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81.
87Sr/86Sr ratios of fourteen unaltered limestone and six fossil samples show a range of 0.7066-0.7118 for the depositional water of the Middle to Upper Pennsylvanian Madera Formation. The variation of these 87Sr/86Sr ratios may be due to the restricted depositional basin and nature of the source of the Madera Formation.While fossil and limestone samples are equally good for determination of strontium isotopic composition of depositional waters, leaches of calcareous shales contain significant amount of 87Sr leached from the noncarbonate fraction during acid treatment. 相似文献
82.
83.
Arabinda Mukhopadhyay 《Pure and Applied Geophysics》1970,81(1):64-75
Summary This paper deals with the stresses produced by a moving stress discontinuity between two semi-infinite transversely isotropic media. The solutions for the stresses have been obtained in simple closed forms for certain types of moving stress discontinuity. Discontinuities in the normal stress as well as in the shear stress has been considered. The case in which one or both of the media are isotropic may be deduced as a special case from the results obtained here. 相似文献
84.
An approach for GIS-based statistical landslide susceptibility zonation—with a case study in the Himalayas 总被引:14,自引:1,他引:14
Ashis K. Saha Ravi P. Gupta Irene Sarkar Manoj K. Arora Elmar Csaplovics 《Landslides》2005,2(1):61-69
Landslide susceptibility zonation (LSZ) is necessary for disaster management and planning development activities in mountainous regions. A number of methods, viz. landslide distribution, qualitative, statistical and distribution-free analyses have been used for the LSZ studies and they are again briefly reviewed here. In this work, two methods, the Information Value (InfoVal) and the Landslide Nominal Susceptibility Factor (LNSF) methods that are based on bivariate statistical analysis have been applied for LSZ mapping in a part of the Himalayas. Relevant thematic maps representing various factors (e.g., slope, aspect, relative relief, lithology, buffer zones along thrusts, faults and lineaments, drainage density and landcover) that are related to landslide activity, have been generated using remote sensing and GIS techniques. The LSZ derived from the LNSF method, has been compared with that produced from the InfoVal method and the result shows a more realistic LSZ map from the LNSF method which appears to conform to the heterogeneity of the terrain. 相似文献
85.
We analysed local earthquake waveforms recorded on a broad-band seismic network in northwestern Himalayas to compute the intrinsic and scattered attenuation parameters from coda waves. Similar to other tectonically active and heterogeneous regions, attenuation-frequency relation for western Himalaya is Q −1 c = (113 ± 7) f (1.01±0.05) where Qc is the coda Q parameter. Intrinsic ( Q −1 i ) and scattering ( Q −1 s ) attenuations was separated using Qc and direct S -wave Q data ( Qd ) . It is observed that estimated Q −1 c is close to Q −1 i and both of them are much larger than Q −1 s suggesting that coda decay is predominantly caused by intrinsic attenuation. At higher frequencies, both the attenuation parameters Qc and, Qd are similar indicating that coda is predominantly composed of back-scattered S waves at these frequencies. 相似文献
86.
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
87.
Phosphate sorption and desorption experiments were conducted with four ferruginous soils (alfisols) of Eastern India, in view of the low native phosphate concentrations in tropical Indian soils. From the P-isotherm curve, standard P requirement (SPR) of the soils was determined. Phosphate sorption data were fitted to both Langmuir and Freundlich equations and mean sorption maximum values obtained for the different soil series were in the decreasing order as Matimahal > Anandapur > Mrigindih > Kashipur. The fraction of added P sorbed followed the same trend as SPR, P sorption maximum (Pmax), phosphate affinity constant (K), maximum phosphate buffering capacity (MPBC), Freundlich constant K′ and phosphate desorption values. Phosphate sorption maximum was significantly correlated with MPBC, Freundlich 1/n, SPR, clay and different forms of Fe and Al. The value of K (bonding energy) was significantly correlated with MPBC, Freundlich K′ and pyrophosphate extractable Fe and Al. The MPBC was significantly correlated with Freundlich K′, Freundlich constant 1/n, clay, oxalate and dithionite extractable, amorphous and crystalline form of Fe and Al. Freundlich K′ was significantly correlated with Freundlich 1/n, pHwater, clay, dithionite extractable and crystalline form of Fe and Al. The results suggested that the soils having higher amount of extractable and reactive Fe and Al shared higher P sorbtion capacity and such soils may need higher levels of P application 相似文献
88.
Mahender Singh Ram Niwas M. L. Khichar Manoj K. Yadav 《Journal of the Indian Society of Remote Sensing》2006,34(1):1-5
Field experiments were conducted during 1998–99 and 1999–2000 at research farm of the Department of Agricultural Meteorology,
CCS Haryana Agricultural University, Hisar. Five wheat cultivars: WH 542, PBW 343, UP 2338, Raj 3765 and Sonak were sown on
25th November, 10th and 25th December with four nitrogen levels viz., no nitrogen. 50, 100 and 150% of recommended dose. Leaf area index, dry matter at
anthesis, final dry biomass and grain yield were recorded in all the treatments. Chlorophyll and wax contents of wheat leaves
were estimated at different growth stages. Multiband spectral reflectance was measured using hand-held radiometer. Spectral
indices such as simple ratio, normalized difference, transformed vegetation index, perpendicular vegetation index and greenness
index were computed using the multiband spectral data. Values of all the spectral indices were maximum in 25 November sown
crop with maximum dose of nitrogen (180 kg N ha-1). PBW 343 showed higher values of all the spectral indices in comparison with other cultivars. The spectral indices recorded
during maximum leaf area index stage were correlated with crop parameters. Using stepwise regression, empirical models for
chlorophyll, leaf area index, dry biomass and yield prediction were developed. The ’R2’ values of these models ranged between 0.87 and 0.95. 相似文献
89.
Dipnarayan Ganguly Anirban Mukhopadhyay Rahul Krishna Pandey Debasish Mitra 《Journal of the Indian Society of Remote Sensing》2006,34(4):431-435
Study of landforms in Sundarbans deltaic estuary is necessary in regular basis due to its importance and impact on ecology,
climate and economy. Remote sensing has proved as an important tool to study this. Multi-temporal satellite data helps to
delineate the various geomorphic classes in different time domain and also provide inputs to study the coastal erosion and
accretion. Finer spatial and better temporal resolution will be an added adventure for this kind of study. 相似文献
90.
An overview of the Tertiary geology and hydrogeology of the northern part of the Arabian Gulf region with special reference to Kuwait 总被引:2,自引:0,他引:2
Tertiary sediments constitute the main source of usable groundwater in Kuwait. Tectonics, depositional environment, lithology and the hydrogeology of these sediments have been reviewed on a regional scale, with special reference to Kuwait. The review showed that Kuwait was situated at the boundary of the stable shelf towards southwest and the unstable shelf towards northeast throughout the Tertiary period. The Tertiary sedimentation started in this area with a marine transgression in the Palaeocene. Shallow marine to sabkha conditions prevailed in the area until the end of the Eocene; a carbonate-evaporite sequence (Umm Er-Radhuma, Rus and Dammam Formation) was deposited during this period. The sea regressed at the end of Eocene, and a widespread unconformity, causing the absence of Oligocene deposits over most of the area, marked the event. The karstification of the Dammam Limestone Formation, that provides localized easier pathways for ground water, took place during this period. The deposition of the clastic sediments of the Kuwait Group and its equivalents on the stable shelf, under mostly continental conditions, started in the early Miocene. The Tertiary aquifers of the area are recharged by occasional rainstorms in the outcrops of Saudi Arabia and Iraq. The water flows towards the north and east in the direction of the regional dip and discharges along the present-day coast of the Gulf. The water quality deteriorates in the same direction, being more mineralized as it flows through the aquifers. The aquifers are presently being exploited at a comparatively high rate. Since the aquifers extend beyond the political boundaries, cooperation among the countries of the region is recommended to ensure the optimum utilization of the scarce water resources of this desert environment. 相似文献