MERCURY CONCENTRATIONS AND MERCURY STABLE ISOTOPE VARIATIONS AT THE PETM: VOLCANIC LOADING SIGNAL OF THE NORTH ATLANTIC IGNEOUS PROVINCE?

The Paleocene-Eocene Thermal Maximum (PETM) represents one of the most abrupt (~2 kyr onset; < 220 kyr duration), large-magnitude (~5 to 8 °C; global average) warming events of the Cenozoic. Associated with the PETM are extensive benthic marine extinctions, with significant ramifications for terrestrial biomes globally. A proposed mechanism for the initiation of the PETM is climate forcing from volcanogenic volatile emissions (principally CO₂) produced by North Atlantic Igneous Province (NAIP) flood basalts, and a subsequent positive feedback response involving destabilization of shallow seafloor clathrates (gas hydrates, principally CH₄). Here, we present a record of total Hg [THg] concentrations of ocean sediments from three localities ranging from the Arctic Ocean to the South Atlantic. We observe a record of elevated [THg] coincident with well-documented carbon isotope (δ¹³C) excursions in the same marine sediment cores at Walvis Ridge (South Atlantic), Bass River (New Jersey), and Svalbard (Norway), where measured maximum [THg] at each site ranged from 0 to 16.2, 12.6 to 31.5, and 5.2 to 91 ng/g, respectively. Elevated [THg] at each of these localities may be the result of increased volcanogenic Hg emissions from the NAIP. Volcanic emissions of gaseous elemental mercury (Hg⁰), thought to be the largest time-averaged source of Hg to the atmosphere, represent a small fraction of total volatiles released from eruptions of the NAIP, and would occur in conjunction with CO₂ and other gases responsible for climate forcing. We also document a large magnitude (≥ 3‰) δ²⁰²Hg excursion across the PETM at Walvis Ridge, coincident with peak [THg] values. Further investigation of stable Hg isotopic variations at each site is ongoing, and will help further constrain the mechanism(s) behind rapid PETM warming.