SANTA CLARA VALLEY : SOUTHERN SULPHUR MOUNTAIN. 43 
Adjacent to the line of division between this shale and the suc¬ 
ceeding formation there is in places a body of earthy shale, the general 
color of which is brown and through which are threaded thin-bedded 
sandstones from a few inches to a few feet in thickness. All in all, 
this shale somewhat resembles others of doubtful age that are encoun¬ 
tered in the oil fields of the Santa Susana Mountains and is not unlike 
certain beds that underlie the more siliceous shale of the Modelo for¬ 
mation in the region of Hopper Canyon. The question regarding the 
beds referred to in the Santa Susana Mountains is whether the shale 
actually belongs to the Modelo or to a younger formation, although 
perhaps still of Miocene age. The same uncertainty holds for the 
shale of the Sulphur Mountain localities until detailed work shall have 
determined its proper reference. A possible characteristic that may 
prove to be of value in distinguishing this shale from those of the 
Modelo, the more finely laminated beds of which are of a like brown 
color, is the mud-like texture and consistency of the younger shales. 
The younger clays are, moreover, decidedly arenaceous, and are also 
commonly associated with sandstones. 
The formation regarded as Fernando forms the mass of the hills 
between Santa Clara River and Sulphur Mountain, except, perhaps, a 
Pleistocene fringe along the immediate valley. Some of the lower 
sands are bituminous, this characteristic appearing to become more 
conspicuous as Sulphur Mountain is approached. The clays associ¬ 
ated with the lower sands are brown or blue. The conglomerates of 
this series include pebbles of sandstone, quartz, granite, black chert, 
and siliceous shale, the last evidently derived from the Modelo and 
probably from Sulphur Mountain itself. The succession of beds here 
described is encountered also, though with some variation, in the 
Santa Paula Valley and in the several canyons to the west of Adams 
Canyon. 
By reason of the uncertainty regarding the age of the brown shale 
referred to above it is evident that the line between the Fernando 
and the Modelo formation is indefinite. It is worthy of note in passing 
that there is a considerable difference in the gravity of the oils derived 
from the Modelo shales and the Fernando sands and gravels in this 
field, that from the Modelo being much the lighter. 
Deposits of sand and coarse gravel occurring in the lower portion 
of Adams Canyon are doubtfully referred to the Pleistocene series. 
These have the appearance of being an outlier of the more prominent 
body of like sediments east of the San^a Paula Valley. The deposits 
have, however, received but passing attention and have little or no 
bearing on the geology of the Sulphur Mountain oil district. 
