THE INFLUENCE OF VOLCANISM AND METEORITE IMPACT ON SILICEOUS MICROFOSSIL COMMUNITIES OVER THE CRETACEOUS-PALEOGENE EXTINCTION EVENT RECORD FROM SEYMOUR ISLAND

The Cretaceous-Paleogene (K-Pg) extinction event is known because of its catastrophic impact on climate and biological diversity. Seymour Island, located on the northeastern tip of the Antarctic Peninsula, includes well-exposed outcrops of Maastrichtian to Danian marine strata that contain rich and diverse fossils that record details of the K-Pg event. The initial siliceous microfossil characterization at this site marked it as an important area to understand siliceous microfossils' extinction, recovery, and evolutionary response during this dynamic period in Earth's history. Recent observations highlight the potential influence of Deccan volcanism on the siliceous microfossil record, in addition to the environmental calamity due to the meteorite impact. Marine diatoms in these sections provide a history of nutrient availability and paleoenvironmental changes that are useful to understand the response of polar oceans during this significant event. To increase the stratigraphic resolution to better resolve the response of siliceous communities to these events, material from the Polar Rock Repository (OSU) and Burke Museum (UW) were analyzed.

This study reports on siliceous microfossil assemblage change across a 400m stratigraphic interval from 120m below the K-Pg Boundary (KPB) to 270m above the KPB. This work documents: 1) initial baseline of siliceous microfossil community dynamics pre-Deccan influence; 2) the response of marine diatom and silicoflagellate communities across these events; and 3) the post-K-Pg recovery. Vegetative cells dominate the fossil diatom community in the interval 120 to 70m below the KPB. After this stable period, there is an increase in diatom resting spore abundance at the inferred end of a pulse of Deccan volcanism about 40m below the KPB. Diatom abundance is low following this event, suggesting a change in nutrient source, with preservation and abundance returning one meter below the KPB. Resting spores dominate sediments above the KPB and increase to about 50% of the assemblage at the transition to the Sobral Formation. This coincides with the presence of a unique silicoflagellate assemblage, suggesting another environmental perturbation. Future taxonomic and cell volume studies are planned to differentiate the relative influence of Deccan volcanism and the impact event on marine siliceous microfossils in the Polar Regions.