I907.] CRANDALL— SAN FRANCISCO PENINSULA. 7 



This phase of the series is well exposed in the large quarries 

 in the city of San Francisco. One just northwest of Ocean View, 

 and another about one half mile south of Ocean View show especially 

 good sections. The black shales that occur in this sandstone are 

 well exposed in the cuts made at Visitation Point and north of there, 

 along the line of the new bay shore road of the Southern Pacific 

 railway. 



The top of this sandstone series is a few hundred feet of sand- 

 stone that is very generally characteristic wherever found. The 

 noticeable thing is the form in which it weathers, a soft light yellow- 

 ish gray rock with pink spots throughout it. The persistence of 

 this character of the rock has been noted at the several places where 

 it is exposed, even when the exposures are some distance apart. 

 It is best shown about half a mile east of the ClifT House, but 

 specimens from the southwest side of the San Bruno mountains, and 

 Sawyer's Ridge near San Francisco, and from Alum Rock canyon 

 and San Felipe Valley, in the Mount Hamilton region, are macro- 

 scopically identical. It is to be noted here that in all four of these 

 places the horizon is the same, that is directly under the lowest 

 bed of the red jasper. 



5. Jaspers. — The next group of beds in the Franciscan series is 

 the jasper. This consists of three beds, which in this area, have been 

 mapped separately. At the bottom of the group is the lowest jasper. 

 This is a bed approximating five hundred feet in thickness. Lying 

 upon this are sandstones, shales, tuffs, and lignites with an approxi- 

 mate thickness of four hundred feet. Over this is the upper bed 

 of jasper which is at least a thousand feet in thickness. 



These jaspers are thinly bedded flinty layers, varying from a 

 fraction of an inch to an inch in thickness, and very persistent in 

 character. They are dull reddish, stained with iron oxide, but vary- 

 ing in places to green, white and other colors more locally. In places 

 the jaspers are traversed by white veins of quartz or calcite. 



6. Telegraph Hill Sandstone. — The top of the Franciscan series, 

 as exposed at San Francisco, consists of eight hundred or a thousand 

 feet of sandstones and shales that is very similar to that underlying 

 the jaspers. This sandstone is particularly well exposed in Tele- 

 graph Hill where it is quarried extensively. The shales of this 



