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Abstract: Gravity Anomalies Associated with Rift Faulting in Southern Oklahoma


Faulting during rifting can act to control the flow of intrusives into the shallow crust. As the intrusives migrate into the shallower sections of the footwall, laccoliths and/or sills can form in the shallow footwall sections of major rift faults. As a result, shallow intrusive bodies associated with a rift event may sometimes be indicative of where the footwalls of major rift faults were located. If the intrusives are more dense than the crust into which they are injected, the intrusives will show up as gravity anomalies which can be used to locate the footwalls of the major rift faults.

The normal faults associated with the rifting that took place in southern Oklahoma during the Cambrian are difficult to identify because of tectonic overprinting. However, two gravity anomalies in southern Oklahoma are interpreted to be the results of major intrusions guided by rift faulting during the Cambrian rifting. One of the gravity anomalies is associated with a basalt zone along the southern rim of the Wichita mountains. The second anomaly is just north of the Arbuckle uplift. The implication is that the Anadarko and the Ardmore-Marietta basins were the sites of two opposing half-grabens formed by major rift faults. The grabens acted to confine and control the extent of extrusives while the fault geometry affected the distribution of intrusivies into the footwall. Later, the rift geometry ultimately influenced the Pennsylvanian tectonics and mountain building in southern Oklahoma.

AAPG Search and Discovery Article #90944©1997 AAPG Mid-Continent Section Meeting, Oklahoma City, Oklahoma