SANTA CLARA VALLEY: STRUCTURE. 
31 
tain. The northernmost fault lies between the rusty Vaqueros beds 
and the Modelo shale. South of this is the second fracture of the 
system, the block between them being composed of Modelo shale. 
Between the second and third faults, the latter passing immediately 
north of Lion Ridge, is a narrow block of rusty beds of the Vaque¬ 
ros type. South of this is a comparatively broad zone of the Sespe 
formation, which in turn is separated from the Modelo shale, consti¬ 
tuting Sulphur Mountain, by one of the most extensive faults of the 
region. South of Sulphur Mountain there is a fifth fault, marked by 
a line of seepages and oil wells. The evidence of faulting, however, 
must not be confused with the unconformity which exists between 
the Modelo and the Fernando. The shale of Sulphur Mountain is 
considerably crumpled, at least two marked anticlines (one of which 
is locally overturned) and the intervening syncline being present 
through nearly its whole length. The conglomerate, sand, and shale 
of the Fernando formation, south of their contact with the Modelo 
shale of Sulphur Mountain, maintain a southerly dip with marked 
persistency, at most varied only by minor and localized flexures. 
The structural features west of Santa Paula Creek continue to the 
east for 4 or 5 miles, in front of Santa Paula Ridge and San Cayetano 
Mountain, but the faults terminate one by one or coalesce, until at the 
easterly apex of the region the disappearance of interfault blocks has 
brought the late Tertiaries into contact with the much earlier Topa- 
topa formation, the great San Cayetano fault alone separating them. 
In the Sespe district it is to be observed that the formations enter 
the Camulos quadrangle at its northern border from their passage 
around the east end of the axis of the Topatopa anticline, which lies 
between 1 and 2 miles to che north. Within the quadrangle crump¬ 
ling begins near its northern border—at first gentle, then severe. The 
major features resulting from this movement are the Coldwater anti¬ 
cline, southeast of the broad table of red beds, and still farther south 
the syncline, whose eastern extension passes through the summit of 
Oat Mountain. South of the western part of this syncline is the great 
northward-dipping monocline of Topatopa beds on the north flank of 
Mount San Cayetano. Near the mouth oFSespe Canyon the beds are 
greatly disturbed by the close approach of the San Cayetano fault and 
the syncline just mentioned. 
In the region east of Sespe Creek the more important of the subor¬ 
dinate or secondary folds include a partially overturned anticline 
southwest of Hopper Mountain; the Oat Mountain syncline, already' 
referred to; an anticline that crosses lower Pole Canyon at its sharp 
turn from south to west, and another anticline a mile farther south. 
Each of these folds is a conspicuous feature of the geology from one or 
another point of view, but the syncline is perhaps the most marked, 
involving, as it does, the strata from the upper Modelo shale to the red 
