I.AWSON.] 



Coast of Northern California. 



271 



and we have no evidence on the coast of preexisting river valleys 

 which were filled flush with delta material, as in the case of the San 

 Benito Valley. The plain of truncation, also, is much more pro- 

 nounced in northern California than to the south. 



The peneplain here recognized as of Pliocene and in part of 

 post-Pliocene development, is very probably the same as that which 

 Mr. Diller has so ably and graphically described as extending in a 

 deformed condition around the upper end of Sacramento Valley.* 

 If this supposition should prove correct, there would seem to be 

 necessity for a revision of the evidence upon which Mr. Diller 

 bases his conclusion as to the Miocene age of the peneplain. On 

 the coast there seems to be no reason for doubt as to its Pliocene 

 and in part post-Pliocene age. 



The next event in the diastrophic record, and perhaps the most 

 interesting to Californians because of its recency, is the subsidence, 

 to the extent of at least 378 feet, of the coast at the mouth of the 

 Sacramento River, flooding the lower portion of the valley, giving 

 us the magnificent harbor at San Francisco, and making of a river 

 gorge the far-famed Golden Gate. 



Seemingly the last event is a slight uplift in the vicinity of the 

 Straits of Carquinez. 



Geological Laboratory, 



University of California, November, i&'cjj.. 



'■'Journal of Geology, Vol. II, No. 1, p. 32. 



