MUIR, S. G., WZI Inc./Sierra Bravo Company, Bakersfield, CA, D. J. PIERCE, Terra-Soft Inc., Bakersfield, CA, and W. S. HART, WZI Inc./Sierra Bravo Company, Bakersfield, CA

ABSTRACT: Regional Gravity and Aeromagnetic Anomalies Related to Geologic Structure of the West-Central Antelope Valley, California

Detailed aeromagnetic and gravity data were acquired over the west-central parts of the Antelope Valley, California, in support of oil and gas exploration of this region. The surveys are bounded approximately by the Garlock fault on the north and the San Andreas fault on the south.

The magnetic survey included more than 3300 line-mi of closely spaced, high-precision (0.5 gamma) total field and horizontal gradient aeromagnetic data flown at an attitude of 300 ft. The gravity survey consisted of more than 135 mi of high-precision (0.1 mGal) gravity profiling with station spacings of 220 and 330 ft. Magnetic and gravity anomalies were evaluated using 2-dimensional and 2-1/2 dimensional forward and inverse modeling procedures.

The modeling (1) confirmed the presence and mapped the lateral extent of several deep and one shallow area of structural downwarping where early Tertiary and younger marine and nonmarine sediments may have accumulated, (2) mapped the locations of previously identified high-angle faults where they extend under Quaternary alluvial deposits and have no surface expression, and (3) identified high-angle reverse or thrust faults or fault zones that exist north of the San Andreas fault where crystalline basement rock may have been translated northward over middle and lower Tertiary sediments by as much as 2 mi.

Recent oil and gas exploratory drilling in this area completed after the geophysical surveys were conducted suggests the geologic section depth estimates from the potential field models are within approximately 20% accuracy of actual depths reportedly encountered.

AAPG Search and Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach, California, May 5-7, 1993.