GEOLOGY AND OIL RESOURCES OF THE 
SANTA MARIA OIL DISTRICT, SANTA 
BARBARA COUNTY, CAL. 
By Ralph Arnold and Robert Anderson. 
INTRODUCTION. 
PURPOSE OF THIS REPORT. 
During the last three years the region near the Pacific coast in the 
northern part of Santa Barbara County, Cal., has shown promise of 
becoming one of the most productive oil fields of the West, if not of 
the whole United States. The developed fields lie on the low, rolling 
hills between the Santa Maria and Lompoc valleys, where the oil has 
accumulated in great abundance in the Monterey shale, of middle 
Tertiary age, which underlies this region. The lightness of the oil, 
which averages from 25° to 27° Baume, and the great productiveness 
of the wells, which yield as high as 3,000 barrels a day, with an 
average of 300 to 400 barrels, arb among the features for which the 
district has become noted. Large areas in the same general region 
as the productive fields have been known for some time to be analo¬ 
gous, so far as surface evidence went, to the proved territory, and it 
was thought that geologic investigations of the region might furnish 
valuable information and aid in the extension of developments. 
Accordingly, with the purpose of studying the occurrence of the oil, 
the extent and structure of the oil-bearing formations, and their rela¬ 
tions to associated formations, the writers carried on the field work 
leading to the present report during the summer and autumn of 
1906. The geology of the region covered by the accompanying geo¬ 
logic map (PI. I, in pocket) has not been completely studied in all 
parts. Between the San Rafael and Santa Ynez ranges it has been 
worked with considerable detail, but the mapping of the mountainous 
regions has been more in the nature of a reconnaissance outside of 
the areas of the Monterey formation. 
A preliminary paper containing the features of this report most 
immediately pertinent to the oil developments and an outline map 
has been published as Bulletin No. 317 of the United States Geolog¬ 
ical Survey. 
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