64 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
HOPPER-PIRU FIELDS. 
LOCATION. 
The district discussed in this section embraces the territory con¬ 
tiguous to Hopper and Nigger canyons, the lower portion of Piru 
Creek, and its tributaries Modelo, Blanchard, Lime, and Reasoner 
canyons on the west and Santa Felicia and Holser canyons on the east. 
The topography, especially about Hopper Canyon, is very rugged, 
but considerable portions of the district are accessible over the roads 
which follow the canyons. Piru, at the mouth of Piru Creek, is the 
only town of importance in the district. 
STRUCTURE. 
WEST OF PIRU CREEK. 
Within the drainage area of Hopper Canyon the structure varies so 
abruptly that to indicate it completely would require cross sections 
every quarter or half mile; a general idea of it may, however, be 
gained by the examination of sec. G-G', PI. IV, which represents a 
north-south section through Piru Peak. 
The Hopper Canyon section proper reveals at its north end a short, 
though pronounced anticline of northeasterly trend, with a narrow 
core of Vaqueros beds exposed at its center and the Modelo sandstone 
arching over and about its end a short distance to the east. In the 
Piru Peak section this anticline is probably represented by the slight 
pucker near the north end. Near the middle of the section is the 
sharply compressed Modelo anticline, showing in massive beds of the 
lower Modelo sandstone. Between this anticline and that first men¬ 
tioned are several sharp puckers, the most pronounced being that on 
the syncline which passes south of Piru Peak. For this portion of the 
section the thickness of the Modelo sandstone is estimated at about 
3,000 feet. 
The Modelo anticline is one of the most conspicuous of the secondary 
folds in the field. The arch shows to best advantage at the head of 
Modelo Canyon, where the lower Modelo sandstone on either side is 
sharply compressed. The dips are between 60° and 80°, but the 
southern limb of the fold is perhaps a little steeper than the northern 
limb. The anticline may be traced westward to Hopper Canyon, 
beyond which it either disappears or merges with one or another of 
the folds that occur in the Vaqueros shale. Eastward the fold is 
traceable to Piru Creek, where it seems to disappear, unless it should 
by a sharp curve merge with the Holser anticline, half a mile to the 
south. In the lower portion of Modelo Canyon the upper sandstone 
of the formation, together with the underlying shale, shows marked- 
crumpling, the crest of the fold being carried past the vertical. The 
