Oceanic Anoxic Event 2 triggered by Kerguelen Plateau volcanism

Abstract

AbstractLarge Igneous Province (LIP) volcanism is thought to have been the main cause of global warming, ocean anoxia and carbon cycle perturbations associated with Cretaceous Oceanic Anoxic Event 2 (OAE2, ~94 Ma). However, there is still no consensus on the timing and role volcanism played in triggering carbon cycle changes, or the source of the volcanism that has been previously ascribed to either the Caribbean LIP or High Arctic LIP. Here, we refine the stratigraphic position of OAE2 and the Mid-Cenomanian Event (MCE, ~96.5 Ma) at two sites in the Mentelle Basin (offshore southwestern Australia), and use sedimentary mercury (Hg) abundance to determine the timing of volcanism. Contrary to many Northern Hemisphere records, we report elevated levels of Hg and Hg/total organic carbon (TOC), suggesting OAE2 was initiated by a volcanic source proximal to the Mentelle Basin, such as the Kerguelen LIP. Distinct Hg/TOC pulses preceding the onset of OAE2, and in conjunction with its main phase, suggest volcanic emissions played a central role in triggering and controlling climatic and carbon cycle changes within OAE2. By contrast, we find little evidence to suggest a Southern Hemisphere volcanic episode initiated the MCE. Benthic foraminiferal assemblages and bulk sediment isotopes indicate volcanism caused elevated productivity and probable upwelling in the Southern Hemisphere Mentelle Basin for the duration of OAE2, similar to Northern Hemisphere records.