Voz. IIT] ANDERSON—FURTHER STRATIGRAPHIC STUDY ea) 
series contains above the basal conglomerates a great thickness 
of clays and shales, some of which are diatomaceous and 
chalklike in their physical appearance. 
The wells drilled for oil in the Midway and Sunset dis- 
tricts, although they probably derive their oil from this series 
of strata, do not penetrate to the basal sands for their pro- 
ductive horizon. In fact the better wells so far drilled have 
been less than 2000 feet in depth, and some of the oil has been 
found in strata not altogether sandy. Near Sunset the oil 
sands often outcrop in unmistakable exposures, sometimes 
showing well defined beds of bituminous sand, 30 to 60 feet 
or more in thickness. Near the refinery of the “Sunet Oil 
Company” a layer of hard sand immediately overlying such 
an exposure contains: 
Crytomya californica CONRAD Solen sp. 
Tapes stanleyi GABB Macoma sp. 
Some miles farther to the east on Lobos and Muddy creeks 
the same formation has yielded, according to W. L. Watts’: 
Crassatella collina CoNRAD Tapes stanleyi GABB 
Glycimeris generosa GOULD Crytomya californica CONRAD 
Macoma secta ConRAD Macoma sp. 
Neverita recluziana PEt. Tapes sp. 
Dosinia mathewsoni GABB 
As this locality has also yielded Pseudocardium gabbi Remond, 
it is likely that the Crassatella given in the above list is identi- 
cal with this species, since the forms are somewhat alike. 
These beds in the Sunset and Midway districts overlie the 
immense series of white shales described in the preceding pages 
as Monterey, and the evidences of unconformity are all that 
could be asked for. Not only are there abrupt and great litho- 
logical changes, as well as a change in faunas, but an angular 
difference in dip and strike is clearly seen at many points along 
the range. From an examination of the lists here given and 
of the facts herewith presented, it will be seen that the Coalinga 
beds have been clearly identified in the foothills about the 
southern end of the Great valley, and this identification can 
be confirmed by many other facts that are not here presented. 
1 Bull. no. 3, Calif. State Min. Bur. pp. 38 and 40. 
