44 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
STRUCTURE. 
Secs. A-A' and B-B', PI. Ill, show the probable structural relations 
of the different formations in the Sulphur Mountain region. The 
relation between the Modelo shale and the succeeding formation along 
the southern base of Sulphur Mountain is primarily that of uncon¬ 
formity, but faults are here and there suggested by the sharp contrast 
of the beds in contact and by the flexures that have particularly 
affected the strata in proximity to the line of the suspected fracture. 
The fault, if it exists, is in harmony with the other structural features 
of the region and is supplemental to those farther north already 
described. It is the southernmost component of the system radiating 
from the San Cayetano fracture a mile or two east of the Santa Paula 
Valley. In each of the canyons in the southern face of Sulphur 
Mountain evidences of the fracture are more or less distinct. 
Of the flexures in the area under discussion the sharpest occur in 
the interfault block of the Modelo shale. The most conspicuous one 
occurs halfway up the face of Sulphur Mountain. It consists of a 
zone of severely crushed strata 100 to 200 feet broad. 
A short distance south of the suspected fault, in the younger for¬ 
mation of clay, sandstone, and conglomerate that is possibly the 
Fernando, there may be here and there detected an anticlinal fold, its 
axis having the general strike of the formation, varying from N. 65° E. 
at the eastern terminus of the mountain to N. 80° E. farther west. 
The southern limb of the anticline extends beneath the foothills to 
the Santa Clara Valley, the dip varying from 45° to 80°, but usually 
approaching the lesser angle. The northern limb is steep, short, and 
truncated by the plane of the fault. This structure appears in several 
of the canyons and hill areas, but its continuity from point to point 
has not been established. Instead of an anticline it may be, perhaps, 
but a bending downward of the strata, a crumpling of the beds due to 
compression adjacent to the fracture. In Adams and Wheeler can¬ 
yons the anticlinal feature is somewhat stronger, while in Aliso Canyon 
general crumpling seems to prevail. Farther west, however, in the 
region of Harmon Canyon, the anticline again appears; the northern 
limb is still short and terminates in a sharp reverse flexure, or perhaps 
at the fault, which marks the junction of a series of table-like benches 
with the main body of the mountain. The entire region north of 
this fault to the Topatopa Range is a succession of displaced blocks, 
crumpled in the manner just described. From the axis of this dis¬ 
turbance southward to the Santa Clara Valley the strata maintain 
their southerly dip with marked persistency, at most varying only by 
minor and localized flexures. 
