Molecular and isotopic evidence for episodic environmental change across the Permo/Triassic boundary at Meishan in South China

Lipid biomarker abundances and δ13C values were determined across the Permian–Triassic (P–Tr) boundary at Meishan of southern China. The δ13C values of n-alkanes showed large ( 9‰) fluctuations, which suggest major episodic changes in oceanographic conditions during faunal mass extinctions. Environment-related biomarker ratios, including pristane to phytane ratios (Pr/Ph), gammacerane to C31 homohopane ratios (γ/C31HP) and C27 18α(H)-22,29,30-trinorneohopane to C27 17α(H)-22,29,30-trinorhopane ratios (Ts/Tm), vary extensively throughout the section, with values typically associated with anoxic conditions coinciding with maximum δ13C values. In particular, both faunal mass extinction horizons (beds 25 and 28) are characterised by biomarker ratios consistent with anoxic conditions and elevated n-alkane δ13C values. The records of environment-related biomarkers and n-alkane δ13C values clearly signify multiple environmental perturbations in association with faunal mass extinctions.