National Center for Earth Science Studies
National Center for Earth Science Studies
Selvakumar S.,Manonmaniam Sundaranar University |
Chandrasekar N.,Manonmaniam Sundaranar University |
Kaliraj S.,National Center for Earth Science Studies |
Magesh N.S.,Anna University
Environment, Development and Sustainability | Year: 2017
Groundwater pollution from anthropogenic sources is a serious concern affecting several river basins and coastal aquifer environment. It is very important to acquire the impacts of the enhanced anthropogenic pressure and climatic changes on the evolution of groundwater characteristics in this study. The present study aims to concentrate on the hydrogeochemical characteristics by evaluating the groundwater quality through geographical information system (GIS) and multivariate statistical approach. Fifty groundwater samples were collected from the river basin and analyzed for major physicochemical parameters. The analytical results were interpreted in GIS and multivariate statistical techniques and demarcated the spatial variation of groundwater quality and their site-specific influencing factors over time. The presence of Na–Cl facies reflects the saline nature in groundwater in and around salt pan area. Factor analysis reveals the characteristics of four factors, and it accounted for 88.7% total variability. Significant correlation between TDS with major components of Na+, Mg2+, Cl− ions indicate the presence of saline influence on the groundwater. Cluster I and Cluster II represent fresh to slightly saline in nature, Cluster III mainly indicates the average concentration of EC (8615 µS/cm), chloride (2738 mg/l), and salinity (4.67 mg/l) is mainly due to small-scale industrial effluents, salt pan, agricultural activities, and rock–water interaction with related minerals in evaporite deposits. © 2017 Springer Science+Business Media Dordrecht
Padmalal D.,National Center for Earth Science Studies
Environmental Monitoring and Assessment | Year: 2015
The paper deals with the hydrochemical characterization and water quality assessment of springs emerging from the Archaean crystalline basements at the foothills of Western Ghat mountains in the highlands and Neogene sedimentary formations in the coastal lowlands of Kerala in south west India. A total of 19 springs from two important river basins of southern Kerala such as Ithikkara and Kallada river basins were studied for 18 physico-chemical (temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), total hardness (TH), Na+, K+, Ca2+, Mg2+, CO3 2−, HCO3 −, Cl−, SO4 2− , NO3 −, SiO2, Fe2+, and F−) as well as bacteriological parameters. The discharge computations show that free-falling type of springs in the area discharge about 256.23 million liters of water a year. A comparative study between the spring water samples of highland and lowland regions reveal that the quality of spring water, except pH and bacteriological contents, satisfies the standards set by the Bureau of Indian Standards and World Health Organization for drinking water. Spring water samples collected from the lowlands register high value of Na+ and Cl− compared with the highlands. Bicarbonate, Ca2+, Mg2+, and K+ values are high in highland than lowland springs. The present study reveals that the spring water sources in the region can be developed as an alternate source for drinking water, provided pH correction and proper disinfection are done prior to its end use. © 2015, Springer International Publishing Switzerland.
Noujas V.,National Center for Earth Science Studies |
Thomas K.V.,National Center for Earth Science Studies |
Badarees K.O.,National Center for Sustainable Coastal Management
Ocean Engineering | Year: 2016
Coastal processes along the Munambam to Chettuwa coastline located at the south-west part of India have been studied to understand the role of a mudbank and artificial structures like breakwaters in causing shoreline changes. The mudbank occurring along this coast is different from those in South America, Lousiana and China. The morphology and coastal processes of the coast have been studied by collecting nearshore and beach data from 2009 to 2013. Location of the mudbank area has been shifting over the years from north to south. The beach at the mudbank and its north is accreting while the southern side is eroding. Harbor breakwaters and seawalls are other factors influencing beach stability. An erosion hotspot along this mudbank coast is identified and management interventions proposed based on numerical model studies using MIKE 21 SW model and LITPACK. The model results are calibrated and validated with field observations. Sediment transport along this sector was estimated using LITDRIFT module. Shoreline change was calculated using the LITLINE module. The production run was carried out with different management options and the most suitable option is recommended for the eroding sector. The other sectors do not require any intervention to sustain the beaches. © 2015 Published by Elsevier Ltd.
Sheela Nair L.,National Center for Earth Science Studies |
Sundar V.,Indian Institute of Technology Madras |
Kurian N.P.,National Center for Earth Science Studies
Procedia Engineering | Year: 2015
Accurate estimation of longshore sediment transport (LST) along the entire coastal stretch of Kerala is challenging as the sediment transport pattern varies both spatially and temporally depending on the nearshore wave climate, nearshore bedslope, shoreline orientation, coastal morphology, presence of hard structures etc. While majority of the locations show a net northerly drift, there are certain stretches of the coast which are dominated by southerly transport. For the estimation of longshore sediment transport the three commonly used formulae viz. CERC (SPM (1984)), Van Rijn (1991) and Kamphuis (2002) were considered. After detailed analysis of the computed LST results for different sectors of the coast using these formulae, the formula of Kamphuis (2002) which considers all the important parameters like the nearshore bed slope, sediment grain size and peak wave period in addition to the usual input parameters like the wave breaker height and wave breaker angle was selected as the most appropriate one. To understand the spatial and temporal variation in the LST pattern along the Kerala coast, the LST rates for eight important locations - viz. Trivandrum, Quilon, Aleppey, Andhakaranazhi, Nattika, Calicut, Kannur and Kasargod spread along the Kerala coast were computed adopting the Kamphuis (2002) formula. For computation of the LST rates for the eight locations, the one year site specific nearshore wave data derived from numerical model studies was used. For validation, the results were compared with that of the earlier estimations available in literature. It was observed that even though the net magnitude was of the same range, there were deviations in the direction. However, when the results were compared with field observations (where morphological indicators were used) a reasonable agreement could also be established for the directions. The net annual longshore sediment transport was found to vary between 0.32 × 105 m3 and 2.3 × 105 m3 along the Kerala coast and the net transport direction was pre-dominantly northerly for almost all the locations selected for the study. The maximum gross sediment transport of 12.85 × 105 m3 was obtained for Trivandrum but the net transport for this station was much less, and therefore comparable with other locations. © 2015 The Authors. Published by Elsevier Ltd.
Ravindra Kumar G.R.,National Center for Earth Science Studies |
Sreejith C.,National Center for Earth Science Studies |
Sreejith C.,P.A. College
Lithos | Year: 2016
The Kerala Khondalite Belt (KKB) of the southern India encompasses volumetrically significant magmatic components. Among these, orthopyroxene-bearing, felsic ortho-granulites, popularly known as charnockites in Indian context, constitute an important lithology. In contrast to the well-known phenomena of arrested charnockitization, the geochemical characteristics and petrogenesis of these ortho-granulite suites remain poorly studied, leaving geodynamic models envisaged for the KKB highly conjectural. In this paper, we try to bridge this gap with detailed results on orthopyroxene-bearing, felsic ortho-granulites spread over the entire KKB and propose a new petrogenetic and crustal evolution model. Based on geochemical characteristics, the orthopyroxene-bearing, felsic ortho-granulites (charnockites sensu lato) of KKB are classified into (1) tonalitic (TC), (2) granitic (GC), and (3) augen (AC) suites. Members of the TC follow sodic (characterized by decreasing CaO/Na2O), whereas those of the GC and AC follow calc-alkaline trends of differentiation. Geochemical patterns of the TC resemble those of the Archaean tonalite–trondhjemite–granodiorite (TTG) suites, with slightly magnesian character (average Mg# = 33), moderate LREE (average LaN = 154), low HREE (average YbN = 6) and Y (1–53 ppm; average 11 ppm). The TC is also characterized by positive to slightly negative europium anomalies (Eu/Eu* = 0.7 to 1.67). The GC and AC suites, on the other hand, resemble post-Archaean arc-related granites. The GC displays ferroan nature (average Mg# = 22), low to moderate degrees of REE fractionation (average [La/Yb]N = 34.84), high contents of Y (5–128 ppm; average 68), and low Sr/Y (1–98) ratios. Significant negative Eu anomalies (Eu/Eu* = 0.18–0.91; average 0.50) and low Sr (65–690 ppm) are also noted in the GC. Similar chemical characteristics are shown by the AC, with ferroan nature (average Mg# = 21), low to moderate degrees of REE fractionation (average [La/Yb]N = 26), high contents of Y (71–99 ppm; average 87), and low Sr/Y (average 2) ratios with significant negative Eu anomalies (Eu/Eu* = 0.03–0.31; average 0.23) and low Sr (average 160 ppm) contents. The protoliths of the TC are interpreted as being derived from partial melting of thickened oceanic-arc crust composed of Archaean mafic composite source rocks (i.e., eclogite and/or garnet amphibolite) with a garnet amphibolite residue. Geochemical features of the GC, such as high Rb/Sr (average 1.80) and Ba/Sr ratios (average values > 6), are considered as evidence for crustal reworking in their genesis, suggesting remelting of a quartzo-feldspathic (TTG) source, within the plagioclase stability fields. The geochemical features of the felsic ortho-granulite suite, substantiated with published geochronological data on members of the TC, GC, and AC suites, suggest a four-stage crustal evolution of the KKB. The first stage is marked by the formation of an over-thickened oceanic-arc. Zircon Hfc model ages of the TC and GC suites constrain the time of this juvenile magmatic crust-forming event as Meso- to Neoarchaean (2.8 to 2.6 Ga). The second stage corresponds to the production of TTG magmas by melting of the over-thickened oceanic-arc crust, subsequent to basaltic underplating during Palaeoproterozoic (ca. 2.1 Ga). The third stage was initiated by a transition in subduction style from shallow to steep due to continent-arc accretion. This stage is marked by the formation of granitic magmas through partial melting of the TTG crust and their differentiation into GC and TC. The zircon crystallization ages (1.89 and 1.85 Ga) of the GC indicate arc accretion occurred during the Palaeoproterozoic. The fourth stage of crustal evolution is correlated with the Mesoproterozoic (~ 1.5 Ga) emplacement of megacrystic K-feldspar granites (protoliths to the AC and augen gneisses). The distinct petrography, geochemistry and crystallization ages of the AC suggests recurrence of megacrystic, high-K calc-alkaline granitoids as the product of final phases of crustal-remelting marking subduction cessation. All these magmatic events are fairly well correlated with the major episodes of crustal growth observed in the once contiguous continental fragments (Sri Lanka and Madagascar) and worldwide events (2.7, 1.9, and 1.2 Ga) implying similar episodic nature in the lower crustal evolution of the KKB. © 2016 Elsevier B.V.
Kroner A.,Chinese Academy of Geological Sciences |
Kroner A.,University of Mainz |
Santosh M.,China University of Geosciences |
Hegner E.,Ludwig Maximilians University of Munich |
And 9 more authors.
Gondwana Research | Year: 2015
SHRIMP dating of magmatic zircons from granitoid gneisses and charnockites of the Trivandrum and Nagercoil Blocks in the granulite terrane of southernmost India yielded well-defined protolith emplacement ages between 1765 and ca. 2100Ma and also document variable recrystallization and/or lead-loss during the late Neoproterozoic Pan-African event at around 540Ma. Hf-in-zircon and whole rock Nd isotopic data suggest that the granitoid host rocks were derived from mixed crustal sources, and Hf-Nd model ages vary between 2.2 and 2.8Ga. A gabbroic dyke, emplaced into a charnockite protolith and deformed together with it, only contained metamorphic zircon whose mean age of 542.3±4.0Ma reflects the peak of granulite-facies metamorphism during the Pan-African high-grade event. The Sm-Nd whole-rock isotopic system of several granitoid samples dated in this study was significantly disturbed during granulite-facies metamorphism, most likely due to a CO2-rich fluid phase. Whole-rock Nd model ages are consistently older than zircon-derived Hf model ages.The Trivandrum and Nagercoil Blocks are reinterpreted as a single tectono-metamorphic terrane predominantly consisting of Palaeoproterozoic granitoids interlayered with supracrustal rocks that must be older than ca. 2100. Ma. Ductile deformation, migmatization and anatexis have obliterated the original rock relationships. These blocks probably have their counterpart in the Highland Complex of neighbouring Sri Lanka and in the high-grade Palaeoproterozoic terrane of southern Madagascar. We speculate that the southern Indian khondalites may have their counterparts in the khondalite belt of the North China Craton. © 2014.
Dubey C.P.,CSIR - Central Electrochemical Research Institute |
Tiwari V.M.,CSIR - Central Electrochemical Research Institute |
Tiwari V.M.,National Center for Earth Science Studies
Computers and Geosciences | Year: 2016
New measuring instruments of Earth's gravity gradient tensors (GGT) have offered a fresh impetus to gravimetry and its application in subsurface exploration. Several efforts have been made to provide a thorough understanding of the complex properties of the gravity gradient tensor and its mathematical formulations to compute GGT. However, there is not much open source software available. Understanding of the tensor properties leads to important guidelines in the development of real three dimensional geological models. We present a MATLAB computational algorithm to calculate the gravity field and full gravity gradient tensor for an undulated surface followed by regular geometries like an infinite horizontal slab, a vertical sheet, a solid sphere, a vertical cylinder, a normal fault model and a rectangular lamina or conglomerations of such bodies and the results are compared with responses using professional software based on different computational schemes. Real subsurface geometries of complex geological structures of interest are approximated through arrangements of vertical rectangular laminas. The geological application of this algorithm is demonstrated over a horst-type structure of Oklahoma Aulacogen, USA and Vredefort Dome, South Africa, where measured GGT data are available. © 2015 Elsevier Ltd.
Anoop Krishnan K.,National Center for Earth Science Studies |
Sreejalekshmi K.G.,Indian Institute of Space Science and Technology |
Vimexen V.,National Center for Earth Science Studies |
Dev V.V.,National Center for Earth Science Studies
Ecotoxicology and Environmental Safety | Year: 2016
The prospective application of sulphurised activated carbon (SAC) as an ecofriendly and cost-effective adsorbent for Zinc(II) removal from aqueous phase is evaluated, with an emphasis on kinetic and isotherm aspects. SAC was prepared from sugarcane bagasse pith obtained from local juice shops in Sree Bhadrakali Devi Temple located at Ooruttukala, Neyyattinkara, Trivandrum, India during annual festive seasons. Activated carbon modified with sulphur containing ligands was opted as the adsorbent to leverage on the affinity of Zn(II) for sulphur. We report batch-adsorption experiments for parameter optimisations aiming at maximum removal of Zn(II) from liquid-phase using SAC. Adsorption of Zn(II) onto SAC was maximum at pH 6.5. For initial concentrations of 25 and 100mgL-1, maximum of 12.3mgg-1 (98.2%) and 23.7mgg-1 (94.8%) of Zn(II) was adsorbed onto SAC at pH 6.5. Kinetic and equilibrium data were best described by pseudo-second-order and Langmuir models, respectively. A maximum adsorption capacity of 147mgg-1 was obtained for the adsorption of Zn(II) onto SAC from aqueous solutions. The reusability of the spent adsorbent was also determined. © 2015 Elsevier Inc.
David S.E.,Leibniz Center for Tropical Marine Ecology |
Chattopadhyay M.,National Center for Earth Science Studies |
Chattopadhyay S.,National Center for Earth Science Studies |
Jennerjahn T.C.,Leibniz Center for Tropical Marine Ecology
The Science of the total environment | Year: 2016
Anthropogenic inputs nowadays are the major source of nutrients to the coastal area. While a wealth of data exists from high latitude regions, little is known on the amount and composition of nutrient fluxes from densely populated tropical catchments. The South Indian Pamba River is a prime example in this respect because of its manifold human interventions such as the Sabarimala pilgrimage, the largest pilgrim centre in the world and agricultural practices. In order (i) to identify direct cause-effect relationships, (ii) to quantify land use specific nutrient inputs and (iii) to assess the respective impacts water was sampled along the river course during the pre monsoon, south west monsoon and north east monsoon periods in 2010 to 2012. Sampling segments were chosen according to prevailing land use. A socioeconomic survey on agricultural practices was conducted to collect information on the type, time and quantity of fertilizer application. Our results indicate (i) little human activities in the forest segment resulted in a low nutrient yield; (ii) pilgrim activities led to high ammonium and phosphate yields in the temple segment; (iii) specific fertilizer management resulted in moderate and maximum nitrate yields in the respective agriculture segments. Annual NPK fertilizer inputs to the catchment were 95 kg ha(-1) yr(-1).The average yield for the Pamba River catchment amounted to 3.5 kg ha(-1) yr(-1) of DIN and 0.2 kg ha(-1) yr(-1) of phosphate-P. As opposing predictions for densely-populated regions the N and P yields of the Pamba River are moderate to low on a global scale. It highlights the need for land use specific quantitative estimates from tropical regions in order to improve the global database and local water quality management. Copyright © 2015 Elsevier B.V. All rights reserved.
Harley S.L.,University of Edinburgh |
Nandakumar V.,National Center for Earth Science Studies
Precambrian Research | Year: 2016
In-situ zircon U-Pb isotopic and monazite Th-U-Pb chemical ages from leucosome in migmatitic paragneiss at Kanjampara in the Trivandrum Block, India, demonstrate the occurrence of high-T metamorphism and anatexis at 1.92 Ga. This Palaeoproterozoic tectonothermal event was strongly overprinted by the main Neoproterozoic-Cambrian granulite facies tectonism which itself involved significant partial melting and formation of garnet-bearing assemblages at 0.65 GPa and >820-860 °C. Monazite grains, which enclose zircon grains and locally preserve Palaeoproterozoic chemical age domains, were extensively reset and recrystallized at 565 ± 6 Ma. These monazite grains were further modified to form high-Th cuspate rims at 517 ± 15 Ma, equivalent to the lower intercept age for extensive Pb-loss from the highly discordant 1.92 Ga zircon, 528 ± 18 Ma. These results confirm that at least some of the metasedimentary paragneisses in the Trivandrum Block are polymetamorphic, initially metamorphosed in the Palaeoproterozoic in an event older than the 1.89-1.85 Ga granitic orthogneisses recognised from the area. The nature of the relationship between the paragneisses and older (2.0-2.1 Ga) granitic and charnockitic orthogneisses of the Trivandrum and Nagercoil Blocks, in particular whether they share the same Palaeoproterozoic history or were interleaved after 1.92 Ga, requires further investigation focussed on the presence or absence of the isotopic imprint of this event in both rock suites throughout the area.The growth or recrystallisation of monazite at ca. 565 Ma and its further modification at ca. 520 Ma indicates that the high-T metamorphism in the Pan-African was long-lived, with a duration of at least 45 Myr. This adds further weight to recent proposals, based on zircon-monazite isotopic studies from other localities in the Trivandrum Block, that the region formed the mid- to deep-crust of a long-lived collisional hot orogenic belt that welded Gondwana from ca. 580-510 Ma. © 2016 .