12 CALIFORNIA ACADEMY OF SCIENCES [Proc. 47H Ser. 
In the northern part of the range the rocks are generally 
covered by soil to an extent that renders the stratification 
more or less obscure; so that little attempt has been made 
toward a detailed statement of their lithological characters. 
Mr. Weaver states that the Martinez beds, for the most part, 
consist of thick bedded sandstones containing large quantities 
of glauconite, and that alternating with these are considerable 
beds of shale. 
In the vicinity of Corral Hollow both sandstones and shales 
enter into the composition of the Eocene; but no systematic 
statement of the strata has yet been made, except such as is 
given by Whitney, who did not, however, differentiate the 
Chico from the Tejon. 
The belt of Eocene rocks lying between the Panoche Pass 
and Coalinga probably offers the best exposures and affords 
the best opportunity for both general and detailed lithologic 
study, and possibly an equally good opportunity for a formal 
classification. Along the Cantua creek, and both to the east 
and the west, a thick series of conformable strata can be fol- 
lowed easily for many miles. The aggregate thickness of the 
series is not less than 6000 feet, and is probably more. This 
series is readily divisible into four horizons, as follows: 
Wppershaleswnorcanicneeneeeeee ea oeeeeeeee ee 1800 feet 
Upper sandstones, fossiliferous .............. 2500 ues 
Lower shales, brown clays, etc................- 1000 “ 
Lower sandstones, concretionary ............. 1000), 
Toward the southeast the series becomes perceptibly thinner, 
until in the vicinity of Coalinga it narrows to a point and en- 
tirely disappears below the succeeding series of Miocene. 
The Lower Sandstones.—The lower sandstones of the 
Eocene series have not been thoroughly studied, and fossils 
have not yet been found in them within this area; therefore 
their classification as Eocene is based upon other evidence than 
fauna. They consist of soft and crumbling sandstone with a 
few harder layers, some of which are calcareous and are in 
some places more or less concretionary. A good example of 
these lower concretionary sands is to be seen in the rocky hill 
immediately northwest of “Oil City’, Coalinga field. These 
