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ABSTRACT: Lower Tuscaloosa Clastic Facies Distribution (Upper Cretaceous), Federal and State Waters, Eastern Gulf of Mexico


Lower Tuscaloosa sands were deposited in meander belts, shoreline strandplains, stacked coastal barrier bars, distributary channels, and as reworked deltaic sands in offshore Federal and adjacent State waters of Mississippi, Alabama, and Florida. Stacked coastal barrier bars are found in the Mobile Area with a thickness of 250 feet of interbedded sands and clays. Strandplain sands and shales have a thickness of 225 feet southwest of the updip stacked coastal barrier bars. Blocky distributary channel sands occur east of the stacked coastal barrier facies and have a thickness of 150 feet in the Pensacola/Destin Dome Areas. "Pilot Sands" are reworked deltaic sands that are confined to the northern two tiers of lease blocks in the Mobile Area and have a maximum offshore thickness of 40 feet; the sands are traced to the east as far as Wakulla County, Florida, and to the west into Mississippi state waters.

Shelf and foreshelf shales are found in the Viosca Knoll and Main Pass Areas and do not reflect a large sand accumulation past the shelf edge, unlike the 600-foot sand deposits found in southern Louisiana to the northwest. Lower Tuscaloosa sands are reduced to a 100-foot section in the Destin Dome Area due to a growing Destin Anticline that restricted sand deposition.

Basal Tuscaloosa has been defined lithologically, but paleontologically the Lower Cretaceous boundary is placed at the top of the foraminifer Lenticulina washitensis zone and the highest occurrence of the ostracod Fossocytheridea lenoirensis, found below the basal fluvial sand on the overlying massive sand member.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana