16 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
heavy sandstone that forms so conspicuous a feature immediately 
above the red and gray banded beds at the foot of the main range 
is doubtless the local representative not only of the sandstone bed 
farther west, but also of a considerable proportion of the chocolate 
and gray banded sands and clays that overlie that bed. The change 
in the composition of the beds is gradual and can lie readily followed. 
The correlation of the sandstone is finally established by the pres¬ 
ence of fossils. It carries pebbles of granitic and other debris up to 
4 inches in diameter and concretions which, as already mentioned, 
closely resemble those of the lower Modelo sandstone north of the 
Santa Clara. The full thickness of the bed at Wiley Canyon can 
hardly be less than 600 feet- and is perhaps even in excess of this. 
It is overlain by 100 or 200 feet of gray and brown arenaceous 
shales and sands, a remnant of the beds that are so characteristic 
of the formation farther west, and these are succeeded by approxi¬ 
mately 200 feet of thin-bedded yellow sand and 100 feet of brown, 
gray, and white shale, which constitutes the uppermost member of 
the formation. The total thickness between the red and gray 
banded sandstone and shale of possible Eocene age and the siliceous 
shale of Monterey type capping the crest of the mountain is prob¬ 
ably not less than 1,000 feet. 
The beds cut by Tapo Canyon are broadly separable into the 
same formations as elsewhere in the Santa Susana Mountains, but 
their defining lines are more or less indistinct, and in some places 
it is not certain to which of the two principal formations the 
strata should be referred. There appears to be conformability, not 
to suggest transition, between the Miocene and Pliocene series at 
this point, although unconformability is the rule over the Coast 
Range territory. The younger series is, however, marked by con¬ 
glomerates, while the older is more slialy and its sandstones are 
more thinly bedded. Here and there the older sandstones are con¬ 
cretionary. The shales are brown or chocolate colored, show a sili¬ 
ceous tendency, and increase in proportion to the sandstones as 
depth in the series is gained. In the ridge between the middle and 
east forks of Tapo Creek fully 400 or 500 feet of shale, with a mini¬ 
mum of sandstone, underlies the higher, more sandy members. Both 
shale and sandstone are locally bituminous, and from them come 
several oil seepages of importance. In this series the wells of Tapo 
Canyon have been sunk. The foregoing description of the older 
succession of strata in these canyons suggests correlation with the 
banded sands and chocolate-colored shale of Torrey and Wiley can¬ 
yons and even in part with the Modelo north of the Santa Clara, 
though no fossils have been observed in either group of beds. In 
Tapo Canyon there is not less than 2,000. feet of the formation 
exposed, in Wiley Canyon the thickness is less than 1,000 feet, and 
farther west it is barely 500 feet. 
