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Early Permian peatland dynamics at the northern margin of Gondwana: multi-proxy insights from the Bhareli formation, Siang Window, Eastern Himalaya.

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Title: Early Permian peatland dynamics at the northern margin of Gondwana: multi-proxy insights from the Bhareli formation, Siang Window, Eastern Himalaya.
Authors: Borsaikia, Dipjyoti1 (AUTHOR), Kumar, Govind2 (AUTHOR), Gogoi, Mousumi3 (AUTHOR), Naik, Amiya Shankar2 (AUTHOR), Kumar, Thadoju Satish3 (AUTHOR), Phukan, Sarat1 (AUTHOR) saratphukan@gauhati.ac.in
Source: International Journal of Earth Sciences. Jun2026, Vol. 115 Issue 3, p1-23. 23p.
Abstract: The integrated petrographic, isotopic, and spectroscopic data from the Bhareli Formation, Eastern Himalaya, reveal that Early Permian peat accumulation along the northern Gondwanan margin occurred within a tectonically active fluvio-deltaic setting influenced by fluctuating hydrological conditions and associated changes in redox state. The succession records recurrent wildfire events with vitrinite-dominated assemblages intermittently enriched in inertinite (including micrinite), reflecting phases of combustion and oxidative stress. δ13Corg values (−23.1 to −24.9 ‰) indicate a uniform higher-plant source, consistent with glossopterid vegetation, while variable C/N ratios (14–106) reflect hydrological variability within the peat-forming environment. Reconstructed δ13Cair values (−5.6 to −4.1 ‰) fall within global Permian ranges, although this interpretation is constrained by dataset limitations and uncertainties in fractionation. Pyrite framboid size distributions suggest predominantly reducing porewater conditions, with possible fluctuations linked to changes in the water table; however, their interpretation is influenced by local microenvironments and diagenetic modifications. The Bhareli succession developed under sustained subsidence and high siliciclastic influx within a tectonically active basin setting influenced by regional volcanic activity, in contrast to the broad, relatively stable peatlands of the interior Peninsular Gondwana basins of India. Thermal-maturity parameters (VRo 1.19–1.55%; Raman indices) record significant tectonothermal overprinting during later Himalayan thrusting, producing local maturity reversals unrelated to burial depth. In contrast to the thick, regionally persistent coal seams of the Peninsular Gondwana basins, the Bhareli Formation is characterised by thin, carbonaceous shales that are vitrinite-dominated, but display inertinite enrichment, containing isolated coal streaks and lenses that reflect deposition in a tectonically active, hydrologically unstable depositional system akin in setting, but not in scale, to the Karoo and Sydney-Bowen basins. [ABSTRACT FROM AUTHOR]
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Abstract:The integrated petrographic, isotopic, and spectroscopic data from the Bhareli Formation, Eastern Himalaya, reveal that Early Permian peat accumulation along the northern Gondwanan margin occurred within a tectonically active fluvio-deltaic setting influenced by fluctuating hydrological conditions and associated changes in redox state. The succession records recurrent wildfire events with vitrinite-dominated assemblages intermittently enriched in inertinite (including micrinite), reflecting phases of combustion and oxidative stress. δ13Corg values (−23.1 to −24.9 ‰) indicate a uniform higher-plant source, consistent with glossopterid vegetation, while variable C/N ratios (14–106) reflect hydrological variability within the peat-forming environment. Reconstructed δ13Cair values (−5.6 to −4.1 ‰) fall within global Permian ranges, although this interpretation is constrained by dataset limitations and uncertainties in fractionation. Pyrite framboid size distributions suggest predominantly reducing porewater conditions, with possible fluctuations linked to changes in the water table; however, their interpretation is influenced by local microenvironments and diagenetic modifications. The Bhareli succession developed under sustained subsidence and high siliciclastic influx within a tectonically active basin setting influenced by regional volcanic activity, in contrast to the broad, relatively stable peatlands of the interior Peninsular Gondwana basins of India. Thermal-maturity parameters (VRo 1.19–1.55%; Raman indices) record significant tectonothermal overprinting during later Himalayan thrusting, producing local maturity reversals unrelated to burial depth. In contrast to the thick, regionally persistent coal seams of the Peninsular Gondwana basins, the Bhareli Formation is characterised by thin, carbonaceous shales that are vitrinite-dominated, but display inertinite enrichment, containing isolated coal streaks and lenses that reflect deposition in a tectonically active, hydrologically unstable depositional system akin in setting, but not in scale, to the Karoo and Sydney-Bowen basins. [ABSTRACT FROM AUTHOR]
ISSN:14373254
DOI:10.1007/s00531-026-02589-4