SKETCH OF THE GEOLOGY OF THE SALINAS VAL- 

 LEY, CALIFORNIA 1 



In June and July igoo, under the direction of Dr. J. C. 

 Branner, Mr. L. D. Mills and the writer undertook to trace out 

 and map the formations in Monterey county, California, which 

 appear to bear directly on the underground water supply of the 

 Salinas Valley. During this and two subsequent trips to the 

 same region the data were collected which form the basis of the 

 present paper. 



The Salinas Valley is a long, sword-shaped depression extend- 

 ing nearly southeast from Monterey Bay, to and across the south- 

 ern end of Monterey county. The larger tributaries of the 

 Salinas River run for a good part of their length in troughs par- 

 allel to the main valley, forming with it part of a remarkable 

 series of valleys existing in the Coast Ranges of California, which 

 for a distance of nearly five hundred miles are almost exactly 

 parallel. In the Salinas Valley are evidences of a fault in the 

 older rocks extending very persistently for several miles parallel 

 to the main valley. 



In its northern part, if not throughout its whole length, the 

 Salinas Valley is cut in granite and other crystalline rocks, prin- 

 cipal among which are biotite schists with crystalline limestone 

 lying unconformably on them. The granite is intruded into the 

 schists and is apparently the agent which metamorphosed the 

 limestone. The granites, gneisses, and schists cover large areas 

 while the limestone occurs only in patches. Of the crystalline 

 rocks other than those mentioned there is one area of an erup- 

 tive that looks like andesite on top of the water-shed between 

 Monterey and San Benito counties, northeast of the town of 

 Salinas, and an area in the neighborhood of Metz containing a 

 variety of intrusive and eruptive rocks in addition to several kinds 

 of metamorphics. Hand specimens of these have been collected 



1 Published by permission of the director of the U. S. Geological Survey. 



330 



