78 
SANTA MARTA OIL DISTRICT, CALIFORNIA. 
Faults also occur along the Franciscan-Fernando contact in the 
region northwest and southeast of Figueroa Creek, but the resultant 
throw was not determined. A depositional contact is clearly exposed 
along this same line just northwest of Alamo Pintado Creek. 
EVIDENCES OF PETROLEUM. 
Despite the great development of folds within the Monterey area, 
only here and there do seepages of asphaltic material occur. It 
would seem that the fractures produced by sharp folding would give 
adequate channels for the escape of petroleum, and it is surprising 
to find so few seepages. The best developed of these is on Labrea 
Creek at and near its junction with Rattlesnake Canyon, and is 
typical of the localities noted north of Sisquoc River. The oil seep¬ 
age is associated with small springs of strongly saline and sulphurous 
water, and the oil has exuded along the bedding planes of the Mon¬ 
terey shales, here thrown into a pronounced anticline which has been 
flexed in such a manner as to open out the laminae of the shale and 
thus give better opportunity for the passage of oil. Two wells have 
been sunk here, but they are shallow and offer no additional data. 
The following is a brief statement of the asphalt seepages and brea 
deposits occurring in the San Rafael Mountains: 
1. Branch of upper Tepusquet Creek. Slight seepage in bed of creek three-fourths 
of a mile above junction with main stream. At anticlinal axis. Has been located. 
2. On Colson Fork of Tepusquet Creek. Black bituminous streaks, veinlets, and 
pockets, associated with calcareous shales which are considerably folded on a minor 
scale. This also has been located. 
3. Labrea Creek, at and near junction with Rattlesnake Canyon. 
4. Sisquoc dairy. Seepage and asphaltic sands along sharply defined anticline 
which is obscured by later material. Well sunk here, but no record available. 
5. Sisquoc River, one-half mile below Round Corral Canyon. Slight seepage from 
steeply inclined Monterey shale. (Shown in PI. Ill, B, p. 34.) 
6. Fugler Point, 1 mile north of Gary. Veins of asphaltum, parallel in a general 
way to the bedding, which here dips 25° SW., intrude the fossiliferous Fernando 
(lower Pliocene portion). A shaft has been sunk here a few feet for the removal of 
the asphaltum. 
7. Alcatraz mine, 3J miles east of Sisquoc post-office. Vast deposits of asphaltum, 
from a few feet to 200 feet or more in thickness, lie unconforinably above the steeply 
dipping Monterey shales over large areas in the general region of the mine. These 
deposits have been mined on a large scale at one place, but at present the plant is 
idle. The mine is shown in PI. VIII, A. 
8. Zaca Canyon, 5 miles southeast of Sisquoc post-office. Deposits similar to those 
at the Alcatraz mine are found on both sides of La Zaca Creek where it debouches 
from its narrow mountain canyon into the broad valley carved by it through the 
hilly country. 
9. Sisquoc Ridge, If miles north of Sisquoc post-office. A small but significant 
area similar in occurrence to the two preceding. This area overlies the axis of an 
anticline in the Monterey shale. 
