Geochemistry of the sandstones of Punagarh basin: Implications for two source terranes and Arabian - Nubian connection of Aravalli craton?

Sandstones of Punagarh basin of Trans Aravalli region, NW Indian shield were analyzed for their major and trace element contents in conjunction with petrographic modes. The Punagarh basin comprises four formations (Sojat, Bambolai, Khamal and Sowania), amongst which the Sojat Formation in uncoformable contact with overlying formations, is significantly older and enjoys separate status as rest of the formations constitute Punagarh Group. Petrographic attributes suggest that Sojat sandstones contain distinct modal abundances like high content of quartz and low content of feldspar, mica, matrix, rock fragments and cement. In general there is a decrease in the average modal abundance of quartz and mica with concomitant increase of feldspar, chert and rock fragments from base to top in Punagarh sandstones. Sojat sandstones are also geochemically distinct as they possess high SiO₂/Al₂O₃, Th/U and Cr/Th ratios coupled with lowest Na₂O/K₂O ratio and Zr content, least fractionated LREE, more fractionated HREE and largest Eu* anomaly compared to Punagarh sandstones. The weathering indices suggest intense chemical weathering for Sojat sandstones and low to moderate for Punagarh sandstones. Compositionally all the sandstones of the Punagarh basin come under the category of quartzarenite. Compared to PAAS and UCC, both suite of sandstones are generally depleted in REE, HFSE (with exception of Zr, Hf and Ta), and enriched in ferromagnesian trace elements particularly Cr and Co. The chemical data indicate that the sediments were derived from the source(s) of mixed felsic - mafic composition, with the former being dominant. The source rocks were granites, TTG, basalts, and rhyolites. The Sojat sandstones owe their source form Archean crust while Punagarh sandstones got detritus from Mesoproterozic crust. Immobile element ratios and REE abundances of Sojat sandstones closely match with Paleoproterozoic metagreywackes of Ghana of African craton while Punagarh sandstones show near geochemical characteristic with Gogunda, Kumbalgarh and Vindhyan quartzites of Aravalli craton. This geochemical similarity of Sojat sandstones provides credence to the hypothesis that Trans–Aravalli region of India had been an integral part of Arabian - Nubian shield. The chemical data advocate the deposition of these sandstones in a tectonic setting comparable to modern back arc setting.     

Economic significance of colonial invasions in Khejuri-Hijli coastal sector of Purba Medinipur district,West Bengal: A geographical review

Khejuri- Hijili coastal area, now extends over the Khejuri police station, is situated in the southeastern part of the district of Purba Medinipur of West Bengal, on the western bank of the Hugli river. Between 21°47'42"N-22°4'N latitudes and 87°45'4"E-88°18"E longitudes the area covers about 267.97 sq. km. At the confluence of the rivers Bhagirathi-Hugli and the Bay of Bengal, Hijili emerged as an island from the estuarine surroundings around 1400-1500 A.D. afterward the island became covered with natural mangroves. Gradually it became the abode of fishermen. To gather some primary data, household survey by different questionnaire, topographic survey was done. Secondary data are mainly produced by assembling historical charts, maps, literatures for the specified work of the area concerned. Historical records including documents, survey notes, maps and photographs provided valuable information about the study area. Remains of early structures, monuments, and office buildings have been vigilantly watched and written reports and research articles have been carefully studied for sequencing the socio-economic history of the area. Later on accuracy assessment was performed by comparing two sources of information: classification of map derived from old records and maps and the ground truth information. The output obtained by performing the above steps includes land use and other maps and charts. These outputs were then analyzed to detect the historical significance of Khejuri-Hijili sector of the Hugli estuary and its sequential deterioration. These changes in the study area that were identified from classified maps, charts and diagram were tabulated.     

Petrophysical parameters and modelling of the Eocene reservoirs in the Qadirpur area,Central Indus Basin,Pakistan: implications from well log analysis

The Eocene rock units of the Qadirpur field, Central Indus Basin (Pakistan), are investigated petrophysically for their detailed reservoir characterization. The different petrophysical parameters determined include the following: true resistivity, shale volume, total porosity, effective porosity, density and neutron porosity, water and hydrocarbon saturation, bulk volume of water, lithology, gas effect, P-wave velocity, movable hydrocarbon index and irreducible water saturation and integrated with different cross-plots. The Eocene reservoirs are excellent with high effective porosity (2–32 %) and hydrocarbon saturation (10–93 %). Among these, the Sui Upper Limestone is an overall a poor reservoir; however, it has some hydrocarbon-rich intervals with high effective porosity and better net pay. All the net pay zones identified show low and variable shale volume (5–30 %). The secondary porosity has added to the total and effective porosities in these reservoirs. The main contributors to the porosity are the chalky, intercrystalline and vuggy/fracture types. The thickness of the reservoirs zones ranges from 4.5 to 62 m. These reservoirs are gas-producing carbonates with almost irreducible water saturation (0.002–0.01) and are likely to produce water-free hydrocarbons. The lower values of moveable hydrocarbon index (0.07–0.9) show that the hydrocarbons are moveable spontaneously to the well bore. The proposed correlation model shows that the reservoirs have an inclined geometry and are a part of an anticlinal trap.     

Resistivity imaging survey to delineate subsurface seepage of hydrocarbon contaminated water at Karbala Governorate,Iraq

This research is an attempt to accomplish a 3-D resistivity imaging survey, which was carried out near a water well contaminated with hydrocarbon materials in Karbala governorate. Two-dimensional resistivity imaging measurements were collected along four parallel profiles, using a Wenner array with electrode spacing of 1 m. The RES3DINV program was used to invert the apparent resistivity data. The results displayed a resistivity distribution of the subsurface in a three-dimensional volume. Thus, both the horizontal and vertical extents of the contaminated zone were displayed. This technique revealed a low resistivity zone at depth ranges from 3 to 6 m in the investigation area, but the seepage starts at depth ranges between 2 and 3 m and continues down depth (may be to the groundwater level). This low resistivity zone is the most likely location for a subsurface seepage of contaminated water. It is clear that the sufficient measurement points along 2-D lines in a small area can increase the 3-D imaging resolution, and nearly real 3-D imaging can be achieved, when the size of subsurface anomaly compared with the electrode spacing (a) of the Wenner array is taken into consideration.     

Multispectral remote sensing for mapping grassland degradation using the key indicators of grass species and edaphic factors

Land degradation is believed to be one of the most severe and widespread environmental problems. In South Africa, large areas of land have been identified as degraded, as shown by the lower vegetation cover. One of the major causes of grassland degradation is change in plant species composition that leads to presence of unpalatable grass species. Some grass species have been successfully used as indicators of different levels of grassland degradation in the country. This paper, therefore explores the possibility of mapping grassland degradation in Cathedral Peak, South Africa, using indicators of grass species and edaphic factors. Multispectral SPOT 5 data were used to produce a grassland degradation map based on the spatial distribution of decreaser (Themeda triandra) and increaser (Hyparrhenia hirta) species. To improve mapping accuracy, soil samples were collected from each species site and analysed for nutrient content. A t-test and machine learning random forest classification algorithm were applied for variable selection and classification using SPOT 5 data and edaphic variables. Results indicated that the decreaser and increaser grass species can be mapped with modest accuracy using SPOT 5 data (overall accuracy of 75.30%, quantity disagreement = 2 and allocation disagreement = 23). The classification accuracy was improved to 88.60%, 1 and 11 for overall accuracy, quantity and allocation disagreements, respectively, when SPOT 5 bands and edaphic factors were combined. The study demonstrated that an approach based on the integration of multispectral data and edaphic variables, which increased the overall classification accuracy by about 13%, is a suitable when adopting remote sensing to monitor grassland degradation.     

Spatial variability of soil erodibility and its correlation with soil properties in semi-arid mountainous watershed,Saudi Arabia

Soil erodibility values are best estimated from long-term direct measurements on runoff-plots; however, in lack of field tests, these values can be estimated using relationships based on physico-chemical soil properties. The study objective was to assess the erodibility and its correlation with soil properties. The average erodibility value was estimated 0.043 t ha h ha^?1 MJ^?1 mm^?1. The areas with heavy textured soil and low organic matter content had the lowest values of erodibility. The erodibility decreases as the sand content increases, whereas silt showed a positive correlation. The erodibility factors and its relation to soil properties were evaluated using multiple regression analysis. Results revealed that sand and organic matter content of soil combinedly explained 78% of variation. Altitudinal increases also seem to affect the soil texture. This study has demonstrated that soil properties and erodibility values can be used as assistance for soil conservation practices and modelling of landscape processes.     

Comparison of seasonal and interannual variability of snow cover in Russian watersheds according to observations and reanalyses

Seasonal and interannual variability of the water equivalent of snow over the period 1966–1996 is analyzed with the use of the ERA/ECMWF reanalysis data, two versions of the NCEP reanalysis, and ground-based instrumental observations. Regions have been determined where snow characteristics from various sources are most consistent. In general, the snow water equivalent data from the ERA reanalysis are closer to the snow survey data than the NCEP reanalysis data. The best consistency of the water equivalent of snow in the reanalyses with measured data is observed in the period when the snow cover begins to form, in November and December, and the largest discrepancies are found for the snowmelt period, April and May. The interannual variability of the water equivalent in Asian Russia in the 1990s is better reproduced by the NCEP/DOE-II reanalysis. The snow cover data from satellite observations are compared with ground-based instrumental observations. It is shown that large discrepancies between the snow surveys and satellite observations may be observed at the snow-cover boundary during periods of snow formation and snowmelt.     

Fatty acid profiles of marine benthic microorganisms isolated from the continental slope of bay of bengal: a possible implications in the benthic Food web

Marine bacteria, actinomycetes and fungal strains were isolated from continental slope sediment of the Bay of Bengal and studied for fatty acid profile to investigate their involvement in the benthic food-web. Fifteen different saturated and unsaturated fatty acids from bacterial isolates, 14 from actinomycetes and fungal isolates were detected. The total unsaturated fatty acids in bacterial isolates ranged from 11.85 to 37.26%, while the saturated fatty acid ranged between 42.34 and 80.74%. In actinomycetes isolates, total unsaturated fatty acids varied from 27.86 to 38.85% and saturated fatty acids ranged from 35.29 to 51.25%. In fungal isolates unsaturated fatty acids ranged between 44.62 and 65.52% while saturated FA ranged from 20.80 to 46.30%. The higher percentages of unsaturated fatty acids from the microbial isolates are helpful in anticipating the active participation in the benthic food-web of Bay of Bengal.     

An analytic solution for propagation of blast waves in stellar interiors

B, V observations of the eclipsing binary RS CVn have been presented. A dip around 0 ^p . I appears to be a wave minimum which fits well in the Wave minimum phase-time relation, but deviates from the Wave aplitude-time relation, derived for the RS CVn. Either, the Wave amplitude-time relation requires a modification or the amplitude of the wave minmum appears masked by the intrinsic variability of one of the components or by the Sun-spot activity of the system. The colour exhibits variation. The secondary component appears active.