Postdoctor SHEN Wenjie and his teacher LIN Yangting study polynuclear aromatic hydrocarbons (PAHs) and black carbon (BC) in sediments at the Meishan section to determine whether wildfire activity occurred at the Permian-Triassic (P/Tr) boundary.

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. Their results show that wildfires could have played an important role in the collapse of the ecosystem in the Meishan P/Tr events.

Shen et al. Evidence for wildfire in the Meishan section and implications for Permian-Triassic events. Geochimica et Cosmochimica Acta. 2011，75: 1992-2006 (Download Here)

Fig. 1 Stratigraphic variation across the P/T boundary at Meishan section for selected combustion-derived PAH concentrations. (Image by SHEN)

Fig.2. BSE images of Black carbon fragments from event beds in the P/T boundary section in Meishan. (Image by SHEN)

Fig. 3. High resolution profile across the mass extinction horizon in the Meishan P/Tr section. (Image by SHEN)