35° University of California. [Vol. 2. 



Basalt Flows 379 



Grizzly Peak Andesite 379 



Beds of Rhyolite Tuff. 382 



Fresh-water Limestone 383 



Erosion Interval between Upper and Lower Berkeleyan 383 



Siestan Formation 384 



Change in Geomorphic Profile 384 



Character of Beds 385 



Their Extent 386 



Synclinal Trough 387 



Stratigraphic Asymetry of Syncline 388 



Northeastern Limb of Siestan Syncline 389 



Fossils 390 



Artesian Water 391 



Geomorphy Controlled by Structure 391 



Basalts above Siestan 392 



Descending Section on San Pablo Slope 393 



Basalts , 393 



Limestone Intercalated with Basalts 393 



Asymetry of Syncline 394 



Andesite, Conglomerate, and Tuft 395 



Amygdaloidal Andesite 395 



Orindan Formation 395 



Subordinate Flexures 396 



Transverse Fault 397 



Intrusive Dolerite 398 



The Campan Series 398 



Limits of Basin 398 



Diastrophic Trough 401 



Probable Volcanic Vent 402 



Lake Beds and Lavas 403 



Period of Faulting 404 



Later Accumulations 405 



Later Faulting 408 



Relations of Campan and Berkeleyan Series 409 



Post-Berkeleyan Deformation and Erosion 409 



Stratigraphic Unconformity 409 



Deformation of Campan and Berkeleyan Contrasted 410 



Microscopic Petrography of the Volcanic Rocks 411 



The Andesites 411 



Constituent Minerals 412 



The Amygdaloidal Andesite 418 



The Grizzly Peak Andesite, Porphyritic Facies 420 



The Grizzly Peak Andesite, Holocrystalline Facies 422 



Aphanitic Laminated Andesite 424 



Chemical Characters 426 



