Vol. 13, No. 6, pp. 175-252, 7 text figures, 1 map, pis. 9-14 June 29, 1922 



UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGICAL SCIENCES 



GEOLOGY OF THE CUYAMACA REGION OF 

 CALIFORNIA 



WITH SPECIAL REFERENCE TO THE ORIGIN OF THE 

 NICKELIFEROUS PYRRHOTITE 



BY 



F. S. HUDSON 



CONTENTS 



PAGE 



Introduction 177 



Geography 178 



Relief 179 



Climate and vegetation 180 



Physiographic problems 180 



Geology 181 



Summary statement 181 



The Julian schist series 182 



Fissile quartz-mica schist 182 



Quart zite 183 



Amphibolite schist 183 



Paragneiss and coarse schist 183 



Injection gneiss 184 



A typical section through the schist series 186 



Origin of the schist series 187 



Conclusions i88 



Age of the Julian schists 188 



Correlation based on lithologic character 190 



The Stonewall quartz diorite 191 



Petrographic description 191 



Age of the quartz diorite 192 



Type of intrusion 192 



The Cuyamaca Basic Intrusive 193 



Constituent minerals 193 



Description of typical rocks 195 



Effect of marginal chilling 199 



Assimilation of wall rock 200 



Texture and grain 201 



