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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 47 (1963)

Issue: 9. (September)

First Page: 1774

Last Page: 1774

Title: Regional Gravity Anomalies in Central California: ABSTRACT

Author(s): H. W. Oliver, D. R. Mabey

Article Type: Meeting abstract


A Previous HitBouguerNext Hit gravity map of central California east of the Coast Ranges has been compiled from over 11,000 observations made by the U. S. Geological Survey, the U. S. Naval Ordnance Test Station, and several oil companies. The Previous HitBouguerNext Hit reductions are based on a rock density of 2.67 g/cm3 and include terrane corrections in all mountainous areas.

Regional gravity lows in the west and south parts of the San Joaquin Valley are produced by a maximum estimated thickness of more than 30,000 feet of Upper Cretaceous and Cenozoic deposits. Gravity lows also occur over local basins south and east of the Sierra Nevada which, in conjunction with limited seismic refraction measurements, indicate the following maximum thicknesses of Cenozoic deposits: Mono Basin and Long Valley--18,000 feet; Death Valley and Cantil Valley--10,000 feet; Owens Valley--9,000 feet; Indian Wells Valley--8,000 feet; Searles Basin, Saline Valley, and Panamint Valley--3,500 feet.

Previous HitBouguerTop gravity values corrected for the effect of the Upper Cretaceous and Cenozoic deposits show a broad, asymmetrical gravity low centered over the eastern Sierra Nevada with the steepest gradients and greatest relief on the west side. This major anomaly disturbs the earth's gravity field from the western San Joaquin Valley to the California-Nevada border. It can be explained by isostatic compensation of the Sierra Nevada and high areas to the east plus the relatively low-density rocks of the Sierra Nevada batholith.

A gravity ridge that extends for several hundred miles along the east side of the San Joaquin Valley shows excellent correlation with a similar magnetic ridge, suggesting that both anomalies are caused by a dense, magnetic mass buried at an estimated depth of 5-10 miles. This depth approaches the approximate 12 mile thickness of the earth's crust under the valley indicated by seismic refraction measurements.

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