Constraining the paleoclimate and paleoecology of the Selandian – Thanetian transition in the Lower Wilcox, Texas Gulf Coast

Nikhil Sharma , Vann Smith, Lorena Moscardelli, Thierry Adatte, Lucas Vimpere, Iulia Olariu, William Ambrose, David Bord, Victor Giraldo-Gómez, Maria A. Lorente, Brahimsamba Bomou, Laszlo Kocsis

The Selandian–Thanetian Transition Event (STTE) represents a relatively understudied interval of carbon cycle instability and environmental disruption during the Paleocene. This study presents a comprehensive sedimentological, palynological, and geochemical record of the STTE based on two shallow marine wells (Moczygemba VT #11 and Vogelsang Frieda #1) from the Texas Gulf Coast. Our multi-proxy approach integrates palynology and nannofossil biostratigraphy to establish age constraints and track ecological changes, organic carbon isotopes to detect regional preservation of the STTE, and use elemental ratios to infer chemical weathering intensity and mean annual precipitation. Results indicate that the STTE along the Gulf Coast was characterized by elevated weathering rates under semi-arid to humid climatic conditions. Palynological assemblages show a marked increase in Thomsonipollis magnificus, suggesting the expansion of mangrove or coastal swamp taxa during inferred warming phases. Notably, negative excursions in organic carbon isotopes, along with increased terrestrial input of organic matter in both cores, confirm the regional expression and impact of the STTE. These findings provide critical constraints on the Selandian–Thanetian Transition Event by linking carbon cycle perturbations to continental-scale source-to-sink responses across North America, and demonstrate how deltaic systems along the Gulf Coast recorded and responded to mid-Paleocene global warming.