36 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
the system the structure is comparatively simple, consisting of a 
main anticlinal fold affected by a few subordinate wrinkles. In the 
eastern portion, however, although the effect of the uplift has been 
the production of a single range crest, there are, nevertheless, three 
distinct folds of a more or less secondary nature, arranged en echelon 
and slightly diagonal in trend to the course assumed by the general 
ridge system. These folds may be designated the Torrey, Tapo, and 
Pico. A fourth, en echelon with the others and known as the Els- 
mere, is in reality the western terminus of the San Gabriel uplift 
itself. Although secondary to the dominant structure these folds 
are well developed and are of especial importance in that they have 
become the loci of several very productive oil fields. There are 
numerous minor crumples and, along the southeastern crest of Oak 
Ridge and the southwestern face of the Santa Susana Mountains, at 
least one fault of considerable throw. 
OIL FIELDS NORTH OF THE SANTA CLARA. 
The oil fields north of Santa Clara River involve an area having an 
east-west length of 35 miles and a width of 7 to 15 miles. For con¬ 
venience of discussion, this area may be divided into the Ojai Valley, 
Sulphur Mountain, Si) ^er Thread or Sisar Creek, Santa Paula Ridge, 
Sespe, Pole Canyon, and Hopper-Pirn fields. (See PI. V.) 
OJAI VALLEY FIELDS. 
LOCATION. 
The Ojai Valley fields comprise the region of the upper and lower 
valleys, lying between the Topatopa Range on the north and Sul¬ 
phur Mountain on the south. Nordhoff, the only town within the 
district, lies about 15 miles north of Ventura, with which it is con¬ 
nected by a spur track of the Southern Pacific Company, and 12 
miles northwest of Santa Paula. 
STRUCTURE. 
PI. Ill, sec. A-A' indicates in a very general manner the structural 
relations of the several formations exposed in this valley. The 
series of beds north of the Lower Ojai Valley is a part of the great 
overturned south flank of the anticline developed in the Topatopa 
Range. The overturning was accompanied by faulting. The delin¬ 
eation of the faults on the map (PI. I) is highly generalized from the 
evidence afforded by soil coloring and isolated outcrops. They will 
be described in the order of their occurrence from north to south. 
The succession of beds from the base of the Topatopa Range, or 
across Lower Ojai Valley, is perhaps without break. If so, there is an 
upper and a lower series of rusty beds separated by a broad belt, 
