94 OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
short intervals thin strata of a siliceous nature and limestones that 
are more or less concretionary. The sandstones and sandy shales 
are also concretionary, and here and there a bed may be found which 
bears a striking resemblance, except for thickness, to the lower Modelo 
sandstone north of the Santa Clara. The entire series has been more 
or less impregnated with bitumen, to which is probably due, in a 
large degree at least, its brown color. Except for local variation in 
the materials composing these beds, there is considerable regularity 
in their appearance as a whole, and the general succession is com- 
.paratively well maintained from one end of the region to the other. 
The local irregularities in composition, however, render it next to 
impossible to correlate the logs of wells a mile or more apart along 
the anticline. The dips are steep in many places, yet the crushing 
that is found in the region of Tapo and Torrey canyons is here 
wanting. 
OIL WELLS. 
PICO CANYON WELLS. 
9 
The wells of Pico Canyon, which belong to the Pacific Coast Oil 
Company, are'located not far from the west end of the Pico anticline, 
which terminates in the divide between Pico and Salt canyons. In 
the western half of the productive territory the axis of the fold has 
a distinct pitch to the west. Between 40 and 50 wells have been 
drilled in the field, some more productive than others, but nearly all 
yielding at least a few barrels of oil. With the exception of three at 
the upper forks of the canyon, all are on the northern limb of the 
anticline, not far distant from the axis. They are sunk not only in 
the canyon, but even on the summits of the sharp knobs on either 
side of the gorge, the lowest and highest having a difference in eleva¬ 
tion of 700 feet. The depth of the wells varies from 600 to 3,000 
feet. The logs were not ascessible to the writer, but the superin¬ 
tendent stated that no two holes showed the same succession of beds 
and that it was impossible to distinguish horizons as between wells. 
It is also stated that there is no clearly defined horizon at which oil 
occurs. As an instance, it is reported that of three wells nearly in 
line of strike, in beds of approximately the same amount of dip, and 
within a distance of but a few hundred feet, one afforded a certain 
oil at a depth of 1,600 feet, another a like oil at 1,200 feet, while the 
third, midway between the other two, was 1,900 feet deep' and 
showed not a trace of oil. The superintendent under whose direc¬ 
tion the wells had been drilled suggests the possibility that the oil 
passes from one horizon to another; this is not contrary to one or 
two observed occurrences, where beds impregnated with asphalt, 
originally petroleum, have been exposed. Of the many wells in this 
canyon the three south of the anticlinal axis are said not to be so 
