--> Abstract: Sequence Development and Expression in a Gulf of Mexico Salt-Floored Basin, by C. S. Lerch and M. O. Mahler; #91012 (1992).

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ABSTRACT: Sequence Development and Expression in a Gulf of Mexico Salt-Floored Basin

LERCH, CHRISTOPHER S., and MICHAEL O. MAHLER,* Shell Offshore, Inc., New Orleans, LA

Pliocene-Pleistocene salt tectonics, eustatic sea level fluctuations, and shifting deltaic depocenters controlled deposition of third and fourth order stratigraphic sequences within Brie basin. Brie basin is a typical Gulf of Mexico "minibasin": a small (400 sq. kilometers) semicircular basin whose formation is intimately tied to local salt tectonics and syntectonic sediment deposition. In Brie minibasin, progradation of early Pleistocene highstand deltaics triggered basin formation by loading a Pliocene salt tablet. After the salt was evacuated, accommodation space became limited and sediments prograded beyond the basin.

The deltaic basin fill represents the highstand systems tract of a third-order eustatic sequence on which fourth-order sequences are superimposed. The sequences can be identified by seismic facies, shale resistivity patterns, faunal blooms, and changes in paleo-water depth. Formation of the fourth-order sequences is driven by a combination of local salt tectonics and deltaic progradation/avulsion. Reservoir quality sand and shaly potential source rock intervals can be identified in the fourth-order sequences based on their seismic character: sandy intervals exhibit discontinuous to chaotic reflectors with variable amplitude and shaly intervals exhibit continuous reflectors with constant amplitude. Furthermore, in the distal, shale-rich part of the sequences, shale resistivity trends f om electric logs can be used to define the sequences.

Brie basin is an example of how eustatic sea level fluctuations and salt tectonism play an important role in the development of stratigraphic sequences and reservoir/seal lithologies in Gulf of Mexico minibasins.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)