--> ABSTRACT: Thin-Skinned Extension in the Black Warrior Foreland Basin of Mississippi and Alabama: Nettieton Field, Mississippi, by R. H. Groshong, Jr. and M. A. Nix; #91021 (2010)

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Thin-Skinned Extension in the Black Warrior Foreland Basin of Mississippi and Alabama: Nettieton Field, Mississippi

GROSHONG, RICHARD H., JR. and MICHAEL A. NIX

The Black Warrior basin in the foreland of the Ouachita and Appalachian fold-thrust belts is broken by numerous west to northwest trending normal faults that offset the youngest Pennsylvanian units and are truncated by the Cretaceous unconformity. The Nettleton gas field in the northern part of the basin in Mississippi is a typical hydrocarbon trap for the basin, a footwall closure against one of the larger normal faults. A seismic line across the field indicates that the normal faults extend into the Cambro-Ordovician Knox Group but do not cross the good reflectors of the underlying Rome and lower Conasauga Formations. An area-balanced cross section developed from well data gives a best-fit area-depth relationship that has a lower detachment at approx. 10,400 feet subsea. Based on a nearby deep well, this depth should be in the Conasauga Formation. Seemingly small changes in the cross section lead to large differences in the area-depth relationship, hence the detachment depth provides tight control on the structural interpretation. In the eastern part of the basin, balanced sections derived from closely spaced coalbed methane wells, coal-mine maps, and outcrop maps, indicate that the lower detachment is near the base of the Pennsylvanian. The data from Nettleton indicate that the area underlain by a thin-skinned extensional detachment is at least 120 miles long parallel to regional strike and 40 miles wide in the dip direction. The detachment dips gently southwest and cuts down section to the west. The late formation and thin-skinned geometry of the faults seem to contradict the traditional model that they were caused by lithospheric bending due to Ouachita thrust loading. 

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.