NOTES ON THE GEOLOGY AND PETROGRAPHY OF 

 BAJA CALIFORNIA, MEXICO. 



BY WALDEMAR LINDGREN, U. S. GEOL. SURVEY. 



The expedition sent by the Academy of Sciences to 

 Baja California in the spring of 1889 brought home, among 

 other collections, some specimens of rocks from various 

 parts of the territory. 



Among these rocks, which Mr. Walter E. Bryant had 

 the kindness to submit to my examination, were a few 

 which seemed worthy of notice and description. 



I. Crystalline Schists. 



The first set of specimens from the Sta. Margarita and 

 Magdalena Islands, opposite Magdalena Bay on the west 

 coast in the southern part of the peninsula (lat. 24° 30') 

 principally consists of crystalHne schists; among the rocks 

 collected were found chloritic, slaty rocks, often contain- 

 ing garnet and magnetite ; specimens of talc with serpen- 

 tine ; further, actinolite in long Hght green radiating 

 prisms and an amphiboHte, a slaty dark green rock, com- 

 posed of prisms of greenish amphibole with scales of a 

 white mica, probably muscovite. 



The geological formation indicated by these specimens 

 — highly compressed series of older schists — is remark- 

 able as differing most decidedly from the geology of the 

 mainland, indicated by Professor Gabb in a section from 

 Magdalena Bay across to the Gulf Coast. 



Along this section there is a gradual rise from the Pa- 

 cific to a peninsular divide, from which an abrupt descent 

 leads down to the shores of the Gulf of California. 



The whole distance is occupied by horizontal or gently 



2D Seb., Vol. III. (3 ) April 16, 1890. 



