PALEOENM OF CEPHALOPODS AT THE K/PG BOUNDARY USING BOTH LITHOLOGICAL PROXIES AND GLOBAL CLIMATE MODEL DATA IN THE ATLANTIC AND GULF COASTAL PLAINS

The Cretaceous/Paleogene (K/Pg) boundary extinction is the latest of the big five mass extinctions to have occurred in Earth’s history, leading to the current day biota. Patterns of survivorship and extinction have often been suggested to correlate with geographic range size. Here we investigate changes in abiotic habitat size (a major component of biogeographic range) using a Paleo-ecological Niche Modelling (PaleoENM) framework, which correlates taxon occurrences with the specific environmental factors in which they occur, providing a prediction of suitable abiotic habitat. Using this method, we can indirectly observe changes in suitable habitat area and continuity. Models are trained in the Maastrichtian by using abiotic environmental factors most closely associated with occurrences to determine their suitable habitat area. The predicted suitability spectrum is then projected into the Danian to determine the availability and size of a taxon’s suitable habitat after the extinction interval. Since PaleoENM is still a relatively new technique, it is important to test its application with different forms of available abiotic data used to describe conditions during this important time interval. Abiotic habitat size in the Maastrichtian and Danian was first characterized using sedimentological proxies such as grain size, percent carbonate material, inferred water depth, and degree of bioturbation. Following this, previously compiled Global Climate Model (GCM) data was used to train and project the models using various measures of temperature, humidity and evaporation. Several species of extinct cephalopods belonging to prominent genera of the Atlantic and Gulf Coastal Plains (e.g., Discoscaphites, Eubaculites, Sphenodiscus, Eutrephoceras and Hercoglossa) were modeled to test whether their extinction or survival is associated with notable changes in suitable habitat area using each method. Similarities and differences between the performance and predictions of the two methods were then evaluated to inform future use of these data within the context of PaleoENM, and of the mechanisms contributing to the K/Pg boundary Mass Extinction.