PUENTE HILLS: PUENTE FIELD. 
117 
cline, but there is much confusion in the details of structure, and 
these have not been determined. The changes in structure so fre¬ 
quently encountered in the Puente Hills are well exemplified in the 
present locality. Within a quarter to half a mile to the east the folds 
are less complicated, but the flexures continue to the Puente oil field, 
with faults, doubtless, in considerable number, but difficult of detec¬ 
tion in the homogeneous shale. 
The La Habra locality is noteworthy also in that the line of faulting 
and unconformity traceable westward from the Olinda and Brea 
Canyon fields here approaches the system of successive folds that 
characterizes the region of the Puente Oil Company’s wells. Farther 
west the relations of these folds are even more intimate, and the zone 
of disturbance carrying them is greatly contracted. 
OIL WELLS. 
The only wells of the La Habra district are those of the Union and 
New England oil companies. They lie in two groups; the Sansinena 
wells, belonging to the Union Company, are situated in the gulch 
bottom a little south of the axis of what to the east is probably the 
main anticline; the other group is on the crest of the ridge, half a mile 
to the northwest, in highly disturbed strata close to the axis of one of 
the subordinate folds. The production of these wells is not large and 
the oil is comparatively heavy. A maximum depth of nearly 2,000 
feet has been attained, although most of the wells are said to be much 
shallower. Oil is reported to the depth of 1,850 feet. The forma¬ 
tions in the deeper wells embrace 300 or 400 feet of Fernando con¬ 
glomerate at the top, followed by shale and sandstone below, in part, 
perhaps, of the Fernando, in part older. 
PUENTE FIELD. 
LOCATION. 
The Puente oil field lies along the crest of the Puente Hills and of 
the general anticline forming them. It is about 1§ miles northwest of 
the mouth of Brea Canyon and 3 miles east-southeast of the developed 
territory of La Habra Canyon. The productive area is approxi¬ 
mately 1} miles long by one-eighth mile wide, the length correspond¬ 
ing with the general strike of the beds (N. 70° W.). 
GEOLOGY 
The formation underlying the region of the Puente field is the 
lower Puente shale, which, as shown by the well logs, is here largely 
interstratified with beds of fine sand varying in thickness from a few 
inches up to 100 feet or more; an unbroken thickness of 100 feet is, 
Bull. 309—07-9 
