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ABSTRACT: Refinement of a Mature Exploration Model: the Hackberry Play of Louisiana

Stephen P. J. Cossey, Richard E. Jacobs

The Hackberry is a middle Oligocene bathyal sequence restricted to the subsurface in an embayment in southeast Texas and southwest Louisiana. Previous workers have subdivided the Hackberry into the updip play north of a line of salt domes, and the downdip play to the south. The updip play in Louisiana is an area of rotational block faulting, but its relationship to the productive Hackberry channel sands was unclear. Seismic and dipmeter interpretation shows the updip Hackberry is an area of rotational slumping of a pre-Hackberry (lower Frio) delta-front sequence. Slumping was initiated by salt withdrawal and occurs a few miles updip of the salt domes in minor embayments of the shelf edge. Large volumes of lower Frio delta-front sands were eroded from the unconformable cre ts of the slump blocks and were probably redeposited in the Hackberry deep-water turbidite sands downdip. Paleotopographic lows formed between the slump blocks contain strike-oriented, sandy, fill sequences probably deposited by base-of-slope currents. Narrow (^sim2000 ft) deep-water turbidite channels with unconformable bases originate immediately downdip of the slumped areas and were deflected around the paleotopographically high salt domes, forming stratigraphic traps on their northern flanks. Edgerley field is on the northern flank of a salt dome and is productive from both the pre-Hackberry delta-front sequence and a Hackberry channel sand. The key to interpretation and mapping of the sequence is the log character of the sand, the identification of the unconformities, and the identi ication of key log markers in the pre-Hakberry sequence.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990