Lawson.] 



Coast of Northern California. 



269 



of the subsequent uplift of the coast, sinking its trench as the uplift 

 proceeded. This being the case the waters of the ocean could not 

 have had access to the Valley of California at any time during the 

 uplift. It is, therefore, probable that there are no marine deposits 

 of post-Pliocene age in the Valley of California. 



It may, perhaps, be well to state here that in those portions of 

 the coast which once served as areas of Pliocene sedimentation, as 

 in the vicinity of the Bay of San Francisco, much of the geomorphic 

 character was evolved in pre-Pliocene time, and has simply been 

 revealed and modified by the stripping off of the Pliocene accumu- 

 lations. 



Associated with the subsidence which flooded the Bay of San 

 Francisco there were probably other deformations of the crust 

 which seem to have had an important influence on the drainage. 

 The most notable instance of this kind is the shifting of the divides 

 of the hydrographic basin of the Russian River. This stream once 

 clearly flowed down through Petaluma Valley to the main drainage 

 outlet at the Golden Gate. A low divide in the middle of the old 

 valley now causes the drainage to flow westward at right angles to 

 its former southerly course, and seek the coast by the present trans- 

 verse route. The change in the drainage ma)' be due to stream 

 capture or to crustal warping. The latter is most probably the 

 cause; but the problem has not yet been studied sufficiently. 



SUMMAKV. 



From the foregoing observations and discussions it w ill be ap- 

 parent that there is an essential harmony in the results here arrived 

 at and those relative to the diastrophic record of the coast south of 

 the Golden Gate, presented in a former paper.* The Wild-cat 

 Series is the correlative of the Merced Series. Both seem to have 

 accumulated under analogous conditions of a general coastal de- 

 pression, accentuated locally by subsidence concomitant with the 

 progress of sedimentation in the respective basins. Both, after at- 

 taining a thickness of at least one mile, were sharply deformed by 

 orogenic movements to a similar degree. These movements were 



*This Bulletin, Vol. 1, No. 4. 



