94 University of California Publications in Geology [Vol. 8 



one thousand feet, but Cache Lake beds of fine-grained argillaceous 

 sandstone and gray sandstone with gray shale, strike N 30° E and 

 dip 20° E, unconformably overlie the Martinez. An outcrop of 

 Martinez one hundred feet thick which yielded Pholadomya nasuta, 

 Dcntalium cooperi, Schizaster lecontei, and Modiolus ornatus is next 

 found. These beds are composed of fine-grained, massive sandstone 

 dipping northward. Five hundred feet down the creek from this point 

 similar beds about one hundred feet thick appear with a high dip to 

 the north. Even in this partial section we have at least 3500 feet of 

 Martinez strata present. That this is not complete is seen when we 

 study the upper portion of the Martinez on the other limb of the 

 syncline. At least three hundred to five hundred feet of gray-green 

 shales lie above the last-mentioned fine-grained tan sandstone at this 

 place. A minimum estimate is between thirty-eight hundred and four 

 thousand feet for the total thickness of these beds. 



A small area of the Cache Lake formation which was originally 

 described by Becker 24 is found unconformably overlying the Martinez 

 north and east of Lower Lake village. It is best observed in Herndon 

 Creek, where its fine-grained, argillaceous sandstones and gray shales 

 have a dip of 15°-20° E. Near the mouth of Herndon Creek are seen 

 about two hundred feet of a coarse gray tuff which appears to be the 

 uppermost portion of these fresh-water beds. The tuff beds are folded 

 in an asymmetric syncline, the south limb of which dips 60° to the 

 north. The total thickness of these beds appears to be from seven 

 hundred to eight hundred feet. The Cache Lake beds, like the Mar- 

 tinez, are cut off on the west by andesitic lava flows which appear to 

 overlie them. According to Stearns, who determined the fresh-water 

 fossils found in these beds by Becker, they are of Pliocene age. 



Rocks of Tejon age occupying an elliptical area two and one-half 

 miles long on the eastern portion of the Lower Lake syncline rest 

 upon the Martinez. Coarse gray to white, conglomeritic concretionary 

 sandstone which gives rise to bluffs make up practically its entire 

 thickness, 1100 to 1200 feet. It is lithologically distinct from the 

 uppermost Martinez which consists of thin-bedded, fine-grained, green- 

 gray sandstone with green shales.. No sharp contacts between the 

 Martinez and Tejon were found and hence their relations to one 

 another are not entirely clear. The dips in the Tejon vary from 30° 

 to 35°, while those of the Martinez are, on the whole much higher. 



2* Becker, G. F., Geology of the Quicksilver Deposits of the Pacific Slope, 

 Monograph 13, U. S. Geological Survey, pp. 219-221, 1888. 



