Geoelectric and geochemical studies for hydrological characterization of canning and adjoining areas of South 24 Parganas district,West Bengal     

R. K. Majumdar  S. Kar  D. Talukdar  T. Duttagupta 《Journal of the Geological Society of India》2014,83(1):21-30

Integrated geoelectric and geochemical investigation were carried out in the Canning and adjoining areas to assess the prevailing groundwater conditions and chemical quality of groundwater. Geologically, the area is constituted of alluvial sediments of Quaternary age. Vertical electrical soundings (VES) in the area of investigation mostly show six layers consisting of top soil, saline water, clay layer, brackish water, clay layer and fresh-water bearing zone of appreciable thicknesses at depths of 137 to 182 meter at six locations and from 370 to 430 meter for other two locations under confined conditions. The result of VES studies significantly correspond with the borehole litholog and well log data. A litho-resistivity relationship is established for this area of investigation A Fence diagram is constructed to show the spatial variation of the sub-surface lithology and hydrological characteristics. Chemically the ground water is fresh and mixed cation and anion type as revealed from Piper-Trilinear diagram with TDS ranging from 699 to 1547 mg/l. The geochemical parameters like Total hardness (TH), Sodium absorption ratio (SAR), Soluble sodium percentage (SSP), Percentage of sodium (PS), Kelley’s ratio (KR), Residual sodium carbonate (RSC), Corrosivity ratio (CR), Gibbs ratios (GR), Chloro alkaline indices (CAI), Sea water contamination (SWC) are also calculated for examining the quality of groundwater in the area. The depth of occurrences of freshwater bearing ground water zones for drinking and irrigation purposes are occurring at depths from 137 meter to 430 meter in this area.  相似文献   

Petrological and Geochemical Constraints on the Evolution of the Alkaline Complex of Koraput in the Eastern Ghats Granulite Belt, India     

S. Bhattacharya  Rajib Kar 《Gondwana Research》2005,8(4):596-602

The Koraput Alkaline Complex in the high-grade Eastern Ghats Belt, India, is synkinematically emplaced in a pull-apart structure and far from the Bastar cratonic margin. The suite comprises four distinct members, namely, mafic syenite, felsic syenite, nepheline syenite and perthite syenite. Fe-rich orthopyroxene rims on olivine in mafic syenite indicate iron-enrichment in the early stage of differentiation. With plagioclase of andesine composition it could be described as alkali-norite, the plutonic equivalent of hawiite. Felsic syenite with both alkali-feldspars and plagioclase of oligoclase composition could be described as two-feldspar syenite, the plutonic equivalent of mugearite. Albitic rims on nepheline indicates subsolvus reaction. Chemical trends in amphiboles and plagioclase feldspars, progressively more ferroan and more sodic respectively, are strong indications of mineral fractionation in the Koraput suite. Chemical trends in the variation diagrams are compatible with feldspar fractionation in the Koraput suite. A weak Fe-enrichment trend in the early stage of differentiation, as observed in the AFM diagram, is compatible with that of the alkali-basalt series. Nb anomalies, both positive and negative, are indicative of crustal contamination as expected in synkinematic plutons. In terms of Gondwana assembly and break up, the alkaline complexes are supposed to represent rift-related magmatism along the continental margin. In spite of petrological evidence of the magmatic character of the Koraput Complex, anorogenic setting is contra-indicated by mesoscopic and microscopic fabrics, more akin to synkinematic intrusion during F 2 folding in the host country rocks. The Proterozoic alkaline complexes in the Eastern Ghats Belt, could alternatively trace the path of moving Gondwana continent over mantle plumes.  相似文献   

Sensitivity Studies of Convective Schemes and Model Resolutions in Simulations of Wintertime Circulation and Precipitation over the Western Himalayas     

P. Sinha  P. R. Tiwari  S. C. Kar  U. C. Mohanty  P. V. S. Raju  S. Dey  M. S. Shekhar 《Pure and Applied Geophysics》2015,172(2):503-530

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The youngest volcanic eruptions in East‐Central Europe—new findings from the Ciomadul lava dome complex,East Carpathians,Romania          下载免费PDF全文

D. Karátson  D. Veres  S. Wulf  R. Gertisser  E. Magyari  M. Bormann 《Geology Today》2017,33(2):60-65

Violent explosive eruptions occurred between c. 51 and 29 thousand years ago—during the Last Glacial Maximum in East‐Central Europe—at the picturesque volcano of Ciomadul, located at the southernmost tip of the Inner Carpathian Volcanic Range in Romania. Field volcanology, glass geochemistry of tephra, radiocarbon and optically stimulated luminescene dating, along with coring the lacustrine infill of the two explosive craters of Ciomadul (St Ana and Mohos), constrain the last volcanic activity to three subsequent eruptive stages. The explosivity was due to the silicic composition of the magma producing Plinian‐style eruptions, and the interaction of magma with the underlying, water‐rich rocks resulting in violent phreatomagmatic outbursts. Tephra (volcanic ash) from these eruptions are interbedded with contemporaneous loess deposits, which form thick sequences in the vicinity of the volcano. Moreover, tephra layers are also preserved in the older Mohos crater infill, providing an important archive for palaeoclimate studies. Identifying the final phreatomagmatic eruption of Ciomadul at c. 29.6 ka, which shaped the present‐day landform of the 1600‐m‐wide St Ana explosion crater, we were able to correlate related tephra deposits as far as 350 km from the source within a thick loess‐palaeosol sequence at the Dniester Delta in Roxolany, Ukraine. A refined tephrostratigraphy, based on a number of newly found exposures in the Ciomadul surrounding region as well as correlation with the distal terrestrial and marine (e.g. Black Sea) volcano‐sedimentary record, is expected from ongoing studies.  相似文献   

A note on strong mass loss from early sun and warm and wet Mars     

J. Kar 《Earth, Moon, and Planets》1996,73(2):187-192

Recently, the possibility of strong mass loss from an early sun has been proposed in connection with the lithium depletion problem along with early solar system problems. However, the time scale for this enhanced mass loss is uncertain. Using an empirical relation for the dependence of the Martian surface temperature on solar luminosity and surface pressure, we find that the mass loss time scale for a 1.1 M sun should be about 1 × 10⁹ years or longer if Mars had liquid water on its surface 3.8 billion years ago. The minimum surface pressure on early Mars should be about 5 bars of CO₂.  相似文献   

Long-period fading in atmospherics during severe meteorological activity and associated solar geophysical phenomena at low latitudes     

A. B. Bhattacharya  S. K. Kar  M. K. Chatterjee  R. Bhattacharya 《Annales Geophysicae》1998,16(2):183-188

The records of VLF atmospherics over Calcutta and then over Kalyani (West Bengal) during the torrential rainfall, caused by violent monsoon and post-monsoon depressions, exhibit distinct long-period fadings both at day and night. Interesting results obtained from an analysis of round-the-clock atmospherics data and associated meteorological parameters are reported in this paper. A possible correlation between the severe meteorological activity with the solar geophysical phenomena was studied. The results are indicative of an interesting sequence of solar-terrestrial events. A tentative conclusion is reached, suggesting an origin of the fading from atmospheric gravity waves generated in the centre of activity of the depressions concerned.Currently at: Department of Physics, Serampore College, Serampore, 712 201 West Bengal  相似文献   

Glacial lake outburst flood at Kedarnath,Indian Himalaya: a study using digital elevation models and satellite images     

Sayantan Das  Nabendu Sekhar Kar  Sunando Bandyopadhyay 《Natural Hazards》2015,77(2):769-786

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Generation of granitic plutons during Crustal orogenesis: An example from the Eastern Ghats granulite belt     

Rajib Kar 《Journal of the Geological Society of India》2012,80(5):653-666

Stock-like granite plutons in the Eastern Ghats belt and their host granulites exhibit similar solid state fabric. Both mineralogically and chemically these plutons are peraluminous and granitic in composition with S-type granite affinities. The granite plutons are product of a variety of mica dehydration melting reactions, as evident from their (1) compositional plots in the (FeO + MgO) ?? Na₂O.Al₂O₃ ?? K₂O.Al₂O₃ (MNK) pseudoternary diagram and (2) trace element contents. Muscovite and/or biotite breakdown reaction with or without plagioclase are the characteristic melting reactions. Restitic signature is evident in the host metapelitic granulites, locally known as khondalites (Qtz-Kfs-Grt-Sil-Fe-Ti oxides-bearing gneisses). The compositional variability of the associated khondalites can be a result of (1) original compositional variation and (2) they represent different stages of restites. Trace element monitoring following restite separation model suggests that these granite plutons are largely saturated equilibrium melts. The granites are chemically discriminated as syn-collisional. The plutons could also be the product of segregation during the regional exhumation of the Eastern Ghats terrain.  相似文献   

Middle to Late Holocene climate,vegetation and sea-level changes in NW Tripura,northeast India,based on palynological and mineral magnetic evidence     

Mehrotra  Nivedita  Shah  Santosh K.  Basavaiah  Nathani  Kar  Ratan 《Journal of Paleolimnology》2022,68(3):297-313

Journal of Paleolimnology - The sediment deposits of northwestern Tripura, northeast India, revealed the enhanced proximity to the marginal marine environments, forest cover variations and...  相似文献   

Discovery of Gondwana plant fossils and palynomorphs of Late Asselian (Early Permian) age in the Karakoram Block     

R. Upadhyay  R. Chandra  A.K. Sinha  R.K. Kar  S. Chandra  N. Jha  H. Rai 《地学学报》1999,11(6):278-283

We report the discovery of Early Permian (late Asselian, ∼280–275 Ma) plant fossils and associated palynomorphs from a marine sedimentary sequence of the eastern Karakoram plate, in northern India. These specimens show affinities with those found in marine Lower Gondwana sediments of the Indian subcontinent. This supports the contention that during the Early Permian Period, the Karakoram plate was Peri-Gondwanan. It is suggested to have had an intermediate position between the Indian plate and the Qiangtang–Lhasa microcontinents, at a latitude of about 35° south.  相似文献