Photogeological mapping for regional studies of the Vindhyan rocks around Bundi area,Rajasthan     

A. Bhattacharya  A. K. Roy  K. Thiyagarajan  K. K. Naik 《Journal of the Indian Society of Remote Sensing》1983,11(2):19-29

An area of 2300 sq km s has been mapped around Bundi based on aerial photo-interpretation, with selected field checks at key areas. The oldest rocks exposed are Aravallis comprising a thick pile of argillaceous sediments with thin interbeds of quartzite. The Aravalli rocks have been subjected to two phases of folding and have undergone a low grade of metamorphism. The Vindhyan rocks which comprise arenaceons, argillaceous and calcareous sediments constitute the Kaimur, Rewa and Bhander groups. These rocks occur south of the Aravallis with a faulted contact (Great Boundary Fault) for the major part, and also with unconformable contact at places. The upliftment of the Aravallis on the northern side of the Great Boundary Fault might have created the Vindhyan Basin south of it. The movement appears to have been gradual, keeping pace with the Vindhyan sedimentation, and was possibly revived even after the Vindhyan sedimentation as evidenced by the presence of folding and faulting in Vindhyans in the vicinity of the boundary fault. Strike faulting parallel to the boundary fault is very conspicious resulting in the repetition of the Vindhyan strata in the area east of Bundi. The Vindhyans of Bundi area indicate deposition of sediments in shallow water coastal barrier and lagoonal set-up as evidenced by sedimentary features such as tabular current bedding, ripple marks, huge blankets of sandstone, alternation of shale and limestone etc. Geomorphologically the area may be divided into three units namely:-(a) Pediment on Aravallis, (b) Structural hills on Vindhyan, expressing generally as hogback and cuesta ridges and strike valleys, and (c) Piedmont and alluvial plains (Chambal valley). The photo characters of the different litho-units have been described.  相似文献   

Conservation of biodiversity of the coastal resources of Sundarbans,Northeast India: an integrated approach through environmental education     

Sarkar SK  Bhattacharya AK 《Marine pollution bulletin》2003,47(1-6):260-264

The Indian Sundarbans, a diversified coastal wetland on the southern fringe of the State of West Bengal, harbors a luxuriant biodiversity and acts as a potential refuge of living marine resources. Girdled with thick mangrove foliage, this estuarine delta system offers an excellent nursery ground for most of the brackishwater finfish and shellfish. Since supply of hatchery-produced tiger prawn seed (Penaeus monodon) is highly inadequate in West Bengal, the aquaculture farms of this region largely depend on the supply from natural resources. Being motivated by a regular cash income, the majority of coastal people from Sundarbans have adopted prawn seed collection as their profession almost throughout the year as an important source of earning. The users are neither trained nor guided at any stage from collection to marketing and are fully dependent on traditional methods. They first sort out the tiger prawn seeds (mainly the postlarval stage PL 20) accounting only 0.25-0.27% of the total catch and thereafter the major portion of the haul are thrown away on the beach flats or the tidal mudflats. This wasted by-catch contains the juveniles of economic and uneconomic varieties of finfish and shellfish along with a bulk of holoplankters and meroplankters (non-target species). This practice causes several ecological and occupational consequences, namely, (i) the huge destruction of the pelagic biota that can lead to severe stock depletion as well as hamper the energy transference through the marine ecosystem food webs; (ii) constant dragging of nets along the coast and tidal creeks paves the way for soil erosion, uprooting the mangrove seedlings and saltmarsh vegetation; (iii) the water quality is deteriorating in the catchment areas due to mud erosion and (iv) due to constant contact with the seawater, the collectors are affected with waterborne diseases, skin infections, reproductive tract disease in women and many other contagious diseases.This paper, in addition to identifying the challenge to environmental quality and resource abundance, emphasizes the need for grass-root public education so that local people come to understand, support and implement sustainable resource conservation and environmental protection activities now and in the future. As a follow-up course of action, the authors have initiated a general awareness program for developing consciousness among the coastal people regarding proper use of natural resources. Initiatives are taken for educating coastal people by holding workshops and seminars with the use of educational resource materials. Exclusive awareness camps and grass root level training for coastal people are also being proposed as a future course of action by means of exhibitions, audiovisuals etc. It is proposed that local government bodies come forward to mitigate this problem with scientific and rational approaches and to take proper actions towards conservation.  相似文献   

Facies, dissolution seams and stable isotope compositions of the Rohtas Limestone (Vindhyan Supergroup) in the Son valley area, central India     

S. Banerjee  S. K. Bhattacharya  S. Sarkar 《Journal of Earth System Science》2005,114(1):87-96

The early Mesoproterozoic Rohtas Limestone in the Son valley area of central India represents an overall shallowing-upward carbonate succession. Detailed facies analysis of the limestone reveals outer- to inner-shelf deposition in an open marine setting. Wave-ripples, hummocky cross stratifications and edgewise conglomerates argue against a deep marine depositional model for the Rohtas Limestone proposed earlier. Stable isotope analysis of the limestone shows that δ¹³C and δ¹⁸O values are compatible with the early Mesoproterozoic open seawater composition. The ribbon limestone facies in the Rohtas Limestone is characterized by micritic beds, each decoupled in a lower band enriched and an upper band depleted in dissolution seams. Band-wise isotopic analysis reveals systematic short-term variations. Comparative enrichment of the heavier isotopes in the upper bands is attributed to early cementation from sea water and water derived from the lower band undergoing dissolution because of lowering of pH at depth. The short-term positive shifts in isotopic compositions in almost every upward gradational transition from a seamed band to a non-seamed band support the contention that dissolution seams here are of early diagenetic origin, although their formation was accentuated under overburden pressure.  相似文献   

Delineation of arsenic-contaminated zones in Bengal Delta, India: a geographic information system and fractal approach     

Basab Mukhopadhyay  P. K. Mukherjee  Debkumar Bhattacharya  S. Sengupta 《Environmental Geology》2006,49(7):1009-1020

Groundwater extracted from shallow aquifers in the Bengal Delta is contaminated with arsenic. The fluviodeltaic process that creates aquifers, ironically, extends its role to also contaminating them with arsenic. The arsenic distribution maps show a spatial association of arsenic-contaminated wells with palaeo/cut-off/abandoned channels. Weight-on-evidences analysis indicates that the zones of contamination occur around palaeo-channels within a corridor of 500–700 m that contains most of the contaminated wells. These corridors are interpreted to be the zone of channel shifting. Contaminated wells represent point fractal geometry that can be separated into isolated points and clusters. Clusters occur within the zone of channel shifting as obtained by weight-on-evidences analysis. Isolated points occur within floodplain or back swamp areas. Clusters and isolated point fractals are interpreted to reflect the process of arsenic release into groundwater. The migration of biomass within the permeable sandy domain of channel deposits is proposed to be the predominant process in generating clusters. The isolated points represent restricted biomass spreading in less permeable clay-silt dominated floodplains.  相似文献   

Nature, origin and evolution of the granitoid-hosted early Proterozoic copper-molybdenum mineralization at Malanjkhand, Central India – a reply     

S. C. Sarkar  S. Kabiraj  S. Bhattacharya  A. B. Pal 《Mineralium Deposita》1997,32(6):622-622

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Response of thunderstorm and lightning activity to solar modulation of atmospheric electrification     

A. B. Bhattacharya  S. K. Kar  R. Bhattacharya 《Theoretical and Applied Climatology》1997,58(1-2):95-103

Summary The influence of thunderstorms on the atmospheric radio noise field strength (ARNFS) over Kalyani (West Bengal) at 27 kHz has been analyzed over a two-year period. The results show that the median noise level decreases during the winter and reaches a maximum during the monsoon months. A comparison of the seasonal occurrence of thunderstorm-days with ARNFS indicates that both of them have similar trend over time. However, the trend is more pronounced during daytime, indicating relationship between solar activity, thunderstorms and ARNFS. In this paper, we have attempted to investigate how tropical thunderstorm and lightning activity might be responsible for the solar modulation of atmospheric electrification. The influence of ionizing radiation on the electrical global circuit of the atmosphere is also critically analyzed.With 7 Figures  相似文献   

Diffuse solar radiation and associated meteorological parameters in India     

A. B. Bhattacharya  S. K. Kar  R. Bhattacharya 《Annales Geophysicae》1997,14(10):1051-1059

Solar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another.  相似文献   

Oxygen and hydrogen isotopic ratios in groundwaters and river waters from India     

S. K. Bhattacharya  S. K. Gupta  R. V. Krishnamurthy 《Journal of Earth System Science》1985,94(3):283-295

A comprehensive set of measurements of oxygen and hydrogen isotopic ratios in groundwaters as well as waters from rivers, lakes, hot springs etc. taken from a variety of locations in India has been carried out for the first time. Isotopically the most depleted samples occur in the high altitude precipitations in the Himalayas e.g. in the lakes of Bhutan and the source water of the Ganga. The shallow groundwater data display a continental effect where the heavy isotope content decreases with distance from the coast (about 4 to 6 per mil decrease in δ¹⁸O per 1000 km). The δ D and δ¹⁸O of these fresh waters are linearly related and an analysis of this relation vis-a-vis the meteoric water line shows the unambiguous effect of enrichment due to evaporation from soils.  相似文献   

An orthopyroxene-garnet thermometer and its application to the Madras charnockites   总被引：5，自引：0，他引：5  

S. K. Sen  A. Bhattacharya 《Contributions to Mineralogy and Petrology》1984,88(1-2):64-71

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Grenvillian thermal event and remnant charnockite: Isotopic evidence from the Chilka Lake granulite-migmatite suite in the Eastern Ghats belt, India   总被引：1，自引：0，他引：1  

S. Bhattacharya  M. P. Deomurari  W. Teixeira 《Journal of Earth System Science》2002,111(4):391-399

Spectacular exposures of granulite-migmatite occur in the Chilka Lake area of the Eastern Ghats belt. The garnetiferous granite gneiss of peraluminous granitic composition, often contains restitic metapelite inclusions and is demonstrably a product of biotite-dehydration melting in pelitic rocks. On the other hand, older layers and bands of charnockitic rocks frequently occur as dismembered patches within the peraluminous granite, thus imparting a measled appearance of the granite exposures. The partial melting and emplacement of the peraluminous granite represent the Grenvillian thermal event, as evidenced by Rb-Sr whole rock and Pb-Pb zircon dating. On the other hand, minor patches of charnockite represent migmatized relict, as evidenced by some older zircons, in addition to those of Grenvillian age.  相似文献