84 
SANTA MARTA OIL DISTRICT, CALIFORNIA. 
mentioned on Burton Mesa exposes hard shale that is low down in 
the Monterey, and it is probable that with the removal of all of the 
higher portion opportunity has been offered for the escape of the 
greater part of the oil from the basal beds. 
A low anticlinal fold occurs in the northeast corner of Burton Mesa 
and plunges toward the southeast. As indicated by the dotted line 
on the map, it is possibly a continuation of the anticline south of 
Antonio before mentioned and another on the east edge of the mesa 
that is discussed in connection with the Purisima Hills. The evi¬ 
dence of folds in this northeastern portion of the mesa is scanty, but 
it is probable that where they occur accumulations of oil are present. 
The brittle calcareous and flinty shale of the lower portion of the 
Monterey that is exposed along the coast edge of Burton Mesa is very 
bituminous. The petroleum slowly oozes out in some places and 
collects in tarry patches over the shale. Up Oak Canyon the shale is 
bituminous, pockets of tar being found in places in the flint on the 
surface. On the northern border of the mesa, near the point where 
the road to Lompoc comes up the grade, a 3-inch bed of bituminous 
sand was found traversing the shale fairly high in the formation. 
PURISIMA HILLS. 
FOLDS. 
The Purisima Hills are formed by one broad anticline which has its 
axis on the south side of the summit of the dominating ridge. Through 
the major portion of this anticline’s course, from the region north of 
the Hill wells to a point beyond Bedrock Mountain, the beds lie 
almost horizontal on its summit, becoming gradually steeper up to 
an angle of 15° or 20°, or locally even 40°, within a mile or two from 
the axis. The general trend of this fold is more to the north of west 
than that of the Los Alamos or Santa Ynez valleys, but portions of 
it have a more westerly course, as at the west end, where it also 
becomes a steeper fold. At the east end it has the dominant 
northwest-southeast trend characteristic of this part of the hills and 
likewise becomes steeper. It is a fold plunging from either end 
toward the region at the head of Cebada Canyon, where the axis 
of the depression in the anticline occurs. This depression appears 
like a broad syncline crossing the anticline at right angles, with the 
deepest portion of its trough at this point. 
The Purisima Hills anticline can not be traced farther westward 
than is shown on the map, but at the west end there seems to occur a 
structural offset to the northwest, a poorly exposed anticline about 
a mile from the end of the main fold being traceable for a short dis¬ 
tance and seeming to mark the continuation of the general structure 
of these hills. There is a likelihood that oil may be found along this 
fold as well as along the main anticline. 
