--> Abstract: Structure and Evolution of North Choctaw Ridge Field, Alabama, a SaltRelated Footwall Uplift Along the Peripheral Fault System, Gulf Coast Basin, by J. Qi, J. C. Pashin, and R. H. Groshong, Jr.; #90932 (1998).
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Abstract: Structure and Evolution of North Choctaw Ridge Field, Alabama, a SaltRelated Footwall Uplift Along the Peripheral Fault Previous HitSystemNext Hit, Gulf Coast Basin

QI, J.
The University of Alabama, Tuscaloosa, AL;
J. C. PASHIN
Geological Survey of Alabama, Tuscaloosa, AL;
R. H. GROSHONG, Jr.
The University of Alabama, Tuscaloosa

North Choctaw Ridge (NCR) Field is a Previous HitstructuralNext Hit Previous HittrapNext Hit producing from the Jurassic Smackover Formation which is in the Gilbertown graben Previous HitsystemNext Hit, at the updip limit of the Louann Salt. The field is in the footwall uplift below of one of the faults forming the northern boundary of the graben Previous HitsystemNext Hit. The top seal is anhydrite in the overlying Buckner Formation, and the boundary fault provides a lateral seal. The 325-acre field has produced 8.1 million barrels of oil and 4.2 tcf of gas since its discovery in 1972. The geometry and evolution of the structure has been determined from a threedimensional interpretation of the graben Previous HitsystemNext Hit and from a balanced and sequentially restorable cross section derived from it. A graph of graben area versus depth shows that the cross section is both area and length balanced with a lower detachment near the base of the Louann Salt. The graph further indicates that significant Previous HitstructuralNext Hit growth began in Early Cretaceous time. During Early Cretaceous extension, three major southdipping, down-to-the-Gulf faults formed, creating an imbricate Previous HitsystemNext Hit of half grabens (the Melvin fault Previous HitsystemNext Hit) with NCR Field being a salt-cored uplift beneath the southern fault (Melvin C). Subsidence south of the Melvin fault Previous HitsystemNext Hit indicates contemporaneous salt deflation, but the area-depth relationship suggests that the NCR Field was simultaneously uplifted above regional dip, presumably by inflow of salt. The north-dipping boundary fault of the Gilbertown graben Previous HitsystemTop (East Gilbertown fault) developed only after the Lower Cretaceous. Continuing extension produced a full graben between the East Gilbertown and Melvin C faults.

AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas