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OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
along two lines, the northern group following the zone of greatest dis¬ 
turbance, together with the fault, and the southern following the land 
line which separates the properties of the Santa Fe and Fullerton Con¬ 
solidated oil companies and having no connection whatever with the 
structure. 
The oils of the Olinda field vary in gravity from 12° to 35° B., the 
heaviest being found at the west end of the field in members of the 
Fernando, those of 18° to 20° B. in the southwestern part, also in the 
Fernando, and those between 23° and 35° B. in the eastern half of 
the productive area in various horizons of the Puente. 
/ 
CHINO FIELD. 
The Chino oil field occupies a small area on the crest of the divide 
between Soquel Canyon and the Chino Valley, 5 miles southwest; of 
the town of Chino. It is located on what appears to be one of the 
northeast-southwest flexures that radiate from the main Puente anti¬ 
cline. The wells, four in number, are drilled in the axis of the flexure 
and on either side. They pierce the Puente sandstone and under¬ 
lying shale, but the details of their logs were unavailable at the time 
of the writer’s visit. Aside from their commercial value, they are of 
especial interest as suggesting the possibilities of at least some of the 
subordinate folds in the hills. 
CONCEUSIONS CONCERNING FUTURE DEVELOPMENT. 
Whether petroleum will be obtained north of the line of maximum 
disturbance in the Puente fault zone, in rocks adjacent thereto, is 
questionable. Thus far wells in this position have been unsuccessful. 
A reservoir of coarse sand or other open-textured rock is filled with 
oil at the expense of the finer strata in which it may prove to have 
been but temporarily stored, or in some of which it may have even 
originated. Under conditions such as have been described, it may be 
inferred that in the region of the fault, along the southern face of the 
Puente Hills, the oil has been drawn from the beds north of the frac¬ 
ture zone into the more crushed and hence more open and porous 
strata of the same age south of it, and also into the still more receptive 
reservoir of coarse sediments presented in the Fernando formation. 
IIow great an area north of the fault may have thus been drained it 
is impossible to say. 
An argument in favor of productiveness of the Puente formation 
away from the zone of faults is presented by the Puente Oil Com¬ 
pany’s wells, which are drilled in an anticline in the lower division of 
this formation. Similar evidence is also offered by the wells of the 
Chino Oil Company, which penetrate the Puente, including the sand¬ 
stone, on a fold subordinate to the main Puente anticline, yet not far 
from its axis. That the lower Puente shale in these hills is generally 
