178 CALIFORNIA ACADEMY OF SCIENCES [Proc. 30 Ser. 



out by Mr. Owen, in the foothills directly north of Coalinga. 

 It is also a significant fact that for more than sixty miles 

 along the eastern side of the range, between Coalinga and 

 McKittrick, they do not appear, though the Monterey Shales 

 and the Etchegoin Beds are continually in evidence. 

 Throughout the Salinas and other intermontane valleys to 

 the west, the Coalinga Beds appear to be present in con- 

 siderable thickness. 



Etchegoin Beds. 



No other formation in the Mount Diablo Rangfe has so 

 great an areal extent and so great a thickness and continuity 

 as the Etchegoin Beds, which overlie in turn all of the 

 older formations of the region, resting upon each respec- 

 tively with a distinct nonconformity. The relations of this 

 formation to the others in the Coalinga field are shown in 

 the accompanying map (PI. xxxv) and sections (PL xxiv). 



The maximum stratigraphic thickness of the Etchegoin 

 Beds in their greatest development is certainly not less than 

 seventy-five hundred feet, while at other points they do not 

 exceed five thousand feet. In some sections they have the 

 appearance of aggregating the incredible thickness of nine 

 thousand feet, but such a development is probably local. 



Sands, usually but little consolidated, form the predomin- 

 ating element and make up locally three-fourths of the 

 entire series, occurring chiefly at the bottom or in the lower 

 portions. 



The name of this formation has been derived from its 

 characteristic development in the vicinity of the Etchegoin 

 ranch, some twenty miles northeast of Coalinga. 



A detailed description of the divisions of the Etchegoin 

 Beds is hardly possible from our present knowledge of them, 

 but a general statement will perhaps be useful in identifying 

 them in the field and in correlating them with similar forma- 

 tions elsewhere. 



Etchegoin Sands. — Occupying a stratigraphic position 

 at the base of the Etchegoin and forming almost two- 

 thirds of its mass, are unconsolidated sands or gravels in 



