ABSTRACT

A grid of two-dimensional seismic data tied to exploration wells defines four Jurassic sequences in the northeastern Gulf of Mexico. These sequences correlate with well-known northern Gulf of Mexico basin stratigraphic units: the Louann Salt (L sequence), Norphlet and Smackover formations (N-S sequence), Haynesville Formation (H sequence), and Cotton Valley Group (C sequence). The Jurassic section overlies a basement surface characterized by broad highs (Middle Ground arch and Southern platform) and lows (Apalachicola basin and Tampa embayment). This basement structure controlled the distribution, thickness, and paleogeography of all the Jurassic sequences, but its influence became progressively less pronounced as sediment filled the basin.

The Jurassic geologic history of the region is developed from an interpretation of these sequences. Well control documents the presence of Louann Salt in the Apalachicola basin, whereas in the Tampa embayment the interval is interpreted only from seismic data. Salt movement on the West Florida Shelf began early, during Norphlet-Smackover deposition, and slowed dramatically by the end of Haynesville deposition. Smackover paleogeography includes progradation of a carbonate shelf in the Apalachicola basin and the Tampa embayment, as well as development of carbonate buildups updip of basement hingelines, over basement highs, and above early salt structures. In the Apalachicola basin, Haynesville clastic sedimentation updip was coeval with carbonate deposition downdip, and a localized carbonate shelf margin developed to the southwest. Haynesville clastic sedimentation may have prevailed in the Tampa embayment, where oblique clinoforms represent shelf margin progradation. During deposition of the Cotton Valley sequence, the northeastern Gulf of Mexico was characterized by delta-plain and delta-platform sedimentation with seismically defined shelf margin progradation only in the Tampa embayment. Jurassic sedimentation culminated with progradation of the Knowles Limestone.

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