Evidence of Superposed Metamorphism from the Gokavaram Area, Eastern Ghats Belt, and its Relation with the Kemp Land Coast, East Antarctica     

Somnath Dasgupta  Pulak Sengupta  Supratim Pal  Masato Fukuoka 《Gondwana Research》1999,2(2):227

In this paper, we compare the petrological histories of the Kemp Land Coast (east Antarctica), and Gokavaram area (Eastern Ghats), that were supposed to have been juxtaposed. The area around Gokavaram is dominated by different varieties of paragneisses (pelitic, quartzofeldspathic, and calcareous composition) with relatively minor amounts of orthogneisses (mafic, enderbitic, and granitic composition). The rocks were involved in three major phases of deformation, and were finally affected by localised shear movement. On the basis of reaction textures, well preserved in high Mg-Al granulites, and calc-silicate granulites, and geothermobarometric data we deduce a polymetamorphic evolution of the rocks. Following an early M₁ metamorphism culminating at 9.2–9.4 kbar, > 950°C, the rocks cooled nearly isobarically down to 850°C. During a subsequent M₂ metamorphism, near isothermal decompression to 5–6 kbar occurred. This was followed by near isobaric cooling down to 600–650°C. M₃ is a weak amphibolite facies overprint, largely restricted to late shears, which involved hydration as well. Available radiometric data from this area can be interpreted in terms of partial resetting of U-Pb systematics in older sphenes due to M₃ metamorphism at ca. 550 Ma. Despite the absence of sufficient isotopic data on the Eastern Ghats granulites, we document a remarkable similarity in the petrological history of the two supposedly erstwhile neighbours.  相似文献   

Changes In The Stream Courses Around Maithon Reservoir, Eastern India: Observations Using Remote Sensing Data     

S. Sengupta  A. Chatterjee 《Journal of the Indian Society of Remote Sensing》2000,28(4):277-280

  相似文献   

Did the Harappan settlement of Dholavira (India) collapse during the onset of Meghalayan stage drought?     

Torsa Sengupta  Arati Deshpande Mukherjee  Ravi Bhushan  F. Ram  M. K. Bera  Harsh Raj  Ankur J. Dabhi  R. S. Bisht  Y. S. Rawat  S. K. Bhattacharya  Navin Juyal  Anindya Sarkar 《第四纪科学杂志》2020,35(3):382-395

Radiocarbon dating of archaeological carbonates from seven cultural stages of Dholavira, Great Rann of Kachchh (GRK), the largest excavated Harappan settlement in India, suggests the beginning of occupation at ~5500 years BP (pre-Harappan), and continuation until ~3800 years BP (early part of the Late Harappan period). The settlement rapidly expanded under favourable monsoonal climate conditions when architectural elements such as the Citadel, Bailey, Lower and Middle Town were added between the Early and mid-Mature Harappan periods. Abundant local mangroves grew around the GRK sustaining prolific populations of the edible gastropod Terebralia palustris. Oxygen isotope (δ¹⁸O) sclerochronology of Early Harappan gastropod shell suggests seasonal mixing of some depleted (δ¹⁸O ~ −12‰) river water in summer/monsoon months (through ancient Saraswati and/or Indus distributary channels) with seawater that periodically inundated the GRK. Evaporation from this semi-enclosed water body during the non-monsoon months enriched the δ¹⁸O of water/shell carbonates. The humid fluvial landscape possibly changed due to a catastrophic drought driving the final collapse of the settlement of Dholavira exactly at the onset of the Meghalayan (Late Holocene) stage (~4300–4100 years BP ). Indeed, Dholavira presents a classic case for understanding how climate change can increase future drought risk as predicted by the IPCC working group. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献   

Identification and mapping of chromium (VI) plume in groundwater for remediation: A case study at Kanpur,Uttar Pradesh   总被引：1，自引：0，他引：1  

R. K. Singh  B. Sengupta  Rameshwar Bali  B. P. Shukla  V. V. S. Gurunadharao  Rajesh Srivatstava 《Journal of the Geological Society of India》2009,74(1):49-57

With only twenty five percent population living in urban areas, India has cities amongst the biggest in the world. Urban growth in most of Indian cities is concomitant with rise in water demand for community, as well as, for industrial purposes. The complex situation resulting from indiscriminate disposal of waste and its severe impact on groundwater quality is set for continuous worsening mainly for want of sustained effort aimed at site-specific remediation. The study, a prerequisite for actual remediation in an industrial city of Kanpur, India, envisages detailed investigation about pollutant transport, evaluation of concept of Bio-remediation and a range of other options and finally full scale implementation of the best suited. Drilling of piezometers and resistivity survey indicates that the area is constituted of alluvial sands, gravels and their various admixtures. Chemical analysis of water samples collected from piezometers and hand pumps shows the presence of hexavalent chromium rich horizons at various depths. The alarming concentration of this carcinogenic heavy metal of the order of 16.3 mg/l against the permissible concentration (of 0.05 mg/l) for drinking water and high concentration within sediments of the area poses a major threat to the entire ecosystem. The projection of migration contaminant plume of hexavalent chromium as depicted in the paper is indicative of a concentrated extent of core zone existing in shallow alluvial aquifer, which may be targeted for interception by remedial measures. The present work, elaborating on the source, potential and monitoring the migration of the pollutant plume is the first field scale study of its kind in the country. The findings of these studies are of strong relevance in addressing the ground water pollution due to indiscriminate disposal practices of hazardous waste in areas located within the alluvial zones.  相似文献   

Macroseismic study of 20<Superscript>th</Superscript> May 2007 Sikkim earthquake — Its seismotectonic implications for the region     

K. C. Joshi  S. Sengupta  G. C. Kandpal 《Journal of the Geological Society of India》2010,75(2):383-392

An earthquake of magnitude 5.0 with its epicenter in the West Sikkim district occurred on the evening of 20^th May 2007. The macroseismic study revealed an ENE-WSW isoseismal pattern indicating a trend conforming to that of the major tectonic discontinuities in this part of the Himalaya.  相似文献   

Rainfall thresholds for the initiation of landslide at Lanta Khola in north Sikkim,India   总被引：6，自引：3，他引：3  

A. Sengupta  S. Gupta  K. Anbarasu 《Natural Hazards》2010,52(1):31-42

In the Indian Himalaya, a 15 km stretch of the North Sikkim Highway that is exceptionally susceptible to landsliding is characterized by fine-grained, low permeability debris material. Lanta Khola is one of the major debris slides in this stretch and is active every year during the monsoons. Although the relationship between rainfall and landsliding in the area is obvious, there is no previous study of precipitation thresholds for landslide initiation. Review of available rainfall and landslide activity data for the area between 1998 and 2006 suggests that sliding cannot be modeled by typical exponential relationships between cumulative rainfall (E) and rainfall duration (D). An alternative rainfall threshold has been proposed that predicts sliding if normalized cumulative rainfall for more than 15 days exceeds 250 mm. It is suggested that when this cumulative rainfall threshold is exceeded, the debris zone in the affected stretch becomes saturated and fails, causing landsliding.  相似文献   

Statistical Correlation between Iron (Fe) and Arsenic (As) and Probabilities of their Conjugate Occurrences in Groundwater from two Different Areas of West Bengal (southern part), India     

B.J. Sengupta  Sudipto Lahiri 《Journal of the Geological Society of India》2018,92(3):378-378

  相似文献   

Slope failure susceptibility zonation using integrated remote sensing and GIS techniques: A case study over Jhingurdah open pit coal mine,Singrauli coalfield,India     

S Sengupta  A P Krishna  I Roy 《Journal of Earth System Science》2018,127(6):82

The susceptibility of slopes in open pit coal mines to various modes of failure (i.e., plane, wedge, circular and toppling failure) could be envisaged by virtue of processing and analysis of pertinent satellite data. The aim of the present study was to integrate thematic maps generated using remote sensing image processing techniques, in order to finally produce slope failure hazard zonation maps in and around Singrauli coalfield, India. The various failure-inducing factors, variables and parameters can be extracted from different satellite data and imageries. The data acquired by different sensors such as TM, ETM+, etc., of LANDSAT series and CARTOSAT of ISRO Bhuvan was used in this study. All these data were subsequently used to create different thematic maps such as slope map, lithological map, land use/land cover map, principal component analysis map, digital elevation model (DEM), etc. An advanced analysis for extraction of lineament attributes was also undertaken.  相似文献   

Geochemical implications of minerals and environmentally sensitive elements of Giral lignite,Barmer Basin,Rajasthan (India)     

Pramod K. Rajak  Vijay K. Singh  Prakash K. Singh  Asha Lata Singh  Narendra Kumar  Om Prakash Kumar  Vishvajeet Singh  Aniruddha Kumar 《Environmental Earth Sciences》2018,77(19):698

The Barmer Basin of Rajasthan is significant for its Paleogene lignite sequences. The lignite seam occurs in Akli Formation of Barmer Basin at the depth of 06–241 m. A total of 57 lignite samples were collected from the working faces of lignite mine and were subjected to proximate analysis (moisture, ash yield, volatile matter, and fixed carbon), ultimate analysis (carbon, hydrogen, nitrogen, oxygen and sulfur), elemental analysis (Fe, Ca, Mg, Cd, Mn, K, Na, Cu, Co, Ni, Cr, Zn, and Pb) and rock-eval pyrolysis for mineral carbon (MINC). Some elements like Cu, Cd, Co, Ni, Zn, Pb, Na, and K occur in high concentration, while Mg and Ca have their concentrations lower than World Clarke average. In addition, various minerals and functional groups present in the lignite samples were analyzed through X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy. The mineral (weight and atomic) percentage has also been analyzed through scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS).  相似文献   

H i imaging of galaxies in X-ray bright groups     

Chandreyee Sengupta †  Ramesh Balasubramanyam  K. S. Dwarakanath 《Monthly notices of the Royal Astronomical Society》2007,378(1):137-147

Environment plays an important role in the evolution of the gas contents of galaxies. Gas deficiency of cluster spirals and the role of the hot intracluster medium in stripping gas from these galaxies is a well-studied subject. Loose groups with diffuse X-ray emission from the intragroup medium (IGM) offer an intermediate environment between clusters and groups without a hot IGM. These X-ray bright groups have smaller velocity dispersion and lower temperature than clusters, but higher IGM density than loose groups without diffuse X-ray emission. A single-dish comparative study of loose groups with and without diffuse X-ray emission from the IGM, showed that the galaxies in X-ray bright groups have lost more gas on average than the galaxies in non X-ray bright groups. In this paper we present GMRT H  i observations of 13 galaxies from four X-ray bright groups: NGC 5044, 720, 1550 and IC1459. The aim of this work is to study the morphology of H  i in these galaxies and to see if the hot IGM has in any way affected their H  i content or distribution. In addition to disturbed H  i morphology, we find that most galaxies have shrunken H  i discs compared to the field spirals. This indicates that IGM-assisted stripping processes like ram pressure may have stripped gas from the outer edges of the galaxies.  相似文献