Hydrocarbon compound evidence in marine successions of South China for frequent wildfires during the Permian-Triassic transition

Combustion-derived polycyclic aromatic hydrocarbons (PAHs) are frequently used as molecular proxies for wildfire in recent and ancient sediments. Here, we document the abundances of four hydrocarbon compounds, i. e., phenanthrene (Phe), benzo[e]pyrene (BeP), benzo[ghi]perylene (Bpery), and coronene (Cor), across the Permian?Triassic boundary (PTB) in five marine sections of South China. High values of PAHs are present below the end-Permian mass extinction (EPME) horizon, from the Clarkina changxingensis Zone to the Clarkina yini Zone, suggesting strong perturbations to terrestrial ecosystems predating the marine crisis. PAHs peaked in the uppermost C. yini Zone, correlative with the EPME, reflecting simultaneity of the most severe phases of the terrestrial and marine crises. The proxy records document suitable climatic conditions for wildfires (high pO2) throughout the P-Tr transition. The results of the present study are also significant in validating the utility of BeP, Bpery, Cor, and BeP/Phe as proxies for terrestrial wildfires in deep-time marine successions.

Automated summary

This study documented the abundances of PAHs across the Permian-Triassic boundary in South China, indicating severe perturbations to terrestrial ecosystems before the marine crisis. The peak of PAHs in the EPME period suggests simultaneity of the most severe phases of terrestrial and marine crises. The study also validates the utility of certain hydrocarbon compounds as proxies for terrestrial wildfires in deep-time marine successions.