[907. 



CRANDALL— SAN FRANCISCO PENINSULA. 



37 



Lone Mountain- Block. — North of this fault line the folding is 

 more complex. Parallel to the fault is a closely pressed syncline, 

 called the Lone Mountain syncline, which can be followed from 

 near Thirteenth and Market streets to the Calvary Cemetery, and, 

 judging by the structure exhibited by the sandstone underlying the 

 serpentine at the Presidio, it extends still further. Serpentine is 

 exposed in different places, following the bedding planes of the 

 sandstone, dipping toward the northeast or southwest, according to 

 the side of the synclinal axis that it is on, showing that it is present 

 as a true sill. 



Major Folds. — Passing to the northeast of this syncline, the dip 

 of the beds becomes less, averaging about 30° until Lafayette Hill 

 is reached. From there they arch in an anticlinal dome to Russian 



Fig. 14- 

 Bedding of shale in Telegraph Hill series; the exposure on Second street. 



Hill and California Street Hill, in v/hat is called the Lafayette Hill 

 anticline. Between Russian Hill and Telegraph Hill is a syncline, 

 the axis of which is closely followed by Montgomery avenue, which 

 is called the Montgomery avenue syncline. 



Minor Folds. — Lines of minor weakness are represented by a 

 syncline through Rincon Hill, called the Rincon Hill syncline, an 



