144 University of California. [Vol. 2. 



evidence. There is also some evidence in the almost rectilinear 

 character and direction of the depression itself. 



Professor Lawson has described 1 a system of faulting on the 

 San Francisco peninsula, separating the blocks of San Bruno and 

 Montara Mountains, the main line of which presents a throw of 

 7,000 feet, according to estimates made by him. The strike of this 

 fault-line carries it out into the ocean to the west of the Golden 

 Gate. Looking at any good map of the region it is at once 

 apparent that the projection of this fault-line and the Baulinas- 

 Tomales depression almostly exactly coincide. It seems more 

 than probable that the valley and escarpment of Point Reyes penin- 

 sula marks the continuation of the faulting which is so pronounced 

 at San Bruno Mountain. 



Only rough estimates can be made at present as to the amount 

 of faulting that has taken place along this, valley. We have sup- 

 posed the thickness of Miocene sediments on the peninsula to be 

 not less than 500 feet. The lowest member of the series, coarse 

 gray sandstone, is found capping the granite ridge at an elevation 

 of over 1,200 feet. If the whole of the series were supposed to 

 have been superimposed upon this, with perhaps more that at the 

 present does not exist, and the entire body of this complex series 

 to have been lifted from the level of a few hundred feet below the 

 ocean surface to its present elevation, the amount of the uplift can 

 not have been less than 2,000 feet. 



Considerable subsidiary faulting has taken place along the 

 escarpment west of the valley. To the west and southwest 

 of Point Reyes Station the system of faulting has been very 

 complex, especially in the vicinity of the small area of "crushed 

 granite" that has been previously described. It is not impossible 

 that Bear Valley owes its origin to some of the minor faults 

 cutting transversely across the ridge. This, however, remains 

 to be proved. 



The major fault-plane along which the displacement has 

 mainly taken place perhaps lies nearest the western margin of the 

 valley; or, rather, the western margin presents something of the 



1 15th An. Rept. U. S. Geol. Sur., p. 468, etc. 



