Evidence of widespread wildfires in a coal seam from the middle Permian of the North China Basin

The North China Basin is the largest coal-bearing basin in China, and has an areal extent of 800,000 km 2 . We analyzed 138 coal samples and in situ pillar coal samples of the middle Permian from this basin by macropetrography, microscope, scanning electron microscope, gas chromatography, and gas chromatography–mass spectrometer in order to study wildfires. High contents of inertinite (charcoal) and natural coke particles observed in coal samples indicate that vegetation in precursor mires and peats of the middle Permian coal from north China was exposed to far-ranging wildfires. In addition, high-molecular-weight polycyclic aromatic hydrocarbons were detected in the coal samples. These aromatic compounds were formed under high temperatures and provide further evidence of wildfire. These wildfires would have discharged significant CO and CO 2 gases into the atmosphere and affected the paleoclimate and paleoecosystem.