A fresh perspective on extensively researched inquiries sheds new light on the environmental influences behind the end-Cretaceous mass extinction.
This perspective implies that volcanic activities and consequential biological shifts exerted pressure on the global carbon cycle during the Cretaceous/Paleogene (K/Pg) boundary. Beyond unveiling insights into extinction catalysts, this approach holds promise for unraveling intricate perturbations within the Earth system and their corresponding impacts on climate and biology.
Roughly 66 million years ago, the end-Cretaceous mass extinction obliterated all major tetrapods and non-avian dinosaurs. This event was characterized by two significant disturbances on a planetary scale: the Chicxulub asteroid impact and the ongoing eruption of the Deccan Trap flood basalts. Both occurrences likely led to substantial releases of climate-active substances like carbon dioxide (CO2) and sulfur dioxide (SO2) into the atmosphere. These emissions have been suggested as contributing factors in extinction models. However, while the timing of these events in relation to the K/Pg boundary is well-documented, disentangling their individual roles in extinction causes, especially regarding their impacts on the global climate system, remains challenging.
In a bid to comprehend the extinction mechanism and the environmental pressures driving it, Alexander Cox and C. Brenhin Keller merged outputs from the widely used Long-term Ocean-atmospheric-Sediment Carbon cycle Reservoir (LOSCAR) model with an innovative parallel Markov Chain Monte Carlo (MCMC) inversion scheme. This fusion aimed to predict CO2 and SO2 emissions, alterations in carbon export productivity, and changes in remineralization across the K/Pg boundary, independent of the geological incidents that occurred.
As per Cox and Keller, the model’s outcomes align closely with physical proxy records. They reveal disconnected emissions of CO2 and SO2, along with indications of a two-stage decline in carbon export productivity, suggesting a two-stage extinction propelled by volcanic emissions. Furthermore, the authors detect no distinct indication of a sudden release of volatiles at the K/Pg boundary. This observation suggests that the Chicxulub impact might not have exerted a lasting influence on the long-term carbon cycle.
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