Wildfire During The Permian-Triassic Transition In Xinjiang And South China

Recent years,the evidences of wildfire such as charcoal,inertinite and PAHs have been reported in the Permian sediments all over the world.In order to investigate the impact of wildfire activities during the Permian-Triassic(P-T)transition,this paper conducted a quantitative and systematic study of charcoal from two sections in Xinjiang and South China,hoping for providing enlightenment about the relationship between the palaeo-wildfires and the collapse of terrestrial ecosystem during this critical transition.From Dalongkou section in Xinjiang,more than 13 charcoal horizons have been discovered.The abundance and reflectance of charcoals indicate that the temperature and frequency of wildfire reduced during the P-T transition.An abrupt change appeared as the most abundant charcoals and the lowest reflectance in the level of-9m,with a lacking-charcoal stage followed.The drastic fluctuating of?13Corg accorded with this abnormal segment.Besides,the charcoal types based on the anatomical structures,as well as the cuticle study,suggest that the composition of plant has altered before and after the P-T transition.There were multiple wildfire segments in Lengqinggou section in Guizhou province.Most of them are observed in the Xuanwei Formation,with one in the lower part of the Kayitou Formation.Almost all layers show the high diversity of charcoals except the last coal seam in the P-T transition,which consists of nearly a single type of charcoal.The arresting excursion of ?13Corg coincides with it.After this coal bed,the mean reflectance of charcoals reduced from 2.379%to 1.509%,indicating the change of wildfire type.Meanwhile,the proportion of different types of charcoals also exhibits the vegetation transformation from the Xuanwei Formation to the Kayitou Formation.The wildfire events during the P-T transition in Xinjiang and South China were similar.In the beginning of this transition,intensitive wildfires were frequent;then there was a stage that the wildfire showed less active;but following that,an abrupt wildfire event appeared,burying large amount of charcoals in a short time,with wildfire absent subsequent;finally,fire recovered.This pattern probably reflects that terrestrial ecosystem declines under the impact of the drought climate and frequent wildfire activities in the Late Permian.In return,the recession of vegetation limited the wildfire.Then a global event happened abruptly,leading to climate deterioration and the explosion of the wildfires,which further resulted in the collapse of terrestrial ecosystem.In the following stage,wildfire absent for the lack of burning material until vegetation recovered partially in some areas.The similarity of wildfire evolution in Xinjiang and South China suggests that palaeo-wildfire events may have a vital on the terrestrial ecosystem globally.There was a direct relationship between the wildfires and the recession,even the collapse of the terrestrial ecosystem at the end of the Permian.