ASSESSING THE CHEMOSTRATIGRAPHIC RECORD OF SEDIMENTARY MERCURY CONCENTRATIONS ACROSS THE END-CRETACEOUS MASS EXTINCTION EVENT

One of the most contentious scientific debates today concerns the causal mechanisms of the end-Cretaceous mass extinction. The two plausible explanations of this event relate to the impact of an extraterrestrial body or the emplacement of the Deccan Traps. There is geochemical, sedimentological, and biological evidence supporting each of these possibilities. Recently, it has been suggested that mercury (Hg) concentrations of Upper Cretaceous sediments support mass volcanism as the primary driver of the mass extinction. A global compilation of sedimentary Hg data that span the K/Pg boundary, however, reveal contradictory results. Therefore, increasing the number of locations that have been studied will greatly improve our understanding of Hg cycling across an ancient interval of major environmental and biological disturbances. We will present Hg data from a suite of locations from the New Jersey Coastal Plain as well as a site in Sweden.

The Hg geochemistry of the Fort Monmouth 3, Search Farm, and Meirs Farm drill cores will be analyzed to reconstruct Hg cycling from shallow marine settings on the New Jersey paleoshelf. The Maastrichtian New Egypt Formation sediments are composed of bioturbated, clayey glauconitic sands to glauconite clays, whereas the Danian Hornerstown sediments are composed of clayey glauconitic sands. This will result in a unique opportunity to determine if there is regional heterogeneity with regard to Hg cycling, which is vital to assessing the robustness of this burgeoning paleoproxy. We will also analyze the Hg concentrations of the Limhamn-2018 drill core from the Limhamn quarry in Scania, Sweden. The dominant lithology of the Höllviken Formation is Maastrichtian coccolithophore-rich chalk (Kruseberg Member) that transitions into a coarser-grained, bryozoan-rich limestone during the Danian (Limhamn Member). These new sites represent a unique opportunity to study the Late Cretaceous Hg cycle as lithological variation is minimal across the study interval at each site, which lessens the chance of the reconstructed sedimentary Hg values being controlled by major facies changes or significant changes in depositional environment. The resulting data will be included into a global compilation of Hg data across the K/Pg boundary to better resolve the controls on the Late Cretaceous Hg cycle.