• Volume 123, Issue 6

      August 2014,   pages  1197-1449

    • Observed seasonal and intraseasonal variability of the East India Coastal Current on the continental slope

      A Mukherjee D Shankar V Fernando P Amol S G Aparna R Fernandes G S Michael S T Khalap N P Satelkar Y Agarvadekar M G Gaonkar A P Tari A Kankonkar S Vernekar

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      We present data from three acoustic Doppler current profilers (ADCPs) moored off Cuddalore (12°N), Kakinada (16.5°N), and Gopalpur (19°N) on the continental slope of the western Bay of Bengal and one mooring on the slope of the northern bay (89°E, 19°N; referred to as being located at Paradip). The data were collected during May 2009 to March 2013 and the observations show that the seasonal cycle, which includes the annual cycle, the semi-annual cycle, and a peak around 120 days, dominates the observed variability of the East India Coastal Current (EICC). Spectral analysis suggests that the 120-day peak dominates the seasonal variability at Paradip and is strong at Gopalpur and Kakinada. The annual cycle is coherent along the western boundary of the bay, i.e., the east coast of India, but with significant phase differences between moorings. At the semi-annual and 120-day periods, the alongshore coherence is weaker. Intraseasonal variability is weaker than the seasonal cycle, particularly at Cuddalore and Paradip, and it exhibits seasonality: the strongest intraseasonal variation is during spring (February–April). Peaks around 12 and 20–22 days are also seen at Gopalpur, Kakinada, and Cuddalore. A striking feature of the currents is the upward phase propagation, but there are also instances when phase propagates downward. The much lower vertical phase speed in the top ∼100 m at Cuddalore leads to a distinct undercurrent at this location; at other locations, the undercurrent, though it exists often, is not as striking. During spring, however, the EICC tends to flow poleward (eastward) at Cuddalore, Kakinada, and Gopalpur (Paradip) over the top ∼300 m, which is the maximum depth to which observations were made. The cross-shore component of the EICC is much weaker than the alongshore component at Cuddalore and, except for a few bursts during spring, at Kakinada and Gopalpur. It is only at Paradip, on the slope of the northern boundary, that significant cross-shore flows are seen during spring and the summer monsoon (June–August) and these flows are seen to be associated with eddy-like circulations in the altimeter data. We use the ADCP data to validate popular current data products like OSCAR (Ocean Surface Currents Analyses Real-time), ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II), and GODAS (Global Ocean Data Assimilation System). The OSCAR currents at Paradip match the observed currents well, but the correlation is much weaker at the other three locations. Both ECCO2 and GODAS fair poorly, particularly the latter because its variability in this boundary-current regime is extremely weak. Though it performs badly at Paradip, ECCO2 does capture the observed variability on occasions at the other locations.

    • Characterization of the atmospheric boundary layer from radiosonde observations along eastern end of monsoon trough of India

      Sagarika Chandra Arun K Dwivedi Manoj Kumar

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      In this paper, a comparison of two methods for the calculation of the height of atmospheric boundary layer (ABL), using balloon-borne GPS radiosonde data is presented. ABL has been characterized using vertical profiles of meteorological parameter. The gradient of virtual potential temperature (𝜃v) profile for the determination of mixed layer heights (MLH) and the mean value of turbulent flow depth (TFD) obtained from the vertical profile of Bulk Richardson Number ($R_{iB}$) have been used in this study. Oneyear data have been used for the study. There is large seasonal variability in MLH with a peak in the summer and winter whereas the TFD remained steady throughout the year. Results from the present study indicate that the magnitudes of TFD are often larger than the MLH.

    • Measurement of soil-gas radon in some areas of northern Rajasthan, India

      Vikas Duggal Asha Rani Rohit Mehra

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      The health hazards of the radioactive gas radon on general public are well known. In order to understand the level and distribution of 222Rn concentrations in soil-gas in Sri Ganganagar district of Rajasthan, a 222Rn survey was carried out for the first time using RAD7, an electronic radon detector manufactured by Durridge Company (USA), at different locations covering a total area of 10,978 km2, having a population of approximately 20 lakh. The measurement of 222Rn concentration in soil-gas was carried out at four different depths (10, 40, 70, and 100 cm). The radon concentration in soil-gas for 10, 40, 70, and 100 cm depths ranged from 0.09–4.25, 0.15–6.30, 0.50–9.18, and 0.72–10.40 kBq m−3, respectively. The minimum value of radon concentration is observed in 33 GB village at 10 cm depth and maximum for Mohanpura village at 100 cm depth. As expected, our data show an increase of soil-gas radon concentration levels with depth. The present results are compared with the available radon data from other studies.

    • Sensitivity of meteorological input and soil properties in simulating aerosols (dust, PM10, and BC) using CHIMERE chemistry transport model

      Nishi Srivastava S K Satheesh Nadège Blond

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      The objective of this study is to evaluate the ability of a European chemistry transport model, ‘CHIMERE’ driven by the US meteorological model MM5, in simulating aerosol concentrations [dust, PM10 and black carbon (BC)] over the Indian region. An evaluation of a meteorological event (dust storm); impact of change in soil-related parameters and meteorological input grid resolution on these aerosol concentrations has been performed. Dust storm simulation over Indo-Gangetic basin indicates ability of the model to capture dust storm events. Measured (AERONET data) and simulated parameters such as aerosol optical depth (AOD) and Angstrom exponent are used to evaluate the performance of the model to capture the dust storm event. A sensitivity study is performed to investigate the impact of change in soil characteristics (thickness of the soil layer in contact with air, volumetric water, and air content of the soil) and meteorological input grid resolution on the aerosol (dust, PM10, BC) distribution. Results show that soil parameters and meteorological input grid resolution have an important impact on spatial distribution of aerosol (dust, PM10, BC) concentrations.

    • Total column ozone retrieval using INSAT-3D sounder in the tropics: A simulation study

      P Jindal P K Thapliyal M V Shukla A K Mishra D Mitra

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      The present study examines the potential of infrared sounder observations from Indian geostationary satellite INSAT-3D for the estimation of total column integrated ozone over the tropical Indian region. A dataset with diverse profiles was used to create training and testing datasets using forward simulations from a radiative transfer model for infrared sounder channels. A study was carried out for the standard tropical atmospheric profile to examine the sensitivity of ozone band radiance corresponding to the atmospheric temperature, water vapour, and ozone mixing ratios at different atmospheric pressure levels. Further, statistical retrieval technique has been used for the total column ozone estimation using two different approaches: (i) ozone channel observation along with the a-priori estimate of temperature and water vapour profile and (ii) only sounder channels observations. The accuracy of the retrieval algorithms was examined for different errors in the atmospheric profiles for the method (i) and different sensor noise specification for the method (ii). This study has shown that accurate temperature information is very important for ozone estimation and lower instrument noise results in better ozone estimates.

    • Spread-F during the magnetic storm of 22 January 2004 at low latitudes: Effect of IMF-Bz in relation to local sunset time

      R G Rastogi H Chandra P Janardhan Thai Lan Hoang Louis Condori T K Pant D S V V D Prasad B Reinisc

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      The paper describes the results of spread-F at low latitude stations around the world during the magnetic storm starting at 0130 UT on 22 January 2004. The storm can be divided into two phases, first phase up to 1000 UT when interplanetary magnetic field IMF-Bz was highly fluctuating around a small positive value and the second phase after a sudden large southward turning of IMF-Bz at 1030 UT. The first phase produced strong spread-F at Jicamarca, Sao Luis, and Ascension Island and caused complete inhibition of spread-F at Thumba and Waltair in India. It generated weak spread-F at Ho Chi Minh City in Vietnam and strong spread-F at Hainan and Chung Li. The strong spread-F at Hainan and Chung Li were caused by the positive IMF-Bz during the first phase of the storm and not by the negative pulse of IMF-Bz at 1000 UT.

    • The application of a hierarchical Bayesian spatiotemporal model for forecasting the SAA trapped particle flux distribution

      Wayan Suparta Gusrizal

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      We implement a hierarchical Bayesian spatiotemporal (HBST) model to forecast the daily trapped particle flux distribution over the South Atlantic Anomaly (SAA) region. The National Oceanic and Atmospheric Administration (NOAA)-15 data from 1–30 March 2008 with particle energies as < 30 keV (mep0e1) and < 300 keV (mep0e3) for electrons and 80–240 keV (mep0p2) and < 6900 keV (mep0p6) for protons were used as the model input to forecast the flux values on 31 March 2008. Data were transformed into logarithmic values and gridded in a 5° × 5° longitude and latitude size to fulfill the modeling precondition. A Monte Carlo Markov chain (MCMC) was then performed to solve the HBST Gaussian Process (GP) model by using the Gibbs sampling method. The result for this model was interpolated by a Kriging technique to achieve the whole distribution figure over the SAA region. Statistical results of the root mean square error (RMSE), mean absolute percentage error (MAPE), and bias (BIAS) showed a good indicator of the HBST method. The statistical validation also indicated the high variability of particle flux values in the SAA core area. The visual validation showed a powerful combination of HBST-GP model with Kriging interpolation technique. The Kriging also produced a good quality of the distribution map of particle flux over the SAA region as indicated by its small variance value. This suggests that the model can be applied in the development of a Low Earth Orbit (LEO)-Equatorial satellite for monitoring trapped particle radiation hazard.

    • A hydrological simulation of the water regime in two playa lakes located in southern Spain

      Rodriguez-Rodriguez Miguel Schilling Malte

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      The subject of this paper is the detailed hydrological simulation of two playa lakes located in southern Spain from January 2011 to March 2012 on a daily basis. These playas are placed over a 400-km2 shallow aquifer, which is exposed to an increasing stress caused by agricultural activities, mainly olive grove plantations. The objective of the paper is to elaborate a detailed numeric model that simulates the water regime of each playa lake on a daily scale. The simulation is compared to measured water level (WL) data of the playas in order to characterize the groundwater–surface interactions. The ultimate objective of this paper is to assess the environmental impact of the increasing anthropogenic water consumption within the area of research. The results of the GW–surface interaction were very consistent with previous works. One of the playa lakes is groundwater-dependent and the other one is presumably a perched playa lake. The GW discharge of the former playa (214 mm) during the research period stands in sharp contrast to no regional GW discharge in the latter. Water level data prove that the hydrological year (2011–2012) had a very negative water budget. The evapotranspiration estimation was almost as high as double the sum of the precipitation, the runoff, and the groundwater discharge. The simulation of an anthropologically altered water regime proves that water retrieval has a harmful impact on the WL of the playa lakes as well as on the aquifer.

    • Response of bankfull discharge of the Inner Mongolia Yellow River to flow and sediment factors

      Suzhen Hou Ping Wang Yan Guo Ting Li

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      Bankfull discharge is a comprehensive factor reflecting the channel-forming capability of water flow and the flood and sediment transport capacity of a river channel. It is based on the interaction of the flow, sediment, and river channel, of which flow and sediment conditions play crucial roles. Using data recorded since the 1950s, this paper analyses statistically, the characteristics and variations of bankfull discharge at two stations on the Inner Mongolian reaches of the upper Yellow River. Results indicate that flood season variations in bankfull discharge are nonlinear and are governed by flood peak discharge, mean discharge, and the mean incoming sediment coefficients. Variation in bankfull discharge is related not only to the flow and sediment conditions of the current year but also to those of previous years. The 10-year moving average of flow and sediment conditions can be representative of present and previous years. By considering flood season peak discharge and incoming sediment coefficients as independent impact factors, a formula is derived to determine bankfull discharge. The results can be used to predict the bankfull discharge of the Yellow River channel in Inner Mongolia under specific flow and sediment conditions and provide reference for the purpose of further study related to restoring and maintaining the basic functions of the river channel regarding flood discharge and sediments.

    • Analytical solutions for one-dimensional advection–dispersion equation of the pollutant concentration

      Ali S Wadi Mourad F Dimian Fayez N Ibrahim

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      We present simple analytical solutions for the unsteady advection–dispersion equations describing the pollutant concentration $C(x, t)$ in one dimension. The solutions are obtained by using Laplace transformation technique. In this study we divided the river into two regions 𝑥 ≤ 0 and 𝑥 ≥0 and the origin at 𝑥 = 0. The variation of $C(x, t)$ with the time 𝑡 from 𝑡 = 0 up to 𝑡 $\rightarrow \infty $ (the steady state case) is taken into account in our study. The special case for which the dispersion coefficient 𝐷 = 0 is studied in detail. The parameters controlling the pollutant concentration along the river are determined.

    • Predictive permeability model of faults in crystalline rocks; verification by joint hydraulic factor (JH) obtained from water pressure tests

      Hamidreza Rostami Barani Gholamreza Lashkaripour Mohammad Ghafoori

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      In the present study, a new model is proposed to predict the permeability per fracture in the fault zones by a new parameter named joint hydraulic factor (JH). JH is obtained from Water Pressure Test WPT) and modified by the degree of fracturing. The results of JH correspond with quantitative fault zone descriptions, qualitative fracture, and fault rock properties. In this respect, a case study was done based on the data collected from Seyahoo dam site located in the east of Iran to provide the permeability prediction model of fault zone structures. Datasets including scan-lines, drill cores, and water pressure tests in the terrain of Andesite and Basalt rocks were used to analyse the variability of in-site relative permeability of a range from fault zones to host rocks. The rock mass joint permeability quality, therefore, is defined by the JH. JH data analysis showed that the background sub-zone had commonly > 3 Lu (less of 5 × 10−5 m3/s) per fracture, whereas the fault core had permeability characteristics nearly as low as the outer damage zone, represented by 8 Lu (1.3 × 10−4 m3/s) per fracture, with occasional peaks towards 12 Lu (2 × 10−4 m3/s) per fracture. The maximum JH value belongs to the inner damage zone, marginal to the fault core, with 14–22 Lu (2.3 × 10−4 –3.6 × 10−4 m3/s) per fracture, locally exceeding 25 Lu (4.1 × 10−4 m3/s) per fracture. This gives a proportional relationship for JH approximately 1:4:2 between the fault core, inner damage zone, and outer damage zone of extensional fault zones in crystalline rocks. The results of the verification exercise revealed that the new approach would be efficient and that the JH parameter is a reliable scale for the fracture permeability change. It can be concluded that using short duration hydraulic tests (WPTs) and fracture frequency (FF) to calculate the JH parameter provides a possibility to describe a complex situation and compare, discuss, and weigh the hydraulic quality to make predictions as to the permeability models and permeation amounts of different zone structures.

    • Geomorphologic, stratigraphic and sedimentologic evidences of tectonic activity in Sone–Ganga alluvial tract in Middle Ganga Plain, India

      Sudarsan Sahu Dipankar Saha

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      The basement of the Ganga basin in the Himalayan foreland is criss-crossed by several faults, dividing the basin into several sub-blocks forming horsts, grabens, or half-grabens. Tectonic perturbations along basement faults have affected the fluvial regime and extent of sediment fill in different parts of the basin during Late Quaternary. The East Patna Fault (EPF) and the West Patna Fault (WPF), located in Sone–Ganga alluvial tract in the southern marginal parts of Middle Ganga Plain (MGP), have remained tectonically active. The EPF particularly has acted significantly and influenced in evolving the geomorphological landscape and the stratigraphic architecture of the area. The block bounded by the two faults has earlier been considered as a single entity, constituting a half-graben. The present investigation (by morpho-stratigraphic and sedimentologic means) has revealed the existence of yet another fault within the half-graben, referred to as Bishunpur–Khagaul Fault (BKF). Many of the long profile morphological characters (e.g., knick-zone, low width–depth ratio) of the Sone River at its lower reaches can be ascribed to local structural deformation along BKF. These basement faults in MGP lie parallel to each other in NE–SW direction.

    • Forest cover change prediction using hybrid methodology of geoinformatics and Markov chain model: A case study on sub-Himalayan town Gangtok, India

      Anirban Mukhopadhyay Arun Mondal Sandip Mukherjee Dipam Khatua Subhajit Ghosh Debasish Mitra Tuhin Ghosh

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      In the Himalayan states of India, with increasing population and activities, large areas of forested land are being converted into other land-use features. There is a definite cause and effect relationship between changing practice for development and changes in land use. So, an estimation of land use dynamics and a futuristic trend pattern is essential. A combination of geospatial and statistical techniques were applied to assess the present and future land use/land cover scenario of Gangtok, the subHimalayan capital of Sikkim. Multi-temporal satellite imageries of the Landsat series were used to map the changes in land use of Gangtok from 1990 to 2010. Only three major land use classes (built-up area and bare land, step cultivated area, and forest) were considered as the most dynamic land use practices of Gangtok. The conventional supervised classification, and spectral indices-based thresholding using NDVI (Normalized Difference Vegetation Index) and SAVI (Soil Adjusted Vegetation Index) were applied along with the accuracy assessments. Markov modelling was applied for prediction of land use/land cover change and was validated. SAVI provides the most accurate estimate, i.e., the difference between predicted and actual data is minimal. Finally, a combination of Markov modelling and SAVI was used to predict the probable land-use scenario in Gangtok in 2020 AD, which indicted that more forest areas will be converted for step cultivation by the year 2020.

    • Tectonic imprints within a granite exposed near Srinagar, Rajasthan, India

      Trishit Ruj Nilanjan Dasgupta

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      Partial melting in the middle to lower crustal level produces melts of granitic composition during orogeny. Thrusts play a vital role in their exhumation after consolidation of these granitic melts. In this paper we focus on one such granite along the eastern margin of the Delhi Fold Belt (DFB) rocks near Srinagar, Rajasthan, India. This is the first report of granite within the area and holds a key stratigraphic position in the entire rock package. The said granite is found to be intrusive to the DFB metasediments as well as their basement popularly known as the Banded Gneissic Complex (BGC). We disentangle the deformation fabrics seen within the granite and associated DFB metasediments, suggesting that subsequent to emplacement and consolidation, the granite has co-folded along with the country rocks. Three deformational events could be identified within the DFB metasediments namely, D1D, D2D and D3D. The peak metamorphism was achieved in the D1D event. The granite magma is generated and emplaced late syn-kinematic to D1D and thereafter is deformed by D2D and D3D producing D1G and D2G structural fabrics. These compressive deformations resulted in the collapse of the basin; the combined package of DFB rocks and the granite was thrusted eastwards over the basement rocks. The tectonic transport direction during thrusting is suggested eastwards from our structural analysis. Transverse faults developed perpendicular to the length of the granite have led to partitioning of the strain thereby showing a heterogeneity in the development of fabric within it.

    • GPR studies over the tsunami affected Karaikal beach, Tamil Nadu, south India

      V J Loveson A R Gujar R Barnwal Richa Khare G V Rajamanickam

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      In this study, results of GPR profiling related to mapping of subsurface sedimentary layers at tsunami affected Karaikal beach are presented. A 400 MHz antenna was used for profiling along 262 m stretch of transect from beach to backshore areas with penetration of about 2.0 m depth (50 ns two-way travel time). The velocity analysis was carried out to estimate the depth information along the GPR profile. Based on the significant changes in the reflection amplitude, three different zones are marked and the upper zone is noticed with less moisture compared to other two (saturated) zones. The water table is noticed to vary from 0.5 to 0.75 m depth (12–15 ns) as moving away from the coastline. Buried erosional surface is observed at 1.5 m depth (40–42 ns), which represents the limit up to which the extreme event acted upon. In other words, it is the depth to which the tsunami sediments have been piled up to about 1.5 m thickness. Three field test pits were made along the transect and sedimentary sequences were recorded. The sand layers, especially, heavy mineral layers, recorded in the test pits indicate a positive correlation with the amplitude and velocity changes in the GPR profile. Such interpretation seems to be difficult in the middle zone due to its water saturation condition. But it is fairly clear in the lower zone located just below the erosional surface where the strata is comparatively more compact. The inferences from the GPR profile thus provide a lucid insight to the subsurface sediment sequences of the tsunami sediments in the Karaikal beach.

    • Chromian spinel-rich black sands from eastern shoreline of Andaman Island, India: Implication for source characteristics

      Koyel Bhatta Biswajit Ghosh

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      Black sands rich in chromian spinel commonly occur in pockets along the eastern shoreline of Andaman Island where various types of peridotites and volcanics belonging to the Andaman ophiolite suite are exposed in close vicinity. The chemistry of these detrital chromian spinels has been extensively used here in identifying the source rocks vis-à-vis deciphering the source characteristics. The composition of the chromian spinels (Cr#: 0.20–0.88, Mg#: 0.26–0.77, Al2O3: 5.04–48.21 wt.%, TiO2: up to 1.39 wt.% and Fe2+/Fe3+: 1.73–9.12) varies widely signifying multiple sources, of which mantle peridotites and volcanic rocks are relevant in an ophiolitic terrain. The volcanic chromian spinels are relatively fresh, commonly euhedral, sometimes with compositional variations, and contain inclusions in contrast to the mantle peridotitic chromian spinels which are rounded, extensively fractured, and altered. We used a number of geochemical bivariate plots in order to know the provenance protoliths. The volcanic chromian spinels show geochemical characters of MORB, related to spreading centers (either MOR or back-arc) and also boninites/arc-tholeiites, related to active subduction. On the other hand, the peridotitic spinels indicate partially depleted lherzolite and depleted harzburgite source of the ophiolite suite.

    • An appraisal of an iterative construction of the endmembers controlling the composition of deep-sea manganese nodules from the Central Indian Ocean Basin

      R M Renner B N Nath G P Glasby

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      This paper describes an estimation of endmember compositions followed by the assessment of those results by log-ratio variance analysis. As an appraisal, it deals only with the first objective of an endmember analysis namely, to identify endmembers if they exist by estimating their compositions. Following the creation of the endmember estimates, the computation of an array of log-ratio variances was a key innovation in this type of study. Log-ratio variances revealed intrinsic linear associations between the dominant elements on each of the estimated endmember compositions, largely confirming the endmember analysis. The dataset under study contained the concentrations of 16 elements in 93 samples of deep-sea manganese nodules from the Central Indian Ocean Basin. Many previous analyses of these nodules were undertaken to assess the economic potential of the deposits. This study by contrast, quantified the interelement associations that account for the nodule compositions. Four endmembers were identified. The elements loaded on each were: (1) Mn, Zn, Ni, Cu, Mn-rich, (2) Fe, Ti, P, Co, Fe-rich, (3) Si, Al, Na, K, clay minerals, (3) Mg, ultramafic material, possibly including Mn, Cr, V, Ca, Na. These latter elements were also detected by their log-ratio variances to be associated with Mg on the 4th endmember.

    • Ichnofabric analysis of the Tithonian shallow marine sediments (Bhadasar Formation) Jaisalmer Basin, India

      Bhawanisingh G Desai Rajendra Dutt Saklani

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      The shallow marine sedimentary sequence of the Jaisalmer Basin exhibits one of the important and well-developed Tithonian sedimentary outcrops for western India. The ichnology and ichnofabric of the lower part of Bhadasar Formation (i.e., Kolar Dongar Member) belonging to Tithonian age are presented and discussed. The Kolar Dongar Member represents a shallow marine succession that contains 16 ichnotaxa: Ancorichnus ancorichnus, Conichnus conicus, Gyrochorte comosa, cf. Jamesonichnites heinbergi, Imponoglyphus kevadiensis, Laevicyclus mongraensis, Monocraterion tentaculatum, Ophiomorpha nodosa, Palaeophycus tubularis, P. bolbiterminus, Phycodes palmatus, Planolites beverleyensis, Rhizocorallium isp., Rosselia rotatus, R. socialis, and Teichichnus rectus. The ichnofabric analysis divulges five distinct ichnofabrics, each typifying distinct depositional environment within shallow marine conditions. The ichnofabric Ophiomorpha 1 with syn-sedimentary faulting exemplifies high energy conditions typical of lower shoreface environment, whereas the Ophiomorpha 2 ichnofabric typifies upper shoreface environment. The Ancorichnus ichnofabric reflects lower offshore condition of deposition. The high ichnodiversity Ancorichnus–Rosselia ichnofabric is indicative of inner shelf conditions, while low ichno-diversity Teichichnus ichnofabric indicates prevalence of low energy brackish bay environment. Thus, Tithonian Kolar Dongar Member indicates depositional environment ranging from shoreface to offshore to inner shelf and finally to brackish bay environment.

    • First megafossil evidence of Cyatheaceous tree fern from the Indian Cenozoic

      Subir Bera Sudha Gupta Mahasin Ali Khan Aniruddha De Radhanath Mukhopadhyay

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      A part of the compressed tree fern axis with leaf and adventitious root scars in unusual arrangement from Plio–Pleistocene sediments of Arunachal Pradesh, India is described as Cyathea siwalika sp. nov. This record suggests that Cyathea was an important component of tropical evergreen forest in the area during the Plio–Pleistocene and this group subsequently declined in importance within the local vegetation.

    • The chemical composition of tertiary Indian coal ash and its combustion behaviour – a statistical approach: Part 2

      Arpita Sharma Ananya Saikia Puja Khare D K Dutta B P Baruah

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      In Part 1 of the present investigation, 37 representative Eocene coal samples of Meghalaya, India were analyzed and their physico-chemical characteristics and the major oxides and minerals present in ash samples were studied for assessing the genesis of these coals. Various statistical tools were also applied to study their genesis. The datasets from Part 1 used in this investigation (Part 2) show the contribution of major oxides towards ash fusion temperatures (AFTs). The regression analysis of high temperature ash (HTA) composition and initial deformation temperature (IDT) show a definite increasing or decreasing trend, which has been used to determine the predictive indices for slagging, fouling, and abrasion propensities during combustion practices. The increase or decrease of IDT is influenced by the increase of Fe2O3, Al2O3, SiO2, and CaO, respectively. Detrital-authigenic index (DAI) calculated from the ash composition and its relation with AFT indicates Sialoferric nature of these coals. The correlation analysis, Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA) were used to study the possible fouling, slagging, and abrasion potentials in boilers during the coal combustion processes. A positive relationship between slagging and heating values of the coal has been found in this study.

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