TERTIARY DEPOSITS NEAR COALINGA OIL FIELD 29 
Geological Survey. Later publications on the area are those of 
Messrs. Arnold and Anderson in Bulletins Nos. 357, 396, and 395 
of the United States Geological Survey. 
A careful study of these publications indicates that no one has 
been able clearly to differentiate the basal beds of the Tertiary from 
the upper beds of the Cretaceous, and that the parting as drawn 
was purely suppositional. The Tejon was the only member of the 
Eocene positively identified, although Mr. Anderson suggests the 
possible Martinez age of some lower beds. 
In the Neocene, the different divisions were fairly well established 
and while the Monterey or lower middle Miocene fauna seemed 
lacking, the sediment is probably represented by a peculiar forma- 
tion called the Big Blue and the equivalency of the two was 
suggested. 
THE CRETACEOUS-TERTIARY CONTACT 
Through much of this territory the uppermost Cretaceous is 
represented by shales and the basal Tertiary is also shaly in char- 
acter. This fact has made it difficult to clearly distinguish the 
one from the other or to mark their parting. In the earlier pub- 
lications it was supposed that there was no appreciable break in the 
sedimentation of the two periods, and that there was also an over- 
lapping of faunas. This latter supposition was disproved by the 
work of Messrs. Stanton, Merriam, and Weaver in their studies of 
the region north of Mount Diablo, and we now have also conclusive 
proof of great stratigraphic breaks, not only between the Cretaceous 
and the Eocene, but also between the formation to which these 
basal Eocene beds belong and the overlying Tejon, which was 
originally supposed to represent practically the entire Eocene of the 
California section. 
The evidence of the stratigraphic break between the Cretaceous 
and Eocene is somewhat more clearly shown at a point outside this 
territory than has yet been proven within it, and our study of this 
section enables us to trace the parting in the territory under 
discussion. 
Some six or seven miles southwest of Antioch and in the eastern 
foothills of Mount Diablo, there is a short canyon where a slight 
sipe of oil was found, from which circumstance it was given the 
