SANTA CLARA VALLEY: POLE CANYON. 
63 
the region, which may be designated the Oat Mountain syncline, its 
western extremity lying in that mountain. Except for sharp anti¬ 
clinal crumples near its northern and southern edges, this syncline is 
comparatively symmetrical, the outcropping stratum in the trough of 
the fold being the uppermost shale of the Modelo formation. Imme¬ 
diately south of the southern anticlinal crumple is a second fault, 
designated the Sulphur Mountain fault, its trend being N. 60° W., the 
direction of its hade doubtful, though perhaps to the south, the 
downthrow to the south, and the maximum displacement probably 
more than 1,000 feet. This fracture is traceable diagonally across 
Sulphur Mountain to the bottom of the Santa Clara Valley; it is also 
in direct line with certain sharp crumples in Chaffee Canyon, south of 
the valley, to which, therefore, it may be structurally related. To the 
west the fault passes into the ridge running south from Oat Mountain, 
perhaps continuing to Sespe Canyon and merging with the San Caye- 
tano fracture. Over this portion of its course, however, its identifi¬ 
cation is next to impossible, for the strata are but a succession of 
shales which maybe either V aqueros, Modelo, or both. These shales are 
of great thickness and extend southward in unbroken outcrop to the 
Santa Clara Valley, only a narrow fringe of overlying Pliocene sepa¬ 
rating them from the bottom lands for a mile or two along their front. 
The shales display a number of minor folds, but their predominant dip 
is northward. Just before passing beneath the Pliocene, however, 
this seems to change to southward, more or less in conformity with 
that of the younger rocks. Across the Santa Clara Valley, but at a 
distance of nearly 2 miles, the probable upper members of the Sespe 
and lower members of the Vaqueros appear, but the intervening 
structure is unknown. 
In a broad way the folds along the section just described appear to 
divide themselves into three major and half a dozen or more minor 
folds. The major folds include the anticlines at the north and south 
ends of the section and the intervening syncline; the minor folds the 
crumples on the sides of the syncline. Of the major folds the syncline 
extends farthest toward the area of confused structure at the mouth 
of Sespe Canyon, perhaps being involved in it; the northern anticline 
apparently disappears on the southeasterly slope of the general 
Topatopa fold; while the anticline at the south is lost beneath the 
recent deposits of the Sespe and Santa Clara valleys. 
East of the line of the section both major and minor folds in the 
main continue to the center of curvature a mile west of Hopper Can¬ 
yon, where the strata bend from a northwesterly to a northeasterly 
trend. Indeed, the folds seem in places to bend in like manner or at 
least to pass into others of northeasterly trend, similarly developed 
farther east. 
