56 
SANTA MARIA OIL DISTRICT, CALIFORNIA. 
STRUCTURE. 
As has been stated, the Fernando is generally so nearly conform¬ 
able with the Monterey that it is difficult to draw a line between 
them on the basis of a discrepancy in dip. Nevertheless, it is in 
general true that folding has been gentler in the Fernando than in 
the Monterey. It would seem that the older formation had been 
disturbed in varying amounts, in some places severely and in others 
gently, during the process of uplift that put an end to its period of 
deposition. As a result the dips at the present time in the Fer¬ 
nando are apt to be less steep than in the Monterey, but folding has 
gone on largely along old lines, so that conformity in strike between 
the two formations is the rule. 
Wide, low folds are characteristic of the structure in the Fernando 
within the Santa Maria basin region. This is illustrated by the 
broad anticlines in this formation in the Solomon Hills, the broad 
anticline in the Purisima Hills, and the synclines in the Los Alamos 
and Santa Rita valleys, in which the dips range from 5° to 25° as a 
rule for a long way on either side of the fold and rarely become 
steeper than 30° or 35°. In places, as south and west of Sisquoc 
and west of Canada Laguna Seca, the beds are almost if not quite 
horizontal, but this is exceptional. Curves and plunges in the pre¬ 
existing low folds in the Monterey gave rise to structural basins in 
which the Fernando was deposited as a filling. Such was the origin 
of the oval area of Fernando sand covering the eastern portion of 
the Todos Santos y San Antonio grant. This basin is the westward 
extension of a great synclinal basin that runs from that localitv first 
o xJ 
eastward and then southeastward across the Los Alamos, La Laguna, 
and Corral de Quati grants and has determined the position of the 
Los Alamos Valley. The northern arm of this syncline slopes grad¬ 
ually up to the axis of the Solomon Hills, and the southern arm rises 
abruptly into the Purisima Hills, the slope on both sides conforming 
with the topography. The region of low slopes covered by parts of 
the Mission La Purisima and Santa Rita grants is a somewhat simi¬ 
lar wide synclinal basin filled with soft Fernando sediments. The 
Fernando is steeply upturned along the northeastern border of the 
Casmalia Hills, where it stands almost vertically in contact with 
much disturbed and in places overturned beds of the Monterey 
shale. It is upturned also where it rests against the serpentine 
north of Alamo Pintado Creek on the La Laguna grant, and south¬ 
west of Los Alamos it seems to dip very steeply under the brow of 
an overturn in the Monterey. In the San Rafael Mountains patches 
of Fernando deposits occur as remnants, and the beds in many 
places are steepty folded or turned completely on edge. They 
exhibit unconformity with the Monterey. In at least three places 
the Fernando is affected by faulting—a few miles west of Los Ala¬ 
mos, in the neighborhood of Cebada Canyon, and along the fault 
