DID THE COLUMBIA RIVER FLOOD BASALTS INITIATE THE MIOCENE CLIMATE OPTIMUM? CONSTRAINING THE TIMING OF LIP VOLCANISM AND CLIMATE CHANGE USING SEDIMENTARY MERCURY CONCENTRATIONS

The extent to which large igneous province volcanism has driven global climate change throughout the Phanerozoic Eon has been debated. Release of CO₂ during the eruption of the Columbia River Flood Basalts (CRFB), the youngest large igneous province (LIP), is hypothesized to have initiated the Miocene Climate Optimum (MCO), a period of global warming 3-4°C above baseline during the Miocene. However, recent high precision geochronology dates the onset of CRFB volcanism as occurring ~100 kyr after the initiation of the MCO, calling into question the extent to which this LIP volcanism triggered global climate change. Mercury concentrations in sedimentary rocks can be used as a proxy for major volcanic events. Volcanic emissions were a major source of Hg in the pre-anthropogenic Hg cycle and this volcanic Hg can be preserved in sedimentary rocks. Here we report new Hg concentration data from stratigraphic sections of the Majella carbonate platform in the central Apennines (Italy) along with stable isotope data (δ¹³C and δ¹⁸O) and biostratigraphy of the MCO. We also compare the record of Hg in shallow and deep sections of the ramp to better understand the paleoenvironmental conditions that affect its preservation. Correlating Hg concentrations to the global record of the Miocene Climate Optimum will improve the chronology of these events leading to a more refined timeline that can be used to test cause and effect relationships between large igneous province volcanism and global climate change.