SANTA CLARA VALLEY! BARDSDALE FIELD. 
77 
the southern slope of San Cayetano Mountain, north of the Santa 
Clara Valley. While, therefore, the South Mountain-Oak Ridge- 
Santa Susana uplift is undoubtedly an independent unit of structure, 
its development was very probably synchronous with the mountain 
building to the north. Transversely the fold is unsymmetrical at 
nearly all points, the southern limb having much the gentler dip and 
the strata on this side of the axis showing less severity of crumpling 
than those on the north side. The axis of the anticline is also undid a- 
tory, the high points being midway of the length of South Mountain 
and of Oak Ridge. 
A transverse section of the anticline at Sulphur Canyon, which 
practically marks the division of South Mountain from Oak Ridge, 
shows between 1,000 and 2,000 feet of conglomerate, sandstone, and 
shale that are probably Fernando, and at least 500 or 600 feet of chalk 
rock and siliceous shale which have been described as of the Modelo 
type, but concerning the proper stratigraphic reference of which some 
doubt has been expressed. The shale and u chalk rock” occur in 
the axis of the fold, while the conglomerate and its associated strata 
rest unconformably upon its southern flank, forming the higher por¬ 
tions of the ridges and extending far into the Simi Valley. On the 
northern flank the Fernando beds do not appear, the underlying 
shale extending to the Santa Clara Valley. The anticline is some¬ 
what contracted in the region of Sulphur Canyon, and no beds older 
than those of Modelo type outcrop. A short distance to the east and 
west, however, the fold broadens perceptibly and lower formations 
are successively exposed. 
In South Mountain the lowermost beds are red and gray banded 
sandstone and clay, which are tentatively regarded as the partial 
correlative of the Sespe beds north of the Santa Clara, and hence of 
Eocene age. The formation is here especially conspicuous for its 
brilliancy of coloring and the sharp contrasts therein. At least 500 
feet of strata are exposed opposite Santa Paula, but the formation 
occupies the heart of the anticline and its total thickness may be 
much greater. Overlying these are other heavy sandstone and shale, 
resembling in general aspect certain phases of the chocolate-colored 
and gray-banded beds of the Vaqueros formation farther east and 
bearing fossils similar to those of the Vaqueros. Still higher are sili¬ 
ceous shale and “ chalk rock” of the Modelo type, bearing not only 
the customary limestones of that formation, but also several beds of 
fine-grained, gray sandstone. The “ chalk rock ” is somewhat more 
conspicuous in South Mountain than farther east. The formation as 
a whole, however, shows the same general characteristics as in Oak 
Ridge, even to the red, lava-like appearance, the probable result of 
the burning of its petroleum content. The shale, with its brilliant 
