1907.] 



CRANDALL— SAN FRANCISCO PENINSULA. 



29 



distribution is the lowest sandstones and shale beds of the Fran- 

 ciscan series which is represented in San Bruno mountains and 

 which for purposes of differentiation in this paper is called the 

 San Bruno sandstone. It is not definitely known w-hat place this 

 sandstone has in the Franciscan series as compared with the sand- 

 stones and shales exposed at San Pedro Point, but it appears as 

 if the low^est part of the mountains exposed at Sierra Point, was the 

 •equivalent of the middle or upper section at San Pedro. 



This sandstone and shale form San Bruno mountains and the 

 parallel ridge northeast of Guadalupe Valley; the hills known as 

 Columbia Heights ; University Mound in the southwestern part ; 

 and the southw^estern part of San Miguel Hills, partly covered by 

 the sands and disappearing under the lower jaspers. This sand- 

 stone appears in only one place north of the exposures mentioned, 

 and that is at the Cliff House and around Point Lobos to within 

 about a mile of Lobos Creek. 



Jaspers. — The formation that overlies the San Bruno sandstone 

 is the lowest jasper bed. This bed of jasper lies directly upon the 

 San Bruno sandstone along the cliffs north of Golden Gate Cemetery. 

 It disappears under the ^eolian sands and is exposed in only one or 



Fig. 10. 

 Local folding in jasper exposed in a quarry at Golden Gate Park. 



