A petrological approach to understand the signatures of palaeowildfire activities during the formation of Permian coal: A case study of Bastacolla Mine, Jharia Coalfield, India

Abstract

Despite evidence of palaeo-wildfires during the formation of Indian coal deposits, studies on their fire intensity, temporal variability and relation to palaeo-oxygen levels remain limited. A comprehensive investigation of wildfire signatures in Indian Permian coals is required to bridge this knowledge gap. The Carboniferous to Permian Period is characterised by prevalent coal formation and a substantial occurrence of palaeo-wildfires. However, the occurrence of these wildfires and their spatial distribution exhibited temporal variability throughout this period. An inclusive investigation (including petrological compositions, especially inertinites and scanning electron microscopy (SEM)) was executed on coal samples from Bastacolla Mines, Jharia Coalfield, India, to investigate variations in palaeo-wildfire signature and palaeo-wildfire temperature during peat formation. The dominance of vitrinite with a significant inertinite content (as a by-product of palaeo-wildfire) in studied coal samples reveals that wildfire activity occurred during peat formation. The inertinite reflectance values ranging from 1.42% to 2.62% (mean: 1.88%) and 1.20% to 2.48% (mean: 1.67%) in Bottom-II and Top-III seam, respectively, indicate wildfire in Permian was dominated by mainly ground fires and partially surface fires. SEM images show various typical structures, including cellular/fibrous structure, uniseriate and biseriate tracheid, indicating the dominance of gymnosperm flora during peat formation. Further, the presence of typical structures by SEM, charcoal lenses on the sample surface (macroscopic) and high inertinite in investigated coal seams reveals the occurrence of wildfire during its formation. The significantly high atmospheric oxygen levels (pO<inf>2</inf>˃23%) provide compelling evidence for frequent wildfires in the Jharia Coalfield during the coal-forming period. © The Authors 2025. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page (https://us.sagepub.com/en-us/nam/open-access-at-sage).