20 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH Ser. 
At the base of the Temblor beds is a pebbly conglomerate 
that serves to give emphasis to the abrupt change from the 
fine organic white shales upon which they rest. 
It is easy therefore to recognize the unconformity that 
exists between the Temblor beds and the white or brown shales 
provisionally classed as Oligocene. This unconformity is that 
formerly described as conspicuous between the Coalinga beds 
and the Monterey shales. The pebbles of the conglomerate 
include metamorphic schists, jaspers, porphyries, serpentine, 
sandstone, and even some rocks that appear to have come from 
the calcareous concretions of the preceding series. 
The Temblor beds contain the principal oil-yielding strata 
of the Coalinga field, and are well constructed to do so, not 
only stratigraphically and structurally, but also on account of 
the porous and unconsolidated character of the larger sandy 
members. The usual thickness of the Temblor beds is from 
450 to 550 feet. In drilling for oil it has been found that 
various horizons are productive, the oil ranging through almost 
the entire thickness, though locally it is generally confined to 
one or two productive strata. Although in some parts of the 
field oil has also been found in strata both above and below 
the Temblor, the latter may be regarded as the chief source 
of the oil in most cases north of McKittrick. 
In the McKittrick district the Temblor beds are known to 
be oil-bearing, but farther south they do not form the prin- 
cipal productive horizon. They occur, however, on the San 
Emidio and at Kern river, at the base of thick series of sand- 
stones which underlie petroliferous beds. It is perhaps due 
to a change in the character of the strata above the Temblor 
that they do not everywhere contain the principal deposits 
of petroleum. 
The Monterey Shales.—To the north of the Temblor ranch 
house, in western Kern county, is a thick series of white shales 
overlying the Lower Miocene and containing Pecten peckham 
near the top and bottom. Its total thickness has been esti- 
mated at more than 5000 feet. This series of white shales 
has been referred to the Monterey, and there can be no reason- 
able doubt that at least a large part of the formation should 
