Frequent high-temperature volcanic combustion events delayed biotic recovery after the end-Permian mass extinction

Abstract

The Early Triassic after the end-Permian mass extinction was a time of repeated environmental degradation, which delayed biotic recovery. Although repeated volcanic activity during the Early Triassic has been cited as the cause, the evidence for this hypothesis needs to be confirmed with convincing proxies. This study presents sedimentary molecular evidence for the continuity of volcanic combustion events into the Early Triassic. Geochemical analysis of combustion-derived organic molecules from the uppermost Permian to the Lower Triassic exposed in the Chaohu and Qingyan sections, South China, reveals multiple spikes of a polyaromatic hydrocarbon, coronene, formed by high-temperature organic matter combustion (>1200 K), in the transitions of the Permian–Triassic, Dienerian, Smithian–Spathian, and Olenekian–Anisian boundaries. The frequent high-temperature volcanic combustions ceased 2.7 Myr after the end-Permian mass extinction, and substantial biotic recovery began. The Earth's surface system has mechanisms to buffer high CO2 levels and global warming in the long term, as evidenced in the Cretaceous greenhouse period. Nevertheless, if volcanic activity is overly frequent, the Earth's surface buffering mechanisms cannot keep pace. A simple box model based on excess carbon input revealed by frequent combustion events reproduces the observed carbon isotopic record of carbonate. This model implies that combustion events impacted carbon cycle disturbances and the global climate (e.g., global warming and related environmental destruction). Frequent high-temperature volcanic combustion was a crucial mechanism of delayed biotic recovery during the Early Triassic.