109 
PUENTE HILLS: STRUCTURE. 
present in this field, and it is probable, too, that the younger sedi¬ 
ments, as has been found the case with their equivalents elsewhere, 
were laid down upon the already upturned and partially eroded beds 
of the older formation. This would account for many of the irreyulari- 
ties noted along the length of the disturbed belt, but the broken con¬ 
dition of the beds on either side of the line of suspected fracture and 
the steeply inclined, in many places overturned, dip of the Fernando 
sediments in proximity thereto indicate a combined effect of faulting 
and unconformity for the zone in question. The conditions are almost 
a repetition of those in the McKittrick district, in the San Joaquin Val¬ 
ley, along the eastern base of the Coast Range. The oil fields of the 
Puente Hills have been developed in the zone of sharp crumpling and 
in proximity both to the trace of the possible fault and to the line of 
unconformity; the important wells of the McKittrick district have 
been drilled along the fracture and adjacent to the unconformity there 
existing. A guide to development lias been the numerous seepages 
that occur along the belt of severely disturbed strata; but these have 
not always proved reliable indications of a large accumulation of oil. 
COYOTE HILLS ANTICLINE. 
The low east-west ridge known as the Coyote Hills, 3 or 4 miles 
south of the Puente Hills, is an anticline which flanks and is in a 
general way parallel with the Puente fold and was probably devel¬ 
oped synchronously with it. The exposed strata in the west end of 
the Coyote Hills are the Fernando conglomerate and sandstone, but 
no data were obtained indicating how thick they are at this locality 
or at what depth the underlying Puente shale and sandstone lie. 
No seepages have been found in these hills, but toward their west 
end, 3 or 4 miles south of Whittier, is a large gas well. It is proba¬ 
ble that oil also exists in the crest of this anticline, but at what 
depth and in what quantities only future development will show. 
Some of the most productive wells, however, are located in regions 
where the structure is similar to that of this ridge. 
GKO LOGIC RELATIONS OK OIL-REAliING STRATA. 
The distribution of the surrounding mountain masses and the posi¬ 
tion of the Puente Hills in relation thereto do not appear to have 
influenced the accumulation of oil. On the contrary, the significant 
factors appear to be the anticline, the sharply disturbed zone along 
its southern side, the fault that seems to be located within this zone, 
and the unconformity between the Fernando and the Puente forma¬ 
tions. Finally, all the foregoing conditions would be unavailing had 
not the formation of petroleum taken place somewhere within the 
succession of beds in the close vicinity of the hills. 
