92 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
of its occurrence is somewhat perplexing, for it is interspersed among 
the chocolate-colored shale and does not show the individuality of 
the two zones of heavy conglomerate that lie at the base and summit 
of this formation in the region of Wiley and other canyons to the 
west. Unconformity between the two formations probably exists, 
although angular discrepancies were not detected at any point in 
the Pico region. The absence, however, of the heavy mass of sili¬ 
ceous shale between the Vaqueros and the Fernando beds along the 
lower northern slopes of the Santa Susana Mountains is noteworthy. 
South of the Oak Ridge-South Mountain anticline, in the lofty upper 
escarpments, this shale attains a thickness of 300 to 500 feet and 
separates the Vaqueros from the Fernando conglomerate and sand¬ 
stone on the southern slopes of the mountains. The absence of the 
siliceous shale in one locality and its presence in the other, not¬ 
withstanding the short interval between the two,* suggest uncon¬ 
formity between the Fernando and the underlying beds. Moreover, 
there are several areas over which distinct unconformity is observable. 
Fig. 10.—Section through Fryers Peak east of Fryer’s ranch. Dots represent sandstone; fine lines, 
shale; a, b, beds of shale. 
The Pico anticline has proved one of the most productive folds in 
the Santa Clara A alley. It exhibits marked regularity; the fold 
maintains a comparatively uniform elevation from west to east for 
nearly its entire length, and the beds involved are of uniform texture 
and uniformly disposed with reference to one another and to the 
axis of the fold. The inference seems natural, therefore, that such 
conditions would be favorable to the extended field that has been 
developed. 
d he northern slope of the Santa Susana Mountains presents con¬ 
siderable regularity in the succession of beds from the crest nearly 
to the line of the Pico oil field, but to the south of the crest, especially 
m the area opposite the Salt Creek drainage and the more easterly 
tributaries of the Tapo, there is a conspicuous crumpling in a zone 
half a mile wide, trending N. 70° W. The most severe crushing is to 
be seen immediately beneath the summit of the range, where in the 
