New record of Bathonian–Callovian calcareous nannofossils in the eastern Karakoram block: a possible clue to understanding the dextral offset along the Karakoram Fault     

Rajeev Upadhyay  Jyotsana Rai  Anshu K Sinha 《地学学报》2005,17(2):149-157

We report the first record of Bathonian–Callovian calcareous nannofossils from a marine sedimentary sequence of the eastern Karakoram block, in northern India. The calcareous mudstones and packstones, occasionally bearing red chert nodules, yielded calcareous nanofossils and Middle Jurassic Choffatia furcula ammonoids. Middle to Upper Jurassic nannofossil assemblage is dominated by representatives of the genus Watznaueria. The occurrence of Ansulasphaera helvetica whose range is Upper Bathonian–Upper Callovian, indicates a correlation with nannofossil zones NJ12–13. The occurrence of Cyclagelosphaera wiedmannii further infer an Upper Bathonian–Callovian age. These specimens show affinities with those found in a similar sedimentary formation exposed in north Karakoram. This suggests the existence of a narrow and elongated sedimentary basin, oriented in a NW–SE direction, at a latitude of c. 25°–30°N. At that time, the Karakoram block was situated near the already welded Qiangtang block of Asia. The northern and eastern Karakoram blocks were connected during Middle Jurassic. The activity and dextral offset of the Karakoram fault separated the Jurassic sedimentary formations of the northern and eastern Karakoram blocks by c. 150 km.  相似文献   

Modeling water-table fluctuations in a sloping aquifer with random hydraulic conductivity   总被引：1，自引：0，他引：1  

Kirti Srivastava  S. Rai  R. Singh 《Environmental Geology》2002,41(5):520-524

To prevent environmental problems like water logging and increase in soil salinity which are responsible for the degradation of the top productive soils, an optimum ditch drainage design is required. For this purpose a knowledge of the spatio-temporal variation of the water table is essential. In this study the spatio-temporal variation of the water table in a sloping ditch drainage system has been modeled from a stochastic point of view, incorporating randomness in hydraulic conductivity to get the expression for the mean and the standard deviation of the water-table height. The hydraulic conductivity has been considered to be a realization of a log-normal distribution. Application of these expressions in the prediction of mean water-table variation with the associated error bounds has been demonstrated with the help of a ditch drainage problem of a sloping aquifer. The sensitivity analysis has also been carried out to see the effect of variability in the hydraulic conductivity on the water-table fluctuations. The error bounds quantified on the water-table height will thus help in the decision-making process for proper drainage design.  相似文献   

Seismically constrained two-dimensional crustal thermal structure of the cambay basin     

S. Thiagarajan  D. V. Ramana  S. N. Rai 《Journal of Earth System Science》2001,110(1):1-8

The temperature field within the crust is closely related to tectonic history as well as many other geological processes inside the earth. Therefore, knowledge of the crustal thermal structure of a region is of great importance for its tectonophysical studies. This work deals with the two-dimensional thermal modelling to delineate the crustal thermal structure along a 230 km long Deep Seismic Sounding (DSS) profile in the north Cambay basin. In this work P-wave velocities obtained from the DSS studies have been converted into heat generation values for the computation of temperature distribution. The model result reveals the Curie isotherm at a depth of ≈22 km and Moho temperature at around 900‡C.  相似文献   

Laboratory Studies of the Flow of Some Organic Solvents and Their Aqueous Solutions Through Bentonite and Kaolin Clays     

A. S. Abdul  T. L. Gibson  D. N. Rai 《Ground water》1990,28(4):524-533

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Electrical conductivity of a spinel lherzolite and a garnet peridotite to 1550°C: relevance to the effects of partial melting     

M. H. Manghnani  C. S. Rai 《Bulletin of Volcanology》1978,41(4):328-332

Electrical conductivity σ of two ultramafic rocks (a spinel lherzolite and a garnet peridotite) has been investigated to melting temperature at 1 bar under known oxygen fugacity environment. The electrical conductivity of the two rocks is found to increase with degree of partial melting and an ～ 15% melt fraction is necessary for the electrical conductivity to increase by ～ 1 order of magnitude. For a given melt fraction electrical conductivity of a spinel lherzolite is lower than that of a garnet peridotite and may be attributed to the differences in the composition of the melts formed.  相似文献   

辽西─冀北地区铀成矿遥感地质信息的研究     

于宝山  王殿柏  金时华  乔锐 《华东地质学院学报》1996,(4)

本文从辽西—冀北铀矿床成矿地质环境、时空分布及矿床特征出发，在以遥感信息为主，综合地质、物化探、水文等资料的全区性联幅应用开发、复合成图、综合分析以及重点地区的野外详细调查的基础上，运用切合全区地壳运动的演化理论，揭示了区内地壳演化及其结果的构造格局、区域地质背景、铀成矿条件和时空分布规律，建立了不同岩区环弧形构造解译标志，并阐述了其地质成因。解译了火山机构、小型封闭沉积盆地和铀矿密切相关的岩浆岩体，着重解译了控矿构造和矿化蚀变带的产状、类型，强调解译了卫片图像“热晕点”，并讨论了其地质意义和铀矿的关系，最后确定了遥感地质找矿模式和综合预测模型。  相似文献   

Hydromorphogeological Mapping for Groundwater Prospecting Using Landsat-MSS Images — A Case Study of Part of Dhanbad District,Bihar     

A Tiwari  B Rai 《Journal of the Indian Society of Remote Sensing》1996,24(4):281-285

The Dhanbad district in Bihar, feces acate water scareity and is chronically drought prone. The groundwater resources in the area have not been fully exploited. The present study was undertaken to evaluate the groundwater prospective zones, Landsat-5 MSS data of band-2 and band-4 and false colour composite of band 2, 3, 4 were interpreted visually to differentiate different hydromarphogeological units and to delineate the major trends of lineaments. The different geomorphic features identified are linear ridges, residual hills, pediplain, buried pedtment and dissected pediplain, besides lineaments. The study shows that the pediplain and buried pediments are promising zones for groundwater prospecting.  相似文献   

Synergistic Application of Four Remedial Techniques at an Industrial Site     

Jean. M. Dasch  Abdul S. Abdul  Devi N. Rai  Thomas L. Gibson  Noel Grosvenor 《Ground Water Monitoring & Remediation》1997,17(3):194-209

The soil and ground water at a General Motors plant site were contaminated with petroleum products from leaking underground storage tanks. Based on the initial assessment, the site was complex from the standpoint of geology (clay layers), hydrology (a recharge zone with a perched water table), and contaminant (approximately 4800 gallons of mixed gasoline and oil). After a thorough study of remedial alternatives, a synergistic remedial approach was adopted including pump and treat, product removal, vapor extraction, and bioventing. The system was designed and implemented at the site through 22 dual-extraction wells. Over a 21-month period, 4400 gallons of gasoline and oil were removed from the system, including 59 percent by vapor extraction, 28 percent by bioventing, and 13 percent by pump and treat. Synergism between the various remedial methods was demonstrated clearly. Ground water pump and treat lowered the water table, allowing air to flow for vapor extraction. The vacuum applied for vapor extraction increased the ground water removal rate and the efficiency of pump and treat. The vapor extraction system also added oxygen to the soil to stimulate aerobic biodegradation.  相似文献   

Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain     

Raj K. Rai  Larry K. Berg  Branko Kosović  Jeffrey D. Mirocha  Mikhail S. Pekour  William J. Shaw 《Boundary-Layer Meteorology》2017,163(1):69-89

The Weather Research and Forecasting (WRF) model can be used to simulate atmospheric processes ranging from quasi-global to tens of m in scale. Here we employ large-eddy simulation (LES) using the WRF model, with the LES-domain nested within a mesoscale WRF model domain with grid spacing decreasing from 12.15 km (mesoscale) to 0.03 km (LES). We simulate real-world conditions in the convective planetary boundary layer over an area of complex terrain. The WRF-LES model results are evaluated against observations collected during the US Department of Energy-supported Columbia Basin Wind Energy Study. Comparison of the first- and second-order moments, turbulence spectrum, and probability density function of wind speed shows good agreement between the simulations and observations. One key result is to demonstrate that a systematic methodology needs to be applied to select the grid spacing and refinement ratio used between domains, to avoid having a grid resolution that falls in the grey zone and to minimize artefacts in the WRF-LES model solutions. Furthermore, the WRF-LES model variables show large variability in space and time caused by the complex topography in the LES domain. Analyses of WRF-LES model results show that the flow structures, such as roll vortices and convective cells, vary depending on both the location and time of day as well as the distance from the inflow boundaries.  相似文献   

Bridging the gap or broadening the problem?     

Harinarayan Tiwari  Subash Pd. Rai  Kumari Shivangi 《Natural Hazards》2016,80(1):351-365

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