eldridge.] PETROLEUM FIELDS OF CALIFORNIA. 321 
the Santa, Fe, Brea Canyon, and Whittier wells is rendered still more 
complex by the proximity of the line of unconformity between the 
San Pablo and underlying formations. 
The horizons believed to furnish petroleum in the Puente Hills are: 
For the Brea Canyon wells and most of those lying, east of Whittier, 
the sands of the San Pablo formation; for the Santa Fe, the strata of 
uncertain horizon in the disturbed area at the base of the hills in 
their vicinity, in part, at least, of the Miocene; for the Puente wells, 
probably the more sandy horizons in the great body of shales consti- 
tuting the heart of the main anticline in its more contracted part, the 
precise horizon of which in the Miocene is somewhat indefinite. 
The wells in the Puente Hills are of wonderful productiveness, the 
yield of many rising above 200 barrels a day, and in instances ap- 
proaching 1,000 barrels. As in the case of all fields, however, the 
production falls off: in greater or less degree according to the life and 
condition of the wells and the territory drained. The depth of the 
wells is between 900 and 3,000 feet. The gravity of the oil varies 
from about 15° to 33° B. In color, both the black and green varieties 
exist. 
The region is connected by pipe line and rail with the main railways 
of the Santa Ana Valley. 
SUMMARY. 
From the facts established in the preliminary examination of the 
oil fields of California it appears — 
That the productive areas have been in every instance developed 
in connection with anticlines, either in proximity to their axes, along 
their flanks, or about their terminals. 
That in several instances faults, or intense disturbances of the 
strata, have accompanied the folding, causing along their lines inter- 
stitial spaces in which petroleum could accumulate, and thus result- 
ing in an increased supply and yield. 
That there are at least ten or twelve horizons in the 20,000 feet or 
more of strata from Eocene to Pliocene that carry oil in quantities of 
economic value. 
That the reservoirs are either conglomerates, sandstones, or the 
arenaceous members of the great shale groups in the Miocene. 
That oil derived from shales is generally lighter than that of which 
sandstones and conglomerates are the source. 
That the stratigraphic and structural conditions under which oil 
occurs in the known fields are many times repeated elsewhere in the 
Coast Range and the territory contiguous thereto, from which it may 
be argued that additional fields will in turn be discovered; and that 
this view is strengthened by small wells already drilled and by the 
known distribution of petroleum as evidenced by its seepage. 
That the supply is exhaustible. 
Bull. 213—03 21 
