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Char and polycyclic aromatic hydrocarbons (PAHs), which can serve as proxies for wildfire frequency and/or intensity, are widely present in Permian-Triassic boundary (PTB) strata, providing information on volcanism or on climatic control of fuel availability (linked to vegetation type and density) or combustibility (linked to aridity). Here, we present evidence to separate temporal from geographic signals of climate impact on wildfire during the Permian-Triassic (P-Tr) transition. Geographically, char and pyrolytic PAHs for wildfire are concentrated in temperate and tropical regions and show a connection with forest distribution as reflected by occurrences of Upper Permian coals. Temporally, the subtropical terrestrial Dalongkou section of northwestern China provides evidence of two intervals of increased pyrolytic PAHs of combustion origin. The first interval was linked to climatic hyperwarming during the latest Permian, whereas the second interval was associated with rapid climatic drying, as recorded by spore-to-pollen ratios (S/P), during the P-Tr transition. This record suggests that rapid climate change during the P-Tr transition increased wildfire frequency. A climate link is also shown by turnovers of ostracods, conchostracans, and charophytes in conjunction with greater wildfire frequency. The trigger for enhanced wildfires and biotic changes is inferred to have been volcanically induced climatic warming and aridification. Our data thus document important links between wildfires, climate change, volcanism, and mass extinction during the P-Tr transition. • Pyrolitic PAHs document increased wildfire frequency during the P-Tr transition. • Wildfire distribution strongly correlated to tropical/temperate forested regions. • Two intervals of enhanced wildfire frequency coincided with end-Permian biocrisis. • Increased wildfire linked to volcanically induced climate warming and aridification. • Rapid climate change during end-Permian contributed to increase wildfire frequency. [ABSTRACT FROM AUTHOR]

• First evidence of T-J boundary wildfires outside Central Atlantic Magmatic Province. • Lipid profiles document three wildfire episodes during T-J transition in South China. • PPAH index documents provenance from alkyl-PAHs by pyrolytic (combustion) reactions. • Warmer, drier conditions caused by CAMP set stage for TJB wildfires in South China. • Regional aridification related to southward paleo-ITCZ shift was immediate trigger. Emplacement of the Central Atlantic Magmatic Province (CAMP) during the Triassic-Jurassic (Tr-J) transition is believed to have indirectly increased wildfire frequency through climatic warming and drying. To date, evidence for wildfires has come mainly from within the CAMP region. Here, we present biomarker evidence for wildfires in the form of polycyclic aromatic hydrocarbons (PAHs) in two terrestrial Triassic-Jurassic boundary sections in the Sichuan Basin, southwestern China. Pyrolytic PAHs of probable wildfire origin identified in these sections include pyrene, benzofluoranthene, benzo[e]pyrene, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene, and coronene. Sharp increases in the abundances of pyrolytic PAHs normalized to total organic carbon were found during the Rhaetian Stage (R1 and R2) and at the Tr-J boundary. The ratios of pyrolytic PAHs (PPAHs) to methylated homologues document the combustion origin of PPAHs from methylated PAHs during these intervals of increased wildfire frequency. The abundances of oxygenated PAHs with furan structure show the same stratigraphic trend, testifying to enhanced soil erosion or weathering that may have resulted from a reduction of vegetative cover. Although CAMP-induced climate changes probably set the stage for more frequent wildfires in South China, the immediate trigger was probably a southward shift of the paleo-Intertropical Convergence Zone (ITCZ). These observations suggest a complex feedback involving climatic warming, precipitation and evapo-transpiration, vegetation density, and wildfire prevalence during the Tr-J transition. [ABSTRACT FROM AUTHOR]