Change of the locus of organic carbon burial in the aftermath of the Toarcian hyperthermal event: Patterns and drivers

Carbon cycle-climate dynamics were nonlinear through Earth’s history, driven by changes in internal and external forcing processes acting on various geological timescales. This study focuses on determining the relationship between volcanism, orbital parameters, and organic carbon burial during the Aalenian (Middle Jurassic) - a pivotal time at the dawn of the Mesozoic Marine Revolution, marked by a disruption of the carbon cycle and major climate shifts. Here, new high-resolution magnetic susceptibility and trace elements data are combined with previously published organic carbon isotopes and total organic carbon data from two sites in France and Chile. Our dataset shows for the first time a temporal coincidence between the major carbon cycle perturbation during the middle–late Aalenian and the onset of enhanced volcanic activity, suggesting a causality link. We propose that volcanic activity triggered a transient warming episode within the long-term Middle Jurassic coldhouse and played a key role in shifting organic carbon burial from the ocean to terrestrial settings. This period therefore contrasts with other Mesozoic carbon cycle perturbations, which generally record enhanced marine organic matter burial in oxygen-depleted environments during volcanism-triggered warming events.