Academy of Sciences] 

 No. 1] 



AMERICA. 



63 



and diorite. Triassic marine sedimentation was only local, but further volcanic eruptions then 

 broke out, with products similar to those described above. These were continued into Jurassic 



Fig. 18.— Geological map of the Sonora Quadrangle, California. (After Turner and Ransome.) 

 1. Tertiary sediment. 2. Tertiary basalt. 3. Granodiorite. 4. Soda-syenite. 5. Serpentine. 6. Diabase. 

 7. Porphyrite. 8. Amphibolite. 9. Trias-Jura sediment. 10. Limestone. 11. Carboniferous sediment. 



times, when marine sedimentation recommenced, shales and sandstones with some conglomerate 

 and a little chert being the chief deposits; the upper portion seems to be continued in the 

 Franciscan series farther to the south. In intercalated fresh-water beds an extensive flora is 



