Wildfires and deforestation during the Permian–Triassic transition in the southern Junggar Basin, Northwest China

Despite a continuous increase in fossil charcoal records from Late Palaeozoic deposits, which are used as direct evidence for palaeo-wildfires, detailed studies on the charcoal particles are still rare. To investigate the relationship between wildfire activities and the evolution of the terrestrial ecosystem at the end of the Permian, we report on the charcoal recovered from the classic non-marine Permian–Triassic Dalongkou section in Jimsar, Xinjiang Uygur Autonomous Region, Northwest China. Allochthonous and parautochthonous charcoals, identified by both macroscopic and microscopic morphological techniques, were collected from several stratigraphic horizons. These charcoals were classified into 11 categories (which do not represent the taxonomic group) according to their anatomical characteristics and gross morphology. The reflectance values of the charcoals indicate that surface fires were dominant throughout the sequence, with fire regime changing in a distinct interval. The distribution and abundance of all categories and the reflectance of the charcoals suggest that the intensity of wildfires increased in the upper part of the Guodikeng Formation. This trend coincides with the Hg/TOC peaks and a conspicuous excursion in the organic carbon isotope (δ13Corg) values, which may indicate volcanic activities and the disturbance of the carbon cycle that occurred during the Permian–Triassic transition. It is reasonable to infer that the end-Permian mass extinction (EPME) is located at the intensive wildfire interval. The reduction in spore pollen and the decrease in charcoal reflectance hint at a vegetational impoverishment that occurred after this interval. We proposed that increased wildfires, promoted by dry climate conditions and volcanism, aggravated the collapse of the forest ecosystem during the latest Permian.