Palaeofloral assemblages from Tapin Sub-basin, West Bokaro Coalfield, Jharkhand, India and its clue on floral diversity, palaeoclimate, palaeovegetation and palaeoecology

The macro-floristic analysis of Lower Gondwana sequences in Tapin area of West Bokaro Coalfield aims to comprehend the floral diversity, palaeovegetation, palaeoclimate and palaeoenvironment. Additionally, the goal is to determine the stratigraphic position of the studied area within the geologic time scale. The floral impressions retrieved from the Barakar strata of the investigated area have provided an insight into the utmost diversification of Lower Gondwana flora during the late Artinskian-Kungurian age. Altogether two macrofloral assemblages, comprised of two plant groups, specifically Glossopteridales (Glossopteris, Gangamopteris, Vertebraria and stem casts) and Cordaitales (Noeggerathiopsis) are reported from Tapin South and Tapin North Open Cast Projects. Out of the present collection, 12 Glossopterid taxa (Glossopteris tenuifolia, G. densinervis, G. maheshwarii, G. nautiyalii, G. giridihensis, G. raniganjensis, G. spatulata, G. stenoneura, G. searsolensis, G. zeilleri and Gangamopteris angustifolia, G. major) and one cordaitalean species (Noeggerathiopsis minor) have been recorded from the West Bokaro Coalfield for the first time. In reticulate leaves of order Glossopteridales, there is a steady change in the leaf morphology, which shows the biostratigraphic age and climate changes that occurred during sediment deposition in the region. The dominance of narrow mesh Lower Gondwana flora with the presence of typical Karharbari flora (Gangamopteris and Noeggerathiopsis) in the Tapin South area, illustrates the biostratigraphic age as late Artinskian (lower Barakar Formation). However, the intermediate mesh form Glossopteris predominates the collection made from the Tapin North area and the absence of significant Karharbari flora approves that the formation is of Kungurian age (upper Barakar Formation). The main floral morphologies, such as mesh forms, shape, midrib, and venation pattern, show a fairly warm humid climate throughout the sedimentation of the Barakar Formation. The concurrence of huge coal beds with diversified floral assemblages suggests the prevalence of terrestrial large trees and marshy growing plant groups during the deposition of sediments. Adequate insolation with sufficient rainfall can be predicted from the proliferation of Barakar flora in the studied area. A model has been attempted to reconstruct the vegetation of the area.