Evidence for wildfire in the Meishan section and implications for Permian–Triassic events

Polynuclear aromatic hydrocarbons (PAHs) and black carbon (BC) in sediments are powerful tools in the identification of the combustion process throughout geologic history. In this study, combustion-derived PAHs and BC were carefully investigated in sediments from the Global Stratotype Section and Point of the Permian–Triassic (P/Tr) boundary in Meishan, China. Quantitative analyses of combustion-derived PAHs and BC demonstrate anomalously high concentrations in the boundary event beds that coincide with the mass extinction horizon. The prevalence of parent polynuclear aromatics (e.g., phenanthrene) in PAHs, together with non-metric multidimensional scaling analysis, confirms that the PAHs are mainly derived from vegetation burning instead of having a coal and/or oil origin. BC detected in sediment occurs in various forms from large irregular charcoal particles to fine aciniform soot, with an equivalent reflectance of up to 3.5%. The results strongly suggest that a wildfire occurred during the P/Tr boundary, which served as one of the possible triggers of mass extinction on land. The wildfire occurrence indicates that the O2 concentration of the atmosphere during (or before) the P/Tr mass extinction was probably >17%. The temporal coincidence of the mass extinction with intensive volcanic eruption, marine anoxia and wildfire events in the region of the Meishan section provides new insight into the mechanisms of the P/Tr biotic crisis. Our results show that wildfires could have played an important role in the collapse of the ecosystem in the Meishan P/Tr events.