JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Palynofloristic and Palaeoclimatic Investigations of the Lower Gondwana sediments from the West Bokaro Coalfield, Jharkhand, India Chanchal Lakra*, Bacha Ram Jha* and Neha Aggarwal# * University Department of Geology, Ranchi University, Ranchi # Birbal Sahni Institute of Palaeosciences, Lucknow Email: [email protected]; [email protected]; [email protected] Abstract The Present palynofloristic and palaeoclimatic investigation deals with the study of the Lower Gondwana sediments of the Pundi area of West Bokaro Coalfield, Damodar basin, Jharkhand, India. The Coal bearing sediments recovered from the sub-surface samples (borehole WBPS-1) have been characterized with two distinct palynoassemblage i.e. Palynoassemblage I and Palynoassemblage II. Palynoassemblage I (540.6m to 92.1m) is dominated by the abundance of non-striate bisaccate genera represented by Schueringipollenites and sub-dominance of striate bisaccate Striatopodocarpites and Faunipollenites whereas Palynoassemblage II (41.13m) is characterized by the predominance of Faunipollenites and Striatopodocarpites and sub-dominance of non-striate bisaccate Schueringipollenites along with the good percentage of pteridophytic spores. The recovered Palynoassemblages (I and II) have been compared with the known biostratigraphic zones of the other basin and suggested its equivalence to the Lower Barakar (Artinskian age) and Upper Barakar (Kungurian age) palynoflora respectively. The pre-eminence of glossopterids along with the contributory presence of cordaites, conifer, and pteridophytic spores represent a peat swamp forming vegetation in a telmatic environment with periods of standing water. Keywords: Palynofloristic, Palaeoclimatic, Barakar Formation, Artinskian, Kungurian, Damodar basin. Volume VI, Issue III, March/2019 Page No:653 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Introduction The Indian Gondwana coals are the major source of energy producer, about 99% of the coal resources of the country depends on this formation. The Gondwana basin of India represents a motif cycle of sedimentary rock showing varied environmental depositions ranges age from the early Permian to end of the early Cretaceous. These Gondwana sedimentary deposits spreads along five well defined linear belts of intracratonic faulted basins (Damodar valley, Wardha –Godavari valley, Son – Mahanadi valley, Pench –kanhan valley and Rajmahal basin) (Fig. 1). Among these basins excellent development of the Lower Gondwana sediments can be seen in the Damodar basin. No formal stratigraphic classification can be ascribed to this sequence because it is characterized by both lithostratigraphic as well as biostratigraphic characters. From the decades of studies it is proved that spore dispersae is a unique parameter for dating and correlation, in prospecting and economic usage of fossil fuel exploration. There have been seen several palynological studies on different coalfields of the Damoda basin, but very few reports (Surange et. al., 1953, Lele 1975; Srivastava and saxsena, 1984; Bhattacharya et. al., 2005) are available from the West Bokaro Coalfield. The objective of the present investigation is to attribute the quantitative and qualitative analysis of the palynomorphs, age demarcation, identification of botanical affinities and its relation to palaeoenvironment. Geology of the Area The West Bokaro Coalfield covers an area of 207km 2 and a length of 16 km its width is 11 km in the West and 3.2 km in the East at the base of the Lugu hill. The Coalfield is separated from the North Karanpura Coalfield by a narrow stretch of metamorphic and outlier of the Talchir in the West. It lies within latitude 23 045’52’’N to 23 052 ’58” N and longitude 85 030’E to 85 032’37’’E. The coalfield displays a complete geological succession of the Gondwana rocks from the Lower Gondwana and Upper Gondwana. The basin is characterized by the Talchir, Karharbari, Barakar, Raniganj and Supra Panchet formations. Volume VI, Issue III, March/2019 Page No:654 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 The coalfield dominates mainly with coal bearing the Karharbari and Barakar formations. Intrusion of lamproitic and lamprophytic types of dykes and sill can be observed in the Barakar Formation. The occurrence of the Caking coal in the West Bokaro Coalfield was first reported by C.S. Fox in 1934. The stratigraphic sequence inferred on the basis of extensive geological field work has been presented in (Table 1). The Pundi Block is situated in the West Central part of the West Bokaro Coalfield Ramgarh, Jharkhand. It is bound in the North by the Pundi Block, in the West by the Hesagarha Block, in the south by the Kuju block. It lies within latitude 23 045’N to 23 046’N and longitude 85 025’ E to 85 040’ E (Fig. 2). The Pundi Block consists of a large block which is divided into various sub blocks. The exploration of this block carried out by the Indian Bureau of Mines in 1961-1964, however the Pundi extension Block II, Western part was explored in 1963. The Pundi block is marked with the presence of Barren measures, Barakar and Karharbari formations but the absence of Talchir Formation. The area is basically composed of the Barakar sandstone. The fold can be seen in synclinal structure in the Seam IV, they also show the presence of normal fault in the seam V, with the presence of slickenside. Fig.1. Map showing Gondwana basins of India ( after Joyjit Dey, et al., 2018) Volume VI, Issue III, March/2019 Page No:655 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Fig. 2. Location map of Pundi ( after Raja Rao, 1987) Table 1 Generalized stratigraphy of the West Bokaro Coalfield ( after Raja Rao, G.S.I. 1987 ) AGE FORMATION LITHOLOGY Recent Jurassic Recent Intrusive Alluvium and Laterite, Basic and ultrabasic dykes and sills (dolerites and lamprophyres) Upper Triassic Supra Conglomerates, ferruginous sandstone and siltstones Panchet/Mahadeva (500m) Lower Triassic Panchet Fine grained sandstone, green shales and red and chocolate coloured shale and clay (450m) Upper Permian Raniganj Fine grained sandstone, siltstone, carbonaeceous and grey shales with coal seams (550m) Middle Barren Measure Carbonaceous Shales, grey micaceousshales with iron Permian stone bands, siltstone and sandstone (300m) Lower Permian Barakar Conglomerates, pebbly sandstone,very coarse grained to fine grained sandstone, grey shales , carbonaceous shale, fire clay and coal seams(610m) Karharbari Conglomerates, very coarse grained sandstone at place and thick coal sea- 40m to 60m Upper Talchir Diamictite, fine to medium grained greenish and buff Carboniferous coloured sandstone, shale, rhythmite, turbidite,stc. (610m) Precambrian Granite gneisses, schists, amphibolites, quartzites, pegmatites, etc. Volume VI, Issue III, March/2019 Page No:656 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Material and Methods Samples for the present investigation were collected from borehole WBPS-1 drilled by the Central Mining and Design Institute, Ranchi in the West Bokaro Pundi Coalfield (Fig. 3). Samples collected from shaley coal, carbonaceous shale, and coals were processed by following a standard palynological method called maceration. First, the 10-20 gm material was crushed to 2-4 mm size and treated with Hydrofluoric Acid (HF) for two to three days for the removal of silica. After thorough washing of the material, the acid free residue was treated with HNO3 (concentrated nitric acid) for 3-4 days and finally the material is treated with 10% KOH solution (alkali treatment) to bleach the organic matter. After sieving through 400 micro mesh, the material was finally mounted in Canada balsam with the help of Poly Vinyl Chloride (PVC). Eight to ten slides per sample were prepared from each productive sample. Olympus BX61 microscope was used for the palynological investigation and photographs were taken with the help of a DP-25 camera. Qualitative and quantitative studies of palynomorphs were performed at the Birbal Sahni Institute of Palaeosciences, Lucknow. For quantitative analyses, a total of 100 spore/pollen grains were counted for each sample and palynoassemblages are identified. Results Quantitative and qualitative palynological analysis of sediments has divulged two palynoassemblage in borehole WBPS-1. The vertical distribution of various palynomorphs in the borehole WBPS-1 has been shown in Fig. 4. A list of recovered spore-pollen species has been summarized in Table 2 and palynocomposition of the complete borehole WBPS-1 has been shown in Table 3. Stratigraphically significant palynomorphs are shown in Fig. 5. Palynocomposition Palynologically studied succession reveals that the pollen grains are the predominant component which include a number of trilete, monosaccate, bisaccate, taeniates and others. Palynocomposition of two different palynoassemblage are as follows: Volume VI, Issue III, March/2019 Page No:657 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Fig . 3. Showing the litholog of borehole WBPS1 Volume VI, Issue III, March/2019 Page No:658 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Fig. 4 Compilation Figure of the present study Volume VI, Issue III, March/2019 Page No:659 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Table 2 List of recovered spore pollen species and their Botanical affinity (after Beri et al ., 2011; Quadros