Late Eocene-Early Oligocene Paleofloristic Patterns in Southern Mississippi and Alabama, US Gulf Coast

Climate, vegetation and sediment supply are fundamental controls on the palynofloras of depositional sequences. In ancient depositional environments, the diversity and abundance of palynomorphs being transported into, and preserved in the basin of deposition are dependent on these factors as well as burial conditions. Preserved palynomorph assemblages can be used to recognize past floral patterns and climates, and such a model is used here to interpret the Late Eocene Shubuta Member of the Yazoo Formation and Early Oligocene Vicksburg Group in southern Mississippi and southwestern Alabama. Two hundred and sixty spore and pollen taxa have been identified in the strata. Eleven groups representing about 50% of the taxa have been recognized on the basis of abundance, occurrence in most samples and ecological significance. The groups are spores, bisaccate pollen, Sequoiapollenites-Cupressacites, Momipites, Carya, Quercoidites, Fraxinoipollenites, Cupuliferoidaepollenites, Cupuliferoipollenites, Cyrillaceaepollenites, and Siltaria. Statistical analysis on presence-absence data produced five significant cluster groups which were dominated by species of the eleven groups, as well as by Ulmipollenites thompsonianus and Salixipollenites parvus. These cluster groups show some ecological significance because they appear to represent upland, swamp and marsh taxa. The prominence of Quercoidites, Sequoiapollenites, Cupressacites and Cyrillaceiopollenites in the rich palynomorph assemblage, which contains some tropical to subtropical elements, suggests a warm temperate paleoclimate during the Late Paleogene in the eastern Gulf Coast. Although Momipites was generally more abundant in the Eocene and Quercoidites increased during the Oligocene, there was no significant paleofloristic change across the Eocene-Oligocene boundary