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<p>Wildfires are important disturbances in many of the Earth’s ecosystems and are of great significance for understanding the interactions among environmental, atmospheric and vegetational changes in deep time. The Jurassic palaeoclimates were constantly changing, experiencing diverse climate states. Studying Jurassic palaeoclimates and palaeoenvironments provides crucial knowledge for understanding the complexity of our rapidly changing planet in the present day. The well-developed coal seams of Middle Jurassic in northern China are a source of deep-time information, including inertinites as the fossil evidence of palaeowildfires, providing insights into the evolution and behavior of fire-prone ecosystems. In this study, we collected underground coal samples and inertinite content from the Yan’an Formation in the Ordos Basin, and investigated palaeowildfire regime by analyzing coal macerals, inertinite reflectance, and polycyclic aromatic hydrocarbons (PAHs). The presence of high levels of inertinite and abundant combustion-derived PAHs demonstrates that widespread wildfires occurred during the Aalenian in the northeastern Ordos Basin. Inertinite reflectance values, including the data from abundant semifusinite, ranging from 1.42% to 3.21 %Ro, and the low 5/3-ringed and 6/3-ringed PAH ratios provide compelling evidence that palaeowildfires were dominated by lower temperature surface and ground fires. Low contents of high-reflectance inertodetrinite and existence of 5- and 6-ring PAHs suggest that high temperature crown fires occurred occasionally. It is proposed that the abundant inertinites in Jurassic coals were formed as a result of the multi-factorial coupling of palaeo vegetation, palaeoclimates, and palaeoenvironmental evolution. Finally, based on paleoclimate features, the changes in inertinite content are attributed to mesoscale climate changes induced by the lake effect.</p>

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Palaeowildfire regimes and their palaeoenvironmental significance during the Middle Jurassic of the Ordos Basin

  • 期刊论文

  • 发表日期：

    2026年6月15日

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  • Jiamin Zhou,
  • Longyi Shao,
  • Timothy P. Jones,
  • Man Huang,
  • Langlang Wang,
  • Xiaotao Xu,
  • Xiaoyun Yan,
  • Jing Lu

摘要

Wildfires are important disturbances in many of the Earth’s ecosystems and are of great significance for understanding the interactions among environmental, atmospheric and vegetational changes in deep time. The Jurassic palaeoclimates were constantly changing, experiencing diverse climate states. Studying Jurassic palaeoclimates and palaeoenvironments provides crucial knowledge for understanding the complexity of our rapidly changing planet in the present day. The well-developed coal seams of Middle Jurassic in northern China are a source of deep-time information, including inertinites as the fossil evidence of palaeowildfires, providing insights into the evolution and behavior of fire-prone ecosystems. In this study, we collected underground coal samples and inertinite content from the Yan’an Formation in the Ordos Basin, and investigated palaeowildfire regime by analyzing coal macerals, inertinite reflectance, and polycyclic aromatic hydrocarbons (PAHs). The presence of high levels of inertinite and abundant combustion-derived PAHs demonstrates that widespread wildfires occurred during the Aalenian in the northeastern Ordos Basin. Inertinite reflectance values, including the data from abundant semifusinite, ranging from 1.42% to 3.21 %Ro, and the low 5/3-ringed and 6/3-ringed PAH ratios provide compelling evidence that palaeowildfires were dominated by lower temperature surface and ground fires. Low contents of high-reflectance inertodetrinite and existence of 5- and 6-ring PAHs suggest that high temperature crown fires occurred occasionally. It is proposed that the abundant inertinites in Jurassic coals were formed as a result of the multi-factorial coupling of palaeo vegetation, palaeoclimates, and palaeoenvironmental evolution. Finally, based on paleoclimate features, the changes in inertinite content are attributed to mesoscale climate changes induced by the lake effect.