstones- and related pyroclastics constitute the most characteristic 

 portion of these rocks. Tuffs, agglomerates, and flow breccias form the 

 great bulk of the greenstones, and intercalated flows of coarse amygdaloid 

 are of frequent occurrence. Examination in thin-section shows that the 

 greenstones and their ejectamenta are andesites of hyalopilitic and pilo- 

 \axitic textures, more or less thoroughly chloritized, 



