THE PETM IN THE COASTAL OCEAN: LINKING TERRESTRIAL DESTABILIZATION AND COASTAL PRODUCTIVITY IN MID-ATLANTIC SEDIMENTS

Climate events in the geologic record reveal the broad array of Earth’s responses to carbon cycle perturbations, and provide valuable insights to the predicted impacts of future anthropogenic climate change. The Paleocene-Eocene Thermal Maximum (PETM) hyperthermal serves as the best-known analogue for anthropogenic climate change. The injection of ~4500 Gt CO₂ over < 20,000 years of ¹³C-depleted carbon into Earth’s ocean-atmosphere system resulted in a global carbon isotope excursion of 3-5‰, and an abrupt global warming of 5-9 ^oC. Associated changes in ocean redox chemistry, productivity, sediment accumulation, and organic matter sources are implicated by off-shore ocean geochemical records. Numerous studies of biomarkers and organic matter in terrestrial archives reveal upheavals in carbon cycling, hydrology, and weathering across continental landscapes. Currently, we lack organic records from truly coastal environments. This leaves a critical gap in our understanding of carbon dynamics at the land-ocean interface and of how terrestrial and marine biogeochemical cycles were linked globally.

We investigated changes in organic matter provenance, productivity, and redox using recently collected cores from the paleo-Atlantic shelf. These new coastal PETM records provide needed datasets to understand biogeochemical changes in shallow marine environments and the sources of carbon that contribute to these records. Here, we present lipid biomarkers (pristane, phytane, n-alkanes, hopanoids, steranes) and bulk organic carbon isotope data along a transect from proximal pro-delta to more distal inner shelf. Molecular records of the PETM help detail the intensity of enhanced productivity and shifting terrestrial and marine inputs. Biomarker constraints on the marine carbon isotope excursion, organic matter sources, and water column chemistry along the shallow shelf reveal abrupt and more protracted changes in the coastal marine carbon cycle that were linked to intensified terrestrial weathering and landscape destabilization during the PETM.