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Early Permian floral diversity and palaeodepositional environment of the Lower Permian Rajhara sequence of Damodar Basin have been studied based on mega-, microfossil and geochemical proxies. Even though Gondwana sediments are generally considered as fluvio-lacustrine deposits, recent studies indicate marine inundations with patchy records. Here in the present study, an attempt has been made to address the changeover from fluviatile to shallow marine conditions and also to address the palaeodepositional aspects. Luxuriant vegetation during deposition of the Lower Barakar Formation generated thick coal seams. The macroplant fossil assemblage shows Glossopteridales, Cordaitales and Equisetales comprising one palynoassemblage with the dominance of bisaccate pollen grains having glossopterid affinities. However, Lycopsids are absent in the megafloral record and are represented in megaspore assemblage. The present floral assemblage led to envisage the presence of dense forest with swampy conditions and prevalence of warm and humid climate during the deposition of Barakar sediments. Correlation with the coeval Indian assemblages and those from other Gondwanan continents also supports an Artinskian age and reveals a stronger affinity with flora of Africa than that of South America. Biomarker analysis reveals low pristane/phytane values (0.30–0.84), noticeable absence of hopanoid triterpenoids and long-chain n-alkanes that is attributed to the obliteration of organic compounds and subsequent alteration of composition due to thermal effect. The high chemical index of alteration, A–CN–K plot and PIA also suggest severe denudation under a warm/humid climate. The V/Al2O3 and P2O5/Al2O3 indicated freshwater–near-shore conditions. However, signature of possible marine influence is identified from Th/U and Sr/Ba ratios resulted from the eustatic fluctuations during Permian. [ABSTRACT FROM AUTHOR]

A palynological analysis of borehole RB-1, Raniganj Coalfield, Damodar Basin, has been presented here. Based on the quantitative analysis of the spores and pollen grains of the productive samples, three palynoassemblages have been identified: Palynoassemblage-I demarcated at a depth between 335.00 and 284.00 m is distinguished by the dominance of nonstriate bisaccate pollen Scheuringipollenites and subdominance of striate bisaccate pollen Faunipollenites suggestive of an early Permian (Artinskian) age; Palynoassemblage-II identified at a depth between 278.00 and 32.00 m shows the prominence of striate bisaccate mainly Faunipollenites, Striatopodocarpites and subdominance of Scheuringipollenites signifies late early Permian (Kungurian) age, and the youngest Palynoassemblage-III marked at a depth between 30.00 and 03.00 m contains dominance of striate disaccates pollen, viz., Striatopodocarpites, Crescentipollenites, and monosaccate pollen Densipollenites spp. (D. invisus, D. densus, D. magnicorpus) corroborate with the latest Permian Raniganj (Lopingian) age. The rare occurrence of Densoisporites contactus and Lundbladispora warti in the assemblage, define the upper limit of the Raniganj Formation. The assemblages have been correlated with the Indian as well as other Gondwanian continents. The dominance of gymnosperms pollen glossopteridales, conifers, and cordaites, lesser quantitative spores of lycopsids, sphenopsids, filiciopsids algal elements indicate that the palaeoclimatic condition was warm and high humid, during the deposition of these sediments in the study area of the Raniganj Coalfield. Research Highlights: Palynological study has been carried out for the subsurface coal deposits from the borehole RB-1, drilled at Raniganj Coalfield to attempt to establish chronology of the sediments. The palynological investigation reveals three palynoassemblage zones and dated as early to latest Permian (Artinskian to Lopingian) age and this assemblage reveals the dominance of gymnosperms plant group such as Glossopteridales followed by conifers and cordaitales. The FADs (First appearance of Datum) of Densoisporites contactus, Lundbladispora warti and Lunatisporites pellucidus in the assemblage III indicate the end of Permian period. The overall palynological composition suggests that a warm to very hot with medium to low humidity climatic condition were prevailing in the study area. [ABSTRACT FROM AUTHOR]