014844   Ranawat P S;Mohan Kumar K;Sharma N K (Geology Dep, Mohanlal Sukhadia Univ, Udaipur-313 001, Email: psranawat@yahoo.com) : Production of epsom, gypsum and other industrial products from the mill tailings of Jhamarkotra rock phosphate project, India. Curr Sci 2009, 96(5), 713-17.

At the Jhamarkotra rock phosphate mines, the low-grade Proterozoic rock phosphate containing 14-19% P₂O₅ is beneficiated by froth flotation process to produce beneficiated rock phosphate having 32-34% P₂O₅, to provide raw material for fertilizer plants. The process generates considerable quantity of dolomitic tailings which contain 5-6% P₂O₅, 16-18% MgO and 32-34% CaO, that are potentially useful in agriculture. It is therefore necessary to utilize these products to conserve the diminishing, meagre and non-renewable phosphate resources of India. About 1500-1800 tonnes per day (TPD) of dolomitic tailings is produced through the processing of -3000 TPD of the ore, which is collected in the tailing ponds. Investigation carried out on final carbonate tails (FCT) of Jhamarkotra rock phosphate froth flotation beneficiation plant revealed that good quality epsom (MgSO₄-7H₂O)/fertilizer-grade magnesium sulphate, gypsum (CaSO₄-2HO) and magnesium ammonium phosphate (MAP) can be produced by leaching FCT with dilute sulphuric acid (30%) at 60-80°C and subsequent crystallization through evaporation and cooling. MAP also can be produced, which has citrate solubility of about 96%. MAP has proved to be beneficial for rice crop on acid as well as alkaline soils. Additionally, ammonium carbonate/carbon dioxide, hydrogen fluoride/calcium fluoride can also be produced. This scheme will certainly help reduce the wastage of these resources, mitigation of pollution and will generate additional revenue to the company.

5 illus, 5 tables, 15 ref

014843   Ranawat P;Mohan Kumar K;Sharma N K (Geology Dep, Mohanlal Sukhadia Univ, Udaipur-313 001, Email: psranawat@yahoo.com ) : Process for making slow-release phosphate fertilizer from low-grade rock phosphate and siliceous tailings by fusion with serpentinite. Curr Sci 2009, 96(6), 843-8.

Worldwide demand of phosphate fertilizer is met essentially from phosphatic rocks. India imports most of its requirements and produces a small portion through froth flotation of Precambrian stromatolitic rock phosphate. Increasing population and consequent increase in demand for food production necessitated investigation to utilize the large reserves of low-grade rock phosphate to produce an alternative fertilizer. An acceptable phosphate fertilizer was obtained by fusion of low-grade dolomitic and siliceous rock phosphate from Jhamarkotra mines, effluents from beneficiation plants of Jhamarkotra and Maton Rock Phosphate Projects and serpentinite rejects from Rikhabdev decor stone industry, in an electric furnace followed by quick quenching with water. This scheme may be adopted for all low-grade ores in the world, which will help utilize the large reserves of low-grade phosphate. Useful by-products are also recovered and the process is environment-friendly.

2 illus, 4 tables, 22 ref

014842   Ramana D V;Srinagesh D;Chadha R K (NO, National Geophysical Research Institute, Hyderabad-500 007, Email: dvr@ngri.res.in) : Spatial analysis of the frequency-magnitude distribution of aftershock activity of the December 2004 tsunamigenic Sumatra earthquake. Curr Sci 2009, 96(6), 834-7.

The study of aftershocks provides constraints on the fault dimension and the physical properties of materials within a seismogenic volume. To understand the tectonic setting, mode of faulting and other parameters which control the behaviour of the aftershock sequence, it is useful to study the b-value and the Omori decay of any tectonic setting. We have analysed the frequency-magnitude distribution and other parameters using modified Omori's law describing the aftershock activity of the Sumatra earthquake of 26 December 2004. Data from the NEIC catalogue for aftershocks of magnitude larger than 4.0 were used in this study. The rupture length of 1300 km has been divided into four different regions, which includes the main shock and the first major aftershock of magnitude 7.5. The b-values estimated for these four regions were found to vary from 0.9 to 1.2. Interpret these variations in terms of the rupture propagation of the main shock and the inhomogeneities within the aftershock region.

5 illus, 20 ref

014841   Rajeevan M;Bhate J (NO, National Climate Centre, Pune-411 005, Email: rajeevan@narl.gov.in) : High resolution daily gridded rainfall dataset (1971-2005) for mesoscale meterological studies. Curr Sci 2009, 96(4), 558-62.

In this communication, we discuss the development of a very high resolution (0.5° x 0.5 °) daily rainfall data-set for mesoscale meteorological studies over the Indian region. The dataset was developed using quality-controlled rainfall data from more than 3000 rain gauge stations over India. The analysis consists of daily rainfall data for all the seasons for the period 1971-2005. A well-tested interpolation method (Shepard's method) was used to interpolate the station data into regular grids of 0.5° x 0.5° lat. x long. After proper validation, it has been found that the present dataset is better compared to other available datasets. A few case studies have been shown to demonstrate the utility of the dataset for different mesoscale meteorological analyses. However, since the data density is not kept uniform, there is a possibility of temporal inhorao-geneity and therefore, the present dataset cannot be used for trend analysis. The dataset is freely available from the India Meteorological Department, Pune.

4 illus, 11 ref

014840   Raja R;Chaudhuri S G;Ravisankar N;Swarnam T P;Jayakumar V;Srivastava R C (Natural Resource Management Div, Central Agricultural Research Institute, PB 181, Port Blair 744 101) : Salinity status of tsunami-affected soil and water resources of South Andaman, India. Curr Sci 2009, 96(1), 152-60.

Two thousand and four tsunami has created havoc and excessive devastation in terms of human lives and loss of infrastructure in coastal areas of Andaman and Nicobar Islands, and rendered the soil and water resources salt-affected. In order to assess the changes in the relevant soil characteristics, viz. pH, electrical conductivity, sodium adsorption ratio, soluble cations (Na^{+, Ca2+ and Mg2+) and anions (CO2-₃, HCO₃-, SO2-₄ and Cl-), periodical soil and water sampling was done from selected soil series/locations of South Andaman. The results revealed that irrespective of soil series and water resources, the soluble salt concentration increased markedly post-tsunami (2005), making the soil highly saline/saline sodic. However, high rainfall during the subsequent years (3774 mm in 2005 and 3072 mm in 2006) has drastically reduced the salinity levels at these sites to almost close to the pre-tsunami levels. The results indicate the gradual recovery process of the salt-affected sites, which can be further augmented by adoption of appropriate location-specific engineering and agronomic management strategies.}

4 illus, 1 table, 23 ref

014839   Raj R;Yadava M (Geology Dep, Faculty of Science, The M.S. Univ of Baroda, Vadodara-390 002, Email: naveenrachna@gmail.com) : Late holocene uplift in the lower Narmada basin, western India. Curr Sci 2009, 96(7), 985-8.

A late Holocene depositional surface has been identified in the lower Narmada basin of western India. This terraced surface occupies the valley formed by the incision of the mid-late Holocene surface. Radiocarbon dating of organic-rich clay horizons indicates that these terrace sediments were deposited between 1900 and 1200 yrs BP, well corresponding with the large-magnitude palaeoflood records of the central Narmada basin. These terraces occur as 2-4 m high uplifted surfaces and point to a latest phase of tectonic uplift in the lower Narmada during the historical times.

4 illus, 17 ref

014838   Rai A K;Maurya A S (Earth and Planetary Sciences Nehru Science Center Dep, Allahabad Univ, Allahabad-211 002, Email: akrai@sancharnet.in) : Effect of miocene paleoceanographic changes on the benthic foraminiferal diversity at ODP site 754A (southeastern Indian ocean). Indian J Mar Sci 2009, 38(4), 423-31.

Miocene deep sea benthic foraminiferal diversity at ODI' site 754A, in the southeastern Indian Ocean was examined in the present study. Paleoceanographic and paleoclimatic ehangcs were inferred based on the above study. Species diversity was measured in terms of Shannon-Weaver Index [H(S)], Hurlbert's Diversity Index (S₁₀₀), Alpha Index (α) and Equitability (Iv). Values of SIQO show more positive correlation with H(S) and α value. All diversity parameters show almost similar pattern during the study interval. Present study infers that the changing trophic level has much influence on the faunal diversity. More diverse fauna of late early Miocene to early middle Miocene along with low δ^{18O and high δ13C values reflect warm and stable bottom waters with low food supply. This corresponds to the Miocene climatic optimum. This was also an interval of global warming and reduced Antarctic ice-sheet volume. Significant decline in diversity and δ13C values along with abrupt increase in δ18O values at ~ 14 Ma indicate cold, relatively less oxygenated and unstable bottom waters with increased food supply due to higher surface productivity. Development of thermal gradient between low and high latitudes in response to the expansion of Antarctic ice-sheet during 15-12.5 Ma was responsible for increased upwelling and high surface productivity. Decrease in faunal diversity at ~7 Ma onwards along with low δ13 C and high δ18O values corresponds with the Chron-6 negative Carbon shift, expansion of west Antarctic ice-sheets and lowering of sea level.}

4 illus, 65 ref

014837   Prasanti A;Thakur N K;Rao P P;Rajput S (NO, National Geophysical Research Institute, Uppal, Hyderabad-500 007, Email: nkthakur46@yahoo.com) : Modelling of BSRs as prime indicator of gas hydrates. Curr Sci 2009, 96(9), 1258-62.

To understand the complex phenomena associated with the formation of bottom simulating reflector (BSR), the main identifier for the presence of gas hydrate, we have generated synthetic responses of different seismic velocity (hydrate-free gas) models to draw meaningful reflection characteristics. The synthetic response of the model of high-velocity (hydrated) sediment layer underlain by low-velocity free-gas layer indicates a normal polarity reflector generated at the top edge of the hydrated layer and a strong reverse polarity reflector (BSR) at the interface of hy-drated/free-gas layer (base of the gas hydrate). The synthetic response of high-velocity hydrated layer sandwiched in the normal oceanic sediments produces reversely polarized reflector at its base (BSR). The BSR is quite distinguishable when the acoustic velocity of hydrated sediments is appreciably high. Model studies indicate that high-amplitude reverse polarity reflector (BSR) can be generated with only the presence of low-velocity (free-gas) layers overlain by normal sediments at a depth of a few hundred metres below the seafloor. There is appreciable increase in the strength of this reflector with lowering of velocity free-gas layer. The studies indicate that BSR may be generated in most of the cases where a strong impedance contrast exists due to either high-velocity gas hydrates or free-gas layer, and hydrates underlain by free-gas. Out of all three different configurations, hydrates underlain by free-gas produce BSRs with higher strength. The results from drill sites where BSRs were not found associated with gas hydrate may indicate that the BSR might have been produced due to the presence of free-gas only. Places where gas hydrate has been found without BSR may suggest that the gas hydrate may occur in lenses or very thin layers, not giving rise to appreciable impedance contrast for the generation of the BSR.

3 illus, 25 ref

014836   Prasad P S R;Srinivasa Sarma D;Sudhakar L; Basavaraju U;Singh R S;Begum Z;Archarya K B;Chavan C D;Charan S N (NO, National Geophysical Research Institute (Council of Scientific and Ind, Hyderabad-500 606, Email: psrprasad@ngri.res.in) : Geological sequestration of carbon dioxide in Deccan basalts: preliminary laboratory study. Curr Sci 2009, 96(2), 288-91.

Laboratory experiments to probe the carbon dioxide sequestration potential of picritic basalts from the Deccan Basalt volcanic province, Maharashtra are reported. Growth of certain secondary carbonates is clearly seen over the surface of picritic basalts, reacted with water and carbon dioxide in its supercritical condition. The reactions were kept for about 5 months duration at a temperature and pressure of 100°C and 60 bar of CO₂ respectively. Handpicked soft grains of secondary carbonates were characterized using infrared spectroscopy and the observed signatures in two of the picritic basalt samples (IGP-40 and IGP-29) match well with ankerite (Fe-carbonate), with negligibly small amounts of released SiO₂. While in another sample (IGP-36), the secondary carbonates have comparatively larger amounts of SiO₂.

2 illus, 1 table, 15 ref

014835   Pradhan U K;Shirodkar P V;Sahu B K (Chemical Oceanography Div, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: shirod@nio.org) : Physico-chemical characteristics of the coastal water off Devi estuary, Orissa and evaluation of its seasonal changes using chemometric techniques. Curr Sci 2009, 96(9), 1203-9.

Devi estuary is one of the major tributaries of the Mahanadi riverine system in Orissa. Modernization and industrialization in its neighbourhood in the north in the recent past have greatly influenced many tributaries of the Mahanadi and the adjacent coastal environments. To trace the influence of this modernization activity further down south off Devi estuary and to understand the quality of the Devi estuarine water reaching the coastal region, investigations on physico-chemical parameters (temperature, pH, salinity, dissolved oxygen), including dissolved nutrients (PO₄-P, NO₃-N, NO₂-N, SiO₄-Si) were carried out in the water off the mouth of the Devi estuary, during different months of the summer and winter seasons in 2006-07. The multivariate statistics and principal component analysis applied to the datasets, indicated three factors each during the summer and winter seasons influencing the water to the extent of 77 and 80% respectively. Principal axis factoring and alpha factoring have been used to observe the mode of association of parameters and their interrelationships, for evaluating water quality during the summer and winter seasons. The results indicated the addition of phosphates and silicates to the coastal water by the Devi estuary from natural sources during both the seasons. The anthropogenic nitrogenous species, as a fallout from modernization activities in the north, are more clearly observed off the mouth of the Devi estuary during the winter season. The study indicated that the Devi estuary adds sufficiently well-oxygenated, nutrient-rich water to the coastal region.

6 illus, 2 tables, 20 ref

014834   Patnaik R;Sahni A;Cameron D;Pillans B; Chatrath P;Simons E;Williams M;Bibi F (Centre of Advanced Studies in Geology, Panjab Univ, Chandigarh-160 014, Email: rajeevpatnaik@gmail.com ) : Ostrich-like eggshells from a 10.1 million-yr-old miocene ape locality, Haritalyanagar, Himachal Pradesh, India. Curr Sci 2009, 96(11), 1485-95.

Reports fossil ratite eggshells from the site, Dhar-amsala of Dhok Pathan Formation (Middle Siwaliks), dated to 10.1 Ma. A comparative analysis reveals that in their combination of eggshell surface, pore, pore canal morphology and cross-sectional features, the Indian eggshells show closest affinity with the widely distributed Neogene fossil taxon Struthiolithus, and as such are assigned to cf. Struthiolithus. We have carried out a parsimony analysis of all relevant extinct and extant palaeognathous birds of the southern continents, as ingroup taxa. Genyornis, an extinct bird from Australia, and Callus gallus (chicken) were also used in this analysis as ingroup (Neornithes) taxa. The result supports monophyly of Palaeognathae. The present cf. Struthiolithus eggshell and Aepyornis were found to be sister taxa and their forbearers had a common ancestry with Afro-Arabian Struthio and Diamantornis. The Indian subcontinent now has an extended fossil record of struthionid eggshells from the Late Miocene to the Late Pleistocene, implying dispersals through intercontinental migration corridors. Our stable carbon isotope (δ ^{3 CPDB) value of -10.4% of the present eggshells suggests that the ratite bird had a diet mainly of C₃ plants.}

9 illus, 1 table, 72 ref

014833   Pal D K;Bhattacharyya T;Srivastava P;Chandran P;Ray S K (Soil Resource Studies Div, National Bureau of Soil Survey and Land Use Planning, Nagpur-440 010, Email: dkpal@nbsslup.ernet.in) : Soils of the indo-gangetic plains: their historical perspective and management. Curr Sci 2009, 96(9), 1193-202.

The Indo-Gangetic Alluvial Plains (IGP) is among the most extensive fluvial plains of the world and cover several states of the northern, central and eastern parts of India. The IGP occupies a total area of approximately 43.7 m ha and represent eight agro-ecological regions (AER) and 14 agro-ecological subregions. The area of the IGP is nearly 13% of the total geographical area of the country, and it produces about 50% of the total foodgrains to feed 40% of the population of the country. Thus the sustainability of the present cropping system and also the health of the soils demand a review on the historical development of the soils and their management that remained associated with the tectonic, climatic and geomorphic history of the IGP since it came into existence due to collision of the Indian and Chinese plates during the Middle Miocene. This review provides a state-of-the-art information on the historical development of soils of the IGP, their tectonic-climate-linked natural degradation during the Holocene, and changes in the levels of carbon in soils under agriculture (mainly rice-wheat cropping system), practised over the years. In view of the vast area of the IGP, research initiatives on benchmark soils are, however, still needed to record the subtilities in pedogenesis, especially their polygenetic history due to climate change during the Holocene. This way a historical soil-climate-crop databank may be established to help in fine-tuning the existing management interventions of the national agricultural research system and also the system-modellers in predicting future projections on the sustainability issue of the rice-wheat cropping system in the IGP.

9 illus, 79 ref

014832   Nigam R;Prasad V;Mazumder A;Garg R;Saraswat R;Henriques P J (NO, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: abhimazumder@gmail.com) : Late holocene changes in hypoxia off the west coast of India: micropalaeontological evidences. Curr Sci 2009, 96(5), 708-13.

Study has been carried out to understand benthic foraminiferal and sedimentary organic matter characteristics under low dissolved oxygen conditions off the central west coast of India. Based on the strong correlation between the present-day abundance of rectilinear bi- and triserial benthic foraminifera (RBF) and low dissolved oxygen conditions in the northeastern Arabian Sea, the geologic extent of low oxygen zone off the central west coast of India, is inferred from a core collected from the shallow water region. Persistently high relative abundance of RBF, large proportion of amorphous organic matter and protoperidinioid dinocysts throughout the time-span covered by the core that goes well beyond the beginning of human intervention, indicate that the eutrophication of coastal water and subsequent development of low dissolved oxygen conditions is a natural phenomenon that has been in existence even before anthropogenic influence.

3 illus, 1 table, 39 ref

014831   Neelamani S;Al-Ragum A (Coastal and Air Pollution Dep, Environmental and Urban Development Div, Kuwait Institute for Scientif, 13109 SAFAT, Kuwait, Email: nsubram@kisr.edu.kw) : Wave dissipation characteristics of arrays of crater type barriers. Indian J Mar Sci 2009, 38(4), 418-22.

Wave dissipation characteristics of 4-row and 7-row crater type wave barriers are assessed using physical model investigations. Regular and random wave fields of wide range of wave heights and wave periods are used. It is found that for a constant incident wave height, the coefficient of wave dissipation by the barrier is increased with increased relative water depth, d/L. For a constant wave period, the coefficient of wave dissipation by the barrier is increased with increased incident wave steepness. Present study elucidates that the 7-row crater barrier is consistently better than 4-row crater barriers in increasing the wave energy dissipation. Also, in regular wave fields, the 7-row crater barrier is about 6.4% more effective in increasing the wave dissipation compared to 4-row barrier. Array of craters can be used as an efficient wave absorbers in wave flumes and wave basins occupying a small area of the flume and basin and hence more effective test area is available.

7 illus, 4 tables, 6 ref

014830   Mathur A K;Mishra V P;Singh J (NO, Geological Survey of India, Lucknow-226 024, Email: jaya1957@yahoo.co.in) : Quartz grain surface texture by electron microscopy - a tool in evaluation palaeoglacial sediments in Uttarakhand. Curr Sci 2009, 96(10), 1377-82.

The scanning electron microscope (SEM) study of microtextures in quartz grains in India is still in infancy and restricted mostly to the placer or beach sediments. SEM study of micromorphology of quartz grains from Late Pleistocene-Holocene sediments in Uttarkashi district, Uttarakhand, has been taken up for understanding the depositional environment. In the Netal section the quartz grain micromorphological studies indicate basal part of a valley glacier environment or remnant glacial lake, as the quartz grains are angular with high silica deposition besides other imprints of glacial origin. In the Shiror section the sediment appears to be part of the glacial till. The present study provides a new approach to the much needed palaeoenvironmental evaluation of the Himalayan Quaternary sediments on a nanoscale.

4 illus, 1 table, 21 ref

014829   Martini D;Mursula K;Alex S (NO, Indian Institute of Geomagnetism, New Panvel, Navi Mumbai-410 218, Email: daniel.martini@vipmail.hu) : New digital A_h index of geomagnetic activity at Alibag and other stations. Curr Sci 2009, 96(2), 280-3.

The geomagnetic activity carries important information about various parameters of the near-earth space and the solar magnetic activity on short as well as on long-term scales. In short or moderately long-term studies, the K_p/A_p index is a widely used reliable measure of geomagnetic activity. On the long-term scale, the aa index has, till recently, been the only index offering a sufficiently long registration for centennial studies. However, the long-term robustness of aa index was seriously questioned, and the early registrations until the first decades of the last century are not available in digital form in sufficiently high resolution. Therefore, the aa index cannot be verified, nor its probable error be reassuringly quantified. Here authour further verify the incorrectness of aa, using a recently introduced digital measure of the geomagnetic activity, the A_h index calculated at the Indian Alibag station. Global A_h from a number of long-running stations can be used to reliably extend the A_p series by roughly 30 years, allowing the study of geomagnetic activity for more than a century at the three-hourly resolution. Local A_h indices can also be calculated at any latitudinal region.

2 illus, 14 ref

014828   Manglik A;Arora T;Thiagarajan S;Mallick A (NO, National Geophysical Research Institute, (Council of Scientific and In, Uppal Road, Hyderabad-500 606, Email: ajay@ngri.res.in) : Intraplate stresses due to crustal heterogeneities along the Nagaur-Jhalawar transect, northwestern India. Curr Sci 2009, 96(6), 838-43.

The NW-SE trending Nagaur-Jhalawar deep crustal seismic profile transect across the Aravalli-Delhi Fold Belt to delineate the crustal structure and infer about the tectonics of this region. Seismic and gravity analyses of this profile revealed a complex tectonic structure in the central part of the profile, including the presence of a crustal-scale thrust with surface exposure near Jahazpur and a domal structure beneath the Delhi Fold Belt (DFB). In the present work, authors have estimated elastic intraplate stresses due to density heterogenei-ties and mechanical property variations, induced by such a complex crustal structure, under the plane strain approximation for a range of elastic parameters using finite element method. The results indicate that the mechanical properties of the domal structure beneath the DFB and the lower crust control the level of stress concentration in the upper crust. A significant enhancement in the magnitude of the shear stress in the central part of the profile was obtained for the models in which either the domal structure or the lower crust was mechanically weak in comparison to the models having mechanically strong domal structure and lower crust.

4 illus, 2 tables, 25 ref

014827   Majumder S;Mamtani M A (Geology and Geophysics Dep, Indian Institute of Technology, Kharagpur-721 302, Email: mamtani@gg.iitkgp.ernet.in) : Intensity of shape preferred orientation in a granite and its tectonic implications. Curr Sci 2009, 96(1), 156-60.

Deals with the measurement of intensity of shape preferred orientation in the Palaeo-proterozoic Malanjkhand Granite (Central India). This intensity is measured by calculating the strength of mineral lineation of biotite (KBI). The NE-SW striking Central Indian Suture (CIS) that was formed by the collision of the Bundelkhand and Bastar cratons lies to the north of the granite and K_bi was calculated in 11 samples collected at varying distances from the CIS. The data indicate that K_bi increases towards the CIS. Therefore, it is concluded that tectonic events associated with the CIS have influenced fabric development in the Malanjkhand Granite. Previous studies about the timing of formation of the CIS are described and the time-relationship between fabric development in the Malanjkhand Granite and regional tectonics is discussed.

4 illus, 1 table, 23 ref

014826   Majumdar T J;Bhattacharyya R;Chatterjee S; Krishna K S (Earth Sciences and Hydrology Div, Marine and Earth Science Group, Remote Sensing Applications Area, Space Applications Centre (ISRO), Ahmedabad-380 015, Email: tjmajumdar@rediffmail.com) : Utilization of high resolution satellite geoid data for estimation of lithospheric thickness in the Bay of Bengal. Indian J Mar Sci 2009, 38(4), 382-9.

Very high-resolution database generated from Seasat, Geosat GM, ERS-1 and TOPEX/ POSEIDON altimeters data of the northern Indian Ocean has been used for the first time for preparation of geoid and free-air gravity maps. In the present work, geoid height anomalies have been analyzed across the Ninetyeast and 85 °E Ridges within the Bay of Bengal. Present data sets are more accurate and detailed (off-track resolution: about 3.33 km and grid size: about 3.5 km). Observed geoid height - age and geoid height derivative (with respect to age) - age relationships have been established and compared with the plate model of lithospheric cooling to determine. The present endeavor is to determine the lithospheric plate thickness beneath both ridge structures. Attempts have been made to match the observed value with the computed value over the Bay of Bengal. The lithospheric plate cooling model correlates convincingly with the observed value. It has shown the efficacy of a plate model according to which geoid observations of the Bay of Bengal are better explained by a larger plate thickness of 90 - 125 km for the oceanic crust of age older than 30 Ma.

8 illus, 1 table, 23 ref

014825   Kotoky P;Bezbaruah D;Borah G C;Sarma J N (Geoscience Div, Regional Research Laboratory, Jorhat-785 006, Email: probhatk@yahoo.com) : Do node points play a role in flood proliferation?. Curr Sci 2009, 96(11), 1457-60.

2 illus, 2 tables, 13 ref

014824   Kaur R;Saikumar D;Kulkarni A V;Chaudhary B S (NO, National Technical Research Organisation, New Delhi-110 067, Email: rkaur.rana@gmail.com) : Variations in snow cover and snowline altitude in Baspa basin. Curr Sci 2009, 96(9), 1255-8.

The Himalayas has one of the largest concentrations of glaciers and permanent snowfields outside the polar region. Snow and glacier melt forms an important source for many rivers originating in the Himalayas. Numerous studies suggest that global warming has started affecting snow melt and stream run-off in the Himalayan region. Monitoring the snow-cover changes is therefore essential to assess the future hydrologic cycle. Snowline altitude is an important parameter to assess future changes in snow cover. Variations in snowline altitude and snow cover for the years 2004-05 and 2006-07 between October and June for Baspa River Basin located in the Kinnaur District, Himachal Pradesh are reported here. The snow cover was delineated using 54 images of AWiFS senor of Resourcesat-I satellite using NDSI technique and elevation information was generated using SRTM data. About 98% of the basin area is located below the elevation of 5800 m. The average monthly snowline altitude was estimated. The lowest snowline altitude was observed as 2425 m in February 2004-05 and 2846.25 m in March in 2006-07.

7 illus, 11 ref

014823   Kaladhara Rao K P C;Tiwari R K (NO, National Geophysical Research Institute, Hyderabad-500 007, Email: rao.kaladhar@gmail.com) : Principal component and spectral analyses of palaeo-climate time series. Curr Sci 2009, 96(9), 1229-32.

Mathematical modelling and time series analysis techniques are important tools for extracting information from complex geotime series. These techniques also facilitate a fair degree of prediction, which is one of the prime goals of science. The data analysis strategy for such a purpose mainly involves spectral analysis and pattern classification. The aim of pattern classification and frequency analysis is to assign observations or patterns into semantic categories. Traditional statistical methods generally applied during the past years fail to recognize patterns from high dimensional geo-records. Principal component analysis (PCA) is a powerful tool in identifying patterns in such records and provides useful means for reducing the number of dimensions without loss of much information. Here we have carried out spectral analysis and PCA of a climate record for approximately 28,000 yrs spanning from 1.15 to 29.78 kyr, off central Japan in the northwest Pacific. Our analysis reveals a dominant oscillation corresponding to the well known 'Heinrich Cycle'. The physical significance of the results has been discussed and the observed cyclic pattern corresponding to the global 'Heinrich Cycle' originating from the North Atlantic and Greenland ice rafting fluctuations has been linked to the Pacific phenomenon and Asian monsoon system.

3 illus, 12 ref

014822   Juyal K P (NO, Wadia Institute of Himalayan Geology, Dehradun-248 001, Email: kpjuyal@rediffmail.com) : Occurrence of bryozoa Chiplonkarina dimorphopora (Chiplonkar 1939), in the Kakara formation from type area subathu, Himachal Pradesh: its stratigraphic and palaeogeographic significance. Curr Sci 2009, 96(10), 1308-13.

3 illus, 1 table, 24 ref

014821   Joshi R R;Narendra Singh;Damle S H;Pant G B (NO, Indian Institute of Tropical Meterology, Pune-411 008, Email: rrjcpt@tropmet.res.in) : Scale-size calculations, energy dissipation rates and height coverage of a 404 MHz wind profiler at IMD, Pune. Curr Sci 2009, 96(9), 1176-81.

The 404 MHz wind profiler at the India Meteorological Department, Pune, is the first wind profiler of this frequency in India. Therefore, it is necessary to achieve maximum possible height to get valuable data. UHF wind profilers have better height and time resolution, which enables us to make reliable and correct estimations of the wind at various altitudes at regular spacing above the observational site. The height coverage of the profiler depends upon various factors like power aperture product and the operating wavelength vis-avis scale sizes available in the atmosphere. In this study, daily averaged second moment data archived during clear-air conditions have been used to estimate the scale-size parameters in terms of eddy dissipation rates, which explicitly indicates that more height coverage of a profiler depends only on the availability of the scale sizes in the atmosphere to which the radar is sensitive, and that in turn depends on where in the inertial subrange the operating wavelength resides. Power aperture product at various C^{2n values has been estimated. This note explicitly explains why the height coverage of the wind profiler at Pune is limited to 6-8 km under clear-air conditions.}

9 illus, 2 tables, 15 ref

014820   Joseph A, et al. (NO, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: joseph@nio.org ) : Observed thermohaline structure and cooling of Kochi backwaters and adjoining southeastern Arabian sea. Curr Sci 2009, 96(3), 364-75.

Thermohaline structure of Kochi backwaters under fair and rough weather conditions has been examined along with thermal structure of two open-ocean islands in the adjoining southeastern Arabian Sea (Kavaratti and Andrott in the Lakshadweep Archipelago). Longitudinal thermohaline structure of Kochi backwaters was found to be inhomogeneous, where the relatively warm and low-saline head estuary gets easily disturbed by sudden changes in meteorology, manifested by a sharp drop in temperature and salinity. The southernmost location was the most sensitive, and the easternmost location the least sensitive to meteorological changes. Thermohaline stratification was greater at the mouth region during monsoon, where a cap of (~4 m) low-saline water (≤2 psu) floats over a thermal gradient of ~3.5°C (9 m depth). Spring-neap thermohaline behaviour exhibited weak inverse correlation (R^{2 < 0.58), with a relative cooling due to the incursion of seawater during spring tide. However, a stronger correlation was observed between salinity and tide (R2 = 0.64). The thermal variations were mainly attributed to day/night heating/cooling processes, tides and winds. The cooling of island waters due to wind was delayed by half a day, whereas that of the Kochi backwaters was delayed by more than 1.5 days. Temperature variability at the Kochi backwaters was also influenced by its shallow depth, surrounding land mass and vegetation on its periphery. The mouth of the estuary was additionally cooled by upwelled waters from the Arabian Sea.}

24 illus, 1 table, 28 ref

014819   Joseph A;Vijaykumar K;Mehra P;Unnikrishnan A S;Sundar D;Prabhudesai R G (National Institute of Oceanography, , Dona Paula, Goa-403 004, Email: joseph@nio.org) : Observed tides at Mumbai high offshore region near the continental shelf break in the eastern Arabian sea. Curr Sci 2009, 96(9), 1233-5.

The observed large tidal range (up to 3 m during spring tide) at the Mumbai High offshore region located near the continental shelf break, off the central west coast of India, is described based on simultaneous tidal measurements (30 s average) at 15 min sampling interval using four tide gauges deployed from an oil drilling platform of the Oil and Natural Gas Corporation of India. All the four gauges provided identical measurements. The measured tides were harmonically analysed and the amplitudes and phases of the five major constituents, i.e. M₂, S₂, K1, O₁, and N₂ were compared with those observed at the closest coastal station (Apollo Bandar, Mumbai). It was found that the observed tidal range at this offshore location was unusually larger than those found in the open-ocean regions. This large tidal range was found to be associated with the large width of the continental shelf off the central west coast of India.

3 illus, 2 tables, 17 ref

014818   Janardhana Raju N;Dey S;Das K (Hydrogeology Div, Geology Dep, Banaras Hindu Univ, Varanasi-221 005) : Fluoride contamination in groundwaters of Sonbhadra district, Uttar Pradesh, India. Curr Sci 2009, 96(7), 979-85.

Fluoride (F^{-) concentration over and above the permissible limits (1.5 mg/l) in drinking water leads to human health hazards, such as dental and skeletal fluorosis affecting millions of people in many parts of India. Preliminary investigations indicate that severe health disorders have been identified in parts of the Kachnarwa region, which is in the upper Panda river basin, Sonbhadra District, Uttar Pradesh, due to excess intake of fluoride through drinking water. The lithological units of the study area mainly consist of granite and gneissic complex rocks of the Chota-Nagpur Plateau. In order to understand the probable source of fluoride and its concentration, 17 groundwater samples mostly from granite and phyllite regions were collected for fluoride estimation during May 2006. The concentration of fluoride in the groundwater of the study area varies from 0.483 to 6.7 mg/1. Among the 17 samples analysed, 8 exceeded the maximum permissible limits of fluoride in the study area. The source of fluoride in the groundwater of the study area is mainly from geological occurrence (i.e. fluoride-bearing minerals, viz. apatite and biotitic mica). Microscopic analysis of the rock samples showed 5-10% apatite and 20-25% biotite, but other fluoride-bearing minerals like fluorite and hornblende were characteristically absent. X-ray diffraction studies showed that apatite mineral peak profile of the rock samples corroborated with the fluorapatite of the standard set by the JCPDS. The worst fluoride-affected villages are Rohiniyadamar, Madhuri, Neruiyadamar, Gobardaha and Kunrwa. Most people in these villages suffer from dental and skeletal fluorosis such as mottling of teeth, deformation of ligaments, bending of spinal column and ageing problem. An urgent need is to educate the people on the causes of fluorosis, encouraging rainwater harvesting and providing fluoride-free drinking water in the study.}

4 illus, 4 tables, 45 ref

014817   Goyal V;Jhorar B S;Malik R S;Streck T (NO, Krishi Vigyan, Sanjay Nagar, Dibiyapur-206 244, Email: vishal_goyal11@rediffmail.com) : Simulation of groundwater recharge from an aquifer storage recovery well under shallow water-table condition. Curr Sci 2009, 96(3), 376-85.

A finite-element groundwater flow model, HYDRUS 2D, was used to simulate drawup and drawdown of piezometric pressure heads in the aquifer storage recovery cycles of varying buffer storage volumes and residence times in a highly brackish, semi-confined aquifer under shallow water-table condition. Physical flow region implemented in HYDRUS 2D involved a soil profile of 500 m width and 69 m depth, with an exocen-tric elliptical cavity of 1 m radius at 54 m depth. No flux boundary was given at the soil surface, at the bottom and at the lateral sides of the flow region. Saturated hydraulic conductivity was estimated through inverse modelling technique using experimental pressure head time pairs during the first aquifer storage recovery cycle from a piezometer and an observation well. High regression coefficient (0.96), low sum of squared differences of predicted and experimental mean (1.12), and low root mean square error (RMSE; 0.81) between predicted and experimental pressure heads while calibrating the first ASR cycle indicate the high level of accuracy of estimating field-saturated hydraulic conductivity. Modelling efficiency was higher in the piezometer (99.86) than in the observation well (94.57). Overall, the HYDRUS 2D model performed well for simulating drawup and drawdown with RMSE values ranging from 0.26 to 1.29 and modelling efficiency ranging from 94.57 to 99.9 during validation in the second to sixth ASR cycles. Radial influencing zone increases with buffer storage volume with a mean value of 122 m during recharge, indicating that the next tube well should be installed at least 122 m away from the existing aquifer storage recovery well.

11 illus, 6 tables, 23 ref

014816   Gopinath G (NO, Centre for Water Resources Development and Management, Kozhikode-673 571, Email: girish114@yahoo.co.uk) : Determination of sediment characteristics through cone penetration test in shallow marine areas using electrical compression cones. Curr Sci 2009, 96(2), 206-8.

Cone penetration test (CPT) is a simple technique which can be used for compaction studies in soft clay and fine-to-coarse grained sand. The equipment consists of mechanical, electrical, electronic and hydraulic units, and a coiling system. Data on tip resistance and sleeve friction are collected, which in turn provide the friction ratio, that is used for the textural classification of soils/sediments. Tip resistance and sleeve friction give an idea about the sediment density, which further helps in proper planning and design in shallow marine areas. The CPT is accurate and time dependent rather than vibrocoring.

2 illus, 2 tables, 10 ref

014815   Gopal Krishan;Srivastav S K;Suresh Kumar;Saha S K;Dadhwal V K (Indian Institute of Remote Sensing (National Remote Sensing Center), Indian Space Research Organisation, 4, Kalidas Road, Dehradun- 248 001) : Quantifying the underestimation of soil organic carbon by the Walkley and Black technique- examples from Himalyan and central Indian soil. Curr Sci 2009, 96(8), 1133-6.

Soil organic carbon (SOC) is an important indicator of soil quality and productivity. The present study focuses on the comparative evaluation of the 'wet digestion' and 'oxidative combustion-infrared analysis' methods for determination of SOC with examples from parts of the Himalayan and Central Indian soils. It is found that the commonly used wet digestion (Walkley and Black) method underestimates the SOC significantly. The study estimates a correction factor quite different from the standard adopted in most of the investigations. Considering the importance of SOC stock and dynamics being used as inputs in models predicting global climate change and future global carbon cycle, it is emphasized that appropriate correction factors need to be developed for Indian soils, and applied to the SOC estimates obtained from the Walkley and Black method to improve the accuracy.

3 illus, 1table, 18 ref

014814   De C;Bhattacharyya S (Post Graduate Dep of Microbiology, Vijaygarh Joytish Roy College, Calcutta Univ, Jadavpur, Kolkata-700 032, Email: chandrav_de@yahoo.co.in) : First record of the recent-subrecent diatomaceous earth from the gangetic alluvial floodplains of south 24 Parganas, West Bengal, India. Curr Sci 2009, 96(7), 967-73.

Recent-sub Recent freshwater diatomaceous earth from the Gangetic alluvial plains, West Bengal, has been reported. Under a suitable biogeochemical niche the photosynthesizing diatoms of freshwater habitat form multilevel biomats within the surficial clay-silt layers that mark a major post-flood microbial proliferation event. High rate of reproductive turnover of diatom biomass is favoured by the supply of vegetative nutria-ents, monsoonal water and sunlight selectively in moist geomorphic depressions, the earlier relict patches of low-lying floodplains of the Hoogly river. Regional geo-environmental (moist clay-silt in freshwater setting) and geomorphological (depressed relict floodplains) attributes favour far more extensive occurrence of freshwater diatomaceous earth in the Gangetic delta plains than what is reported here and thus enhances its economic viability.

3 illus, 42 ref

014813   Chidambaram S;Prasanna M V;Ramanathan A L; Vasu K;Hameed S;Warrier U K;Manivannan A R;Srinivasamoorthy K;Ramesh R (Earth Sciences Dep, Annamalai Univ, Annamalai Nagar-608 002, Email: chidambaram_s@rediffmail.com) : Stable isotopic signatures in precipitation of 2006 southwest monsoon of Tamil Nadu. Curr Sci 2009, 96(9), 1224-9.

Southwest monsoon (SWM) controls the majority of the agricultural activities in Tamil Nadu (TN), though the amount of rainfall received due to this is relatively less. The nature and behaviour of water vapour over TN reveal the other dynamic processes that are in operation during this period of the year. Hence, the stable isotope signatures of δ^{18 O and δ D obtained here were used to derive the first local meteoric water line for the State with SWM precipitation. The d-excess parameter was also used in conjunction and it was found that three dominant processes were in operation during this period: (i) vapours from southeast Arabian Sea, (ii) local evaporating vapours from inland tanks and (iii) vapours from the Indian Ocean.}

6 illus, 1 table, 33 ref

014812   Chaujar R K (NO, Wadia Institute of Himalayan Geology, Dehradun-248 001) : Climate change and its impact on the Himalayan glaciers-a case study on the Chorabari glacier, Garhwal Himalaya, India. Curr Sci 2009, 96(5), 703-8.

Glaciers and small ice caps in temperate environments are sensitive indicators of the change in climate. Mountain glaciers provide a valuable tool for reconstruction of Holocene climate changes. The present work, thus, deals mainly with climatic change and its impact on the Himalayan glaciers based on the dating of lichens, developed on loops of moraines formed due to various stages of advance and retreat of the glacier. Here it has been shown that the date of the largest lichen on the loop of moraine that indicates the position of maximum advance of the glacier is 258 years. It shows the period when the Chorabari glacier started receding from the point of its maximum advancement in this part of the Himalaya. Earlier work in the Dok-riani Bamak (glacier) has shown that the period of retreat in the respective part of the Himalaya is around 314 years. Research on various glaciers of the northern and southern hemisphere has shown that most of them started their retreat in the mid-eighteenth century, thereby indicating the end of the Little Ice Age maximum. These results suggest that climatic changes in the world started during early to mid-eighteenth century, though this needs further work for confirmation. There is every possibility that its effect was sensed first in the zone close to the equator by the north-facing Himalayan glaciers such as the Dokriani Bamak.

8 illus, 1 table, 37 ref

014811   Chauhan P;Sanwlani N;Navalgund R R (Space Applications Center, Indian Space Research Organization, Ahmedaad-380 015) : Aerosol optical depth variability in the northeastern Arabian sea during winter monsoon: a study using in-situ and satellite measurements. Indian J Mar Sci 2009, 38(4), 390-6.

The study consists the results of the Sun photometer measurements of aerosol optical depth (AOD) over the northern Arabian Sea during December 4-17, 2004 along with OCEANSAT-1 Ocean Colour Monitor (OCM) data derived AOD estimates. In-situ AOD ranged between 0.15-0.38 at 500-nm wavelength (with a mean of 0.274). Relatively higher values of angstrom exponent (mean=1.8) were observed during the cruise period, indicating presence of smaller particles, which seem to have advected from Indian subcontinent and associated with favorable wind conditions as shown by wind vector data from Quickscat scatterometer. The Spatial distribution of the AOD over the study area was derived using OCEANSAT-1 OCM satellite data. OCM derived AOD images showed plumes of high aerosol optical depth originating near the coastal regions and dispersing over oceanic regions. The satellite data derived AOD values were also compared with in-situ measurements. OCM derived AODs matched well with in-situ measurements having an RMSE of sixteen percent for seven match-up points.

4 illus, 1 table, 15 ref

014810   Chakravarthi V (NO, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007, Email: vcvarthi@rediffmail.com) : Automatic gravity inversion for simultaneous estimation of model parameters and regional gravity background: an application to 2D pull-apart basins. Curr Sci 2009, 96(10), 1349-60.

An automatic inversion using Marquardt algorithm has been developed to simultaneously estimate the parameters of 2D pull-apart basins and regional gravity background from the observed gravity anomalies. The density contrast is assumed to vary continuously with depth based on a parabolic equation. The salient feature of this inversion is that the initial parameters of the basin are not a required input. The applicability and efficacy of the inversion is demonstrated with a synthetic model of a pull-apart basin. The synthetic gravity anomalies have been analysed (i) solely due to the structure, (ii) in the presence of a regional gravity background, and (iii) in the presence of both random noise and regional gravity background. The analysis showed that the modelled structure closely mimics the true one irrespective of the degree of the polynomial that is used to describe the regional background. In the presence of both random noise and regional background, the estimated dips of the boundary faults and the regional background show modest variation from the assumed ones. Two real-field anomalies observed over a set of pull-apart basins associated with the suture zone of the Eastern Ghats Mobile Belt in Northeast India have been interpreted. The estimated depth in each case is consistent with the available borehole information.

9 illus, 4 tables, 23 ref

014809   Braganca J M;Furtado I (Microbiology Dep, Goa Univ, Taleigao Plateau, Goa-403 206, Email: ijfurtado@unigoa.ac.in) : Isolation and characterization of haloarchaea from low-salinity coastal sediments and waters of Goa. Curr Sci 2009, 96(9), 1182-4.

2 illus, 2 tables, 19 ref

014808   Biswal T K;Thirukumaran V;Ratre K; Sundaralingam K (Earth Sciences Dep, Indian Institute of Technology Bombay, Powai, Mumbai-400 076, Email: tkbiswal@iitb.ac.in) : Salem-attur shear zone, east of Salem, Tamil Nadu: a new kinematic interpretation. Curr Sci 2009, 96(10), 1386-90.

A study of the mylonites of the Salem-Attur shear zone at Udayapatti and Sarkar Nattar Mangalam reveals that the shear zone developed in the form of a northeasterly vergent subhorizontal thrust which has been refolded into variable attitude due to late stage folding. The subhorizontal mylonitic foliation with NE trending stretching lineation bears testimony to such an explanation. The earlier impression that the shear zone is vertical comes from the folded part of the thrust as the mylonites have assumed a vertical attitude on the limb of the fold.

5 illus, 21 ref

014867   Verma M B;Maithani P B;Chaki A;Nageshwar Rao P;Prakher Kumar (Atomic Minerals Directorate for Exploration and Research, Southern Region, Nagarabhavi, Bangalore-560 072, Email: mohanbverma@hotmail.com) : Srisailam sub-basin, an uranium province of non-conformity-related deposits in Andhra Pradesh - case study of chitrial uranium exploration, Nalgonda district. Curr Sci 2009, 96(4), 588-91.

Significant surface radioactive anomalies, with values up to 0.177% eU₃O₈ (n = 9), located during 1992 along the non-conformity contact of basement granitoid with the Srisailam Formation, around Chitrial village, Nalgonda District, Andhra Pradesh, led to the establishment of a sizeable uranium deposit by recent exploration. Thus, intensive subsurface exploration resulted in delineating the persistency of the mineralization over a stretch of 4.4 km (E-W) and 2.7 km (N-S). Along micro-fractures of the granitoid, uranium mineralization occurs as veins of pitchblende and uraninite. Preliminary exploration along the fringes of Srisailam outliers indicated the possibility of establishing substantial uranium reserves within the Srisailam sub-basin, due to similar geological set-up. With increasing thickness of cover sediments towards the centre of the sub-basin, possibility of richer concentration exists in the deeper part of the sub-basin. An attempt has been made to synthesize the exploratory history commencing from locating uranium occurrences up to developing them into a workable economic deposit in Chitrial.

3 illus, 1 table, 9 ref

014866   Varikoden H;Harikumar R;Sasi Kumar V;Murali Das S;Sampath S;Mohan Kumar G (Atmospheric Sciences Div, Centre for Earth Science Studies, Thiruvananthapuram-695 031, Email: hamzavarikoden@gmail.com) : Properties of cloud base height during southwest monsoon period over a tropical station, Thiruvananthapuram. Curr Sci 2009, 96(4), 562-8.

The study of the clouds and their properties has remained unexplored, especially during the southwest (SW) monsoon season due to the unavailability of reliable data sets. Here made an attempt to study the cloud base height (CBH) and its characteristics during the SW monsoon period of 2007 using CBH data obtained by a Vaisala Laser Ceilometer (VLC). The VLC was made operational at Thiruvananthapuram since July 2006 to monitor the CBH every 15 s. The relation of CBH with meteorological parameters is studied using the radiosonde observations. We found that clouds during the SW monsoon season have mainly concentrated below 2500 m. A layer with relatively void clouds was present between 2500 and 4000 m. We call this region as cloud-free zone. The amplitude of variability of CBH was less compared to the variability of the cloud frequency. Active monsoon is when the cloud frequency exceeds 70% and break phase is when it is less than 40%. The cloud frequency increases when the wind shear increases in the lower levels. Similarly, temperature is more during break phase of monsoon however, the relative humidity shows an increase during active phase of monsoon. Multiple clouds were also noticed during active phase, but it was negligible during break phases of monsoon.

10 illus, 2 tables, 25 ref

014865   Valsangkar A B;Borole D V;Shejwalkar A S; Kalangutkar N G;Fernandes N O;Dias C C (NO, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: vals@nio.org) : Potential diagenetic and detrital sources for calcareous sediments from the carlsberg ridge, Indian ocean. Curr Sci 2009, 96(8), 1090-9.

Six sediment cores from the Carlsberg Ridge (CR) were studied for elemental concentration, magnetic susceptibility (X), grain size and clay mineral distribution, and sedimentation rate to decipher possible detrital and diagenetic contributions. The sediments were characterized by very low X, moderate total organic carbon, high CaCO₃ content and high accumulation rate (3 cm/kyr). Clay mineralogical and geochemical data suggest major continental source from the Arabian Sea, and very low Mn distribution, absence of tephra and characteristic magnetic signatures rule out volcanic or hydrothermal input. Consistent peaks around 10, 25, 45, 60 and SO cm depth and high uranium are due to sedimentary diagenesis.

12 illus, 4 tables, 30 ref

014864   Valsangkar A B (NO, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: vals@nio.org) : Special core liner for sub-sampling of aqueous sediments. Curr Sci 2009, 96(10), 1382-6.

A portable and reusable special core liner (spcl) has been developed to accomplish real-time sub-sampling of aqueous sediments. Besides being revolutionary, inexpensive and user-friendly, the spcl is capable of collecting undisturbed sediment sub-sections. The spcl also facilitates rapid sub-sampling of sediments onboard with remote possibility of core shortening, sample outflow, contamination or mixing. The proposed method of sub-sampling by spcl saves time, money and manpower, without inducing changes in the physical and biogeochemical properties of the sediments.

4 illus, 1 table, 9 ref

014863   Upadhyay R (Geo-Engineering Dep, Andhra Univ, Visakhapatnam-530 003, Email: nrkakani@yahoo.com) : Present state of the three tidal inlets of the pulicat lake: fact from remote sensing and field surveys. Curr Sci 2009, 96(5), 648-50.

^ssc2 illus, 3 ref

014862   Upadhyay R (Geology Dep, Kumaun Univ, Nainital-263 002, Email: Rajeev_up@yahoo.com) : Melting of the siachen glacier. Curr Sci 2009, 96(5), 646-8.

^ssc6 illus, 15 ref

014861   Uma Devi E;Rao N P;Ravi Kumar M (NO, Indian National Center for Ocean Information Services, Hyderabad-500 055, Email: raonpc@ngri.res.in) : Modelling of sPn phases for reliable estimation of focal depths in northeastern India. Curr Sci 2009, 96(9), 1251-5.

In North East India, reliable estimation of earthquake focal depths has always been a problem, owing to paucity of permanent regional seismic stations, constraints on good quality data and lack of crustal models in a complex tectonic terrane. The depth estimations by international agencies, mostly based on teleseismic data, vary from very shallow to even 60 km, suggestive of earthquake occurrence in the upper mantle region. However, modelling of sPn phases in earthquake waveforms that are highly sensitive to focal depths indicates that the earthquake locations are probably well within the crustal layer. The current method has the advantage that dt, the travel time difference between sPn and Pn, remains constant for a wide range of source-station distances, and hence enables easy identification of the sPn phase, while providing direct and accurate estimate of the focal depth. The approach is also insensitive to location errors and variations in crustal models, a useful feature especially while dealing with sparse data with high location errors. In the present study, earthquakes in the magnitude range 3.0-4.0 recorded by a network of nine broadband stations in NE India have been analysed. Consistent dt values at different stations were observed for each event, enabling precise depth estimation mostly within ±1 or 2 km. In general, depths of 15-20 km in the Shil-long plateau region,> 20 km in the Sylhet basin region and shallow < 10 km in the eastern Himalayan foothills are confirmed, that correlate well with the local tectonics. Further, we propose that the flat characteristics of the dt curve that begin to change for earthquakes below the Moho, can be a potential tool for discriminating between crustal and sub-crustal earthquakes, as well as for delineation of the Moho using dense regional seismic networks in future.

4 illus, 2 tables, 9 ref

014860   Sujatha C H;Benny N;Raveendran R;Fanimol C L; Samantha N K (Chemical Oceanography Dep, CUSAT, Kochi-16, Email: drchsujatha@yahoo.co.in) : Nutrient dynamics in the two lakes of Kerala, India. Indian J Mar Sci 2009, 38(4), 451-6.

Distribution and chemistry of major inorganic forms of nutrients along with physico-chemical parameters were investigated. Surface sediments and overlying waters of the Ashtamudi and Vembanad Lakes were taken for the study, which is situated in the southwest coast of India. High concentrations of dissolved nitrogen and phosphorus compounds carried by the river leads to oxygen depletion in the water column. A concurrent increase in the bottom waters along with decrease in dissolved oxygen was noticed. This support to nitrification process operating in the sediment-water interface of the Ashtamudi and Vembanad Lake. Estuarine sediments are clayey sand to silty sand both in Ashtamudi and Vembanad in January and May. Present study indicates that the sediment texture is the major controlling factor in the distribution of these nutrient forms. For water samples nitrite, inorganic phosphate was high in Vembanad in January and May compared to Ashtamudi. For sediments, enhanced level of inorganic phosphate and nitrite was found in Vembanad during January and May. It had been observed that the level of N and P is more in sediments. A comparative assessment of the Ashtamudi and Vembanad Lake reveals that the Vembanad wetland is more deteriorated compared to the Ashtamudi wetland system.

4 illus, 4 tables, 38 ref

014859   Sridhar A (Geology Dep, Faculty of Science, The M.S. Univ of Baroda, Vadodara-390 008, Email: alpasridhar@rediffmail.com) : Evidence of a late-medieval mega flood event in the upper reaches of the Mahi river basin, Gujarat. Curr Sci 2009, 96(11), 1517-20.

Palaeoflood records are of great significance in revealing the magnitude and frequency of large floods and thus the past monsoon conditions. The Mahi River, one of the major west-flowing rivers of India controlled by the southwest monsoon has preserved deposits of past floods dating back to 5 ka. A flood deposit emplaced by a mega flood event with discharge ~ 7300 m^{3 s-1 has been found at Diapattan in the upper reaches of the Mahi River basin. Based on the pottery available at the site, the event can be said to belong to late-medieval time. The timing of this mega flood event recorded at Diapattan in the Mahi River basin and records of the adjacent river basins suggest that this event represents the strengthened monsoon during the Medieval Warm Period (900-1400 AD). There exists a correlation between the extreme hydrological events in the Mahi, Narmada and Tapi river basins and this can be attributed to a regional monsoon domain.}

3 illus, 13 ref

014858   Sreekanth P D;Geethanjali N;Sreedevi P D; Ahmed S;Ravi Kumar N;Kamala Jayanthi P D (NO, National Research Centre for Cashew, Puttur-574 202, Email: pd_sreekanth@yahoo.com) : Forecasting groundwater level using artificial neural networks. Curr Sci 2009, 96(7), 933-9.

Performance of the artificial neural network (ANN) model, i.e. standard feed-forward neural network trained with Levenberg-Marquardt algorithm, was examined for forecasting groundwater level at Maheshwaram watershed, Hyderabad, India. The model efficiency and accuracy were measured based on the root mean square error (RMSE) and regression coefficient (R^{2). The model provided the best fit and the predicted trend followed the observed data closely (RMSE = 4.50 and R2 = 0.93). Thus, for precise and accurate groundwater level forecasting, ANN appears to be a promising tool.}

4 illus, 3 tables, 24 ref

014857   Soni V;Gosain A K;Datta P S;Singh D (National Physical Laboratory, , New Delhi-110 012, Email: v.soni@airtelmail.in) : New scheme for large-scale natural water storage in the floodplains: the Delhi yamuna floodplains. Curr Sci 2009, 96(10), 1338-42.

The top layer of accumulated sand washed down by floods over millions of years, makes river floodplains into giant aquifers. We propose a scheme for the natural storage of excess monsoon river-water discharge in the extensive and deep sand top layer of the floodplain of the river. The excess monsoon discharge can be used for a regulated inundation of an embanked area of the floodplain - to soak in and store the water. This storage can then be used for the withdrawal of water during the dry months. We illustrate this by an evaluation of the potential of the Yamuna floodplains in the National Capital Territory of Delhi and show that there can be an annual yield of 600-900 MCM of water, which is three-fourths the total water supply to Delhi. This makes it an invaluable natural resource potentially worth about Rs 6000-9000 crores a year of non-invasive use.

1 illus, 1 table, 11 ref

014856   Soni A S;Soni V S (NO, , Kothi no. 444/1 Urban Estate, Patiala-147 002) : Flake-rich assemblage in buried state and in primary context in the NW sub-Himalayas. Curr Sci 2009, 96(8), 1130-3.

A flake-dominated lithic assemblage fabricated on coarse-grained quartzite raw material and found in combination with some potsherds has been recovered from an excavation in north-western Indian sub-Himalayas. The excavated artefacts consist of thousands of fresh, unrolled, and mostly utilized flakes and flake-tools, which were found buried right from about 15 cm below the top to about 1.4 m depth, until the appearance of a clayey bed and the bedrock. This small site exists on an isolated bank of a tributary of Satluj river in Himachal Pradesh, where the raw material had been transported from elsewhere. Different large and small sized flakes and the debitage constitute the bulk of the material, while the cores and core-tools are quite few in the assemblage. Apart from some new tool-types, many artefacts also show signs of edge-grinding. Weathered potsherds mixed with the artefacts, including the edge-ground ones have been found deposited into the bottom of the trench, which points to the existence of a hitherto unknown flake-dominated Holocene lithic industry in the sub-Himalayas.

4 illus, 17 ref

014855   Sinha S;Sen K;Sangode S J;Rohtash Kumar;Ghosh S K (NO, Wadia Institute of Himalayan Geology, Dehra Dun-248 001, Email: sangode@unipune.ernet.in) : Sedimentology and magnetic fabric studies of mio-pliocene fluvial succession in the NW Himalayan foreland basin. Curr Sci 2009, 96(2), 260-7.

Magnetic fabric studies based on anisotropy of magnetic susceptibility (AMS) over mudstone facies from a 1700 m thick Mio-Pliocene Siwalik fluvial sequence infer a dominant control of tectonic fabrics as against the depositional fabrics of the associated channel sandstones. This study integrated with lithofacies variations indicates the prevalence of overall prolate-ness with high 'T, q and L/F' values after 1100 m. Superimposition of the tectonic fabrics vis-a-vis up-section increase in frequency and thickness of the conglomerates infers greater magnitude of the tectonic signatures. The low prolateness of the fabrics between 1000 and 1100 m is inferred as the syn-tectonic lag deposits and reflects some important basin dynamic changes. The AMS approach over mudstone facies thus shows a greater scope of recording and quantifying the basin tectonic impulses in the Himalayan Foreland Basin.

7 illus, 1 table, 48 ref