PALYNOLOGY OF THE PALEOCENE-EOCENE BOUNDARY IN THE WILCOX GROUP AT THE RED HOT TRUCK STOP, EASTERN GULF OF MEXICO, USA

Hydrocarbon exploration in the deep-water GoM (Gulf of Mexico) has fuelled increased investment into the potential for palynology to answer fundamental stratigraphic and depositional problems offshore especially since the calcareous nanno- and microfossils are sparse in these plays. Pollen and spore floras are abundant and rich in the Midway, Wilcox and Claiborne groups of the lower Paleocene to middle Eocene. Placement of the Paleocene-Eocene boundary, and recognition of the Paleocene-Eocene Thermal Maximum (PETM) at 56 Ma, has proved problematic though. Onshore, sediments containing the PETM are usually missing on the eastern GoM due to an unconformity at the base of the Ypresian and in Texas it has not been identified yet. We present palynofloral and stable bulk carbon isotope data from onshore eastern US Gulf Coast that represents the PETM and early Eocene of the Tuscahoma and Bashi/Hatchetigbee fms. The 50 palynology and 24 bulk carbon isotope samples taken from outcrop and core (Walmart #1) at The Red Hot Truck Stop in Meridian, Mississippi indicate the inception, body and part of the recovery of the carbon isotope excursion (CIE) that characterizes the PETM global warming event. This corresponds to >7 m of section. Sediments indicate a distinct environmental change in the upper Tuscahoma Formation from brackish, muddy strand lines with emergent swamps to marginal marine glauconitic facies. The sediments immediately above this sea-level rise contain hyper-abundant Apectodinium spp., including morphotypes typical of the PETM, and a negative shift in δ13C of bulk organics of -2-3‰ approximately 1m above the facies change. Pollen is abundant in the body and recovery of the CIE and the first occurrence of Brosipollis sp. (Burseraceae) and Interpollis microsupplingensis are observed in lower parts of the body. Several undescribed pollen morphotypes are unique to the CIE including Retistephanocolporites sp. that is also observed in the Wyoming. True Platycarya appears in the upper body or recovery. Palm-type pollen (Arecipites and Calamuspollenites) is common and significantly more abundant and so are other angiosperm pollen. Palynology is providing new insights into sedimentary packages in the deep-water GoM because many sporomorphs observed onshore are also observed far offshore.