Print this pageGravity Anomaly Indications of the Cambrian Rift Geometry In Southern Oklahoma
BROWN, RAYMON L.
Listric normal faults associated with rifling can act to influence the distribution of intrusives around a rift zone by creating effective conduits along the footwalls of the faults. As the intrusives migrate into the shallower sections of the footwall, lacoliths and/or sills form in the shallow footwall sections of the 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.
In southern Oklahoma, the recognition of the original Cambrian rift faults is difficult because of the subsequent tectonic overprint during the Pennsylvanian. However, two gravity anomalies in southern Oklahoma are interpreted to be the results of major intrusions guided by rift faulting during the Cambrian rifling. One of the gravity anomalies is interpreted to be the 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 intrusives into the footwall. Later, the rift geometry ultimately influenced the Pennsylvanian tectonics and mountain building in southern Oklahoma.