Petrographic, palaeofloral, and taphonomic characteristics of the Permian coal-bearing sequences in Korba Basin, Central India: Implications for their palaeoecology and depositional settings

Abstract

The coal-bearing deposits associated with the Barakar Formation of the Korba Basin were examined through a multi-disciplinary analysis, including organic petrographic, palynofacies, palynological, and taphonomic techniques. This cohesive approach is decisive for elucidating the genesis and evolution of organic matter, determining age constraints and reconstructing the palaeoecological and depositional environments during peat accumulation. The petrographic studies demonstrate that the vitrinite group of macerals has dominance (average 40.2 vol.%) over the inertinite and liptinite groups in the organic composition. Within the vitrinite group, the telovitrinite subgroup is chiefly comprised of the collotelinite maceral (average 25.7 vol.%), indicating the higher terrestrial influx and the presence of anaerobic environment conditions. While palynofacies analysis reveals dominance of degraded organic matter (average 39.88%). The subsequent degradation of such vegetation, probably caused by bacterial activity (and/or mechanical breakdown), results in substantial amounts of degraded organic matter and vitrodetrinite maceral (average 12.5 vol.%). The studied palynoassemblage is largely dominated by bisaccate pollen represented by Scheuringipollenites, Faunipollenites, Striatopodocarpites, Striasulcites, etc. Based on inter-, intra- and Gondwanan palynological correlation, these palynoassemblages are Artinskian in age. Further, the affinity of palynoassemblage reflects glossopterid-dominated forest along with lower proportions of Coniferales (average 2.3%) and Peltaspermales (average 1.8%) in relatively warm and humid climatic conditions. The appreciable presence of cordaites (average 12.3%), indicated by the monosaccate pollen of Parasaccites and Barakarites, suggests high terrigenous input into the mire. However, the occurrence of the spores of filicopsid and lycopsid indicates a significant contribution from herbaceous vegetation.

Further, the values of various petrographic indices and their cross-plotting suggest that the precursors of the peat-forming vegetation (mainly telmatic) were deposited in wet forest settings under mesotrophic hydrological conditions with intermittent fluctuation to rheotrophic conditions. Likewise, the palynofacies analysis indicates that organic matter deposition occurred under suboxic conditions in distal settings. The diverse palynofacies elements retrieved indicate that organic matter deposition occurred under suboxic conditions in distal settings. The taphonomic studies reveal the predominance of buoyant saccate taxa (Group E) and the rarity of spores in the recovered palynoassemblage, indicating an allochthonous origin for the organic matter and the influence of depositional environment on the palynocomposition.