Taking the pulse of the carbon release during the onset of the Paleocene-Eocene thermal maximum

The Paleocene-Eocene thermal maximum (PETM) (~55 Ma) is a warming event characterized by a negative carbon isotope excursion (CIE) representing a large and rapid injection of carbon into global reservoirs. Debate continues regarding the mechanism, magnitude, and tempo of the carbon released. A few terrestrial and marine sediment records document two distinct δ13C excursions a pre-onset excursion (POE) and CIE interpreted as evidence of multiple carbon injections. We generated geochemical records of ocean carbonate chemistry and temperature using cores drilled by the U.S Geological Survey (USGS) that recovered expanded sections of the PETM onset along the mid-Atlantic coastal plain. Our stable isotope (δ13C and δ18O) planktonic foraminifer records from South Dover Bridge (SDB), Maryland USA exhibit prominent anomalies across the Paleocene-Eocene boundary consistent to proximal coastal sites. δ13C records of mixed-layer (Acarinina spp.) and thermocline (Subbotina spp.) dwelling planktonic foraminifera show two negative carbon excursions that include a 2 ‰ POE and 3-4 ‰ CIE that return to baseline values between events in conjunction with bulk carbonate trends. Remarkably, contemporaneous foraminifer δ18O records exhibit only a minor response during the POE. This could be an artifact of preservation, or at face value, indicative of little to no warming. For the latter, this would require a rapid, but relatively small carbon release. To test the coupled link between atmosphere and surface ocean δ13C records we aim to integrate our geochemical results with model simulations to establish the duration and global extent of multiple carbon releases.