Pulsed volcanism and rapid oceanic deoxygenation during Oceanic Anoxic Event 1a

Abstract Widespread oceanic anoxia, biological crises, and volcanic activity are associated with the onset of Early Aptian (ca. 120 Ma) Oceanic Anoxic Event 1a (OAE1a). Reconstructions deoxygenation its links to broadly contemporaneous volcanism, however, remain poorly resolved. We use geochemical data, including δ53Cr ratios rare Earth element abundances, define timing tempo submarine volcanism global across this event. Pacific Ocean sediments deposited in run up OAE1a record multiple phases marine emplacement Ontong Java Plateau lavas. Rapid followed initial a biocalcification crisis. Large swaths oceans likely became anoxic from Tethys Oceans <30 k.y. anoxia persisted for almost one million years after was sustained through intensified continental weathering. These results paint new picture which crisis, separated time linked system responses that operate on scales tens thousands years.