Ｗｉｌｄｆｉｒｅｓ ｒｅｃｏｒｄｅｄ ｉｎ Ｍｉｄｄｌｅ Ｊｕｒａｓｓｉｃ ｃｏａｌｓ ｉｎ Ｅａｓｔｅｒｎ ｏｆ Ｊｕｎｇｇａｒ Ｂａｓｉｎ ｉｎ Ｘｉｎｊｉａｎｇ， Ｃｈｉｎａ

The argument that the inert group in coal is the product of incomplete combustion of plants has been accepted by more and more scholars, and its significance of indicating ancient wildfires has become more prominent. In this paper, the content characteristics of 16 kinds of polycyclic aromatic hydrocarbons in coal and rock samples were obtained through the information of inertinite content and reflectivity of coal seam samples of Middle Jurassic Xishanyao Formation in the eastern Junggar Basin, and the content characteristics of 16 kinds of polycyclic aromatic hydrocarbons in coal samples were comprehensively analyzed. Ancient wildfires experienced during the deposition of coal formations. The experimental results show that content of inertinite ranges from 31.14% to 82.64%, with an average of 55.78%, and the average reflectivity is from 1.08% to 1.54%. The high content of inertinite is the main characteristic of this coal of Xishanyao Formation. The experimental results of PAHs show that the variation range of PAHs between different layers is relatively large, ranging from 3 881 to 6 525 ng/g, with an average value of 4 433 ng/g, and the content of different types of PAHs in the same layer varies greatly. A comprehensive analysis of the characteristics of inertinite content, inertinite reflectivity and PAHs content shows that the coal seam has experienced at least three periods of frequent wildfires during the deposition. The temperature interpretation based on the charcoal reflectivity showed that the types of wildfires in these three periods were all ground fires of medium and low temperature. At the same time, from the perspective of global carbon cycle, theoretical analysis and speculation are made on the possible climate and environment impact caused by wildfires. The accumulation of peat has a net cooling effect on global climate, but the occurrence of wildfires can weaken this effect to a limited extent and release a large amount of carbon into the atmosphere. In this study, the wildfire events in Junggar Basin were identified and analyzed for the first time by combining the PAHs, which will provide some reference for the future research on coal geology in this area.