Marine diagenesis of tephra aided the Palaeocene-Eocene Thermal Maximum termination

Abstract

The Palaeocene-Eocene Thermal Maximum (PETM) was a period of intense global warming that began ∼55.9 million years ago and lasted about 170,000 yrs. Various mechanisms have been proposed to cause this warming, including the emplacement of the North Atlantic Igneous Province (NAIP). Equally, many mechanisms have been invoked to explain sequestration of carbon from the ocean-atmosphere system necessary to promote the recovery to more temperate conditions. Here we propose that an important path for carbon sequestration was tied to NAIP volcanism through the precipitation of calcium carbonate (CaCO3) cements within the tephra layers. These cements formed after the deposition and burial of tephra over a wide area of the North Atlantic Ocean during the late Palaeocene and early Eocene. We find strong evidence that authigenic CaCO3 cements formed shortly after tephra deposition. Monte Carlo simulations suggest that this process may have been responsible for a quarter of the carbon sequestered during the PETM recovery phase, providing a major, but previously unconsidered sink of isotopically-light carbon, and one which may have persisted into the Eocene.