eldripge] PETROLEUM FIELDS' OF CALIFORNIA. 317 
Ojai Valley. The wells of this field vary in depth from 1,000 to 2,000 
feet. The oil is said to have a minimum gravity of about 12° B., 
and a maximum of about 25° B. The yield of old wells varies from 1 
i to 20 or 30 barrels a day, though that of new ones rises considerably 
above this. 
REGION SOUTH OF SANTA CLARA RIVER. 
On the south of the Santa Clara Valley, separating it from that of 
the Simi, are the Santa Susana Mountains and their westward exten- 
sion, Oak Ridge. The former of these is in direct continuation also 
with the San Gabriel Range, farther to the east. This linear series 
of ridges in its entirety may be regarded as a unit both topographic- 
ally and structurally. The San Gabriel Range has an altitude of 
over 5,000 feet, the Santa Susana Mountains of nearly 4,000 feet, and 
Oak Ridge rises a little above 3,000 feet. The northern face of the 
uplift is particularly rugged. 
The formations entering into the composition of the Santa Susana 
Mountains and Oak Ridge are as follows: At the base, heavy-bedded 
yellow sandstones, here and there pebble-bearing; overlying these, in 
their most differentiated form, are from 300 to 500 feet of conspicu- 
ously banded red and gray arenaceous clays, clayey sandstones, and 
grits; above this, a yellow and gray sandstone, vaiyingly prominent; 
still higher, from 400 to (500 feet of alternating gray and chocolate- 
brown shales, sandstones, and thin fossiliferous limestones. These 
are followed by from 200 to 500 or more feet of chalky and siliceous 
shales of the Monterey type, and these, again,. unconformably, by a 
great mass of heavy, coarse, granitic sands and conglomerates. Of 
the foregoing beds the last may be the equivalent of the San Pablo, 
while the portion underlying the siliceous shale is, in part, perhaps 
wholly, of the Lower Miocene, fossils of this age occurring a short 
distance above the banded red and gray series. Correlation, how- 
ever, of this series of beds with those north of the Santa Clara Valley 
has only in part been possible. The San Gabriel Range is a crystal- 
line complex. 
While the Santa Susana Mountains and Oak Ridge may be regarded 
as a structural unit, there are, nevertheless, within the limits of the 
uplift many anticlinal flexures, at least four of which derive especial 
importance from being the loci of highly productive oil areas. Of 
these anticlines one extends from the western end of Oak Ridge for 
fully three-quarters of its length, the axis lying in the lower slopes 
bordering the Santa Clara Valley. The second, third, and fourth anti- 
clines, instead of paralleling the general ridge, lie diagonally trans- 
verse to it and en echelon with one another. The western of these 
extends along the easterly fourth of Oak Ridge and crosses the divide 
in the gap between it and the Santa Susana Mountains; the middle 
anticline follows diagonally the northern face of the Santa Susana 
Mountains, crossing the divide a mile or two west of the low point 
