RAPID GLOBAL OCEANIC (DE)OXYGENATION DURING OCEANIC ANOXIC EVENT 1B REVEAL INTERACTIONS OF VOLCANISM, WEATHERING, AND ORBITAL FORCING

Drivers of the initiation and termination global oceanic deoxygenation are poorly understood. Here we present a thallium isotope record that reveals global deoxygenation during the Cretaceous Oceanic Anoxic Event (OAE) 1b. This record reveals three successive rapid global deoxygenation intervals within OAE 1b that are not directly associated with previously identified large igneous province activities. Rather, new strontium isotope data reveal that gradually enhanced continental weathering following volcanism led up to the three deoxygenation intervals. However, global deoxygenation was only achieved via atmospheric circulation reorganization associated with orbital forcing that pushed the climate system beyond regional organic carbon burial. The combined influences of long-term weathering under climate control and short-term orbital modulation are consistent with the abrupt termination of each OAE 1b deoxygenation interval. These dynamic oceanic oxygenation responses in the OAE 1b thus highlight the role of these processes for understanding the consequences and potential termination of the currently observed oceanic deoxygenation.