ABSTRACT

In southwestern Alabama, the Paleocene consists of about 1,300 ft of marginal marine and marine terrigenous and carbonate sediments. Based on regional stratigraphic, sedimentologic, and paleontologic data, eight 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 (Pine Barren Member of the Clayton Formation), the TP1.1b ("Turritella rock" beds of the Pine Barren Member and McBryde Limestone Member of the Clayton Formation and calcareous clays and limestones of the lower member of the Porters Creek Formation), the TP1.1c (marls and clays of the lower member of the Porters Creek Formation), the TP1.2 (cross-bedded sands of the lower member and Matthews Landing Marl Member of the Porters Creek Formation and Oak Hill Member of the Naheola Formation), the TP1.3 (Coal Bluff Marl Member of the Naheola Formation), the TP2.1 (Gravel Creek Sand, "Ostrea thirsae beds" and Grampian Hills Members of the Nanafalia Formation and lower beds of the Tuscahoma Sand), the TP2.2 (Greggs Landing Marl Member and middle beds of the Tuscahoma Sand), and the TP2.3 (Bells Landing Marl Member and upper beds of the Tuscahoma Sand).

Planktonic foraminiferal zone boundaries recognized for these strata correspond to relative rises in sea level and usually occur at sequence boundaries or transgressive surfaces. Zonal boundaries occurring in this fashion include Subbotina pseudobulloides Interval Zone, Morozovella uncimata Interval Zone, Morozovella angulata Interval Zone, Planorotalites pusilla pusilla Interval Zone, Planorotalites pseudomenardii Range Zone, and Morozovella velascoensis Interval Zone. The zonal boundary for the Subbotina trinidadensis Interval Zone also corresponds to a relative rise in sea level and occurs in transgressive or condensed section deposits.