SANTA CLARA VALLEY: PTCO FIELDS. 
93 
chocolate-colored shale and its accompanying sandstone of the Vaque- 
ros two or three anticlines, with their intervening synclines, occur 
in close succession; indeed, surface conditions suggest faulting similar 
to that shown in fig. 10. Within this zone or possibly slightly south 
of it is a dry well, the depth of which is unknown to the writer. The 
linear extent of the zone is unknown, but disturbance of the strata 
may be detected as far as the divide between the Simi and San Fer¬ 
nando valle}^s, and this series of fractures may prove continuous 
with the great fault suggested by the Whitney survey as south of at 
least the eastern half of the Santa Susana Range. 
It is very evident that there is a pronounced unconformity be¬ 
tween the Fernando conglomerate, sandstone, and clay and the older 
formations of Miocene, Eocene, and Cretaceous age south of the Santa 
Susana Mountains. The line dividing the Fernando from the older 
formations is, however, indicated only in a general way on the map, 
for the region was not studied with a view to geologic detail, being 
somewhat beyond the areas of developed oil fields. 
PRODUCTIVE FIELDS OF THE PICO DISTRICT. 
The productive fields of tne Santa Susana Mountains, enumerated 
from west to east, include those of Pico, Dewitt, Towsley, Wiley, 
Rice, and East canyons, all on the northern slope. With the excep¬ 
tion of those in Dewitt Canyon, which are apparently on a secondary 
crumple, all are ranged along the main Pico anticline, some to the 
north, others to the south of the axis. The anticline apparently 
maintains a uniform elevation except at the extremities, where it 
pitches east and west, respectively. This uniformity of level may 
account for the fact that the anticline has been found productive for 
so large a proportion of its length. This is in marked contrast to 
the development along the Oak Ridge anticline, the axis of which is 
decidedly undulating and which has been proved productive only 
at its point of maximum elevation opposite the town of Bardsdale. 
Doubtless many other factors enter into the explanation of the rela¬ 
tive productiveness of the two anticlines, but the conditions above 
mentioned are to be considered in any attempt to account for it. 
Only a single formation, the Vaqueros, is present in the productive 
oil fields of the Santa Susana Mountains. Its correlation is based 
on lithologic similarity to recognized lower Miocene beds of other 
localities, no fossils having yet been found in it in this district. The 
strata include a large proportion of brown argillaceous and arena¬ 
ceous shale, much interbedded sandstone, and considerable con¬ 
glomerate. Brown and white bands, a feature characteristic of this 
formation from Chaffee Canyon westward, are far less conspicuous 
in front of the Santa Susana Mountains, but conglomerate has a 
much greater development. As elsewhere, the shale includes at 
