1907.] CRANDALL— SAN FRANCISCO PENINSULA. 45 



hills and Black Point and Russian Hill represents broken down 

 anticlines while that between Russian and Telegraph hills along 

 Montgomery avenue is a synclinal trough. 



The flat in the business portion of the city with its sands and 

 mud obscures the structure of the gap between California street 

 hill and Rincon Hill. Rincon Hill being folded in a syncline parallel 

 to the minor lines of folding, has the dip of the beds in a different 

 plane from the dip of California Hill beds. The apparent solution 

 is that Market street has been the direction of drainage of a stream 

 passing between the two hills, through an eroded anticline. 



There are no streams now draining this flat but if there were 

 their drainage would be northwest-southeast along the axes of fold- 

 ing and at right angles to the direction of the streams on the tilted 

 blocks. 



The series of elevations and depressions to which this area has 

 been subjected have not all left traces upon it. Various places 

 around the bay show an old raised shore line. There are two ter- 

 races along Buri-Buri ridge — one at an elevation just a little above 

 the floor of IMerced \'alley, the other at an elevation of five hundred 

 feet. This last one is the pre-Pliocene terrace previously mentioned.^ 



VI. General Discussion. 



Age of the Franciscan Series. — The age of the Franciscan series 

 is not definitely and directly known from paleontological evidence, 

 but must be arrived at indirectly by the age of the superimposed 

 beds. The Franciscan series of sandstones and jaspers is very much 

 broken up, metamorphosed and silicified by the dynamic movements 

 through which it has passed. By this and by its constant macro- 

 scopic and petrographic characters it may almost always be rec- 

 ognized. 



The conclusions of Dr. Fairbanks and Dr. Becker from their 



^ Lawson, A. C, Geology of the Sari Francisco peninsula. 15th Ann. 

 Rept. U. S. Geological Survey, p. 464. 



G. H. Ashley, Neocene Stratigraphy of Santa Cruz Mountains, Proc. 

 Gal. Acad, Sci., Series 2, V, 354. 



A. C. Lawson, Geomorphogeny of the Coast of Northern California, Bull. 

 Dept. Geology L'J'niversity California, I, No. 8, p. 241. 



