Thiruvananthapuram, India
Thiruvananthapuram, India

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Radhakrishna T.,Center for Earth Science Studies | Chandra R.,Bundelkhand University | Srivastava A.K.,Bundelkhand University | Balasubramonian G.,Center for Earth Science Studies
Precambrian Research | Year: 2013

Mafic dykes in the central Indian Bundelkhand and eastern Indian Bastar cratons are potential sources for tracing the location of the Indian shield within Palaeoproterozoic supercontinent reconstructions. A total of 610 oriented core samples were collected from 27 mafic dykes (342 samples) in Bundelkhand craton and 20 dykes (268 samples) in Bastar craton. The characteristic magnetisations identify distinct groups of directions. The derived palaeopoles are integrated with recently reported U-Pb isotopic ages from the Bundelkhand and Bastar cratons and correlated with palaeopoles from the mafic dykes in the Dharwar craton, South India. Characteristic remanence (ChRM) identified in these dykes are classified into (i) steep upward/downward components further sub-grouped as ca. 2.37Ga steep 1 (λ=10.2°S; F{cyrillic}=75.0°E; A95=18.1° in Bundelkhand and λ=22.3°N; F{cyrillic}=71.4°E; A95=21.6° in Bastar), component comparable with ca. 2.4-2.45Ga steep 2 group from one dyke in Bundelkhand (λ=14°S; F{cyrillic}=101°E; A95=26.1°) and one dyke in Bastar (λ=6°N; F{cyrillic}=113°E; A95=26.5°). A steep component (λ=60.4°N; F{cyrillic}=45.3°E; A95=9.7° in Bundelkhand and a comparable component λ=49°N; F{cyrillic}=129°E; A95=15.1° from one dyke in Bastar) is not assigned an age at present. (ii) ca. 2.18Ga shallow easterly and antipodal shallow westerly components (λ=0.4°S; F{cyrillic}=347°E; A95=21.6° in Bundelkhand and λ=18.0°N; F{cyrillic}=344.0°E; A95=8.1° in Bastar) and (iii) 1.99Ga shallow northwest and antipodal shallow southeast (λ=57.5°N; F{cyrillic}=309.0°E; A95=4.7° in Bundelkhand and λ=39°N; F{cyrillic}=321°E; A95=28° in Bastar). A group (iv) of ~2.2Ga northeast shallow components (λ=36.0°S; F{cyrillic}=357.0°E; A95=9.4°) is found only in the Bundelkhand craton. The distinct groups of palaeomagnetic pole determinations from dykes of the Bundelkhand and Bastar craton exhibit a remarkable match with palaeomagnetic poles determined from Precambrian mafic dykes in the Dharwar craton. The close comparison of mafic dyke magnetisations between the cratons suggests close proximity since 2.45-2.5Ga. Models suggesting amalgamation of crustal blocks along the Central Indian Tectonic Zone at 1.8Ga or a 1.0Ga collision along this zone to form Rodinia are untenable. Testing of proposed NeoArchaean-Palaeoproterozoic supercontinent reconstructions showing a north China-India linkage or India's close proximity to Slave craton to form a supercraton 'Sclavia' are not supported. Instead, the data are compatible placing India in close proximity to the Yilgarn block of Western Australia. © 2012 Elsevier B.V.

Betsy J.,Government Dental College | Prasanth C.S.,Center for Earth Science Studies | Baiju K.V.,Government Womens College | Prasanthila J.,Government Dental College | And 2 more authors.
Journal of Clinical Periodontology | Year: 2014

Aim To evaluate the potential of antimicrobial photodynamic therapy (aPDT) as an adjunct to scaling and root planing (SRP) in the treatment of chronic periodontitis. Material and Methods In a single-centred randomized and controlled clinical trial, 90 patients (51 females and 39 males) with untreated chronic periodontitis were randomly assigned to receive SRP with aPDT (test group) or SRP alone (control group). Clinical parameters and halitosis were recorded for 6 months after treatment by a periodontist who was blinded to the procedure. Results Inter-group and intra-group statistical analyses were performed. Significant difference between the two groups with respect to each variable was assessed using non-parametric Rank Order ancova. Probing pocket depth and clinical attachment levels showed statistically significant reduction in the test group on evaluation at 3 months and 6 months as compared to the control group (p < 0.05). A statistically significant improvement in gingival index and gingival bleeding index was seen for the test group after 2 weeks and 1 month of aPDT (p < 0.01), whereas the improvement in gingival index and gingival bleeding index at 3 months and in plaque index at 2 weeks after aPDT was less (p < 0.05). Also, a significant difference was detected for the test group at 1 month in terms of halitosis (p < 0.05), which did not persist for long. Conclusions Antimicrobial photodynamic therapy acts as a beneficial adjunct to SRP in non-surgical treatment and management of chronic periodontitis in short-term. Further studies are required to assess the long-term effectiveness of aPDT. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Kuttippurath J.,University Pierre and Marie Curie | Bodeker G.E.,Bodeker Scientific | Roscoe H.K.,British Antarctic Survey | Nair P.J.,Center for Earth Science Studies
Geophysical Research Letters | Year: 2015

Equivalent effective stratospheric chlorine (EESC) construct of ozone regression models attributes ozone changes to EESC changes using a single value of the sensitivity of ozone to EESC over the whole period. Using space-based total column ozone (TCO) measurements, and a synthetic TCO time series constructed such that EESC does not fall below its late 1990s maximum, we demonstrate that the EESC-based estimates of ozone changes in the polar regions (70-90°) after 2000 may, falsely, suggest an EESC-driven increase in ozone over this period. An EESC-based regression of our synthetic "failed Montreal Protocol with constant EESC" time series suggests a positive TCO trend that is statistically significantly different from zero over 2001-2012 when, in fact, no recovery has taken place. Our analysis demonstrates that caution needs to be exercised when using explanatory variables, with a single fit coefficient, fitted to the entire data record, to interpret changes in only part of the record. Key Points Presents a thorough analysis on the EESC-based regression The EESC-based regression is inappropriate for estimating ozone trends Recommends a reinterpretation of the previous EESC-based trend estimates ©2014. American Geophysical Union. All Rights Reserved.

Radhakrishna T.,Center for Earth Science Studies | Joseph M.,Geological Survey of India
Bulletin of the Geological Society of America | Year: 2012

New geochemical and paleomagnetic results are presented on two Late Cretaceous dikes of the 85-90 Ma leucogabbroic and doleritic dikes and the 65-70 Ma dolerites in Kerala, India. The dikes are rich in incompatible elements, have fractionated patterns with light rare-earth element enrichment and are akin geochemically to Cretaceous basalts on the east coast of Madagascar. The magmas were formed at garnet lherzolite depths above the Marion plume, constituting part of a large igneous province in Madagascar. In contrast, the 65-70 Ma dolerites are moderately depleted in incompatible elements, with almost flat, rare-earth element patterns and resemble the upper formations of the Deccan Traps and the tholeiitic dikes of the Seychelles. These dolerites were formed by melting of spinel lherzolite over the Reunion plume. Paleomagnetic data from the dikes and the other coeval igneous units from south India provide the 90 Ma pole (latitude: 24°; longitude: 293°; A95 = 5.9; N = 18 sites) for India. The 65-70 Ma dolerites possess both normal and reverse polarities, and the mean pole (latitude: 36°; longitude: 283°; A95 = 5.7°; N = 10 sites) compares well with the Deccan superpole. Paleolatitude estimates indicate ~5° southward migration for the Marion plume and a northward migration for the Reunion plume, in conformity with global mantle-circulation models; however, distinguishing migration of the Reunion plume from the effects of true polar wander is difficult. Furthermore, the geodynamic reconstructions extending the shear zones of southern Madagascar into south India are not tenable. © 2012 Geological Society of America.

Whitehouse M.J.,Swedish Museum of Natural History | Ravindra Kumar G.R.,Center for Earth science Studies | Rimsa A.,Swedish Museum of Natural History | Rimsa A.,Lund University
Contributions to Mineralogy and Petrology | Year: 2014

Zircon crystals from a locally charnockitized Paleoproterozoic high-K metagranite from the Kerala Khondalite Belt (KKB) of southern India have been investigated by high-spatial resolution secondary ion mass spectrometry analysis of U-Th-Pb and rare earth elements (REE), together with scanning ion imaging and scanning ion tomography (depth-profiled ion imaging). The spot analyses constrain the magmatic crystallization age of the metagranite to ca. 1,850 Ma, with ultrahigh-temperature (UHT) metamorphism occurring at ca. 570 Ma and superimposed charnockite formation at ca. 520-510 Ma, while the ion imaging reveals a patchy distribution of radiogenic Pb throughout the zircon cores. Middle- to heavy-REE depletion in ca. 570 Ma zircon rims suggests that these grew in equilibrium with garnet and therefore date the UHT metamorphism in the KKB. The maximum apparent 207Pb/206Pb age obtained from the unsupported radiogenic Pb concentrations is also consistent with formation of the Pb patches during this event. The superimposed charnockitization event appears to have caused additional Pb-loss in the cores and recrystallization of the rims. The results of depth-profiling of the scanning ion tomography image stack show that the Pb-rich domains range in size from <5 nm to several 10 nm (diameter if assumed to be spherical). The occurrence of such patchy Pb has previously been documented only from UHT metamorphic zircon, where it likely results from annealing of radiation-damaged zircon. The formation of a discrete, heterogeneously distributed and subsequently immobile Pb phase effectively arrests the normal Pb-loss process seen at lower grades of metamorphism. © 2014 Springer-Verlag Berlin Heidelberg.

Joseph S.,Lund University | Ouseph P.P.,Center for Earth Science Studies
Water and Environment Journal | Year: 2010

The status of nutrients in Cochin Estuary in relation with other physico-chemical variables was assessed using monthly data from seven locations for a period of 3 years. Seasonal comparative assessments were made and the probable sources of nutrients were modelled using principal component analysis (PCA). The results pointed out that the nutrients have higher concentration in premonsoon season compared with other seasons. The correlation coefficients of nutrients pointed out that strong correlation exists indicating that their source of origin could be same. Factor analysis extracted three principal components (PCs) in which the first component attributed to run-off, the second to influx of marine water and the third to intensive human activities. The proposed statistical model based on PCA gave a reasonable explanation on relation between physico-chemical parameters and environmental factors which have far reaching implications in the management of water systems. © 2009 The Authors. Journal compilation © 2009 CIWEM.

Anoop Krishnan K.,Center for Earth Science Studies | Sreejalekshmi K.G.,Indian Institute of Space Science and Technology | Baiju R.S.,Center for Earth Science Studies
Bioresource Technology | Year: 2011

Bioavailability of Nickel in the form of hydrated Nickel(II) attributes to its toxicological effects and hence its removal from aqueous solution is of great concern. Adsorption is used as an efficient technique for the removal of Nickel(II), hereafter Ni(II), from water and wastewaters. Activated carbon obtained from sugarcane bagasse pith (SBP-AC), a waste biomass collected from juice shops in Sarkara Devi Temple, Chirayinkeezhu, Trivandrum, India during annual festival, is used as adsorbent in the study. The process of adsorption is highly dependent on solution pH, and maximum removal occurs in the pH range of 4.0-8.0. Moreover, the amount of Ni(II) adsorbed onto SBP-AC increased with the time increase and reached equilibrium at 4. h. Adsorption kinetic and equilibrium data were analyzed for determining the best fit kinetic and isotherm models. The overall study reveals the potential value of steam pyrolysed SBP-AC as a possible commercial adsorbent in wastewater treatment strategies. © 2011 Elsevier Ltd.

Sreebha S.,Center for Earth Science Studies | Padmalal D.,Center for Earth Science Studies
Environmental Management | Year: 2011

In the past few decades, the demand for construction grade sand is increasing in many parts of the world due to rapid economic development and subsequent growth of building activities. This, in many of the occasions, has resulted in indiscriminate mining of sand from instream and floodplain areas leading to severe damages to the river basin environment. The case is rather alarming in the small catchment rivers like those draining the southwestern coast of India due to limited sand resources in their alluvial reaches. Moreover, lack of adequate information on the environmental impact of river sand mining is a major lacuna challenging regulatory efforts in many developing countries. Therefore, a scientific assessment is a pre-requisite in formulating management strategies in the sand mining-hit areas. In this context, a study has been made as a case to address the environmental impact of sand mining from the instream and floodplain areas of three important rivers in the southwestern coast of India namely the Chalakudy, Periyar and Muvattupuzha rivers, whose lowlands host one of the fast developing urban-cum-industrial centre, the Kochi city. The study reveals that an amount of 11.527 million ty -1 of sand (8.764 million ty -1 of instream sand and 2.763 million ty -1 of floodplain sand) is being mined from the midland and lowland reaches of these rivers for construction of buildings and other infrastructural facilities in Kochi city and its satellite townships. Environmental Impact Assessment (EIA) carried out as a part of this investigation shows that the activities associated with mining and processing of sands have not only affected the health of the river ecosystems but also degraded its overbank areas to a large extent. Considering the degree of degradation caused by sand mining from these rivers, no mining scenario may be opted in the deeper zones of the river channels. Also, a set of suggestions are made for the overall improvement of the rivers and its biophysical environment. © 2010 Springer Science+Business Media, LLC.

Sreejith C.,Center for Earth Science Studies | Ravindra Kumar G.R.,Center for Earth Science Studies
Journal of Geodynamics | Year: 2013

The Proterozoic Kerala Khondalite Belt (KKB), southern India preserves a distinct high-grade terrain that is interpreted to have been situated adjacent to Madagascar and Sri Lanka during Gondwana assembly. As such, it has become a major focus for testing models of supercontinent amalgamation and dispersal. The lithounits of KKB have remarkable petrological similarities to the Highland Complex (HC) of Sri Lanka and south-central Madagascar. However, there is no well-constrained petrogenetic model for the KKB that fits explicitly within a supercontinent reconstruction model. We present here results from our on-going studies on the origin and evolution of K-rich (potassic, where K2O/Na2O>1) gneisses of KKB in relation to Proterozoic supercontinent events. Our results show, in a major departure from earlier metasedimentary origin, that potassic gneisses are metamorphosed granitoids. The metagranitoid samples display high K2O contents and low Al2O3/(FeO+MgO+TiO2) values. They are moderate to strongly peraluminous (ASI values ranging from 1.05 to 1.47) rocks showing mineralogical, petrological, and geochemical characteristics distinctive of the high-K calc-alkaline suites. Typical of igneous suites, the high-K metagranites show minor variation in chemical compositions with most oxides showing negative correlation with SiO2. Geochemistry illustrates distinctive features of arc-related magmas with LILE (K, Rb, and Th) and LREE enriched patterns and considerable depletion of HSFE (Nb, Zr, and Ti). The high-K metagranites are further characterized by strong negative anomalies of Eu (Eu/Eu*=0.10-0.44) and Sr, suggesting melting in plagioclase stability field and retention of plagioclase in the residual phase. Petrogenetic discrimination for granitoids, using major and trace elements demonstrates that the high-K metagranites of the KKB formed by partial melting of igneous source in lower- to middle-crust levels. Overall the geochemical features are supportive of origin in relation to a convergent margin setting, possibly in a continental magmatic arc system, which can be connected to the amalgamation and dispersal of continental fragments in a supercontinent event. This study, therefore, provides a lead towards more robust comparisons between the Proterozoic supercontinent events and processes. © 2012 Elsevier Ltd.

Radhakrishna T.,Center for Earth Science Studies | Krishnendu N.R.,Center for Earth Science Studies | Balasubramonian G.,Center for Earth Science Studies
Earth-Science Reviews | Year: 2013

Palaeomagnetic study of Palaeoproterozoic mafic dykes in the basement along the margins of the Cuddapah basin, the largest Precambrian sedimentary basin in south India, is presented in detail for a general discussion of Palaeoproterozoic igneous activity in India. The results are compared with all earlier published data on mafic dykes in India and are integrated with recently-published high-precision U-Pb baddeleyite ages to provide a comprehensive account of Palaeoproterozoic igneous activity in India. The analysis consolidates palaeomagnetic poles for six age divisions between 2.45 and 1.85Ga with robust statistical criteria. Our best estimates of overall mean poles from 241 dykes are situated at (1) λ=17.7°N; Φ=106.0°E (A95=9.0°; 7N=24) at c. 2.45Ga, (2) λ=7.1°N; Φ=57.2°E (A95=4.5°; N=69) at c. 2.37Ga, (3) λ=41.6°S; Φ=5.5°E (A95=5.1°; N=34) at c. 2.22Ga, (4) λ=4.7°N; Φ=343.0°E (A95=4.4°; N=31) at 2.18Ga, (5) λ=49.2°N; Φ=332.9°E (A95=4.8°; N=24) at 1.99-1.89Ga and (6) λ=73.7°N; Φ=282.6°E (A95=2.9°; N=39) at 1.86Ga. The data permit us to construct an apparent polar wander path for the Indian shield for an ~600Ma interval of the Palaeoproterozoic eon (2.45-1.85Ga). Testing and evaluation of continental reconstructions for this interval, which are mostly based on geological correlations, reveal many inconsistencies. Between 2.45 and 2.37Ga, the Indian shield was situated at higher latitudes similar to the Yilgarn craton of Australia. It was subsequently located near the equator at 2.22, 2.18, 1.99 and 1.86Ga. Thus, an India-Australia connection is supported during these times, but a proposed Australia-Kaapvaal link in "Zimvaalbara" and a Dharwar (India)-Slave connection in "Sclavia" or a Superior-Zimbabwe-India connection in "Superia" are inconsistent with Indian data. In addition, the close palaeomagnetic comparison between the Palaeoproterozoic dykes of Dharwar-Bastar-Bundelkhand cratons in India indicates an age of >2.45Ga for orogenic activity along the central Indian tectonic zone; hence, matching this zone with the 2.0-1.8Ga Trans-North China orogenic belt, or positioning North China adjacent to India or juxtaposition of the Indian shield along the western margin of Laurentia in the Columbia reconstructions is not supported. The Indian data appear to be in accord with the essential features of the refined Protopangaea model and the original Ur configuration. Finally, the results are interpreted in terms of four dyke emplacement events in the age range 2.45-2.18Ga linked to short-lived (5-10Ma) LIPs developed over mantle plumes. The dykes of ~1.99-1.89Ga age probably relate to continued long lived igneous activity while the ~1.86Ga dykes are relatively fewer in number and may represent waning stage of a large igneous event related to a major mantle plume. © 2013 Elsevier B.V.

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