112 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
conglomerates that in the vicinity of the Home wells outcrop in close 
proximity to the fault line may be those cut at considerable depth in 
the Murphy and Central group. 
The Puente shale north of the fault line is in part siliceous, in part 
earthy, and in places it is brown from the presence of bitumen as well 
as of iron. In many of the layers may be found traces of the low 
organisms, foraminifera, etc., which are usually present in the Miocene 
formations, especially the Monterey. Limestone concretions also 
occur. Whether the shale outcropping adjacent to the fault belongs 
above the Puente sandstone or below was not positively determined. 
All three divisions of the formation perhaps occur at one point or 
another in the field, but the contorted and faulted condition of the 
beds requires the utmost detail of study for their successful correla¬ 
tion, and this the present reconnaissance did not permit. It is suffi¬ 
cient for the immediate purposes of this report that the Miocene shale 
(Puente) has been identified in faulted or unconformable contact 
with the oil-bearing members of the Fernando. 
The number of oil-bearing horizons in the Fernando formation 
adjacent to the fault line and the fact that they are in contact with 
the bituminous shale of the Puente suggest a passage of the oil from 
the older formation into the various members of the younger, the 
fault having been not only a disturbing element affecting the positions 
of the strata, but also, perhaps, the means of affording a channel for 
the transfer of the fluid from the entire thickness of Puente shale to 
the several horizons of the Fernando. The fault plane, in fact, here 
seems to have performed in an enhanced degree the same function as 
the plane, of unconformity between the two formations, so conspicuous 
an element in many of the oil fields of California. The }T)unger for¬ 
mation of open, porous sandstone and conglomerate lies in contact 
with the bitumen-bearing shales of the Puente; in the one instance by 
faulting, in the other by deposition. In both instances the receptive 
strata of the younger formation, which happen to lie against or upon 
the older beds, have become impregnated with the bitumen capable of 
removal through wells. 
That the surficial relation between the Fernando and the Puente 
beds is one of faulting rather than simple unconformity is argued from 
the irregularities of strike and dip of the various strata, but beneath 
the surface the unconformity which exists at the base of the upper 
Miocene at almost every point in the Coast Range is undoubtedly also 
present. 
STRUCTURE. 
The nature of the Puente fault zone is exhibited in a complex of 
fractures observable a few hundred feet north and northwest of the 
principal group of Central wells. It consists of two principal breaks. 
