148 



University of California. 



I Vol. i. 



relating the lower and major portion of the delta which thus fills the 

 Valley of California with the marine delta which constitutes the 

 Merced series, both being due to the same geological causes and 

 processes operating at the same time. The delta gravels exposed 

 on the San Benito to a thickness of at least 1,200 feet are, also, as 

 will be shown in the sequel, of Pliocene age, and are the direct 

 equivalent of the Merced series. 



Depression and Uplift. — The character of both the Merced series 

 and of the delta which fills the Valley of California, so far as it is 

 known from the record of wells, indicates that the accumulation 

 could only have proceeded with a concomitant depression of the 

 coast. This depression will not here be further discussed beyond 

 the statement that it is in harmony with other facts, which have 

 been elsewhere noted, indicating that the Pliocene generally on the 

 west coast was a time of epeirogenic depression. It is desired 

 rather to direct attention to the evidence of general and local move- 

 ment, which has affected this part of the coast in post-Pliocene 

 time.* 



The fact of finding fossiliferous Pliocene strata at elevations of 

 over 700 feet is, of course, absolute demonstration of an elevation 

 of the coast to that extent in post-Pliocene time. This itself might, 

 however, be due to the general uplift which has affected the entire 

 coast. This general uplift is but a factor in the total effect of the 

 movements which have been active on the San Francisco Peninsula 

 in post-Pliocene time. The occurrence of a volume of Pliocene 

 strata over one mile thick inclined at high angles (up to 75 °) is 

 absolute demonstration of very important differential movements of 

 a local character. The base of this great volume of strata exposed 

 above sea at the same level as the summit of the series, with so 

 small a horizontal interval between summit and base, tells us, in 

 language more forcible than words, the measure of this differential 

 movement. The pre-Pliocene surface, on which flourished the Mont- 

 erey pine, has, since the inauguration of Pliocene sedimentation, 



*The only reference which the writer can find to this subject is a brief note 

 by Mr. Amos Bowman on "Coast Surface and Scenic Geology," Proc. Cal. 

 Acad. Sci., July 1, 1872, which, though somewhat poetic in character, has the 

 merit of recogni/ing a post-Pliocene uplift of 700 feet on this part of the coast. 



