Evolution of the basalts from three back-arc basins of southwest Pacific

Petrography, petrochemistry, and mineral chemistry of basalts from the Woodlark, Manus, and Lau basins from the southwest Pacific, have been studied to understand their magmatic evolution. Basalt from the western Woodlark Basin (Dobu Seamount) indicates mixing of a near-primitive magma with fractionated basaltic melt in shallow magma chambers. Basalts from Manus Basin and Central Lau Spreading Center (Lau Basin) are typical N-MORBs, and they exhibit olivine fractionation under high oxidizing conditions while basalts from Mangatolu Triple Junction (Lau Basin) are enriched in Al₂O₃, K₂O, and Zr indicative of a contribution from a subducting plate.     

Hidden Markov Model for quantitative prediction of snowfall and analysis of hazardous snowfall events over Indian Himalaya

A Hidden Markov Model (HMM) has been developed for prediction of quantitative snowfall in Pir-Panjal and Great Himalayan mountain ranges of Indian Himalaya. The model predicts snowfall for two days in advance using daily recorded nine meteorological variables of past 20 winters from 1992–2012. There are six observations and six states of the model. The most probable observation and state sequence has been computed using Forward and Viterbi algorithms, respectively. Baum–Welch algorithm has been used for optimizing the model parameters. The model has been validated for two winters (2012–2013 and 2013–2014) by computing root mean square error (RMSE), accuracy measures such as percent correct (PC), critical success index (CSI) and Heidke skill score (HSS). The RMSE of the model has also been calculated using leave-one-out cross-validation method. Snowfall predicted by the model during hazardous snowfall events in different parts of the Himalaya matches well with the observed one. The HSS of the model for all the stations implies that the optimized model has better forecasting skill than random forecast for both the days. The RMSE of the optimized model has also been found smaller than the persistence forecast and standard deviation for both the days.     

Major ion chemistry,weathering processes and water quality assessment in upper catchment of Damodar River basin,India

The chemical characteristics of surface, groundwater and mine water of the upper catchment of the Damodar River basin were studied to evaluate the major ion chemistry, geochemical processes controlling water composition and suitability of water for domestic, industrial and irrigation uses. Water samples from ponds, lakes, rivers, reservoirs and groundwater were collected and analysed for pH, EC, TDS, F, Cl, HCO₃, SO₄, NO_3, Ca, Mg, Na and K. In general, Ca, Na, Mg, HCO₃ and Cl dominate, except in samples from mining areas which have higher concentration of SO₄. Water chemistry of the area reflects continental weathering, aided by mining and other anthropogenic impacts. Limiting groundwater use for domestic purposes are contents of TDS, F, Cl, SO₄, NO₃ and TH that exceed the desirable limits in water collected from mining and urban areas. The calculated values of SAR, RSC and %Na indicate good to permissible use of water for irrigation. High salinity, %Na, Mg-hazard and RSC values at some sites limit use for agricultural purposes.     

Palaeo-path investigation of the lower Ajay River (India) using archaeological evidence and applied remote sensing

Numerous palaeochannels, oxbow lakes and elongated sediment fills in Eastern India, particularly along the lower Ajay River, provide a record of channel shifting during the Late Quaternary. Proper characterization of these features is useful for discussing the dynamic evolution of the river system in the Ajay-Damodar Interfluve region. Remote sensing data, archaeological evidence and sedimentology aid in reconstructing the geomorphic history of the lower Ajay River. Archaeological studies help in calculating the rate and direction of channel migration. The channel migration rate varies from 0.32 to 3.41 m/year in the study area. Bouguer gravity anomalies suggest that the rate of channel migration may be controlled by the density variations of the basement rocks. Furthermore, neotectonics activity played a significant role in the migration of Ajay River towards north-east direction.     

GPS measurement of land subsidence in Gandhinagar,Gujarat (Western India), due to groundwater depletion

A continuous GPS measurement site, ISRR, at Gandhinagar (Western India), documented ~?5 mm/year of surface subsidence rate during 2009–2016. Preliminary modelling using an analytical solution indicates that the observed surface subsidence rate at the ISRR site is consistent with the ground water depletion reported from Gandhinagar. An assessment of data from GPS sites at Lucknow and Varanasi in the Indo-Gangetic plains in Northern India does not indicate any significant subsidence at these sites which is also consistent with the in situ observations of insignificant depletion of ground water in the region.     

Study of fossil wood from the Middle–Late Miocene sediments of Dhemaji and Lakhimpur districts of Assam,India and its palaeoecological and palaeophytogeographical implications

In order to reconstruct the palaeoclimate, a number of fossil wood pieces were collected and investigated from two new fossil localities situated in the Dhemaji and Lakhimpur districts of Assam. They belong to the Tipam Group considered to be of Middle–Late Miocene in age and show affinities with Gluta (Anacardiaceae), Bischofia (Euphorbiaceae), Bauhinia, Cynometra, Copaifera-Detarium-Sindora, Millettia-Pongamia, and Afzelia-Intsia (Fabaceae). The flora also records a new species of Bauhinia named Bauhinia miocenica sp. nov. The assemblage indicates a warm and humid climate in the region during the deposition of the sediments. The occurrence of some southeast Asian elements in the fossil flora indicates that an exchange of floral elements took place between India and southeast Asia during the Miocene.     

Source and distribution of metals in bed sediments of Subarnarekha River, India

The study was taken up to establish the distributions of metals as well as to assess the extent of anthropogenic inputs into the Subarnarekha River. Bed sediments were collected; analyzed for metals; and assessed with the index of geo-accumulation (I _geo), enrichment factor (EF) value, concentration factor (CF) and pollution load index (PLI). Metals in the sediment were variable in the river and there are major pollution problems at certain locations. The average concentrations of Fe, Cu, Cr, Pb, Mn, Ni, Zn, Co and Ba in mg/kg was found to be 30,802 ± 11,563, 69 ± 57, 111 ± 74, 75 ± 61, 842 ± 335, 42 ± 22, 100 ± 39, 15 ± 4 and 698 ± 435, respectively. The I _geo, EF, CF and PLI indices showed that the contamination of Pb and Cu was more serious than that of Ni, Zn, Co and Ba, whereas the presence of Fe, Mn and Cr might be primarily from natural sources. The contamination of the sediments with metals at few locations is attributed to mining, industries and other anthropogenic causes. Principal component analysis was employed to better comprehend the controlling factors of sediment quality. The statistical analysis of inter-metallic relationship revealed the high degree of correlation among the metals indicated their identical behaviour during transport. PCA outcome of three factors together explained 83.8 % of the variance with >1 initial eigenvalue indicated both innate and anthropogenic activities are contributing factors as source of metal profusion in Subarnarekha River basin.The overall study reveals moderately serious pollution in the river basin principally in some locations under the anthropogenic influences.