UNIVERSITY OF CALIFORNIA 



Bulletin of the Department of Geology 



Vol. 1, pp. 61=70, PI. 5. ANDREW C. LAWSON, Editor. 



THE 



SODA-RHYOLITE NORTH OF BERKELEY.* 



HY 



Charles Palache. 

 Fellow in the University of California. 



CONTENTS. 



T*AGE. 



Occurrence 6i 



Geological Relations 62 



General Petrographical Character 62 



The Porphyritic Facies 63 



The Spherulitic Facies 63 



The Massive Spherulitic Variety 63 



The Laminated Spherulitic Variety 64. 



The Glassy Facies 65 



Distribution of the Different Facies 66 



Summary of Microscopic Study 67 



Chemical Characters 67 



Nomenclature 69 



Other Occurrences 69 



OCCURRENCE. 



The rock which forms the subject of this paper is found on the 

 crest and western slope of a ridge of the Contra Costa hills, which 

 extends northward from Berkeley to near the village of San Pablo. 

 So far as is at present known, its occurrence is limited to a belt 

 about five miles in length and one mile in width. The rock is 

 most abundant in the southern portion of this area, and it there lies 

 well down from the ridge. Further north, where the ridge is lower, 



*My acknowledgments are due to Professor A. C. Lawson, with whose 

 advice, and under whose supervision, both the field work and laboratory investi- 

 gations detailed in this paper have been carried out. 



