SANTA CLARA VALLEY : SILVER THREAD FIELD. 
47 
ose limestones, which carry fossils that have been determined to be 
Eocene. These rusty beds are a part of the overturned south hank 
ol the great anticline to the north, and pass directly beneath the 
great body of older Topatopa quartzite and shale that occupies the 
very heart of the range. 
The red beds, probably belonging to the Sespe formation, are exposed 
in a narrow belt little more than 100 yards wide, along the upper por¬ 
tion of the face of. the ridge north of Sisar Canyon. They outcrop 
south of the rusty beds, passing beneath them, however, with a north¬ 
erly dip, as part of the overturned series. They consist of coarse 
sandstone, streaked red and white, and shale colored in like manner, 
as in the Sespe region. In the Silver Thread field, as well as in the 
Ojai Valley, there is, stratigraphically below the red beds, a con¬ 
spicuous layer of white sandstone from 20 to 30 feet thick, which is 
locally bituminous and carries small lenticular bodies of green and 
purplish clay. Stratigraphically above the red beds in the Ojai 
Valley are rusty beds, but these are not exposed in the Silver Thread 
region. 
South of the red beds is the Modelo shale, occupying the slopes of 
Sisar Canyon and Sulphur Mountain. The formation here has the 
typical appearance, consisting of earthy to siliceous shale, brown, 
gray, and white in color, more or less organic, impregnated with gyp¬ 
sum, sulphur, and bitumen, and carrying lenses of limestone that 
weather a bright yellow. This shale is thrust down against the forma¬ 
tions already described by a displacement, which may be called the 
Silver Thread fault. This is probably the principal westerly branch 
of the San Cayetano break and may be the continuation of the principal 
fault of the Ojai Valley. If this connection is correct, the displace¬ 
ment amounts probably to several thousand feet. Immediately south 
of the fracture the beds are folded into an anticline, the axis of which is 
coincident with the lower part of Sisar Canyon. In Sulphur Mountain 
they lie in a syncline, the axis being coincident with the crest of the 
mountain. A little- farther south there is a second anticline, beyond 
which, with the exception of minor flexures, the southerly dip of the 
strata is maintained to the valley of Santa Clara River. 
In the bluffs of Santa Paula Canyon, at the base of the oil-yielding 
hills, there is immediately north of the anticlinal axis an outcrop of 
200 or 300 feet of earthy, micaceo-quartzitic shale, chalky in color 
and bearing yellow to gray limestone concretions and thin beds of 
sandstone. This shale resembles the chalky Modelo shale in Hopper 
Canyon and is probably its equivalent. Immediately south of the 
anticlinal axis, at the mouth of Sisar Creek, the more siliceous shale 
sets in. It is possible, therefore, that some faulting has taken place 
along- the crest of the fold, so that the series is not the same on both 
sides. On the other hand, it may be that the appearance of the shale 
