Massive wildfires followed oceanic anoxic events during the Late Devonian Frasnian-Famennian mass extinction.

Abstract

Extensive wildfire profoundly influences Earth system feedback and can drive major ecosystem disturbances, yet its timing and role in the Late Devonian Frasnian-Famennian (F-F) mass extinction remain unclear. To determine whether wildfires were a driver or consequence of contemporaneous oceanic anoxic events (OAEs), we present a high temporal resolution multiproxy record (biomarkers, microfossils, and trace metals) from the Chattanooga Shale in the southeastern United States. Pyrogenic PAHs and inertinite macerals increased after peaks in δ¹³C_org and redox-sensitive proxies, indicating that wildfire activity intensified in response to post-OAEs oxygen rise rather than triggering anoxia. Modeling of global δ¹³C records reveals that the lag between OAEs/organic carbon burial and wildfire onset reflects the time required for atmospheric oxygen to accumulate to levels sustaining widespread combustion. Together, these results provide the first high-resolution dataset capable of resolving the temporal sequence between OAEs and wildfire activity, enabling the establishment of their causal linkage during the catastrophic F-F environmental disruptions.