COAST RANGE CORRIDOR IN CALIFORNIA 



165 



cene, affecting the eastern part of the Central Coast Ranges and the 

 Southern Coast Ranges generally. The last surge is still in its 

 climactic phase as the present is a time of active orogeny. The mid- 

 Pleistocene orogeny is associated with the final disappearance of 

 Tertiary troughs of deposition and the foundering of considerable 

 segments of the Coast Ranges into the Pacific Ocean. Also, and of 

 particular importance to the corridor concept, a marked uplift of 



PLIOCENE AND 

 LOWER PLEISTOCENE 

 PALEOGEOGRAPHY 



Fig. 3. Pliocene and early Pleistocene paleogeography, showing archi- 

 pelagic nature of Coast Range region, and presence of strait connecting 

 Pacific with San Joaquin embayment. (After Eardley.) 



epeirogenic proportions affected the continent generally and the 

 area of the corridor in particular following the peak of mid- Pleisto- 

 cene orogeny. (At present, dissected erosion surfaces exist at levels 

 of several thousand feet elevation in the San Gabriel Mountains.) 

 Volcanism appears to have occurred sparingly in the area of the 

 corridor and has contributed little to its crust, 



Paleogeography of the Pliocene and early Pleistocene (Fig. 3) 

 suggests that the Central and Southern Coast Ranges constituted a 

 reasonably continuous land mass probably extending far northward 

 but separated at the southern end from the continent proper by a 

 wide strait. Distribution of terrestrial plant and mammalian locali- 

 ties (Fig. 4) of Pliocene and early Pleistocene age suggests that the 



