SEDIMENTARY MERCURY CONCENTRATIONS AND ISOTOPES ACROSS THE END-CRETACEOUS MASS EXTINCTION EVENT FROM NEW JERSEY

Today, a debate exists concerning the causal mechanism(s) of the end-Cretaceous mass extinction. Two possible scenarios are supported through geochemical, sedimentological, and biological evidence, which relate to the impact of an extraterrestrial body or the emplacement of the Deccan Traps, a massive volcanic province. Mercury (Hg) chemostratigraphy, both concentrations and isotopes, of Upper Cretaceous sediments have been used to support massive volcanism as the primary driver of the mass extinction. The global compilation of sedimentary Hg data that span the K/Pg boundary, however, suggest that the Hg cycle was more complex than is generally appreciated. Although sedimentary Hg anomalies have been traditionally interpreted as the result of enhanced volcanism, there are several alternate pathways that can accumulate Hg in sediments. To better deconstruct possible controls on Hg cycling across the K/Pg boundary, we have paired Hg concentrations with Hg isotopes from the New Jersey Coastal Plain.

The Hg geochemistry of the Fort Monmouth 3, Search Farm, and Meirs Farm drill cores was 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. Sedimentary Hg concentrations are slightly more elevated in the New Egypt Formation (~0.01 – 0.03 mg/kg) than the Hornerstown Formation (~0 – 0.01 mg/kg). Mercury isotopes will be generated to attempt to determine the source(s) and mode of deposition of Hg to each study site. If the Deccan Traps emplacement was the cause of K/Pg sedimentary Hg enrichments, then this may be manifested in the Hg isotopic composition of the sediments from each site. This research sheds light upon the impact of local Hg cycling on what is preserved in the sedimentary Hg record and its utility as a proxy to reconstruct the global Hg cycle.