STRUCTURE AND CONDITIONS AFFECTING PRESENCE OF OIL. 85 
FAULTS AND ASPHALT DEPOSITS. 
A thrust fault is well exposed in two forks of Cebada Canyon, where 
the Monterey has been thrust to the southwest up over the Fernando. 
The dip of the fault plane is toward the northeast at an angle of about 
30°. The movement has amounted to a few hundred feet. The 
fault zone seems to continue for a considerable distance toward the 
northwest and to be marked near the Wise & Denigan oil well No. 8 
by large asphalt deposits occupying fractures in the Fernando that 
dip at an angle corresponding to that of the fault plane. The asphalt 
back of the Wise & Denigan well No. 1 is probably due to oil that 
has seeped through the same fractured zone and collected in the 
sandy capping. 
The structure of these hills is further complicated by a prominent 
overturned anticline in the Monterey along the contact with the 
Fernando southwest of Los Alamos and by what appears to be a fault 
exposed near the mouth of Canada Laguna Seca. In this fault the 
Fernando limestone and sand are thrown down several hundred 
feet on the north, at the edge of the Los Alamos Valley. 
In addition to the deposits above noted, asphalt occurs in great 
abundance south and east of Redrock Mountain, surrounded by 
a large area of ver}^ bituminous shale and burnt shale. Undoubtedly 
an immense amount, of petroleum has escaped here, but it is not 
probable that the supply is exhausted. On the contrary, the pres¬ 
ence of this petroliferous material on the surface, coupled with the 
favorable structural conditions, points strongly to the existence of 
rich oil deposits beneath. 
A large mass of asphalt is present in the much-fractured Monterey 
shale west of La Zaca Creek, and very bituminous shale approach¬ 
ing asphalt in character occurs on the creek south of Zaca station. 
The shale is bituminous throughout the zone of disturbance traversed 
by this creek south of Zaca. On account of the low position of the 
strata in the formation and the severe fracturing and folding that 
have taken place, it seems probable that the conditions have been 
favorable in this eastern portion of the Purisima Hills for the escape 
of much of the petroleum. 
Small beds of bituminous sands interbedded with soft shale occur 
in the upper portion of the Monterey just east of Canada de la Puenta, 
about three-fourths of a mile south of the Los Alamos Valley; also 
on the north side of the Purisima Hills ridge, about 2 miles south 
of Harris. A small patch of shale that is saturated with bituminous 
material is exposed in the canyon followed by the road 1 mile south 
of the Los Alamos Oil and Development Company well No. 1, and 
the shale is bituminous in the neighborhood of the Todos Santos well. 
