Paleocene Sequence Stratigraphy of Southwestern Alabama

Ernest A. Mancini, Berry H. Tew

In southwestern Alabama, the Paleocene consists of about 1,300 ft (396 m) of marginal marine and marine terrigenous and carbonate sediments. Based on regional stratigraphic, sedimentologic, and paleontologic data, up to seven unconformity-bounded depositional sequences resulting from relative changes in coastal onlap during the Paleocene are recognized in these strata. These sequences are, in ascending order, the TP1.1a, comprised of the Pine Barren Member of the Clayton Formation; the TP1.1b, comprised of the "Turritella rock" beds of the Pine Barren and the McBryde Limestone Member of the Clayton Formation, and the clays and marls of the lower member of the Porters Creek Formation; the TP1.2, comprised of the cross-bedded sands of the lower member and the Matthews Landi g Marl Member of the Porters Creek Formation, and Oak Hill Member of the Naheola Formation; the TP1.3, comprised of the Coal Bluff Marl Member of the Naheola Formation; the TP2.1, comprised of the Gravel Creek Sand, "Ostrea thirsae beds, and Grampian Hills Members of the Nanafalia Formation, and the lower beds of the Tuscahoma Sand; the TP2.2, comprised of the Greggs Landing Marl Member and the middle beds of the Tuscahoma Sand; and the TP2.3, comprised of the Bells Landing Marl Member and the upper beds of the Tuscahoma Sand.

Planktonic foraminiferal zonal boundaries recognized for these strata generally correspond to relative rises in sea level and occur at sequence boundaries or transgressive surfaces. Zonal boundaries occurring in this fashion include Subbotina pseudobulloides interval zone (lower Clayton/lower Pine Barren), Subbotina trinidadensis interval zone (middle and upper Clayton/middle and upper Pine Barren, McBryde and lower Porters Creek), Morozovella angulata interval zone (Matthews Landing), Morozovella pusilla pusilla interval zone (Coal Bluff), Planorotalites pseudomenardii range zone (Nanafalia and lower Tuscahoma), and Morozovella velascoensis interval zone (middle and upper Tuscahoma). The zonal boundary for the Morozovella uncinata interval zone (middle and upper Porters Creek clays a d marls), however, corresponds to a relative fall in sea level and occurs in upper condensed section or highstand regressive deposits.

AAPG Search and Discovery Article #91036©1988 GCAGS and SEPM Gulf Coast Section Meeting; New Orleans, Louisiana, 19-21 October 1988.