Print this pageAbstract: A Comparison of Surface and Subsurface 
Structure
,Elwood
Oil Field, Santa Barbara County, California
BARTLETT, W. L., Department of Geological Sciences, University of California, Santa Barbara 93106
Elwood oil field in Goleta, California, was one of the first oil fields
in California to produce oil commercially from the lower Miocene Vaqueros
Formation. Discovered in 1928 by field mapping, the oil field reached its
peak production in 1930. The oil field straddles the shoreline, extending
eastward onto Ellwood Mesa and westward into the offshore.
Recent field work along the beach and sea cliffs of Ellwood Mesa along
the eastern part of Elwood oil field yielded detailed surface stratigraphy
and structure of the middle Miocene Monterey Formation. Thus, from the
surface to a depth of 600 m, the structure of the Monterey Formation in
the Elwood oil field is mainly anticlinal, complexly deformed by faulted,
chevron folds associated with two major east-west striking, oblique-slip
faults. The folds plunge generally eastward and are offset by minor northeast-
striking, oblique-slip faults.
By contrast, interpretations from well data and old field maps indicates
that the subsurface structural trap in the Vaqueros Formation is a relatively
broad, east-west trending anticline with a shallow central saddle, both
east and west closure, and a faulted northern flank.
Between the Vaqueros and Monterey formations is the comparatively incompetent
Rincon Formation, a mudstone unit that accommodates the disparate styles
of the formations above and below it by thickening and thinning. The disharmonic
relationship between the relatively simple structure in the subsurface
and the complex faulting and folding of the overlying Monterey Formation
is a characteristic deformation style in the western Transverse Ranges
of southern California.
AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California
