8 



CRANDALL— SAN FRANCISCO PENINSULA. 



[January 4, 



series are also exposed here but are best shown where Second 

 street has been cut through Rincon Hill, from Mission street east- 

 ward. In this part of the series the volcanic tuffs are also to be 

 seen but only in small exposures. 



So far as is known the Franciscan series is a unit, and though 

 the complete section cannot be crossed continuously, owing to struc- 

 tural features, outside of the unconformity between the two jasper 



Fig. 3- 



Jointing planes in massive sandstone exposed in a quarry on the northeast 

 side of Telegraph Hill. 



beds, which is regarded as local, the series is here geologically a 

 continuous one. 



The Franciscan series as a whole is much fractured, folded and 

 metamorphosed, even more so in other regions than on the San 

 Francisco peninsula. This deformation seems to have been general 

 and the unaffected regions are smaller and more local than the af- 

 fected ones. 



The effects of this deformation are shown in the present state 

 of the beds. The peculiar shapes into which the San Pedro shales 

 break are due to the movements to which they have been subjected. 

 The most noticeable effect in the sandstones is the many joint planes 



