ABSTRACT

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 ft of interbedded sands and clays. Strandplain sands and shales have a thickness of 225 ft southwest of the up-dip stacked coastal barrier bars. Blocky distributary channel sands are east of the stacked coastal barrier facies and have a thickness of 150 ft in the western Pensacola/Destin Dome Areas. Pilot Sands are reworked deltaic sands that are confined to the northern two tiers of blocks in the Mobile and Pensacola Areas and have a maximum offshore thickness of 40 ft. The Pilot Sands may be traced as far east as Wakulla County, Florida, and to the west into Mississippi State waters.

Foreshelf shales have been encountered in the Viosca Knoll and Main Pass Areas and do not reflect a large sand accumulation past the shelf edge, unlike the 600 ft sand deposits found in southern Louisiana to the northwest. Lower Tuscaloosa clastics are reduced to a 100 ft 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 washitaensis zone and the top of the ostracod Fossocytheridea lenoirensis zone occurring below the lowermost basal fluvial-deltaic sand member.