PUENTE HILLS: PUENTE FIELD. 
119 
cident with the crest of the ridge, and the oil territory has been devel¬ 
oped chiefly in proximity to this axis on either side. (See PL XI, 
sec. E-F.) From the Puente field eastward oil development has fol¬ 
lowed the line of the suspected fault and unconformity, although the 
main anticline has been but slightly prospected. Wells north of the 
line referred to, however, have been generally unsuccessful. The 
axis of the anticline has a gentle westerly pitch, which is maintained, 
except for modification by faulting, to a point beyond the New Eng¬ 
land Oil Company’s wells. 
Whether faulting has taken place in the immediate region of the 
wells is undetermined. It is suggested, however, both by the sharp 
crumpling which the beds have undergone and by the fact that the 
line of development is directly in the trend of the fault which has 
been recognized at the head of the east fork of La Habra Canyon. 
The locus of the main Puente fracture (or of its alternative, the uncon¬ 
formity) lies at the southern base of the hills and is traceable eastward 
to the Brea Canyon district and westward to the head of La Habra 
Canyon. The lack of confirmatory evidence to the contrary and the 
irregularity in the trend of the interformational line argue rather for 
unconformity than for faulting, although the possibility of the latter 
must be admitted. A feature of the field is the convergence of the 
axes of several folds that farther east are of considerable prominence. 
OIL AVELLS. 
The wells of the Puente oil field are those of the Puente Oil Com¬ 
pany, which now penetrate the lower shale of the Puente formation 
to a depth of nearly 2,000 feet, although for years 800 or 900 feet was 
the maximum. Oil is drawn from many layers of sand of varying 
thickness, some of the lower being especially productive and others 
affording but a minimum yield. The depth of 2,000 feet attained by 
the drill, together Avith the amount of erosion that must have taken 
place from the arch of the fold, indicates that this division of the 
Puente is at least 2,500 feet thick, the thickness of the entire formation 
being still undetermined. 
The wells of the Puente Oil Company are among the oldest in Cali¬ 
fornia, dating back to the year 1885. Their production until recently 
has never been large, but has been maintained with marked con¬ 
stancy. Some of the newer wells have yielded 100 to 200 barrels of 
oil a day; but, as in the case of all other fields, this amount has 
decreased as the pressure has diminished and the territory has become 
drained. During 1905 but a few of the Avells in this field Avere being 
pumped, and these only to avoid flooding. The oil is of an olive-green 
to black color by reflected light and varies in gravity from 22° to 35° B. 
