318 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
between them and the San Gabriel Range ; the eastern flexure conforms 
to the western extremity of this latter range, its axis, however, pass- 
in «• into the lower slopes of the Santa Susana Mountains about a mile 
north of the middle anticline. In addition to the foregoing are sev- 
eral intermediate flexures of minor importance. Faults, also, are 
present, the most prominent region of fracture and general dis- 
turbance being that of the Torrey wells, opposite the town of Piru. It 
is noteworthy that the line of this disturbance is in the direct trend of 
one to the north of the Santa Clara that may prove to be connected 
with the San Cayetano fault. 
The productive oil wells of the Santa Susana Mountains and Oak 
Ridge lie in proximity to the axes of the anticlines or to the zones of 
crushing described. The horizons from which the oil is derived 
include one several hundred feet below the lowermost sandstones 
exposed in Oak Ridge; another, perhaps these sandstones themselves; 
a third, some of the sands in the brown and gray banded shales; and 
a fourth, possibly the lower beds of the probable equivalent of the 
San Pablo formation. The depth of the wells varies from 1,000 to 
2,000 feet, according to location and the strata pierced. Their yield 
has been much greater than al present, except in instances where the 
territory is comparatively new. The gravity of the oil varies from 
14° to 40° B., the former in the eastern portion of the field, the latter 
in certain of the wells in front of the Santa Susana Range and Oak 
Ridge. 
I, OS ANGELES FIELD. 
Los Angeles occupies an area about 8 miles square, the greater por- 
tion lying west of the Los Angeles River at its debouchement from 
the low hills which to the west pass gradually into the Santa Monica 
Range and to the east into the San Rafael Hills and the Verdugo 
Mountains. The Elysian Park Hills north of the city attain an alti- 
tude of about 750 feet above sea level, about 500 feet above the 
city itself. Their trend is northwest-southeast, their southwestern 
slope gentle and extending well within the city limits, their north- 
eastern slope abrupt and paralleling the Los Angeles River. The 
area of productive oil wells extends in a belt one-fourth of a mile wide 
from a point near the river at the northern edge of town to the west- 
ern limits of the city in the vicinity of Third street, a distance of 
about 3| miles. Still farther to the west, 8 or miles beyond the 
municipal boundary, are a half dozen more wells that may prove to 
be in an area structurally related to the Los Angeles field proper. 
The formations involved in the geology of the oil field embrace a 
series of heavy-bedded, quartzose, somewhat concretionary sandstones, 
with thin, interbedded shale and an occasional calcareous layer, con- 
stituting the main portion of the hills north of the city; overlying 
these, at least 300 or 400 feet of siliceous shale of Monterey type, 
and above this a succession of sandstones and sandy clays which 
