GEOLOGY OF SAN FRANCISCO PENINSULA 7 1 



"erogenic movements which effected the deformation and fault- 

 ing of the Franciscan series" as well as of the relative sequence 

 of these disturbances and the peridotitic intrusions. This is, of 

 course, excusable in one studying only a narrow field where a 

 part of the record is wanting, but too much is at present known 

 of the wider field of Coast Range geology for one to plead 

 ignorance on these questions. 



The initial disturbance of the Golden Gate series, with the 

 exception of that produced by the contemporaneous intrusions 

 and flows, dates from the post-Jurassic upheaval. Leaving out 

 of account the serpentine, there is evidence that many of the 

 eruptive bodies associated with this series were subsequently 

 formed. The intrusive nature of the diabase at Hunters point 

 is recognized by Professor Lawson, and he is certainly correct. 

 To the presence of these eruptives, I believe, is to be attributed 

 the extreme disturbance in local areas. 



As to the age of the Franciscan series^ of Professor Lawson 

 nothing more definite is advanced than the evidence of a few 

 imperfect fossils, which cannot be determined specifically and 

 in many cases not even generically. These fossils are supposed 

 to favor the old view of a Cretaceous age. He says : " Evidence, 

 such as it is, is confirmatory of the opinions of Whitney and 



Becker The series as a whole is very probably older than 



the Knoxville Aucella horizon of California. The writer has no 

 doubt upon this point." 



Professor Lawson gives no reason for assuming the series to 

 be older than the Knoxville, and since Mr. Stanton's^ work 

 places the Knoxville Aucella horizon at the base of the Creta- 

 ceous, it is difficult to understand how these pre-Knoxville 

 rocks can be included in the Cretaceous. 



'This designation (American Geologist, June 1895) embraces the same aggregate 

 of strata to which I have given the name Golden Gate series (Journal of Geology, 

 May-June 1895) from its characteristic exposures at the entrance to San Francisco 

 Bay. As to which name shall finally be accepted I am, for my part, willing to rest 

 the case, although another claim might with great justice be added, on the truth or 

 falsity of my published statements as to its age and stratigraphic position. 



= Bull., No. 133, U. S. Geol. Sur. 



