DIVERSITY AND PALEOECOLOGY OF GULF COASTAL PLAIN FORAMINIFERA PRIOR TO THE END-CRETACEOUS MASS EXTINCTION

We investigated spatiotemporal change in foraminiferal community composition leading up to the end-Cretaceous mass extinction event in the Gulf Coastal Plain (GCP) of North America. Maastrichtian outcrops were sampled at regular intervals in a west to east transect from Starkville, MS to Braggs, AL. Along this transect, paleoenvironments changed from limestone-dominated rocks to poorly indurated quartz-rich sediments. Forams extracted from below the K/Pg boundary indicate homogeneous late-Maastrichtian deposition with no mixing of late-Maastrichtian and basal Danian taxa. This result supports the reliability of uppermost Maastrichtian deposits for analyzing patterns of diversity and paleoecological change. Shannon-Wiener diversity indices (H(S)), species richness, P/P+B percentages, and infaunal/epifaunal percentages were calculated and used to compare Maastrichtian foram communities across sites.

Preliminary results indicate that water depth was greatest in the middle of the transect and organic flux generally increased from west to east. However, foram species richness and diversity indices were very similar across the changing environments. Further, these data inform how Upper Maastrichtian foraminiferal community paleoecology changes spatiotemporally with environmental change. This study supports the high fidelity of the foram record for paleoenvironmental reconstructions in the GCP leading into the end-Cretaceous mass extinction event. Understanding organismal responses to long term environmental changes are essential for understanding the trajectory of our current Earth system’s ecological response to global climate change and rising sea level.