GRAVITY AND MAGNETIC CHARACTERIZATION OF FAULTS IN THE HUNTON ANTICLINE AREA OF THE ARBUCKLE UPLIFT, SOUTH-CENTRAL OKLAHOMA

The geological configuration of the Arbuckle Uplift in the vicinity of Chickasaw National Recreation Area (CNRA) in south-central Oklahoma plays a governing role in the occurrence of fresh and mineral springs and artesian wells in and around the park. A confining layer of well-cemented conglomerate lies immediately below the surface of the recreation area, and groundwater migrates from an area of meteoric recharge where rocks of the Arbuckle-Simpson Aquifer crop out as close as two kilometers to the east of the park in the Hunton Anticline. Prominent, Pennsylvanian-aged faults are exposed in the aquifer outcrop, and two of the fault traces project beneath the conglomerate cover toward two groups of springs within the northern section of the park. We conducted gravity fieldwork and analysis to investigate the subsurface extensions of these major faults beneath CNRA. By defining gravity gradient signatures of the faults where they are exposed, we infer that the Sulphur and Mill Creek Faults bend to the south-west where they are buried. The South Sulphur Fault may project westward linearly if it juxtaposes rocks that have a density contrast opposite that of that fault's density configuration in the Sulphur Syncline area. The South Sulphur Fault dips steeply northward, and its normal sense of offset suggests that the Sulphur Syncline is part of a graben. The Mill Creek Fault is vertical, and the Reagan Fault dips southward, consistent with its being mapped as a thrust fault. The Sulphur and Mill Creek Synclines may have formed as pull-apart basins in a left-lateral, left-stepping strike-slip environment. The presence of relatively high-density Precambrian basement rocks in a broader region suggests that significant gravity anomalies may arise from variations in basement topography. High-resolution gravity and ground magnetic data recently (May 2007) collected between the Reagan and Sulphur Faults will improve our characterization of the geophysical signatures of these faults and our understanding of the importance of topography of the basement surface. Recently collected helicopter electromagnetic and aeromagnetic data provide complementary views of the structure and geology.