Orbitally paced global oceanic deoxygenation decoupled from volcanic CO2 emission during the middle Cretaceous Oceanic Anoxic Event 1b (Aptian-Albian transition)

Abstract

Abstract The ongoing oceanic oxygen loss will have a profound impact on the distribution and density of life on Earth. However, drivers of the initiation and termination of global oceanic deoxygenation are poorly understood. Here we present a thallium isotope record that reveals three rapid (50 k.y.) global deoxygenation intervals during the mid-Cretaceous that postdate massive volcanism by at least 1 m.y. New strontium isotope data reveal gradually enhanced continental weathering under a warmer climate following volcanism. However, global deoxygenation occurred only under the combined influences of a long-term increase in weathering rates in a warmer climate and short-term orbital modulation that led to atmospheric-circulation reorganization. Interactions of multiple drivers are consistent with the abrupt termination of each deoxygenation interval. Dynamic oxygenation responses in the mid-Cretaceous highlight the role of these processes for understanding the consequences and potential termination of the current oceanic deoxygenation.