SANTA CLARA VALLEY : HOPPER-PIRU FIELDS. 
65 
succession of strata on the two sides of this fold does not appear to 
be exactly the same, the relative proportion of sandstone and shale 
being somewhat at variance. This probably is due to concealed 
faults a short distance south of the axis. 
The Modelo anticline is the seat of two important fields of oil. 
One is developed close to and on either side of the axis of the fold, 
along the upper course of Modelo Canyon and at the divide between 
this canyon and the drainage flowing to the west; the other is devel¬ 
oped by the Sunset wells near stream level in Hopper Canyon. Other 
portions of the anticline are as yet undeveloped, but there is no evi¬ 
dence to show that such areas do not contain oil, and it seems probable 
that search by the drill would be rewarded. 
South of the Modelo anticline are two successive synclines separated 
by a fault. These appear both on the general section (PI. Ill) and 
on sec. G-G' (PI. IV). The rocks involved are the lower and upper 
Modelo sandstones and the intermediate and overlying shales. The 
evidence of the fault lies in the irregularity of outcrop at the head of 
the south fork of Modelo Canyon, in the succession of strata in Lyons 
Peak and farther west, and in the fractured condition of the beds 
overlooking Hopper Canyon. As exposed at the surface, the fault 
seems to be confined to the shale between the two Modelo sandstones. 
It is difficult to estimate the amount of throw that may have taken 
place, but it is at least 500 feet at the point of maximum development 
and perhaps much greater. To the east the fractured condition of 
the rocks continues for at least half the length of Modelo Canyon 
but here possibly the fault dies out on the southern limb of an exceed¬ 
ingly sharp fold that appears in a prominent knoll just north of the 
gorge, directly in line with the axis of the Modelo anticline. The 
effects of the fold doubtless extend as far east as Piru Creek, possibly 
beyond. The western terminus of the fault is uncertain. South of 
the fault the upper Modelo sandstone appears to have been folded 
into a sharp syncline. 
Less than half a mile south of the syncline just mentioned lies the 
Lyons anticline, which is the third important anticline of the region 
and which crosses the lower portion of Nigger Canyon. The arch is 
well shown in the divide immediately east of the Lyons wells in the 
upper Modelo sandstone and the shales immediately above and below. 
The shale is more conspicuous in the heart of the anticline to the west, 
while the sandstone may be seen on the slopes toward Piru Valley, 
curving about the underlying bed. The trend of this anticline is 
approximately N. 80° E. from Nigger Canyon eastward and S. 65° W. 
from half a mile west of Nigger Canyon westward. This curve con¬ 
forms to that of the other folds both to the north and to the south. 
To the east the Lyons anticline was not recognized with certainty 
