UNIVERSITY OF CALIFORNIA 



Bulletin of the Department of Geology 



Vol. I, No. 7, pp 193=240. Pis. 12=14. ANDREW C. I.AWSON, Editor 



THE 



GEOLOGY OF ANGEL ISLAND 



BY 



F. Leslie Ransome, 

 Fellow in the University of California. 



CONTENTS. 



PAGE. 



General Statement of the Geology 193 



The Sedimentary Formations 196 



The San Francisco Sandstone 196 



The Radiolarian Chert 198 



The Fourchite 200 



Occurrence 200 



Petrographic Character 202 



Contact Metamorphism 211 



The Serpentine 219 



Occurrence 219 



Petrographic Character 220 



Contact Metamorphism 222 



Some Peculiar Inclusions in the Serpentine 226 



Chemical Analyses 231 



Conclusion 232 



Appendix — Note on the Radiolarian Chert from Angel Island, and from 



Buri-buri Ridge. San Mateo County, California. By George J. Hincle. . 235 



GENERAL STATEMENT OF THE GEOLOGY. 



Angel Island, lying about three and one-half miles north of the 

 city of San Francisco, is the largest and most diversified of the 

 several small islands scattered about in San Francisco Bay. It is 

 separated from Tiburon Peninsula, the nearest mainland, by Raccoon 

 Strait, a passage about half a mile in width in its narrowest part, 

 and with a maximum depth of thirty-nine fathoms. 



