Upper Jurassic Sequence Stratigraphy, Onshore to Offshore Alabama, Eastern Gulf of Mexico

Jamal A. Obid
Department of Geological Sciences, University of Alabama, Tuscaloosa, Alabama 35487

The Upper Jurassic-Lower Cretaceous mixed siliciclastic and carbonate section in the northeastern Gulf of Mexico is comprised of the Oxfordian Norphlet and Smackover Formations, the Kimmeridgian Haynesville Formation and the Tithonian to Berriasian/Lower Valanginian Cotton Valley Group. Using selected onshore Alabama, north of the Wiggins Arch, and offshore, south of the Wiggins Arch, well logs and concepts of transgressive-regressive sequences, three transgressive-regressive sequences, J1, J2 and J3, were recognized in the onshore and offshore sections. A fourth transgressive-regressive sequence, LK1, was recognized only in the offshore section, south of the Wiggins Arch.

The transgressive-regressive J1 sequence (Oxfordian-Kimmeridgian) consists of non-marine and shoreface deposits of the Norphlet, subtidal lime mudstones of the lower Smackover, shoal and shoreface grainstones and packstones of the upper Smackover, and sabkha anhydrites of the lower Buckner Anhydrite Member of the Haynesville Formation (i.e. lower Haynesville deposits-offshore). The transgressive-regressive J2 sequence (Kimmeridgian-Tithonian) includes the subaqueous anhydrites of the upper Buckner Anhydrite Member (i.e. lower Haynesville deposits-offshore), lagoonal interbedded shales and anhydrites of the lower Haynesville, shallow marine interbedded shales and limestones of the middle Haynesville, marginal marine interbedded shales and sandstones of the upper Haynesville, and marginal marine and coastal plain sandstone deposits of the lower Cotton Valley. The transgressive-regressive J3 sequence (Tithonian-Berriasian) is comprised of marine shelf shales of the upper Cotton Valley, and nearshore marine and fluvial sands of the upper Cotton Valley. The offshore transgressive-regressive LK1 sequence (Berriasian-Lower Valanginian), is comprised of marine shelf, shoal and reef deposits of the upper Cotton Valley (Knowles Limestone). These transgressive-regressive sequences are useful for regional correlation across the northeastern Gulf of Mexico.

AAPG Search and Discovery Article #90080©2005 GCAGS 55th Annual Convention, New Orleans, Louisiana