Gondwana Supergroup Research Articles

Palaeolithic investigations at Morpani, Central Narmada Basin, India

Morpani is a recently discovered Palaeolithic complex in the central Narmada Basin (Madhya Pradesh, India), discovered during the course of field investigations carried out by the Narmada Basin Palaeoanthropology Project. This site is situated in a region of the Gondwana Supergroup formations, south of the Narmada River. Regions to the north of the river, dominated by rock outcrops of the Vindhyan Supergroup formation present a multitude of Palaeolithic sites, in stark contrast to the southern region, dominated by the Gondwana Supergroup and Deccan Trap formations. This site is one of the few Palaeolithic sites in this southern region, and this paper reports on the recent Palaeolithic investigations undertaken at the site and the results of the lithic analyses of the recovered lithic assemblage. These investigations were carried out to qualify the nature of the Palaeolithic occupation in this region, as well as probe into the possible factors for the underrepresentation of the archaeological record here, especially when juxtaposed to the rich archaeological context noted to the north of the river. Lithic analyses indicates that Morpani represents an expedient lithic assemblage, located along the banks and bed of an ephemeral stream channel, and in regions where suitable raw material clasts are available. More work and collections are needed to securely characterise and attribute the technological features of this Palaeolithic site.

STUDIES OF THE AREA AROUND SINGRAULI COAL FIELD & ENERGY BELT, DISTRICT SIGRAULI, MADHYA PRADESH INDIA

STUDIES OF THE AREA AROUND SINGRAULI COAL FIELD & ENERGY BELT, DISTRICT SIGRAULI, MADHYA PRADESH INDIA

Implications of Late Palaeozoic postglacial marine transgressive‐regressive (T‐R) cycles recorded in the Talchir Formation, Son Valley Basin, peninsular India: A sequence stratigraphic paradigm

The signature of Late palaeozoic glaciation, a pan‐Gondwanaland palaeoclimatic event, is recorded in the Talchir Formation (Late Carboniferous to Early Permian), the basal‐most litho‐unit within the Gondwana Supergroup (Late Carboniferous–Early Cretaceous) in peninsular India. About 200 m thick sedimentary succession of the Talchir Formation, exposed in the Hasdeo River section in the Son Valley Basin, Central India, manifests signatures of deposition by melting of glaciers near to the ice‐grounding line. Evidence of glacial influences is prevalent in the lower‐middle part of the succession and represented by glacial tillites with faceted/striated gravels and bullet‐shaped clasts, dropstones and ice‐rafted debris (IRD), associated with various sediment gravity flow deposits. In the middle‐upper part of the succession, records of post‐glacial marine incursions are preserved as thick sandstone and sandstone‐mudstone heteroliths of a shallow marine shore‐shelf depositional regime. These are characterized by abundant tidal and wave signatures, with marine bivalve fossils and trace fossils of marine invertebrates. The upward decrease in size and abundance of the IRDs indicates a gradual decrease in glacial influences, with landward incursion of the marine depositional systems over the proglacial systems. Multiple stacked progradational and retrogradational stratal stacking patterns formed by alternating glacigenic and marginal marine dominated processes signify multiple transgressive‐regressive (T‐R) cycles, manifesting repeated advancements and retreats of the glacier, associated with sea level rise and marine incursions into the land. The top part of the succession, characterized by fine‐grained siltstone/mudstone without any IRD, suggests sedimentation at a relatively deeper part of the basin, indicating the strong influence of the eustatic rise caused by significant melting of the retreating ice sheet. Stacked T‐R cycles bounded by distinct facies architecture define multiple system tracts confined within three major deglaciation sequences within the studied Talchir Formation, suggesting multiple phases of advance‐retreats of the ice sheet and significant marine onlaps within the continental Gondwanaland under the Late Palaeozoic icehouse‐greenhouse climatic change.

Geochemistry of Permian carbonaceous shales from Raniganj sub-basin, Damodar Valley, India: Implications for provenance, weathering, tectonics and source of organic matter

Raniganj sub-basin, the easternmost depository of Damodar Valley encompasses the entire succession of Gondwana Supergroup, the lower and upper Gondwana sequences. The present investigation of Permian carbonaceous shales belonging to Barakar, Barren Measure and Raniganj formations of lower Gondwana sequence from this basin is an integrated study of inorganic and organic geochemical characteristics viz. major/trace elements, stable isotopic composition and kerogen type to ascertain source rock attributes such as provenance, tectonic setting, prevailing weathering/climatic conditions as well as source and type of organic matters. Trace element indices, such as La/Sc, Th/Co, Th/Sc, (Gd/Yb)CN, Eu/Eu*, Cr/V, Y/Ni, reveal that the shales are originated from felsic/granitic source rock. Prominent Eu-anomaly, enrichment of chondrite normalised light rare earth element (LREE) values and a flat heavy rare earth elements (HREE) pattern reflect post-Archean felsic source for the shales. The major element composition, especially relative enrichment of Al over readily soluble elements, Ca, Na and K yielding high CIA (74.9–84.6%) and CIW (87.1–97.5%) as well as low ICV (0.64–1.32) values, establishes significantly weathered and matured nature of the shales. The distribution of redox-sensitive elements (U/Th, V/Cr, Ni/Co, Ce/Ce*) as well as low ICV, depleted K2O/Al2O3 ratios and high CIA values point towards an oxic environment and warm-humid climatic condition during deposition of these shales. The conventional method for determining tectonic setting using major and trace element composition fails to clearly delineate the tectonic setting for the current shales. The samples show wide scattering across active and passive continental margin in the K2O/Na2O–SiO2 diagram, whereas the samples are concentrated near the active in the continental margin in the Th–Sc–Zr/10 diagram contradicting the geological framework of Raniganj sub-basin. Discriminant functions-based approach which categorises the tectonic setting into continental/oceanic arc, continental rift and continental collision settings has been proved to be suitable in the present case and reveals continental-rift setting for the shales from Raniganj sub-basin. The carbon isotopic signature (δ13Corg) of the shales reveals a range (−24.5 − −22.9‰) intermediate between that of marine and terrestrial (C3 plants) organic matters indicating possible mixed type of organic matters. The fluvio-marginal marine depositional condition obtained from K2O/Al2O3 and MgO/Al2O3 ratios further implies the possibility of mixed nature of organic matter. The geochemical parameters of the organic matter (Rock-Eval pyrolysis parameters S1, S2, TOC, HI, OI etc.) indicate that the studied shales contain thermally matured mixed Type III/II gas-prone kerogen and are derived predominantly from terrestrial sources with significant marine input.

The Arapey group: confining basalts of the Guarani aquifer in Uruguay

With the increasing demand of drinking water for agricultural use, takes special importance the geological and hydrogeological knowledge of the infrabasaltic aquifer known as Guaraní Aquifer in the South Cone. The different stratigraphic concepts historically managed for the geological formations of the top of Gondwana Supergroup in Uruguay, carrying great volumes of groundwater with thermal potential, agricultural use (irrigation) and urban supply are discussed. Geological units of Guaraní Aquifer are described: Buena Vista, Cuchilla Ombú, Tacuarembó and Rivera Formations. Geometry and thickness of its confining unit - Arapey group - condition the economic possibilities of taking advantages using groundwater from Guaraní Aquifer. Such group has been divided - according to lithostructural criteria - on six formations for which a brief description is given. A preliminary tridimensional geometry of Arapey group´s basaltic lava and its relation with Guaraní Aquifer is showed. This geometry is related to the basaltic thickness to cross in a borehole in order to obtain groundwater with an error margin of about 30 meters. This is very relevant, specialy in lithosol zones of the basaltic area, where the installation of irrigation systems would mean a sustancial agrarian improvement in these areas.

Geochemical Studies of some Heavy Metals’ Toxicity in Groundwater with their Plausible Sources around Gondwana Supergroup, Wardha Valley Coalfields, Maharashtra

Abstract The study is designed for groundwater assessment in terms of some sorted heavy metals’ toxicity and their probable source in Wardha valley coalfields, Maharashtra. For both seasons, 45 groundwater samples were collected separately to assess Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn by AAS. Among them, 22 were found contaminated as per BIS (2012) concerning Cd, Fe, Ni and Pb. The major contributors in both seasons were Fe, Zn, Cu and Al. The PCA study has shown sound relationships among Fe-Ni, Cd-Ni, and Al-Cu-Zn. The contamination intensities in various samples indicates that the mining region as a prime cause. The Kamthi and Barakar formations in the study area were considered as a contamination source. The significant role of lower pH environment in enhanced contamination was revealed in the correlation analysis. Accordingly, the probability of acid mine drainage was supposed. The EPMA and SEM-EDS/X studies reveal the presence of sulphide phases in Barakar Formation and sulphur in associated carboniferous strata confirming the source of lower pH. Accordingly, the acid mine drainage was anticipated to be responsible for heavy metals’ dissolution and migration to groundwater in mining areas.

Spatial distribution of Palaeolithic sites in relation to raw material sources in the central Narmada Valley, India

Abstract Landscape adaptation in central India is quite exceptional, as more than 300 Lower Palaeolithic occurrences have been reported in different contexts. The present work deals with these assemblages and associated raw material sources in the central Narmada Valley. The central Narmada Valley is rich in various rock types that were used as raw material by various hominin populations. The Narmada River divides the region into northern and southern parts. In the north, there are mainly the Vindhyan Supergroup and Deccan Trap, whereas, in the south, there are primarily the Gondwana Supergroup, the Deccan Traps and the Mahakoshal Group. Along the river, there are exposures of the Vindhyan Supergroup and thick deposits of Quaternary alluvium. The main raw material types in the north of Narmada are quartzite and sandstone (Vindhyan Supergroup), whereas, in the south of Narmada, the main raw materials are quartzite (Gondwana Supergroup) and chert (Deccan Trap). Acheulean sites are mostly found along the foothills of Vindhyan, as well as along the banks of the Narmada River and its tributaries. In this chapter, the author has tried to link these raw material sources with the occurrences of Palaeolithic sites in order to have a better understanding of past hominin land-use patterns and ecological adaptations.

Characterization of groundwater nitrate exposure using Monte Carlo and Sobol sensitivity approaches in the diverse aquifer systems of an agricultural semiarid region of Lower Ganga Basin, India

Prevalence of nitrate in different aquifer systems is a growing environmental and public health concern. Efforts were made for the first-time to achieve a higher accuracy in health risks characterization associated with the nitrate in groundwater of the diverse aquifer systems on the residents of a semi-arid rural tract of Lower Ganga Basin using Monte Carlo Simulations and Sobol Sensitivity analyses. The nitrate levels in groundwater varied between 0 and 508.3 mg/L with a mean of 19.79 ± 32.78 mg/L and 0–435.0 mg/L with a mean of 24.44 ± 35.15 mg/L during the pre-monsoon and post-monsoon periods, respectively. About 847.12–1000.25 km2 area of the survey area (total area 4545 km2) exhibited nitrate concentrations (C) > the pre-intervention limits (45–50 mg/L). Minor populations, especially the infants from the granite gneiss, Rajmahal traps, laterite, recent alluvial and old alluvial aquifer zones under the Central Tendency Exposure (CTE) condition and all the aquifer zones (including the Gondwana supergroup aquifer zone) under Reasonable Maximum Exposure (RME) scenarios, were characterized as being at high risks of methemoglobinemia, primarily due to ingestion of untreated nitrate contaminated groundwater. Residents of the alluvial aquifer zones of the study area were found to the most vulnerable to the groundwater nitrate toxicity through oral and dermal exposures. The study validated the prediction accuracies of different interpolation methods including the Spline, Kriging, polynomial and Inverse Distance Weighted and revealed that Kriging predicted the Spatio-seasonal variations of groundwater nitrate of the district more accurately. Sobol Sensitivity analysis revealed C and the interaction effects of C and groundwater Ingestion Rate (IR), and C and Fraction of skin area contacted with groundwater (F) as the influential parameters for oral and dermal health risks exposure models. Therefore, the study recommends to residents of the study area to consume treated groundwater to mitigate nitrate related health morbidities.

Facies Analysis, Markov Model and Linking of Sub-environments in the Early Permian Barakar Coal Measures of Godavari Gondwana Basin of Southeastern India

Abstract The early Permian Barakar coal measures Formation of Gondwana Supergroup in the Godavari basin comprise siliciclastic fluvial facies of passive continental margin. The lithofacies relationship and their sequences are analyzed quantitatively using embedded Markov Chain analysis along with improved binomial probability method. Summarized lithofacies sequence show the following order: (CGSD= Matrix supported conglomerate, gritty to pebbly / coarse-grained tabular and trough cross bedded sandstones) →(MGSD= Medium grained trough and planar cross bedded sandstones)→(FGSD= Fine-grained parallel and ripple drift cross-laminated sandstones)→ (SH= Shale/inter-bedded sandstone-shale and gray shale)→ (C=coal/shaly coal and carbonaceous shale)→ (CGSD= Matrix supported conglomerate, gritty to pebbly/coarse-grained planar and trough bedded sandstones). These repetitive cycles accumulated in a low sinuosity, high gradient braided streams which became moderately sinuous at places. The lithofacies relationships showing fining upward tendency suggest a progressive upward decline in current competency. The sequence is considered as the classical example of a sand dominated braided river. The lateral changes in lithofacies association indicate shifting of subenvironments from stream channel, overbank levee and peat forming back swamp to flood plains of fluvial system. It is suggested that the channel wandering along with differential intra-basinal tectonism and subsidence controlled cyclic repetition during early Permian sedimentation in the Godavari basin.

Fluvial facies and petrography of Late Pleistocene Baneta sediments, Central Narmada Basin, Madhya Pradesh, India

Baneta Formation, comprising of fining upward sequences of pebbly conglomerate, sandstone and siltstone, exhibits development of five distinct lithofacies, viz., massive pebbly conglomerate, large scale tabular cross bedded sandstone, horizontal parallel bedded coarse-grained sandstone, parallel laminated fine-grained yellowish sandstone and siltstone; representing channel lag, point bar and overbank flood plain deposits of mixed load meandering river. In these sediments, development of nodular, buckled bedded calcrete, rhizoliths and tepee is noticed. Granulometric studies of these sediments revealed presence of wide range of grain size classes, polymodal grain size distribution, moderate to very poor sorting, positive skewness and leptokurtic nature, supporting fluvial environment of deposition. Lithic arenitic nature, heavy mineral assemblage with dominance of augite and low ZTR index of these sediments indicate mineralogical immaturity and presence of illite, kaolinite and montmorllionite together with geochemical composition indicate their derivation from mixed provenance of Precambrian granite, metapelites, Vindhyan Supergroup, Gondwana Supergroup, Deccan trap basalt, and laterite. The thin sections studies reveal signatures of meteoric phreatic and vadose zone diagenesis related with semi-arid climate and subaerial exposure. The δ13C and δ18O content of calcretes indicate their pedogenic and/or shallow groundwater origin under semi-arid climatic conditions, and C3–C4 mixed vegetation with dominance of C4 vegetation. OSL and 14C dates of the samples from Baneta Formation suggest deposition of these sediments in Late Pleistocene.

Palaeocurrent and environmental implications from anisotropy of magnetic susceptibility (AMS): a case study from Talchir and Barakar formations, Raniganj Basin, West Bengal, India

Oriented cylindrical cores of rock samples were collected from the Talchir and Barakar formations of the Lower Gondwana Supergroup of the Raniganj Basin exposed in and around Kalyaneshwari and Maithon areas. The cores (2.54 cm diameter and 2.2 cm height) were studied in the low field anisotropy of magnetic susceptibility (AMS) measurement to determine the nature of magnetic fabrics, to correlate it with the sedimentological characteristics and to determine the palaeocurrent patterns. The results derived from the statistical parameters (especially the q-factor), the shapes of the susceptibility ellipsoids and directional data of the AMS indicate that the magnetic fabrics within the studied units are primary (depositional) and are correlatable form the palaeoenvironmental features. The orientation of the maximum (K1), intermediate (K2) and minimum (K3) susceptibility axes is dispersed on the lower hemisphere equal area diagram rather than strong clusters which is not because of secondary (tectonic) influence but due to the moderate to high-energy environment of deposition of the sediments in the studied units. Based on the q-factor (which is 0.581 for Barakar Formation and 0.565 for Talchir Formation which are both < 0.7), it is suggested the AMS indicates that the imbrication of the K1 axis is the indicator of palaeocurrent. Also, the magnetic foliation (average value = 1.255) exceeds the magnetic lineation (average value = 1.107) and the shape parameter exceeds 0 in most cases pointing towards an oblate fabric. The palaeocurrent in the present study as indicated by the K1 axis imbrication is very similar in both the units under study and is due SW. However, apart from this precise palaeocurrent direction, there exists a certain degree of randomness of the susceptibility axes which are very clear indication of corresponding depositional environments.

First record of Reduviasporonites from the Permian–Triassic transition (Gondwana Supergroup) of India

Kar, R. & Ghosh, A.K., May 2018. First record of Reduviasporonites from the Permian–Triassic transition (Gondwana Supergroup) of India. Alcheringa XX, XXX–XXX. ISSN 0311-5518.We have performed a palynological study from an outcrop succession within the Gondwana Supergroup in India, spanning the end-Permian event. The sampled succession is located within the Tatapani-Ramkola Coalfield, in the Balrampur District of Chhattisgarh State, India. Diverse and well-preserved palynological assemblages representing non-marine successions were identified and four assemblage zones were distinguished: the upper Permian Zone I: Striatopodocarpites–Densipollenites, and Zone II: Striatopodocarpites–Crescentipollenites; the Lower Triassic Zone III: Falcisporites–Klausipollenites and Zone IV: Densipollenites–Lunatisporites. Importantly, the fossil genus Reduviasporonites Wilson is recorded across the Permian–Triassic transition in this study. Although the affinity of Reduviasporonites has been disputed (both fungal and algal affinities have been proposed), the genus is an important constituent of the palynological assemblages from the upper Permian and Lower Triassic deposits in different parts of the world. Here we report the first record of Reduviasporonites from the Permian–Triassic continental sediments in India, adding another significant data point for their presence at the Permian–Triassic boundary (PTB). We further discuss the affinity and palaeoecological perspectives of the taxon.Ratan Kar [ratankar@yahoo.com] and Amit K. Ghosh [akghosh_in@yahoo.com] Birbal Sahni Institute of Palaeosciences, 53 University Road, Lucknow 226 007, Uttar Pradesh, India. Received X.X.2017; revised X.X.2017; accepted X.X.2018.

A Discontinuous Ephemeral Stream Transporting Mud Aggregates In A Continental Rift Basin: The Late Triassic Maleri Formation, India

Abstract: Finer-grained components of fluvial sediments are usually deposited in overbank environments, and their preservation in the rock record is generally subordinate to that of the coarser-grained channel fills. However, though the fossil record and lithological characteristics of the Late Triassic Maleri Formation, Gondwana Supergroup of the Pranhita–Godavari continental rift basin, India, indicate that it is a fluvial deposit, the formation is characterized by thin sandstone bodies vertically separated by thicker fine-grained sediments. With the help of petrographic and sedimentological features, this study characterizes the fluvial system that produced a deposit dominated by fines. These syn-rift sediments provide valuable clues towards understanding the spectrum of fluvial processes operating in continental rift-basins. We observe that the formation is dominated by stratified siltstone (mudrocks) rather than massive mudstones. These mudrocks contain a large quantity of silt to fine-sand-size pedogenic mud aggregates, and the preserved primary structures indicate transportation by traction currents. The internal organization of the mudrock units reveals that an admixture of pedogenic mud aggregates along with other sand-grade siliciclastic grains were transported through the channelized and unconfined reaches of a network of discontinuous ephemeral streams constituting the axial drainage of the rift basin. However, evidence for accumulation of fines in swamp-like environments is preserved in a few pedogenically modified mudstones that occur in between much thicker intervals of stratified mudrocks. On the other hand, the small bodies of cross-bedded carbonate grainstones and laminated marls indicate that the conditions suitable for precipitation of freshwater carbonates prevailed in some of these swampy areas. The sedimentary features of the thinner sheet-sandstone bodies associated with the mudrocks suggest that though the overall character of the fluvial system remained unchanged the sandstones were deposited during the phases of higher discharge. We suggest that the basin was persistently fed with a sediment load rich in mud aggregate produced in the vertic soils forming on the shales and limestones in the source area under a warm climate and seasonal rainfall.

Petrography and geochemistry of sandstone–mudstone from Barakar Formation (early Permian), Raniganj Basin, India: Implications for provenance, weathering and marine depositional conditions during Lower Gondwana sedimentation

Post‐glacial Permian coal‐bearing sedimentary successions are traditionally interpreted as fluvially deposited within the Gondwanaland continental set‐up throughout the globe. Recent attempts to reinterpret such successions in terms of marine flooding events, mainly based on sedimentological and ichnological attributes, raised doubt on the existing palaeogeographic model of the Late Palaeozoic Gondwanaland. Reassessing these sedimentary successions using other proxies, like petrographic and geochemical properties, may provide more reliable clues to improve the present understanding.In this paper, petrographic and geochemical analysis of sandstones, sandstone–mudstone heteroliths, and mudstones of the early Permian Barakar Formation of Lower Gondwana Supergroup, Raniganj coal Basin, India, is presented to understand the provenance, palaeoweathering pattern and palaeodepositional conditions. Petrographically, the sandstones are arkosic to sub‐arkosic in nature, with abundant unstable components and heavy minerals. Clay minerals in the matrix and the mudstones are dominated by kaolinite, illite‐smectite with authigenic glauconite, indicating a marine diagenetic realm. Mineralogical assemblage attests to sedimentation in craton interior passive margin conditions. Geochemically, the lithounits show large variations in major element and trace element (including rare earth element) concentrations. Chemical index of alteration and A–CN–K ternary plot indicate moderate to strong chemical weathering, leading to deposition of compositionally immature sediments close to their source without much recycling. Ratios of major elements (e.g., MgO, K2O, Fe2O3, Al2O3, and SiO2) signify a continental–marine transitional depositional environment developed in a stable passive margin setting under gradually warming up climatic conditions. Trace element ratios manifest an estuarine depositional setting during Barakar sedimentation, comparable with modern major river mouth estuaries.Thus, this paper provides unequivocal evidence of significant marine influence during sedimentation in the Lower Gondwana basins in India, particularly during the Permian time, and signifies the importance of re‐examining the so called “continental fluvial” coal‐bearing deposits as considerably marine‐influenced. The interpretations provide important clues in understanding and reconstructing the Permian Lower Gondwana palaeogeography in eastern peninsular India.

High Resolution Multispectral Satellite Data Interpretation and Limited Ground Checking: A Proxy for Geological Mapping and Uranium Exploration in Mahakoshal Fold Belt of Son Valley Area, Madhya Pradesh

Abstract: This research aims at integrating remote sensing data and field studies to prospect for uranium mineralisation in the Palaeoproterozoic Mahakoshal Group of rocks in the Son valley area, Central India. In present work, a revised geological map of Mahakoshal Fold Belt (MFB) bounded by Son-Narmada north fault (SNNF) and Son-Narmada south fault (SNSF) along Chorhut-Sidhi-Chitrangi sector falling in Sidhi, Rewa and Shahdol districts of Madhya Pradesh has been prepared based on interpretation of digitally enhanced satellite images. The satellite image interpretation is supported by limited field works, radioelemental measurements (eU, eTh and % K) of in-situ rocks by four channel Portable Gamma Ray Spectrometer (PGRS) and existing published geological maps of Geological Survey of India. In search for mineral potential areas, accurate and up-to-date geological maps are essential as it represent the most basic information for carrying out further exploration activities. However, available geological maps of MFB and sedimentary formations of Vindhayan Supergroup along SNNF and Chhotanagpur Granite Gneissic Complex (CGGC) and Gondwana Supergroup along SNSF available in public domain are discontinuous and multi-scaled. Optical bands of Landsat Enhanced Thematic Mapper Plus (ETM+) and Indian Remote Sensing (IRS) PAN of the study area were used in mapping lithological units, structural features and small intrusive bodies. Principal Component Analysis (PCA), Image Fusion, Linear Contrast Stretch, Histogram Equalisation and False Color Composite (FCC) of various band combination and ratio maps were performed in the digital image processing of geo-rectified satellite imageries. In analyzing and interpreting high resolution multi-spectral images, certain standard norms were employed to acquire information about litho-structural features such as topographic, geomorphic and tectonic facets. The main criteria are colour and tones, geomorphology, drainage patterns and vegetation anomalies. The processed Landsat ETM+ images were interpreted and classified to delineate detailed lithological units and structural features in order to update existing geological maps. To validate the prepared litho-structural map, ground survey was carried out along critical geological sections for checking the geological features like rocks, folds, faults, fractures and foliations. While comparing with the ground geological data to that obtained from the satellite imagery, it is observed that remote sensing interpreted litho-structural map is in a class with the ground observations. Various data sets such as unconformable geological contacts, fault breccias zone, lineaments and gamma ray spectrometric data (eU, eTh and % K) based on PGRS study were integrated and modelled using Geographical Information System (GIS) for identifying important prospective horizons for uranium mineralisation in the MFB of Son valley area. It is concluded that the revised large scale geological map is of practical use for not only for mapping of litho-structural architecture, but also in identifying potential areas for ‘vein –type’ uranium mineralisation along the structurally deformed zones of the SNNF, Asmi-Jiawan fault (AJF) and SNSF; and ‘unconformity- type’ of uranium mineralisation in the outliers of Jungel Group. The revised map and radiometric data acquired are useful in formulating exploration strategy for the ongoing uranium exploration in this area

Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite

The late Aptian (118–115 Ma) continental flood basalts of the Rajmahal Volcanic Province (RVP) are part of the Kerguelen Large Igneous Province, and constitute the uppermost part of the Gondwana Supergroup on the eastern Indian shield margin. The lower one-third of the Rajmahal volcanic succession contains thin layers of plant fossil-rich inter-trappean sedimentary rocks with pyroclasts, bentonite, grey and black shale/mudstone and oolite, whereas the upper two-thirds consist of sub-aerial fine-grained aphyric basalts with no inter-trappean material. At the eastern margin and the north-central sector of the RVP, the volcanics in the lower part include rhyolites and dacites overlain by enstatite-bearing basalts and enstatite-andesites. The pyroclastic rocks are largely felsic in composition, and comprise ignimbrite as well as coarse-grained tuff with lithic clasts, and tuff breccia with bombs, lapilli and ash that indicate explosive eruption of viscous rhyolitic magma. The rhyolites/dacites (>68 wt.%) are separated from the andesites (<60 wt.%) by a gap in silica content indicating their formation through upper crustal anatexis with only heat supplied by the basaltic magma. On the other hand, partially melted siltstone xenoliths in enstatite-bearing basalts suggest that the enstatite-andesites originated through mixing of the upper crust with basaltic magma, crystallizing orthopyroxene at a pressure-temperature of ∼3 kb/1150 °C. In contrast, the northwestern sector of the RVP is devoid of felsic-intermediate rocks, and the volcaniclastic rocks are predominantly mafic (basaltic) in composition. Here, the presence of fine-grained tuffs, tuff breccia containing sideromelane shards and quenched texture, welded tuff breccia, peperite, shale/mudstone and oolite substantiates a subaqueous environment. Based on these observations, we conclude that the early phase of Rajmahal volcanism occurred under predominantly subaqueous conditions. The presence of grey and black shale/mudstone in the lower one-third of the succession across the entire Rajmahal basin provides unequivocal evidence of a shallow-marine continental shelf-type environment. Alignment of the Rajmahal eruptive centers with a major N–S mid-Neoproterozoic lineament and the presence of a gravity high on the RVP suggest a tectonic control for the eruption of melts associated with the Kerguelen plume that was active in a post-Gondwana rift between India and Australia-Antarctica.

Seismites in Permian Barakar Formation, Raniganj Basin, India: implications on Lower Gondwana basin evolution

Fault-bound half-graben-type Raniganj Basin in eastern peninsular India hosts thick sedimentary succession of the coal-bearing Barakar Formation (Early Permian), which constitutes a part of the Lower Gondwana Supergroup. Sedimentological attributes of the upper Barakar succession are portrayed in two predominant facies associations, viz., (i) the lower part characterized by meandering fluvial facies association with distributary channel systems and (ii) the upper part represented by a transgressive, tide-wave-influenced, fluvio-estuarine facies association. Distinct beds with various soft-sediment deformation structures (SSDSs) manifesting paleoseismic events are reported as seismites from the upper Barakar succession. The SSDSs include convolute laminae, complex deformations with folded strata, syn-sedimentary growth faults, pseudonodules, loop bedding, and various water-escape structures including sand–silt flows/dikes. The seismites are restricted at two distinct stratigraphic horizons (S1 and S2) within the upper Barakar succession, separated by undeformed beds in between. The seismites record episodes of paleoearthquake events triggered by syn-sedimentary reactivation of basin marginal faults in the half-graben-type Raniganj Gondwana Basin. These demarcate phases of significant shift in the depositional conditions from fluvial-dominated to a transgressive tide-wave-influenced estuarine system, caused by post-glacial basinal adjustments in the peninsular Indian Gondwanaland.

&lt;I&gt;Glossifungites&lt;/I&gt; Ichnofabric Signifying Crustacean Colonization in Early Permian Barakar Formation, Talchir Coal Basin, India

Early Permian Barakar Formation (Gondwana Supergroup) in peninsular India was earlier interpreted as deposited in braided-meandering fluvial system. Intense burrowing by decapod crustaceans of marginal marine affinity led to Thalassinoides-Ophiomorpha- Rhizocorallium ichnoassemblage, belonging to Glossifungites ichnofacies, within the sandstone-mudstone heterolithic facies near the upper part of the Barakar sedimentary succession, Gouduni River, Talchir coal basin, Odisha, India. An early cementation of the sandstone-mudstone interbeds under changed salinity condition is attributed to mixing of fluvial channels with tide-wave influenced marine depositional systems. This resulted in a semi-consolidated firmground, favouring incipient crustacean colonization during prolonged phases of marine incursion within a fluvial-marine interactive estuarine system during the early Permian in eastern peninsular India.

ORGANIC GEOCHEMICAL CHARACTERIZATION AND SHALE GAS POTENTIAL OF THE PERMIAN BARREN MEASURES FORMATION, WEST BOKARO SUB‐BASIN, EASTERN INDIA

This study investigates the shale gas characteristics of the Permian Barren Measures Formation (Gondwana Supergroup) in the West Bokaro sub‐basin of the Damodar Valley Basin, eastern India. A total of 23 core shale samples collected from a borehole located in the western part of the sub‐basin were analysed using organic geochemical techniques and scanning electron microscopy. The samples are black carbonaceous shales composed chiefly of quartz, mica and clay minerals.Rock‐Eval pyrolysis data show that the analysed samples contain a mixture of Type II and Type III kerogen with TOC values of 2.7 to 6.2%. Rock‐Eval Tmax values ranging from 443 to 452 °C correspond to calculated vitrinite reflectance of approximately 0.8–0.9%. A cross‐plot of hydrogen index versus Tmax indicates that the samples have reached peak oil to wet gas maturities. A pristane/n‐C17 versus phytane/n‐C18 cross‐plot, together with biomarker parameters such as the dominance of C29 over C27 and C28 steranes and high moretane/hopane ratios (0.22–0.51), demonstrate that the shale samples contain terrigenous organic matter deposited in a suboxic environment.Scanning electron microscopy images of shale samples show the presence of a complex, mostly intergranular pore network. Both micropores (&gt;0.75μm) and nanopores (&lt;0.75μm) were observed. Some pores are elongated and are associated with layer‐spaces in sheet silicate minerals; others are non‐elongated and irregular in shape. The organic geochemical parameters and the observed pore attributes suggest that the Barren Measures Formation has good shale gas potential.

Lithofacies architecture and palaeogeography of the Late Paleozoic glaciomarine Talchir Formation, Raniganj Basin, India

Talchir Formation (Permo–Carboniferous) of the Gondwana Supergroup records the Late Paleozoic glaciation in Peninsular India. Talchir sedimentary succession of the Raniganj Basin, Damodar Valley Coalfields, Peninsular India, bears ten facies types grouped under three facies associations, viz., the proglacial conglomerate–sandstone facies association (CS), the foreshore–shoreface conglomerate–sandstone–mudstone facies association (CSM) and the prodelta–shelf sandstone–mudstone facies association (SM). Overall facies architecture reflects initial ice–covered terrestrial subglacial sedimentation, which was subsequently reworked and emplaced subaqueously in front of the ice–grounding line, and finally overlapped by storm–laid prodelta–shelf sediments. Repeated glacial advance–retreats with shifts in the position of the ice–grounding line during phases of climatic amelioration led to multiple deglaciation– related fining–up cycles. Decoupled ice sheet and floating icebergs contributed icerafted debris (IRD) to these sediments. Gradual retreat of the ice sheet, however, restricted the supply of IRD towards top of the succession. Overlap of wave–agitated shoreface–shelf sediments on the glaciogenic sediments indicates widespread marine transgression caused by glacier melting during ice–house to green–house climatic transition, and crustal downsagging related to glacioisostasy. Subsequently, complete disappearance of the ice sheet caused basinal exhumation along with crustal uplift due to isostatic rebound, leading to multiple horst–graben bounded basinal systems, which received post–Talchir coal–bearing Gondwana sediments.