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ABSTRACT: Evolution of the Apalachicola Basin (Northeastern Gulf of Mexico) During the Jurassic

Laura Martin Dobson, Richard T. Buffler

A grid of multichannel seismic correlated with well data defines four Jurassic seismic sequences in the Apalachicola basin of the northeastern Gulf of Mexico. These sequences, which developed in response to basin architecture, sea level fluctuations, sediment supply, and salt movement, document the depositional history of the basin during the Jurassic.

Evaporation of water entering the basin resulted in deposition of the (Callovian?) Louann Salt sequence. The Louann generally lacks internal reflections, except updip where discontinuous parallel-divergent reflections probably represent interbedding of salt with clastics around the basin margin. The updip limit of thick salt coincides with a basement hinge line.

The second sequence contains rocks of the Norphlet and Smackover formations. Norphlet clastics were deposited during a sea level rise. As the transgression continued, Oxfordian Smackover carbonates were deposited, and upward shoaling occurred as sea level reached a stillstand. Smackover carbonates prograded over a shallow shelf, and buildups occurred over salt structures, basement highs, and basement hinge lines. The sequence thickens locally into growth faults associated with salt movement.

During deposition of the Kimmeridgian Haynesville sequence, clastics entered the basin updip and carbonate deposition continued downdip. Growth faulting continued, and a prominent shelf margin was established.

Coarse fluvial and deltaic sediments of the Tithonian-earliest Berriasian Cotton Valley group comprise the final sequence. The Knowles Limestone records a transgression toward the end of the sequence. Progradation of the Knowles and establishment of a prominent shelf margin set the foundation for development of the overlying Lower Cretaceous margin.

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