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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 CO 2 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. • Evidence for the continuity of volcanic combustion events into the early Triassic. • Frequent combustion events ceased during the 2.7 Myr after the mass extinction. • After the cease of the combustion events, substantial biotic recovery began. • The combustion events might be too frequent for the Early Triassic life to recover. • The combustion events linked to carbon cycle disturbances in the Early Triassic. [ABSTRACT FROM AUTHOR]

The end-Permian mass extinction was the most catastrophic event for life in the Phanerozoic eon because it impacted numerous organisms, from micro-sized photosynthetic organisms to large (meter-long) animals and fundamentally altered marine and terrestrial ecosystems. C 33 n -alkyl cyclohexane (C 33 -ACH), an angstrom-size molecular fossil of phytoplankton, has been widely found in Permian–Triassic (P-Tr) marine sediments, associated with the collapse of the marine ecosystems at the end-Permian mass extinction. Here, we describe multiple C 33 -ACH spikes in the Lower Triassic succession at the Chaohu section of the South China Block, which imply that phytoplankton blooms occurred repeatedly during the early–middle Early Triassic. Comparison with previous studies shows that C 33 -ACH was not only globally enriched at the P-Tr boundary, but also abundant at the Induan–Olenekian boundary and middle Smithian in both the South China and Boreal seas. In addition, the Chaohu section record reveals a C 33 -ACH peak at the Smithian–Spathian boundary. Moreover, the C 33 -ACH spikes were synchronous with the peaks of mercury and the pristane/phytane (Pr/Ph) ratio. Since the peaks in mercury and the Pr/Ph ratio indicate increased volcanic activity and large influxes of terrestrial source material into the ocean, the correspondence between the high abundance of C 33 -ACH with mercury and Pr/Ph ratio peaks implies that volcanism and riverine nutrient input fertilized the surface phytoplankton, which triggered the expansion of anoxia that in turn delayed the benthic metazoan recovery. • Multiple C33-ACH spikes in the Lower Triassic successions of the South China Block. • Multiple C33-ACH spikes imply recurrent phytoplankton blooms. • The C33-ACH spikes are largest at the Smithian–Spathian boundary. • C33-ACH spikes coincide with Hg spikes. • Volcanism is a potential cause of C33-ACH and Hg spikes. [ABSTRACT FROM AUTHOR]