2 4 2 



University of California. 



LYCL. I. 



writer had the previous year made of the coast south of San Fran- 

 cisco with reference to its post-Pliocene diastrophism.* It is the 

 purpose of this paper to record the observations made during the 

 trip, and to present certain inferences from them. The observations 

 are few and are deficient in detail; but when supplemented by the in- 

 formation afforded by the Coast Survey charts and by the application 

 of certain well-k-nown principles of geomorphogeny, they will be 

 found sufficient, it is believed, to warrant the general hypothesis 

 arrived at. Briefly, this states that the present geomorphy is the 

 result of the following sequence of events: — 



1. The development in Pliocene time of a great coastal peneplain, 

 with correlative accumulation of marine sediments. 



2. The otogenic deformation of parts of this peneplain and the 

 folding of the Pliocene strata, the general altitude of the peneplain, 

 where not so disturbed, remaining about the same. 



3. The reduction of the upturned soft Pliocene strata to base 

 level, and the limited extension of the peneplain in between the 

 uplifted blocks of the other disturbed areas. 



4. The progressive uplift of this peneplain, with its residual 

 monadnocks, to an elevation for the plain of from 1,600 to 2,100 

 feet above the sea level, the adjacent mountainous tracts participating 

 in the same movement. 



5. The advance in the new geomorphic cycle to a stage of late 

 adolescence or early maturity. 



6. A very recent local sag or depression of about 100 miles of 

 the coast adjacent to the Golden Gate, and the consequent flooding 

 of the stream valleys by the ocean. 



EVIDENCES OF GENERAL UPLIFT. 



Traces of an Ancient Peneplain. — The Coast Ranges of northern 

 California comprise, besides the mountains proper, which, except 

 for isolated peaks, are distant from the ocean, a broad coastal tract 

 which may be said to be devoid of true mountain topography- 

 This tract is clearly a dissected plateau, and impresses itself as such 

 upon the observer very forcibly when viewed from any point not 

 lower than its general level. The plateau is now represented only 



*This Bulletin, Vol 1, No. 4. 



