Polycyclic aromatic hydrocarbons (PAHs) evidence for frequent combustion events on land during the Permian–Triassic transition in Northwest China

Abstract

The Siberian Traps large igneous province and intensive continental arc volcanism are regarded as the primary drivers of the severe environmental changes that triggered the end-Permian mass extinction. However, detailed correlations between volcanism and the collapse of terrestrial ecosystems remain ambiguous. This study used polycyclic aromatic hydrocarbons (PAHs) records and mercury spikes from the terrestrial Dalongkou section as refined proxies for volcanic combustion events. The mercury anomalies, PAH concentrations, and PAH ratios provide insight into the terrestrial ecosystem collapse during the Permian–Triassic (P–T) transition. Based on the multiple PAH ratios, the source and composition of PAHs exhibit obvious pyrolytic-derived origins during the late Permian. Combined with the biostratigraphic records and our PAH proxies in the Dalongkou section, terrestrial ecosystems experienced stepwise crisis and change owing to volcanic effects and frequent high-temperature combustion events during the P–T transition. During the main terrestrial P–T crisis interval, the increased PAH concentrations indicate that the combustion events were gradually enhanced under worse climatic conditions. Based on the PAH records, enhanced soil erosion accompanied by frequent wildfires was found to occur under extremely high-temperature climatic conditions caused by intensive volcanic activity during the P–T transition.