Is the modern dry deciduous forest of western Bengal Basin a residuum of Eocene Dipterocarp-dominated vegetation? Palynological evidence

The Bengal Basin has a long geological history, and its westernmost part is included in India in the geographical province of West Bengal. The Palaeogene sedimentary strata of the Bengal Basin are palynofloristically less explored to date. The present work deals with the palynomorph analysis of middle-late Eocene lignite sediments from Panagarh-Domra sector in undivided Bardhaman district, West Bengal, India (23°30ʹ34ʹʹ N, 87°27ʹ19ʹʹ E). The palynoassemblage consists of 54 pollen and non-pollen palynomorph types, where angiosperm pollen grains are predominant (84%), followed by pteridophytic (9%) and fungal morphs (7%). Among the angiosperms, pollen grains of Dipterocarpaceae are the most dominant (27%), having a close resemblance to those of extant genera Dipterocarpus, Shorea and Hopea . Furthermore, the climatic parameters during the time of deposition in the study area have been quantified using the Coexistence Approach (CA). The study suggests that a warm, humid tropical climate was prevalent, supporting the dipterocarp-dominated vegetation harbouring both wet and dry deciduous and evergreen elements during the middle to late Eocene in the western Bengal Basin, the remnants of which perhaps are still present in the form of a tropical dry deciduous forest possibly after experiencing a gradually declined precipitation in the western part of West Bengal.