84 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
Eureka-Tapo anticlines, in the eastern rim of the Torrey amphi¬ 
theater, the facts pointing to an elevation of the strata north of a 
possible plane of fracture. 
The Tapo anticline is traceable for 3 or 4 miles across the northern 
spurs of the easterly portion of Oak Ridge, its axis lying from one-half 
to two-thirds the distance from base to summit. The general trend 
of the fold is about N. 70° W., the dip of the strata on either side of the 
axis varying between 75° and 85°. The heart of the anticline is occu¬ 
pied by a mass of brown shale and interbedded concretionary sand¬ 
stone. These are believed to be the equivalents of the banded choco¬ 
late-colored and gray sandstones and shales in the vicinity of Wiley 
Canyon and farther west, and, if such is the case, are of Vaqueros age. 
On the other hand, the concretionary phase of the sandstone resem¬ 
bles the lower Modelo formation north of the Santa Clara, but no fossils 
have been found to decide the point. Many of the sandstones of Tapo 
Canyon are highly bituminous, and along the crest of the flexure in 
the several forks occur seepages of petroleum of considerable size. In 
the main canyon, either on the axis or slightly to the south of it, is a 
gas well, but its depth and the horizon from which gas is derived are 
unknown. 
The Tapo anticline appears to die out toward the east in a mass of 
crushed strata at the head of the westernmost branch of Salt Creek on 
Santa Susana Mountain. In a westerly direction the geologic condi¬ 
tions are somewhat uncertain, but in the ridge separating West Tapo 
and Eureka canyons the axis has the appearance of bending rather 
sharply to the north. On the other hand, as already suggested, the 
geology of Eureka Canyon and the adjacent slopes is very complicated, 
and for a definite conclusion concerning the relations of the thousands 
of feet of very similar beds additional field work is necessary. The 
position of the Tapo anticline is but tentatively indicated on the map 
(Pk I). 
Between 100 and 200 yards south of the Tapo anticline is a syn¬ 
cline which is pronounced in the region of the main forks of Tapo Can¬ 
yon, but which west of this disappears in the general crumpling on the 
higher slopes in front of Oak Ridge. In an easterly direction its axis 
approaches that of the anticline, and both are apparently lost in a 
common mass of crumpled strata at the end of the Santa Susana 
Mountains. 
The zone of excessive crumpling, embracing the Torrey and Tapo 
anticlines and their associated synclines, passes from Oak Ridge into 
the west end of the Santa Susana Mountains, in part also crossing the 
crest of the range at the low point opposite the head of Tapo Canyon. 
In the region thus indicated the disposition and succession of the 
strata are very anomalous, and from a topographic standpoint there 
is a distinct offset in the alignment of the two ranges, the west end of 
