Mahanadi Basin Research Articles

Palynostratigraphy and palaeoenvironment of the Permian sediments in Mand Coalfield, Mahanadi Basin, Chhattisgarh, India

Palynological investigation of 483.00 m deep subsurface Permian sediments of borehole MSK–1, in Sithra–Kurekela Block of Mand Coalfield, revealed four distinct palynoassemblage zones. These palynoassemblages belong to Lower and Upper Barakar (Early Permian), Barren Measures and Raniganj (Late Permian) palynofloras of Indian Gondwana. The oldest Palynoassemblage–I, (Scheuringipollenites barakarensis) recorded between 483.60–309.00 m depths, shows dominance of non–striate bisaccate pollen grains chiefly ― Scheuringipollenites followed by Faunipollenites in association with Indotriradites, Dentatispora, Verrucosispora and Microbaculispora related to Lower Barakar palynoflora. Palynoassemblage–II, (Faunipollenites varius) recorded between 303.40–139.40 m depths, showing the dominance of Faunipollenitesin association with Scheuringipollenites, Striatopodocarpites, Brevitriletes, Horriditriletes and Striamonosaccites, indicates Upper Barakar palynoflora. Palynoassemblage–III, (Densipollenites indicus) recorded between 135.55 to 92.50 m depths, showing the prominence of enveloping monosaccate pollen (Densipollenites) in association with Faunipollenites, Microfoveolatispora, Striatopodocarpites and Verticipollenites, indicates Barren Measures palynoflora. Palynoassemblage–IV, (Densipollenites magnicorpus) recorded between 90.90–27.00 m depths, is characterized by the dominance of striate bisaccate pollen taxa chiefly Striatopodocarpites and Faunipollenites along with Densipollenites, Navalesporites, Distriatites, Hamiapollenites, Crescentipollenites and Guttulapollenites indicating late Permian (Raniganj) age. Raniganj palynoflora has been demarcated in lithologically designated Barren Measures Formation. This is the first report of Late Permian (Raniganj) palynoflora from Sithra–Kurekela area of this coalfield. The age correlation also gets support from comparative studies with similar palynoassemblages known from Indian Gondwana. Palynofloral evidences indicate the prevalence of warm and humid conditions. Dominance of gymnosperms represented by glossopterids, conifers and cordaites along with low percentage of trilete spores (filicopsids and sphenopsids) suggests that the sediments were deposited under fresh to brackish water environment.

Estimate of gas hydrate saturations in the Krishna-Godavari basin, eastern continental margin of India, results of expedition NGHP-02

Abstract A total of 25 drill sites were established in the Krishna-Godavari (KG) and Mahanadi Basins along the eastern margin of India during the India National Gas Hydrate Program Expedition 02 (NGHP-02) with the goal to identify and characterize gas hydrate occurrences in sand-rich reservoir systems. The objective of this study is to characterize the gas hydrate bearing zones linked with two seismic inferred horizons (R1 and R2) and estimate gas hydrate saturations at two sites in Area B of the KG Basin: Sites NGHP-02-22 and NGHP-02-23. The upper seismic-imaged reservoir section (reflector R1) contains both pore-filling and fracture-filling gas hydrate, while the lower seismic-imaged reservoir section (reflector R2) has only pore-filling gas hydrate. Since electrical resistivity seems to be the most pronounced physical response to the presence of gas hydrate, we have analyzed the resistivity log data using Archie's empirical equation from two sites based on an isotropic reservoir model. In order to assess the gas hydrate saturation, we have also performed isotropic velocity modelling using the three-phase Biot equation (TPBE) and density log derived sediment porosities. At Site NGHP-02-22, the average gas hydrate saturation estimated using the resistivity log data and P-wave velocity modelling are 29% and 17%, respectively in the depth interval of 207–290 mbsf whereas at Site NGHP-02-23, the average gas hydrate saturation obtained from resistivity log data and P-wave velocity modelling are 25% and 60%, respectively in the depth interval of 271–288 mbsf. Estimated results are further validated with the pressure core derived gas hydrate saturations to ensure their reliability at the respective drill sites. It was found that P-wave velocity log-inferred gas hydrates show a slight mismatch with the pressure core derived hydrate saturations while, the electrical resistivity log based result depicts a major mismatch with the pressure core derived hydrate saturations. The reason for this discrepancy is likely due to isotropic resistivity analysis of the reservoir section having anisotropic properties.

India National Gas Hydrate Program Expedition-02: Operational and technical summary

Abstract The India National Gas Hydrate Program is being steered by the government of India's Ministry of Petroleum and Natural Gas (MoPNG) with participation of Directorate General of Hydrocarbons (DGH), Oil and Natural Gas Corporation Limited (ONGC), and the National Oil Companies and Research Institutes of India. The India National Gas Hydrate Program Expedition 01 (NGHP-01) established the presence of gas hydrate in the Krishna Godavari (KG) and Mahanadi Basins and in the offshore area of the Andaman Sea Basin. However, the gas hydrates discovered during NGHP-01 were mainly distributed as fracture-filling material in fine-grained clay-rich sediments. The India National Gas Hydrate Program Expedition 02 (NGHP-02) was carried out with an objective to discover gas hydrate in sand-rich sediment along the eastern offshore margin of India. ONGC planned and executed NGHP-02 on the behalf of the MoPNG. NGHP-02 started on March 3, 2015 and was completed on July 28, 2015 (total 147 days) using the Japanese scientific Drilling Vessel Chikyu (D/V Chikyu). During NGHP-02, 42 holes at 25 sites were drilled, cored, and/or surveyed with downhole logging tools. These sites were located in four areas along the eastern margin of India and formally named Area A (Mahanadi Basin, three sites), Area B (northern part of the KG-Basin, twelve sites), Area C (central part of the KG-Basin, six sites), and Area E (southern part to the KG-Basin, four sites). All 25 sites established during NGHP-02 were first drilled and logged with logging-while-drilling (LWD) tools and an additional 17 holes were then drilled and/or cored with conventional coring tools (HPCS/ESCS) or pressure coring tools (PCTB). Wireline logging was conducted in 10 holes and formation tests using a dual packer Modular Formation Dynamics Tester (MDT) tool were carried out in two holes. The onboard science team used the laboratory facilities on the D/V Chikyu to examine and analyse the physical properties, geochemistry, and sedimentology of all the cores collected during the expedition. Core samples were also analysed in additional post-expedition shore-based studies conducted in numerous domestic and international gas hydrate research laboratories. The NGHP-02 sediment cores were archived at the National Gas Hydrate Core Repository in Mumbai (India), which is associated with the ONGC Gas Hydrate Research and Technology Centre (GHRTC). The necessary data for characterizing the occurrence of gas hydrate, such as interstitial water chlorinities, core-derived gas chemistry, physical and sedimentological properties, thermal images of the recovered cores, pressure core and downhole measured logging data (LWD and/or conventional wireline log data), were obtained from most of the drill sites established during NGHP-02. Almost all the drill sites yielded evidence for the occurrence of gas hydrate; however, the inferred in situ concentration of gas hydrate varied substantially from site to site. For the most part, the interpretation of downhole logging data, core thermal images, interstitial water analyses, and pressure core images from the sites established during NGHP-02 indicate that the occurrence of concentrated gas hydrate is mostly associated with coarser grained (sand-rich) sediments. This paper presents the operational and technical summary of NGHP-02.

Gas hydrate reservoir identification, delineation, and characterization in the Krishna-Godavari basin using subsurface geologic and geophysical data from the national gas hydrate program 02 expedition, offshore India

Abstract During the National Gas Hydrate Program Expedition-02 (NGHP-02), logging while drilling, conventional coring and pressure coring, wire-line logging, vertical seismic profiling and formation pressure measurements were carried out in deep water portions of the Krishna-Godavari (K-G) and Mahanadi Basins along the eastern continental margin of India. A total of 42 research holes were completed for comprehensive data collection and measurements related to gas hydrate reservoir and host sediments properties with an objective to identify producible gas hydrate in sand-rich reservoirs that would be suitable for a future pilot production test. Shipboard and post cruise evaluation of physical properties measurements, pressure core dissociation studies and gas analysis of recovered core samples have confirmed the occurrence of sand hosted gas hydrate deposits in three operational areas named during NGHP-02 as Area B, Area C and Area E in the deep-water portion of the K-G Basin. The energy resource potential of the discovered gas hydrate deposits in the K-G Basin depends on many factors, including the quantity of available gas trapped as gas hydrate in the basin. Therefore, this study was undertaken to identify, characterize and delineate the discovered and confirmed gas hydrate prospects in the K-G Basin. Based on the integrated analysis of regional seismic data and NGHP-02 acquired borehole data, a total of 8 sand-rich reservoir constrained gas hydrate prospects have been identified and mapped in the K-G Basin (Areas B, C, and E) as described in this report.

Hydrologic Impacts of Climate Change : Quantification of Uncertainties

General Circulation Models (GCMs), which are mathematical models based on principles of fluid dynamics, thermodynamics and radiative transfer, are the most reliable tools available for projecting climate change. However, the spatial scale on which typical GCMs operate is very coarse as compared to that of a hydrologic process and hence, the output from a GCM cannot be directly used in hydrologic models. Statistical Downscaling (SD) derives a statistical or empirical relationship between the variables simulated by the GCM (predictors) and a point-scale meteorological series (predictand). In this work, a new downscaling model called CRF-downscaling model, is developed where the conditional distribution of the hydrologic predictand sequence, given atmospheric predictor variables, is represented as a conditional random field (CRF) to downscale the predictand in a probabilistic framework. Features defined in the downscaling model capture information about various factors influencing precipitation such as circulation patterns, temperature and pressure gradients and specific humidity levels. Uncertainty in prediction is addressed by projecting future cumulative distribution functions (CDFs) for a number of most likely precipitation sequences. Direct classification of dry/wet days as well as precipitation amount is achieved within a single modeling framework, and changes in the non-parametric distribution of precipitation and dry and wet spell lengths are projected. Application of the method is demonstrated with the case study of downscaling to daily precipitation in the Mahanadi basin in Orissa, with the A1B scenario of the MIROC3.2 GCM from the Center for Climate System Research (CCSR), Japan. An uncertainty modeling framework is presented in this work, which combines GCM, scenario and downscaling uncertainty using the Dempster-Shafer (D-S) evidence theory for representing and combining uncertainty. The methodology for combining uncertainties is applied to projections of hydrologic drought in terms of monsoon standardized streamflow index (SSFI-4) from streamflow projections for the Mahanadi river at Hirakud. The results from the work indicate an increasing probability of extreme, severe and moderate drought and decreasing probability of normal to wet conditions, as a result of a decrease in monsoon streamflow in the Mahanadi river due to climate change. In most studies to date, the nature of the downscaling relationship is assumed stationary, or remaining unchanged in a future climate. In this work, an uncertainty modeling framework is presented in which, in addition to GCM and scenario uncertainty, uncertainty in the downscaling relationship itself is explored by linking downscaling with changes in frequencies of modes of natural variability. Downscaling relationships are derived for each natural variability cluster and used for projections of hydrologic drought. Each projection is weighted with the future projected frequency of occurrence of that cluster, called ‘cluster-linking’, and scaled by the GCM performance…

Simulating the gas hydrate behavior at equilibrium dissociation: A study from Mahanadi basin of eastern offshore, India

Abstract A suitable model is developed by analyzing the effects of external stimuli such as changes in pressure and temperature on the gas production behavior for the multi-phase fluid system. Our ultimate goal was to assess and understand the response of the Mahanadi basin of eastern India, which is already identified as a prospective zone for gas hydrate exploration, while subjected to dissociation through numerical simulation. Further, a series of simulations were conducted to understand the spatial distributions of several key parameters including hydrate saturation, gas and aqueous phase velocities, heat flux, enthalpy changes, within the system. In this case, we have considered only the equilibrium reaction model to simulate the natural gas production during two vital hydrate dissociation mechanisms such as thermal stimulation and depressurization methods. Coupled equations of heat and mass balance were used in every subdomain of the simulation and the integral difference equations were used to model the hydrate-bearing geologic system of the studied region at different physicochemical environments. The simulation results suggest that the studied field has a great prospect for commercial gas production. Further, we identified that the speed of dissociation front varies with the boundary pressure, and depressurization is the suitable dissociation method to produce more gas from the studied field when compared to the thermal stimulation. The developed model can be used as an avenue for further detailed study of natural gas production from the hydrate reservoir of this region.

Dynamical characteristics of forecast errors in the NCMRWF unified model (NCUM)

Real-time medium-range weather forecasts (up to 10 days in advance) are prepared at the National Centre for Medium Range Weather Forecasting (NCMRWF), India using the UK Met Office Unified Model (NCUM) system. In this study, the dynamical characteristics of systematic errors of the NCUM model at 17 km horizontal resolution during the Indian summer monsoon (July and August 2017) are examined. It is found that the model has problem in maintaining the monsoon circulation and it weakens the monsoon by weakening the divergent winds over the Indian region. The model has a large spin up in global mean precipitation and evaporation from day-1 to day-3. In addition to the spin up problem, the model loses mass as the forecast length increases from day-1 to day-10. However, the mean surface pressure over India increases in forecasts from day-3 up to day-10. An anticyclonic circulation error over north Arabian Sea and adjoining region reduces moisture transport from the sea to the Indian land areas. The model has systematic tendency to forecast less rain as the forecast length increases. Differences between the ERA-Interim and the NCUM analysis in circulation and moisture parameters indicate uncertainties in the initial conditions and imbalance in moisture and divergence. Relationship between circulation errors and rainfall errors over a river basin (Mahanadi basin in Odisha) was studied. There is no linear relation between divergent or rotational components of wind errors and rainfall errors in forecasts over this basin. Even with a very small error in wind, the rainfall error could be as large as 10 cm/day or more in the basin.

High-resolution climate projections for South Asia to inform climate impacts and adaptation studies in the Ganges-Brahmaputra-Meghna and Mahanadi deltas

Climate impacts and adaptation studies often use output from impact models that require data representing future climates at a resolution greater than can be provided by Global Climate Models (GCMs). This paper describes the use of Regional Climate Model (RCM) simulations to generate high-resolution future climate information for assessing climate impacts in the Ganges-Brahmaputra-Meghna (GBM) and Mahanadi deltas as part of the DECCMA project. In this study, three different GCMs (HadGEM2-ES, CNRM-CM5 and GFDL-CM3), all using a single scenario for future greenhouse forcing of the atmosphere (RCP 8.5), were downscaled to a horizontal resolution of 25 km over south Asia using the HadRM3P RCM. These three GCMs were selected based on ability to represent key climate processes over south Asia and ability to sample a range of regional climate change responses to greenhouse gas forcing. RCM simulations of temperature, precipitation, and lower level (850 hPa) atmospheric circulation in the monsoon season (June, July, August, September – JJAS) were compared with observational datasets and their respective driving GCMs to ensure large-scale consistency. Although there are some biases in the RCM simulations, these comparisons indicate that the RCMs are able to simulate realistically aspects of the observed climate of South Asia, such as the monsoon circulation and associated precipitation that are key for informing downstream impacts and adaptation studies. Simulated future temperature and precipitation changes on seasonal and daily timescales suggest increases in both temperature and precipitation across all three models during the monsoon season, with an increase in the amount of extremely heavy precipitation over the GBM and Mahanadi basins. Despite different driving conditions, these results are consistent across all three RCM simulations, providing a level of confidence in the magnitudes and spatial characteristics of temperature and precipitation projections for South Asia.

Development of the Glossopteris flora and its end Permian demise in the Tatapani–Ramkola Coalfield, Son–Mahanadi Basin, India

Diverse macrofloral assemblages recovered from the Barakar, Raniganj, and Panchet formations of Tatapani–Ramkola Coalfield have been analysed. Plant fossils from nine localities represent typical Glossopteris floras of Permian age with Glossopteris as the dominant genus (33 species), whereas younger floral elements recorded from five locations are characterized by the presence of Triassic species, i.e., Glossopteris senii and G. gopadensis along with the genus Dicroidium.The complete flora includes 24 genera and 73 species. Three floristic assemblages identified on the basis of the macrofloras are the Barakar assemblage with 31 taxa, the Raniganj assemblage with 38 taxa, and the Panchet assemblage having 33 taxa. All the available data concerning megaplant remains, palynology, and petrology of this basin are reviewed and analysed to infer the diversity trends of Glossopteris flora through the sequence and its transformation at the Raniganj–Panchet boundary (?Permian/Triassic boundary) in this coalfield. The Barakar Formation has a moderate diversity of Glossopteris (18 species), which increases in Raniganj Formation (26 species) and declines in the Panchet Formation (16 species). There is a gradual upwards change in the taxonomic composition of the Raniganj assemblage, with a decline in diversity, although some typical Permian taxa (e.g., Paracalamites, Schizoneura, Dizeugotheca, Glossopteris, and Vertebraria) continued up to the Panchet Formation.In India, the continental Permian–Triassic boundary has been resolved mainly on the basis of palynomorph and macrofloral data and is conventionally taken to coincide with the boundary between the Raniganj and Panchet formations. The Raniganj–Panchet boundary has been tentatively proposed in one of the sections of this coalfield. At this boundary, the Glossopteris species typical of the Raniganj Formation (i.e., G. stenoneura and G. stricta) disappear. Some of the Glossopteridales taxa, continuing into the Panchet Formation, show relatively little discernable change from those found in the Raniganj Formation. The Panchet Formation exhibits a dominance of Dicroidium and also marks the appearance of ?Autunia, Heidiphyllum, Lepidopteris, Linguifolium, and Rissikia. Therefore, it is envisaged that plant life was only gradually transformed and evolved near this boundary, rather than being the subject of a comprehensive taxonomic turnover. The genus ?Autunia is reported for the first time from Indian Gondwana.

Prioritization of sub-catchments of a river basin using DEM and Fuzzy VIKOR

Abstract Fuzzy VIKOR, a decision making technique, is applied to prioritize 224 sub-catchments of Mahanadi Basin, India. Seven geomorphology based criteria viz., drainage density, bifurcation ratio, stream frequency, texture ratio, form factor, elongation ratio and circulatory ratio are estimated from five digital elevation models (DEMs). Triangular membership functions were formulated for each criterion for each sub-catchment which are based on individual values obtained from individual DEM's. Entropy method is employed for estimation of weights of criteria and a similar mechanism is followed while formulating triangular membership function for weights. Eight groups are formulated with a number of sub-catchments in each group as 5, 26, 69, 65, 29, 11, 12, 7 for taking up conservation measures. Effect of varying strategy weight, (ν) on the ranking pattern is also studied and found that ν value effects ranking pattern significantly.

Rainfall-Runoff Estimation Using SCS-CN and GIS Approach in the Kuakhai Watershed of the Mahanadi Basin of Bhubaneswar Odisha

Rainfall and runoff are significant constitute the source of water for recharge of ground water in the watershed. Rainfall is a major the primary source of recharge into the ground water. Other, substantial sources of recharge include seepage from tank, canals, streams and functional irrigation. Evaluation of water availability by understanding of rainfall and runoff is essential. Hydrometerological and hydrological data are an important role in the assessment of source water accessibility for planning and design of source water accessibility for planning and design of artificial recharge structures. The surface water resources are available in the watershed from runoff from rivers, streams and in surface water bodies. The total area of study is about 453.5km2, of which fall in kuakhai river basin so considered for runoff model assessment in a watershed is a precondition for the design of artificial recharge structures, reservoir and soil erosion control. Surface water resource planning and management is an important and critical issue in the hard rock regions. Runoff in a watershed affected by geomorphological factors, particularly, land use change affects the runoff volume and runoff rate significantly. In the present case study assumed to estimate the surface runoff from a catchment but one of the Curve Number methods is mostly used. The SCS-CN method is useful for calculation volume of runoff from the land surface meets in the river or streams. The proposed construction of artificial recharge structures can be thought of in the given study area. The output is useful for the watershed development and planning of water resources effectively. Rainfall and runoff are important components contributing significantly to the hydrological cycle, design of hydrological structures and morphology of the drainage system. Estimation of the same is carried out to determine and forecast its effects. Estimation of direct rainfall-runoff is always efficient but is not possible for most of the location in desired time. Use of remote sensing and GIS technology can be useful to overcome the problem in conventional methods for estimating runoff. In this paper, modified Soil Conservation System (SCS) CN method is used for runoff estimation that considers parameter like slope, vegetation cover, area of watershed.

Modeling of rising methane bubbles during production leaks from the gas hydrate sites of India

ABSTRACTNatural gas hydrates is considered as a strategic unconventional clean hydrocarbon resource in the energy sector. Understanding the behavior of the rising methane gas bubbles during production leaks from the deep marine gas hydrate reservoirs well head is essential for environmental impact studies and to design environmental monitoring systems. Numerical model for quantitatively characterizing the vertical dissolution pattern of the wellhead released methane gas bubbles is analyzed for three potential gas hydrate locations in India. Simulation results indicate that the methane bubbles with diameter of 10 mm can transport methane gas till 650, 800, and 750 m from the seabed in the Krishna–Godavari(KG), Mahanadi and Andaman basins respectively. Results brought out that potential well head damage during methane hydrate production at 1050 m water depth could release up to 28 m3 of methane gas, in which 50% of the molar mass shall get dissolved within 40 m of water column from the seafloor.

Statistical downscaling of precipitation using long short-term memory recurrent neural networks

Hydrological impacts of global climate change on regional scale are generally assessed by downscaling large-scale climatic variables, simulated by General Circulation Models (GCMs), to regional, small-scale hydrometeorological variables like precipitation, temperature, etc. In this study, we propose a new statistical downscaling model based on Recurrent Neural Network with Long Short-Term Memory which captures the spatio-temporal dependencies in local rainfall. The previous studies have used several other methods such as linear regression, quantile regression, kernel regression, beta regression, and artificial neural networks. Deep neural networks and recurrent neural networks have been shown to be highly promising in modeling complex and highly non-linear relationships between input and output variables in different domains and hence we investigated their performance in the task of statistical downscaling. We have tested this model on two datasets—one on precipitation in Mahanadi basin in India and the second on precipitation in Campbell River basin in Canada. Our autoencoder coupled long short-term memory recurrent neural network model performs the best compared to other existing methods on both the datasets with respect to temporal cross-correlation, mean squared error, and capturing the extremes.

Strain partitioning along the Mahanadi Shear Zone: Implications for paleo-tectonics of the Eastern Ghats Province, India

During Indo-Antarctic collision at c. 1.0 Ga, Eastern Ghats Province (EGP) granulites amalgamated with the Archean Indian craton. The northern boundary of the EGP was subsequently reworked, undergoing dextral strike-slip shearing at 0.5 Ga. This study documents a phase of dextral shearing within the EGP along WNW-ESE trending shear planes in c. 0.5 Ga mylonites of the Mahanadi Shear Zone. Regional structural trends in the EGP show a swing from NE-SW to the south of the shear zone, to WNW-ESE to its north. The mylonitic shear zone foliation has a sub-horizontal lineation associated with a prominent dextral shear sense in near-horizontal sections. Electron Back Scatter Diffraction (EBSD) studies on quartz confirm that mylonitisation was associated with dextral strike-slip movement in the greenschist facies. North of the Mahanadi Shear Zone, strain was partitioned into narrow dextral strike-slip shear zones along which the older granulite fabrics were transposed parallel to later WNW-ESE trending shear planes at lower grades of metamorphism. This regional-scale shearing at ∼ 500 Ma possibly resulted in a significant dextral shift of the northern EGP with respect to the south. The shear zone was reactivated in the Permian time during deposition of Gondwana sediments in the Mahanadi basin.

National Gas Hydrate Program Expedition 01 offshore India; gas hydrate systems as revealed by hydrocarbon gas geochemistry

Abstract The National Gas Hydrate Program Expedition 01 (NGHP-01) targeted gas hydrate accumulations offshore of the Indian Peninsula and along the Andaman convergent margin. The primary objectives of coring were to understand the geologic and geochemical controls on the accumulation of methane hydrate and their linkages to underlying petroleum systems. Four areas were investigated: 1) the Kerala-Konkan Basin in the eastern Arabian Sea, 2) the Mahanadi and 3) Krishna-Godavari Basins in the western Bay of Bengal, and 4) the Andaman forearc Basin in the Andaman Sea. Upward flux of methane at three of the four of the sites cored during NGHP-01 is apparent from the presence of seafloor mounds, seismic evidence for upward gas migration, shallow sub-seafloor geochemical evidence of methane oxidation, and near-seafloor gas composition that resembles gas from depth. The Kerala-Konkan Basin well contained only CO2 with no detectable hydrocarbons suggesting there is no gas hydrate system here. Gas and gas hydrate from the Krishna-Godavari Basin is mainly microbial methane with δ13C values ranging from −58.9 to −78.9‰, with small contributions from microbial ethane (−52.1‰) and CO2. Gas from the Mahanadi Basin was mainly methane with lower concentrations of C2-C5 hydrocarbons (C1/C2 ratios typically >1000) and CO2. Carbon isotopic compositions that ranged from −70.7 to −86.6‰ for methane and −62.9 to −63.7‰ for ethane are consistent with a microbial gas source; however deeper cores contained higher molecular weight hydrocarbon gases suggesting a small contribution from a thermogenic gas source. Gas composition in the Andaman Basin was mainly methane with lower concentrations of ethane to isopentane and CO2, C1/C2 ratios were mainly >1000 although deeper samples were

Paleomagnetic record for the past 80 ka from the Mahanadi basin, Bay of Bengal

High resolution paleomagnetic investigations were performed on a 50.08 m long sediment core (MD161/20) from Mahanadi basin, Bay of Bengal. Core yielded reliable paleomagnetic results for top 20 m below seafloor (mbsf) which spans about 80 ka. Based on the analysis of rock magnetic data, the core is subdivided into five distinct Zones: Zone 1 and Zone 2 cover top 20 mbsf and do not show any abrupt change in magnetic mineralogy, concentration and grain size. Zones 3 and 5 show significant reduction in χLF, χARM and SIRM due to dissolution of magnetic minerals. Zone 4 shows moderate values of χLF and SIRM. The low value of χARM suggests that magnetic signal is mostly carried by magnetic grains in PSD/MD state. The paleomagnetic data for the top 20 mbsf show four prominent geomagnetic excursions at ∼9 mbsf, ∼13.5 to 15 mbsf, ∼16.3 mbsf and ∼18 to 18.2 mbsf. The age-depth relationship is established using stratigraphic correlation between well-dated sedimentary core NGHP-01-19B and the core MD161/20. The ages of the observed excursions correspond to ∼18 to 20 ka, ∼42 to 49 ka, ∼54 to 57 ka and ∼69 to 70 ka. The excursions at ∼42 to 49 ka, ∼54 to 57 ka, and ∼67 to 70 ka is similar to the known excursions the Laschamp and the split Norwegian-Greenland Sea events (NGS-I and NGS-II). The excursion at 18–20 ka is not observed globally and may be related to lithological/sedimentological changes occurring during last glacial maxima (LGM). The virtual geomagnetic path (VGP) of Laschamp excursion traces clockwise loop. All excursions identified in present study fall in the periods of relatively low paleointensity.

Macroscopic charcoal remains as evidence of wildfire from late Permian Gondwana sediments of India: Further contribution to global fossil charcoal database

Although there have been numerous reports of the occurrence of charcoal from the Indian Permian sediments (Kashmir and the Domodar Basin), here we report a new occurrence of charcoal from the Lopingian sediments of Central India, which is evidence of wildfire occurrence in the Permian of Gondwana and an addition to the global fossil charcoal database. Charcoal, a product of incomplete combustion of vegetation, is extensively reported from the Permian sediments of southern and northern hemisphere. Numerous reports have been generated from palaeobotanical and petrographical aspects of Gondwana sediments of India but the presence of macroscopic fossil charcoal has been somewhat overlooked until the past few years by many researchers, though the fusinite (charcoal equivalent term in petrographical studies) from many coalfields of Indian Gondwana has been attributed to pyrogenitic origin. Our study was carried out on macroscopic charcoal fragments retrieved from an exploratory drill core MBKW-3 from Mand-Raigarh Coalfield in the central part of the Mahanadi Basin, eastern India. The analysis involved Scanning Electron Microscopy for study of anatomical features and reflecting microscopy for estimation of the temperature of fire of charcoal formation where the inertinite reflectance data (average of 3.33%) indicate that these charcoals are formed at a temperature above 500°C. Palynomorph composition and their probable botanical affinity indicate that gymnosperms were the major type of vegetation that contributed to fuel load for wildfire while pteridophytes constituted a minor proportion. The palynological data reveal the predominance of arborescent vegetation over herbaceous elements. Fusinite reflectance data indicate that these charcoals are formed at a temperature in excess of 500°C. The almost unabraded edges of these charcoals, their high degree of preservation, and an assorted assemblage of different sizes clearly indicate their hypoautochtonous nature.

Evaluating groundwater prospects using GIS techniques

Evaluating groundwater prospects is important for development and resource management of a region. In this work various features such as geomorphology, lithology, lineament, topography, soil type, and drainage pattern of a part of lower Mahanadi Basin was studied in order to delineate areas that are expected to be suitable for future groundwater exploration in the study region. The area is composed of geological features that vary from hard rock terrain in north-western part to deltaic plain and coastal region in the south-eastern part. An integrated analysis of various parameters provides better estimate of subsurface characteristics from groundwater perspective. On the basis of different weights assigned to geological factors, surface runoff, infiltration, and other factors, it was found that about 42% of the total area has good prospects of groundwater, whereas approximately 21% of the area has relatively feeble prospects. Borewell discharge data collected by the Central Groundwater Board (CGWB) confirm results obtained by GIS analysis. Results are useful for detailed investigations of the region through various geophysical techniques, pinpointing exploratory borewell locations and groundwater resource management for the region.

Permian macro- and miofloral diversity, palynodating and palaeoclimate implications deduced from the coal-bearing sequences of Singrauli coalfield, Son–Mahanadi Basin, central India

The coal-bearing sequences of Barakar and Raniganj formations exposed in Bina and Jhingurdah open-cast collieries, respectively, are analysed for their macro- and miofloral content. The sediment successions primarily comprise of sandstones, shales, claystones and coal seams. In addition to the diverse glossopterid assemblage, four palynoassemblage zones, namely Zones I and II in Bina Colliery and Zones III and IV in Jhingurdah Colliery, have also been recorded in the present study. The megafossil assemblage from the Barakar strata of Bina Colliery comprises of three genera, namely Gangamopteris, Glossopteris and cf. Noeggerathiopsis. Palynoassemblage-I is characterised by the dominance of non-striate bisaccate pollen genus Scheuringipollenites and subdominance of striate bisaccate Faunipollenites and infers these strata to be of Early Permian (Artinskian) age (Lower Barakar Formation). The palynoassemblage has also yielded a large number of naked fossil spore tetrads, which is the first record of spore tetrads from any Artinskian strata in the world and has a significant bearing on the climatic conditions. The palynoassemblage-II is characterised with the dominance of Faunipollenites over Scheuringipollenites and is indicative of Kungurian age (Upper Barakar Formation). The megafossil assemblage from the Raniganj Formation of Jhingurdah Colliery comprises of five genera with 26 species representing four orders, viz., Equisetales, Cordaitales, Cycadales and Glossopteridales. The order Glossopteridales is highly diversified with 23 taxa and the genus Glossopteris, with 22 species, dominates the flora. The mioflora of this colliery is represented by two distinct palynoassemblages. The palynoassemblage-III is correlatable with the palynoflora of Early Permian (Artinskian) Lower Barakar Formation. The assemblage suggests the continuity of older biozones into the younger ones. The palynoassemblage-IV equates the beds with composition V: Striatopodocarpites–Faunipollenites–Gondisporites assemblage zone of Tiwari and Tripathi (1992) of Late Permian (Lopingian) Raniganj Formation in Damodar Basin. The FAD’s of Alisporites, Klausipollenites, Falcisporites, Arcuatipollenites pellucidus and Playfordiaspora cancellosa palynotaxa in this assemblage enhance the end Permian level of the Jhingurdah Top seam, as these elements are the key species to mark the transition of Permian into the Lower Triassic.

Forecasting the Rainfall Pattern on Upstream of Hirakud Reservoir Using L-Moment for Accessing the Inflow

Changes in the rainfall pattern are a challenge for filling schedule of reservoir, when it is fulfilling various demands. In monsoon fed reservoirs, the target remains for attaining full reservoir capacity in order to meet various demands during non-monsoon period and the flood control. The planners always eye towards the inflow trend and perspective frequency of rainfall in order to counter the extreme events. In this study, the case of Hirakud reservoir of Mahanadi basin of India is considered as this reservoir meets various demands as well as controls devastating floods. The inflow trend has been detected by using Mann Kendall test. The frequency analysis of monthly rainfall is calculated using L-moment program for finalizing a regional distribution. The falling trend in inflow to reservoir is visualized in the month of July and August. The Wakeby distribution is found suitable for the monthly rainfall of July, September and October, where as in June and August, General Extreme Value (GEV), General Normal (GN) and Pearson Type-III (PT-III) distributions are found suitable. The regional growth factors for the 20, 40, 50 and 100-year return period rain-falls along with inflow to reservoir observed between 1958-2010 are calculated in this study as a referral for reservoir operation policy.