PUENTE HILLS: WHITTIER FIELD. 
Ill 
the Puente that lie with varied dip on the north of the fault. The 
line of producing wells trends N. 65° W., in marked divergence with 
the strike of the formations, which varies but little on either side of 
an east-west line. The wells, in other words, follow the trend of the 
fault rather than the strike of the beds, and in the Fernando forma¬ 
tion the oil horizons vary with the strata that are brought into con¬ 
tact with the shale across the fracture plane. In the eastern portion 
of the field, for example, the petroleum is in beds considerably higher 
than in the western portion. An apparent exception to this ten¬ 
dency of well development to follow the fault plane exists in the 
long parallel strings of Murphy and Central wells that lie on either 
side of an east-west property line, a little north of the south line of 
sec. 23, T. 2 S., R. 11 W. (See PI. XIII, A.) These wells closely 
follow the strike of the formation, with which, however, the prop¬ 
erty line,, the determining factor in their location, happens to be 
nearly coincident. 
%j 
North of the plane of separation of the Fernando and Puente for¬ 
mations the wells drilled in the Puente beds have been, with a few 
unimportant and slight exceptions, total failures. It would seem, 
therefore, that for this field the productive belt is in the Fernando 
formation adjacent to the plane of fracture or of unconformity. The 
width of this belt is uncertain, but is at least between a quarter and 
half a mile, and the oil is found at greater depths in proportion as it 
is distant from the line of fracture. The strata affording oil in the 
Whittier field are members of the Fernando formation and consist 
•of coarse gray to yellow-brown conglomerate, heavy-bedded sand¬ 
stone, and pulverulent argillaceous sand that shades locally into dis¬ 
tinct! v arenaceous clav. Here and there the clay has been hard- 
ened by the presence of lime, and in some of the sandstone also there 
are hard quartzo-calcareous concretions, such as have been ob¬ 
served in this formation at other points in the hills. Locally, also, 
the sandstone shows the presence of more or less dry bitumen, which 
imparts to the rock a brown color. The exact position of these beds 
in the formation as a whole is unknown, by reason of faulting, because 
of the unconformity which exists between the Fernando and the 
underlying formations, and from the fact that as yet the various 
divisions have not been identified and correlated by their fossil con¬ 
tents. Furthermore, there is an apparent variation in composition 
along the strike of the formation. The relative position of the beds in 
the eastern and western portions of the productive tract may, how¬ 
ever, be traced with comparative precision by reference to strike lines 
which vary but little from east and west; a heavy conglomerate, for 
instance, which lies a quarter of a mile south of the Murphy and Cen¬ 
tral wells in the eastern part of the field is found fully half or three- 
fourths of a mile south of the Home wells in the western part. Other 
