Sulphur study of the Palaeogene coals from Jaintia Hills, Meghalaya, NE India: Implications for palaeoenvironment, utilisation prospects, and environmental impacts

Coal samples of Eocene age (Shella Formation) from four different mines (Bapung, Jaintia, Sutunga, and Lakadong) of the Jaintia Hills of Meghalaya, Northeast India, were collected and investigated to observe the sulphur content and to understand the palaeoenvironment, utilisation prospects, and environmental impact. The study reveals that these coal samples contain sulphur in higher concentration (4.46% to 7.26%) both organic and inorganic forms. There are 3 coal seams exposed in the area. The organic sulphur is higher (2.53%-5.49%) than the inorganic forms (1.26%-1.77%). The upper seam is found to contain higher concentration of sulphur than the lower seam. Intra seam pyritic sulphur also shows an upward increasing trend. The high sulphur content in the coal seams suggests the marine influence in the peat-forming swamps. These coals are classified as High Sulphur coal (>1%) which is the main obstacle in the utilization although high volatile matter and hydrogen content strongly suggest that these coals are good for liquefaction. Moreover, during coal combustion emissions of sulphur dioxide produce acid rain, affecting the environment of the mine areas.

Changing Tropical Estuarine Sedimentary Environments with Time and Metals Contamination, Cest Coast of India

Estuaries are one of the major sub-environments of the coastal zone wherein freshwaters interact and mix with saline waters, and facilitate deposition of finer sediments, organic matter, and metals. Intertidal mudflat and mangrove sediment cores collected from estuaries along the central west coast of India were investigated for various sedimentological and geochemical parameters to understand the changes in the sedimentary depositional environments and various factors influencing the processes. Additionally, estuarine biota was examined to understand the bioaccumulation of metals with respect to bioavailability. The results indicated considerable changes in the depositional environments with time owing to sea-level changes; geomorphology of the estuaries; rainfall and river runoff; anthropogenic activities including construction of dams and bridges. The sediments in the estuaries are considerably polluted by metals and pose toxicity risks to the estuarine biota due to high metal bioavailability. Marine gastropods and mangrove plants act as prospective bio-indicators, and the bioremediation potential of mangroves for contaminated sediments was identified. Metal bioaccumulation in edible benthic biota can be harmful to the human health.

Evaluating the source and Quality of River and Groundwater using hydrochemistry and stable isotopesin Tawi Watershed, Jammu District, Jammu and Kashmir, India

Hydrogeochemical and isotopic composition of river and groundwater in Kandi and Sirowal belts of Jammu District in the Union Territory of Jammu and Kashmir was carried out to understand the recharge source and chemical nature of these waters for drinking water quality criteria. Physical parameters (temperature, pH, Total dissolved solids, total hardness and electrical conductivity), major cations and anions (Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, SO42-, NO3-) and stable isotopes (d18O and d2H) inTawi river and groundwater samples from hand pumps and tube wells were measured. The dominant cation is Ca2+ and the dominant anion HCO3- implyingCaHCO3type water in both river and groundwater. To assess the quality of water for drinking purposes, Groundwater Quality Index (GWQI) has been calculated. The GWQI indicates that Kandi and Sirowal belts are showing “Excellent” to “Good” category for drinking purposes. The stable isotopic composition of river water and groundwater is indicative of meteoric origin and enrichment before groundwater recharge. The stable isotopes in water suggest that the active canals in Sirowal belt,and rainfall and river water near the banks in Kandi belt contribute to ground water recharge.

Exploitation of Beach Sand Minerals in the Offshore Areas – Legal perspective in the light of MMDR Act, 1957 and OAMDR Act, 2002

Beach Sand Minerals (BSM) form by weathering and erosion of the rocks in the hinterland which are liberated, disintegrate by various processes and, are transportation by the streams to the sites of deposition (coastal plains). These minerals get concentrated along the coastal areas due to constant winnowing by wave action. It is well documented that sea level changes have occurred along the coastal areas at different points of time whose signatures on land can be seen in the form of palaeo-strandline occurring up to 15-20 km from the present day coast. On a similar analogy and in view of bathymetric profile of the sea floor, BSM deposits are expected in the offshore areas as well, in continuity to onshore deposits, which possibly are the submerged onshore deposits of the past. Mineral Concessions in respect of onshore BSM deposits are governed with the Mines and Minerals Development and Regulation (MMDR) Act, 1957 and those in the offshore are governed as per the Offshore Areas Mineral Development and Regulation (OAMDR) Act, 2002 and the rules thereunder respectively. This paper deals with various provisions of these Acts and recent policies of the Government to harmonize mineral concession in offshore areas in line with the onshore BSM deposits.

Provenance, Depositional and Diagenetic Reconstruction of the Early Palaeozoic Succession in Kupwara District, Kashmir, North-western Himalaya

Early Palaeozoic succession in Kupwara district of Jammu and Kashmir, North-western Himalaya comprise of sandstone, shale, carbonates and slate. The petrological properties of these rocks were used to work out the provenance, depositional environment and their diagenetic history. The siliciclastic sediments with interbedded carbonate rocks indicate shifts in sea level and consequent changes in energy conditions of the basin as well as biogenic interferences leading to carbonate precipitation in a shallow marine depositional environment. Provenance of these rocks has been of mixed nature with monocrystalline quartz dominant in sandstones indicating greater contribution from igneous sources.

Geochemistry and tectonic setting for the deposition of IOG siliciclastics at the western margin of Bonai Granite, Singhbhum-Orissa Craton, India

Bagiyabahal and Birtola areas are located in the south-western extension of the Noamundi-Koira Iron Ore Group (IOG) basin. Rock types exposed in the area comprises of siliciclastics and volcanics which occurs unconformably over the basement tonalite-trondhjemite granite-gneiss (Bonai Granite Phase-I). The cover rocks show sheared contact with the porphyritic Bonai Granite Phase-II. The IOG basin margin is suggested to be a part of a ‘volcanic passive margin’ as indicated by the geochemical behaviour of the siliciclastics as well as massive emplacements of mafic intrusives (doleritic sill, dyke and gabbro) and extrusives (basaltic lava flow) along faulted continental blocks. The siliciclastics comprise of U and Au bearing quartz-pebble conglomerate (QPC) and quartzite succession. It was deposited along the western margin of the Bonai granite (phase I) in anoxic conditions as indicated by their low Th/U ratios and presence of detrital uraninite grains. Repeated cycles of sedimentation and volcanism led to the formation of alternate layers of siliciclastics and basic bodies in the area. Major, trace and rare earth elements (REE) geochemical data suggests a semi-humid to humid palaeo-climatic environment of during the deposition in the passive continental margin setting characterized by fault-controlled sedimentation over a rift related faulted continental crust and shelf. Geochemical data suggests chemically weathered provenance dominated by clay minerals. Higher content of U, Th, Au, Cr, REE, platinum group of elements (PGE) and other geochemical ratios suggest a mixed provenance for the deposition of the siliciclastics comprising a predominantly acidic/granitic source possibly from the Bonai Granitic Complex (BGC) along with granite derived reworked quartzose sediments, minor basic and ultrabasic sources of Older Metamorphic Group (OMG). This paper attempts to characterize the geochemical behaviour, tectonic setting and provenance of the siliciclastics of Birtola and Bagiyabahal areas by analyzing drill core and surface samples.

Aeolian transportation mechanics and mass movement of surficial beach sands – a case study on Bendi-BaruvaMineral Sand Deposit, Srikakulam District, Andhra Pradesh

Surficial sediment transportation studies carried out in the beach zone of Bendi-Baruva mineral sand deposit show that sand grains are transported by wind (saltation and suspension) beyond the high water line. The sand population of the study area contains heavy mineral sands (~20%) like ilmenite, garnet and sillimanite which covers 95% of the heavy mineral distribution with subordinate amounts of monazite, rutile, and zircon whereas light mineral sands (~80%) contain mostly quartz. Due to the sorted nature of these beach and dune sands the whole spectra falls within a specific range of grain size which shows a bi-modal distribution, primary mode at 0.025cm and secondary at 0.015cm. Due to this variation in density and grain size, mass of these sand particles vary resulting in differential transportation in any energy regime. In the study area, on the beach near the frontal dunes, surficial concentration of garnet grains are observed in patches having an average thickness 0.2cm i.e. around ten times of the dominant grain diameter. This surficial enrichment of garnet grains resting on a semi-uniform sand surface is the result of differential transportation of the dominant mineral grains. As more than 80% of the grain size population show a dominant grain size of 0.025cm, the wind flow parameters for the whole population is standardized with mean grain diameter (D) of 0.025cm. Mass of dominant individual minerals arrived from the grain counting technique was tallied with the theoretical mass considering spherical shape of the grains indicates a difference of mass to be within 5%. For ease of calculation and generalization the grains were considered to be spherical and their theoretical masses were taken into consideration in calculations. Considering the whole spectra of mineralogical distribution, a theoretical mass group distribution for dominant different minerals of different dominant grain sizes were formulated and total six mass groups were identified. Because quartz (~80%), ilmenite, sillimanite and garnet (together ~20%) are the most abundant, their positions were identified specifically in the theoretical mass groups and only these are considered for further discussion. To analyse wind velocity and pressure at different heights from the surface, a sediment trap was fabricated using piezo-electric sensors. A tail was attached to orient the device parallel to the wind flow so that the piezo surfaces always face the wind flow at 900 angle. The device records pressure data and converts those into voltage. Using the velocity data, macroscopic physical quantities of aeolian transportation were calculated for the study area, which empirically show the effect of mass in differential transportation of the dominant minerals that gives rise to these surficial garnet patches.

Grain size variation in sand column along Chhatrapur coast, Ganjam district, Odisha – A clue to the depositional environment

The concentration of heavy mineral placer deposits along the coastal tracts are function of various favourable factors i.e. hinterland geological formations, prevalence of favourable climatic condition, their transportation through intricate drainage systems and various coastal processes, which operated during the geological past. Textural analysis of the available unconsolidated sediments from the present deposits is of vital importance to decode the prevailing depositional environment while grain size analysis is the major parameter used. Present study highlights the grain size analysis of the identified sand column from Chhatrapur Mineral Sand Deposit along the coastal tract of Odisha to infer the environment of deposition of heavy mineral bearing sand and their heavy mineral content variation. Standard procedure of sampling, data analysis and interpretation techniques were adopted. Result shows that, sands from frontal and rear dune are characterized by distinct bi-modal distribution, medium to fine, moderately to well sorted with good positive skewness, whereas, sand from Inter-dunal region shows dominant unimodal, medium to coarse grain, moderately poorly sorted nature and slightly positive skewness. The better heavy mineral concentration (10 to 25 % grade) in frontal and rear dunes is attributed to prevalence of aeolian dune deposition accompanied by good sorting. In contrast, the low concentration of heavy mineral (3 to 6 %) in inter dune region is due to occasional fluvial regime and poor sorting of sediments. Thus, grain size analysis can be an effective tool to decipher local prevailing depositional environment, which has a bearing on heavy mineral concentration as well.

Lithofacies Analysis of the Tista River Deposits, Rangpur, Bangladesh

Eight (8) distinct lithofacies within the fluviatile reach of the Tista River have been recognized by the detailed study of the sediments as exposed along the river bank and river bars. Genetically, the matrix-supported conglomerate (Gms), massive sand (Sm), Trough cross stratified sand (St), planar cross stratified sand (Sp), ripple laminated sand (Sr) comprise the channel deposits whereas, the ripple laminated sand (Sr), parallel laminated sand (Sh), clay with silt (Fl) and massive Clay (Fm) represent overbank fine deposits. The channel deposits were laid down under relatively high energy conditions compared to the sediments of overbank fines. The stratigraphic succession is indicative of fining upward sequence. The dominance of coarser-grained sediments at the base of the lithostratigraphic unit, especially the matrix supported conglomerate (Gms) suggests that the deposition took place in the proximal part of the Tista Fan, which might be of glacial origin. Massive clay (Fm) is the final stage of vertical aggradations in the overbanks, possibly in the floodplains, flood basins, and back swamps when the velocity of the transporting medium was virtually lean that promotes the deposition of clay materials from suspension. The growth of cracks in the sedimentary succession is resulting from the compaction of the sediments and/or instant change in the paleoslope direction. The unimodal distribution of paleocurrent data with high mode value indicates mainly unidirectional sediment transport. The study of the lithofacies manifests that the deposits are produced by the braided river and debris flows. The modification of the depositional pattern from debris flow to overbank fines discloses the change of climatic condition in the Quaternary period.

A Mass Balance Approach in Sediment Budgeting of Large Alluvial Rivers with special emphasis on the Brahmaputra in Assam

Morphology of an alluvial river channel is the consequence of erosion, sediment transport and sedimentation in a river. Sediment budget accounts for the sources, sinks and redistribution pathways of sediments, solutes and nutrients in a unit region over unit time. Human activities are the most important factors that affect the variation in the pattern of river sediment load. This paper discusses sediment budget of a few large rivers by review of literature and estimation of sediment budget of Brahmaputra River in Assam using mass balance approach. An attempt has also been made to discuss human and climatic impact on sediment load of major rivers of the world. Total sediment load in the Brahmaputra River at downstream location (India-Bangladesh border) was estimated to be 814×106 t/year. Considering 10% of sediment load of the Brahmaputra as bed load, suspended sediment load at downstream was estimated to be 733×106 t/year. Tributaries, bank erosion and scouring of river bed were found to contribute 52%, 27% and 21% respectively to sediment load of Brahmaputra at downstream locations. In spite of limitations of the dependable data, future complexity due to climate change impact and hydropower dam initiative in upstream of the River, the study is a simplified approach in sediment budgeting of the Brahmaputra.