COAST RANGE CORRIDOR IN CALIFORNIA 163 



Stebbins. Interest was stimulated by the discovery that southern 

 Cahfornia is an area of relatively high incidence of sympatry be- 

 tween closely related forms in the modern herpetofauna. While 

 searching for the explanation for this phenomenon of distribution, 

 the writers evolved the concept of a Pacific Coast Range corridor 

 culminating in the Pleistocene epoch, accompanied by collateral 

 physical changes and affecting directly the origin and distribution of 

 the modern herpetofauna. The concept is hopefully presented as a 

 useful adjunct to understanding of the problems of origin and dis- 

 persal of faunas of far western North America. 



Evolution of a Coast Range corridor essentially involves the 

 Central Coast Ranges, consisting of western and eastern segments 

 and extending from San Francisco south to Santa Maria, and the 

 Southern Coast Ranges extending from the Santa Barbara region 

 through the Transverse Ranges. The corridor has important con- 

 nections on the south with the Sierra block and with the Peninsular 

 Ranges, both of which are genetically related to the Basin and Range 



PRESENT EXTENT OF 



FRANCISCAN SERIES 

 m GRANITIC BASEMENT 



AND OLDER ROCKS 

 n POST-JURASSIC 



SEDIMENTS 



/v 



Fig. 1. Lithologic provinces of California. The present Great Valley 

 and Central and Southern Coast Ranges are the site of extensive marine 

 deposition (to 50,000 ft. thick) from Cretaceous into early Pleistocene 

 time. (After Camp.) 



