Astronomically tuned age model for the early Eocene carbon isotope events: A new high-resolution δ13Cbenthic record of ODP Site 1263 between ~ 49 and ~ 54 Ma

Abstract

The early Eocene represents a time of major changes in the global carbon cycle and fluctuations in global temperatures on both short-and long-time scales. These perturbations of the ocean-atmosphere system have been linked to orbital forcing and changes in net organic carbon burial, but accurate age models are required to disentangle the various forcing mechanisms and assess causal relationships. Discrepancies between the employed astrochronological and radioisotopic dating techniques prevent the construction of a robust time frame between ~ 49 and ~ 54 Ma. Here we present an astronomically tuned age model for this critical time period based on a new high-resolution benthic δ13C record of ODP Site 1263, SE Atlantic. First, we assess three possible tuning options to the stable long-eccentricity cycle (405-kyr), starting from Eocene Thermal Maximum 2 (ETM2, ~ 54 Ma). Next we compare our record to the existing bulk carbonate δ13C record from the equatorial Atlantic (Demerara Rise, ODP Site 1258) to evaluate our three initial age models and compare them with alternative age models previously established for this site. Finally, we refine our preferred age model by expanding our tuning to the 100-kyr eccentricity cycle of the La2010d solution. This solution appears to accurately reflect the long-and short-term eccentricity-related patterns in our benthic δ13C record of ODP Site 1263 back to at least 52 Ma and possibly to 54 Ma. Our time scale not only aims to provide a new detailed age model for this period, but it may also serve to enhance our understanding of the response of the climate system to orbital forcing during this super greenhouse period as well as trends in its background state.