UNIVERSITY OF CALIFORNIA 



Bulletin of the Department of Geology 



Vol. I, No. 5, pp. 161-180. ANDREW C LAWSON, Editor 



THE 



LHERZO LITE-SERPENTINE 



. V\ AND 



ASSOCIATED ROCKS OF THE POTRERO, SAN FRANCISCO. 



BY 



Charles Palache, 

 Honorary Fellow in the University of California. 



CONTENTS. 



PAGE. 



Introduction 161 



The Serpentine 163 



Outcrops 163 



Petrographical Character 163 



Relations of the Serpentine to the San Francisco Sandstone 170 



The Intrusive Rock 171 



Occurrence... 171 



Petrographical Character 172 



Relations Jo Other Formations 178 



The San Francisco Sandstone 179 



INTRODUCTION. 



The portion of the city of San Francisco known as the Potrero 

 is a triangular area of about one. square mile, lying between San 

 Francisco Bay and Mission Valley. It is occupied by a ridge of 

 hills with northwest and southeast trend, which attain an elevation 

 of 360 feet near the center of the area, and on the land side gradually 

 diminish in height and pass into the floor of the valley. On the 

 bay side the hills in places approach the shore in high bluffs, but 



