Ldridge.] PETROLEUM FIELDS OF CALIFORNIA. 313 
LA GRACIOSA DISTRICT. 
This district lies in La Graciosa Hills, 10 miles south of Santa 
Maria, in the northwestern part of Santa Barbara Count}- . The hills 
attain an altitude of 500 or 600 feet above sea level, and 1heir trend 
is northwest-southeast, coincident with the structural development of 
the country. Their surface aspect is that of grassy pasture lands or 
of areas more or less densely covered with the live oaks peculiar to 
the Pacific coast. The region is rendered accessible by a line of rail- 
way to Santa Maria and San Luis Obispo. 
The geology of the region embraces an underlying series of folded 
Monterey shale, of both the soft and more organic material and that 
which is hard and siliceous, the former predominating. So far as 
observed by the writer, this series of beds is not exposed at any 
point in its entirety. Overlying the Monterey unconformably is a 
heavy and extensive deposit of Pliocene sands, grits, and conglom- 
erates. The composition of these is chiefly quartzose, although there 
is a mingling of other debris derived from the underlying shales and 
from the granite and eruptives of more or less distant localities. 
The full thickness of the Pliocene deposits is undetermined. 
The structure of La Graciosa Hills is that of an anticline, the axis 
of which has a general trend of N. 55° W. The Monterey shales, 
which occupy its heart and are exposed over considerable areas, are 
greatly contorted, but the younger sands of the Pliocene, where 
mantling the older formation, dip to the northeast and southwest 
from but 2° to 25°, according to their position on the flanks of the 
fold. A marked unconformity exists between the Pliocene and 
Miocene deposits, and it is impossible to suggest the surface con- 
figuration of the sea floor upon which the younger of the two forma- 
tions was laid down. 
The developments in the fall of 1902 were chiefly confined to the 
Carreaga ranch, on the southwestern slope of the anticline and hills, 
but drilling was being prosecuted at a number of points west of the 
producing area. On the Carreaga ranch the wells start in the Plio- 
cene conglomerates and sandstones, passing into shale below, and 
thence to the oil sands. Whether the shale was of the Monterey or 
not is a question for future determination.. Difficulty will attend its 
solution because of the uncertainty of measurements by reason of the 
uneven surface attendant upon the unconformity existing between 
the siliceous shales and the younger sands. Texture, however, 
may aid, 
The wells of this territory are large producers and the oil is of high 
gravity. 
SUMMERLAND FIELD. 
This oil field extends along the Pacific shore for nearly a mile in 
front of the small village of Summerland, 5 miles east of Santa Bar- 
