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Abstract: Sequence Stratigraphy of the North Louisiana-South Arkansas (NL-SA) Basin
N. Sullivan, C. Krotzer, A. Lowrie, I. Lerche
Analysis of electric log and seismic reflection data in the North Louisiana-South Arkansas (NL-SA) Basin reveals that sequence stratigraphic techniques may be applied to this peripheral basin underlain by continental crust. Major interpretational difficulties result from the high rate of basin subsidence relative to low sedimentation rates, as contrasted with the more usual situation of passive continental margins where sedimentation generally exceeds regional subsidence. Similarly, sediments along passive margins with a large fluvial drainage system tend to be terrigenous clastics with low structural strength. In a tropical environment, sediments along shelves of peripheral basins such as NL-SA include carbonates, characteristically of high structural strength. These "strong" layers have served as barriers to the rise of buoyant salt pillows, inhibiting the growth of salt diapirs. Occasional diapirs exist where there is sufficient salt accumulated to provide enough buoyancy to rupture restraining carbonates. Diapirism in the deeper part of the basin suggests that less "strong" layers were deposited there.
Pronounced basement tectonics acts both as a break between salt pillows in the northern basin slope and basement horsts in the deeper central basin which serve as bases for the few salt diapirs. The salt pillows rose with the progradation of the Smackover and Cotton Valley formations. Deposition proceeded from north to south, suggesting that the basin began with Triassic rifting. Examples of onlap abound as deposition prograded up to and then engulfed the rising salt pillows. Water depth apparently increased into the basin as evidenced by onlapping. Abundant channeling, both erosional and aggradational, as well as major deltas, are found.
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