Implication of drainage basin parameters of Chhoti Gandak River,Ganga Plain,India     

Dhruv Sen Singh  Amit Awasthi 《Journal of the Geological Society of India》2011,78(4):370-378

The drainage basin parameters of the groundwater-fed Chhoti Gandak River originating in the terai area of the Ganga Plain were analyzed using topographical sheets, satellite data, and field documentation with emphasis to its implication for flood mitigation and recharging of groundwater. The analyses indicate dominance of first order streams, gentle slope gradient, low surface run-off, low sediment production, high infiltration rate, and low value of basin relief. The low water storage capacity, spreading of water and concentration of peak discharge in the distal part of the river basin explain that whenever precipitation is high in the catchment area there is flood in the distal part of the basin. The bifurcation ratio value (4.34) of this basin describes that the drainage is carved naturally by slope and local relief and not influenced by geological structures like lineaments and faults.  相似文献   

Landslide susceptibility along NH-39 between Karong and Mao,Senapati district,Manipur     

C. D. Singh  K. K. Behera  W. S. Rocky 《Journal of the Geological Society of India》2011,78(6):559-570

National Highway-39 is the only lifeline of the state of Manipur. The sector between Karong and Mao is highly landslide prone and frequently blocked the NH-39. The area is represented by Disang and Barail Groups of rock. Considering the importance of NH-39, landslide susceptibility zonation studies along NH-39 between Karong and Mao were carried out following GSI guideline, a modified form of BIS (1998).  相似文献   

Structural analyses of the crystalline rocks between Dirang and Tawang,West Kameng district,Arunachal Himalaya     

Hari B. Srivastava  Vaibhava Srivastava  Rajesh K. Srivastava  Chandra Kant Singh 《Journal of the Geological Society of India》2011,78(1):45-56

In Kameng Valley of Arunachal Pradesh, the crystalline rocks of Se La Group of Higher Himalaya are thrust over the Lesser Himalayan rocks of Dirang Formation, Bomdila Group along the Main Central Thrust and exhibit well preserved structures on macro- to microscopic scales. Detailed analysis of structures reveals that the rocks of the area have suffered four phases of deformation D₁, D₂, D₃ and D₄. These structures have been grouped into (i) early structures (ii) structures related to progressive ductile thrusting and (iii) late structures. The early structures which developed before thrusting formed during D₁ and D₂ phases of deformation, synchronous to F₁ and F₂ phases of folding respectively. The structures related to progressive ductile shearing developed during D₃ phase of deformation, when the emplacement of the crystalline rocks took place over the rocks of Dirang Formation along the Main Central Thrust. Different asymmetric structures/kinematic indicators developed during this ductile/brittle-ductile regime suggest top-to-SSW sense of movement of the crystalline rocks of the area. D₄ is attributed to brittle deformation. Based on satellite data two new thrusts, i.e. Tawang and Se La thrusts have been identified parallel to Main Central Thrust, which are suggestive of imbricate thrusting. Strain analysis from the quartz grains of the gneissic rocks reveals constriction type of strain ellipsoid where k value is higher near the MCT, gradually decreases towards the north. Further, the dynamic analysis carried out on the mesoscopic ductile and brittle-ductile shear zones suggest a NNE-SSW horizontal compression corresponding to the direction of northward movement of Indian Plate.  相似文献   

Late pleistocene and early holocene climate of Ny-Alesund,Svalbard (Norway): A study based on biological proxies     

Vartika Singh  Anjum Farooqui  Naresh. C. Mehrotra  Dhruv Sen Singh  Rajni Tewari  Neerja Jha  Ratan Kar 《Journal of the Geological Society of India》2011,78(2):109-116

Subsurface sediments of a 120 cm deep trench from Ny-Alesund, Svalbard, were analysed for pollenspores and other organic matter contents. This study is supported by two AMS ¹⁴C dates (27, 200 yrs BP and 8,762 yrs BP) at the bottom and topmost litho-unit of the trench, respectively. The pollen record provides an evidence of a warm interval at about 27,200 yr BP (Late Weichselian and MIS 3) and cooling episode around 8,762 yr BP. This is also supported by the amount and type of organic matter as well as sediment type and depositional history of the trench sediments.  相似文献   

Thermodynamic study of the association and separation of copper and gold in the Shizishan ore field, Tongling, Anhui Province, China   总被引：1，自引：0，他引：1  

Xiao-chun Xu  Zan-zan Zhang  Qi-neng Liu  Jing-wei Lou  Qiao-qin Xie  Ping-li Chu  Ray L. Frost 《Ore Geology Reviews》2011,43(1):347-358

The Shizishan ore field is the largest gold–copper ore field in the Tongling ore district of Anhui Province, China. Copper and gold deposits in the district are present as one-commodity deposits or as deposits with both commodities. Copper and gold mineralization are either cogenetic or are temporally and spatially distinct. We present the results of systematic geochemical analysis of fluid inclusions from typical Au–Cu deposits in the Shizishan ore field; these data are used to determine the solubility of Cu and Au in the ore-forming fluids and to ascertain the mechanisms and factors that controlled variations in the association and separation of copper and gold mineralization. Our results indicate that copper in the ore-forming fluids was transported as CuCl₂⁻ and CuCl⁰ complexes and that the solubility of copper was controlled by variations in Cl⁻ concentration. In addition, the precipitation of copper was controlled by changes in temperature, pH, fO₂, and fO₂. In comparison, gold in the ore-forming fluids was transported as Au(HS)₂⁻ and Au₂S(HS)₂²⁻ complexes, and the solubility of gold was controlled by variations in total sulfur concentration; the precipitation of gold was controlled by temperature, pH, fO₂, and fO₂. These differences between the two elements meant that copper and gold in the ore-forming fluids responded in different ways to changes in physicochemical conditions. Copper precipitated under relatively acidic conditions at high temperatures, while gold precipitated under weakly alkaline conditions at relatively low temperatures; this dissociation resulted in the temporal and spatial separation and zonation of copper and gold mineralization in the Shizishan ore field.  相似文献   

Natural hazards in the Ghaghara River area, Ganga Plain, India     

Dhruv Sen Singh  Amit Awasthi 《Natural Hazards》2011,57(2):213-225

The Ganga Plain is one of the most densely populated regions of the world due to its fertile soil and availability of water. The rivers of this plain are the lifeline for millions of people of this vast alluvial plain. All rivers of this plain are characterized by narrow channel confined within wide valley. Continuously increasing pressure of population on this plain has led to the intensification of settlement even into the valley of the river. This unplanned expansion has enhanced the damage due to flooding during high-discharge period and lateral erosion during low-discharge period. Flooding and lateral erosion are identified as fluvial hazards in the Ghaghara River area. Extensive studies have been carried out on flooding, but not much attention has been paid to the phenomenon of lateral erosion. However, it has been observed that lateral erosion is an independent fluvial hazard that operates during low-discharge period. Low degree of compaction due to the presence of sandy and silty facies in the river valley deposits, mass movement, palaeocurrent pattern, and fractures initiates and enhances the lateral erosion. The present paper deals with the fluvial hazards in the Ghaghara River area.  相似文献   

Regional landslide susceptibility: spatiotemporal variations under dynamic soil moisture conditions   总被引：1，自引：0，他引：1  

Ram L. Ray  Jennifer M. Jacobs  Thomas P. Ballestero 《Natural Hazards》2011,59(3):1317-1337

Quantification of landslide susceptibility variability in space and time in response to static and dynamic conditions is a fundamental research challenge. Here, we identify and apply new modeling and remote sensing observation techniques to statistically characterize susceptibility distributions under dynamic moisture conditions. The methods are applied at two study regions: Cleveland Corral, California, US and Dhading, Nepal. The results show that the temporal variability of safety factors is lower during the wet season than the dry season, but this variability, when scaled by mean seasonal stability, is constant annually. Relative variability differs by region with lower variability in Nepal, the highly susceptible region. L-Moment evaluations indicate that Nepal has a consistent, regional probability distribution, but that California has two distinct distributions. The variability in time is not normally distributed for either region. For both regions, transitional characteristic of safety factors show a strong power law relationship between the average duration and number of periods during which sites are highly susceptible. Because the mapped landslide locations typically had frequent crossings with brief unstable conditions, a consistent physical mechanism is pointed to as a possible cause of slope failure.  相似文献   

Concealed thrusts in the Middle Gangetic plain,India – A ground penetrating radar study proves the truth against the geomorphic features supporting normal faulting     

Pitambar Pati  B. Parkash  A.K. Awasthi  Vivekanand Acharya  Satvindar Singh 《Journal of Asian Earth Sciences》2011,40(1):315-325

As no evidence for thrusting has yet been reported from the Indo-Gangetic plain so, the Himalayan Frontal Thrust (HFT) has been considered to be the southern most limit of the Siwaliks to the Indo-Gangetic plain. The present study highlights the thrusting activities between the Gandak and Kosi megafan area in the Middle Gangetic plain. As these thrust sheets are concealed beneath thick sediment cover, direct surficial studies of the discontinuity planes are not possible. Further, the topographic breaks formed by the backward erosion of the uplifted thrust faces resemble normal faults with hanging walls to south. Due to gradual decreasing upliftment and/or erosion from north to south, the area shows a step like topographic appearance. Ground penetrating radar (GPR) studies reveal the concealed thrust planes beneath the sediments and the topographic breaks looking like normal faults are interpreted to be the relief created by backward erosion of the thrust sheets along with the overlying sediments. Out of four GPR profiles taken using 100 MHz antennae, three are across the topographic breaks along which most of the terminal fans are formed and one across the basement fault to study its subsurface nature. Initially GPR failed to strike any subsurface discontinuities at the topographic breaks. However, at certain distance to the south of the topographic breaks, GPR was able to strike the northerly dipping subsurface discontinuity planes. By combining the seismological signatures (distribution of earthquake epicenters) with geomorphology, these discontinuities are identified as thrusts. The GPR profiles show a gradual decrease of dip of the thrust planes from north to south across the area. Hence, by the geomorphology, seismological behavior, topography, orientation and continuity, other topographic breaks can be compared with the proven thrusts. GPR study on the basement fault revealed that the NE–SW trending basement faults are not active in the area. The compression between the South Muzaffarpur fault and the peninsular shield led to the generation of the N–S trending extensional Hathauri–Simariaghat fault with downthrown block towards east. Due to depth penetration limit, the GPR study was confined within 15 m depth. The presence of the discontinuity planes up to the base of the GPR profiles indicate their continuity at least up to the base of Holocene sediments. Although this study brought out the presence of concealed thrusts to the south of the HFT, more detailed work is needed further to study their depth extension, relation to the basement and their implication in Himalayan tectonics in a broad manner. At present, we consider these thrusts to be the splays of the HFT. For confirmation, we propose to carryout detail seismic surveys in future research work.  相似文献   

Formation pressure testing at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Operational summary, history matching, and interpretations   总被引：2，自引：0，他引：2  

Brian Anderson  Steve HancockScott Wilson  Christopher EngerTimothy Collett  Ray BoswellRobert Hunter 《Marine and Petroleum Geology》2011,28(2):478-492

In February 2007, the U.S. Department of Energy, BP Exploration (Alaska), and the U.S. Geological Survey, collected open-hole pressure-response data, as well as gas and water sample collection, in a gas hydrate reservoir (the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well) using Schlumberger's Modular Dynamics Formation Tester (MDT) wireline tool. Four such MDT tests, ranging from six to twelve hours duration, and including a series of flow, sampling, and shut-in periods of various durations, were conducted. Locations for the testing were selected based on NMR and other log data to assure sufficient isolation from reservoir boundaries and zones of excess free water. Test stages in which pressure was reduced sufficiently to mobilize free water in the formation (yet not cause gas hydrate dissociation) produced readily interpretable pressure build-up profiles. Build-ups following larger drawdowns consistently showed gas-hydrate dissociation and gas release (as confirmed by optical fluid analyzer data), as well as progressive dampening of reservoir pressure build-up during sequential tests at a given MDT test station.History matches of one multi-stage, 12-h test (the C2 test) were accomplished using five different reservoir simulators: CMG-STARS, HydrateResSim, MH21-HYDRES, STOMP-HYD, and TOUGH + HYDRATE. Simulations utilized detailed information collected across the reservoir either obtained or determined from geophysical well logs, including thickness (11.3 m, 37 ft.), porosity (35%), hydrate saturation (65%), both mobile and immobile water saturations, intrinsic permeability (1000 mD), pore water salinity (5 ppt), and formation temperature (3.3-3.9 °C). This paper will present the approach and preliminary results of the history-matching efforts, including estimates of initial formation permeability and analyses of the various unique features exhibited by the MDT results.  相似文献   

Variations in vapor pressure and standardized precipitation evapotranspiration index since AD 1861 over the western Himalaya in India: inference from tree ring-width records     

Somaru Ram  H. N. Singh  Ramesh Kumar Yadav  Hamza Varikoden  S. S. Nandargi  Manoj K. Srivastava 《Theoretical and Applied Climatology》2020,140(1):157-166

A regional tree ring-width index chronology prepared from various tree core samples of the western Himalaya has been analyzed in relation to climate fluctuations. The correlation analysis of tree ring chronology shows significant positive correlations with regional rainfall and standardized precipitation evapotranspiration index (SPEI) and negative correlations with temperature and vapor pressure (VP) during the spring season. The correlation coefficients (CCs) of tree ring-width index chronology with rainfall, temperature, SPEI, and VP during 1901–1990 are 0.50, −0.49, 0.65, and −0.51, respectively. All CCs are significant at 0.1% level. The highly significant CCs between tree ring-width index chronology and SPEI indicate that tree growth over the western Himalaya is more sensitive to soil moisture availability than rainfall, whereas the rising VP is found to have a significant moisture stress condition to tree growth by accelerating the evapotranspiration, which is not conducive for the development of tree growth in the region. So, based on the strong association between tree ring-width index chronology and SPEI; the reconstructions of SPEI and VP are developed back to AD 1861, that show the long period of dryness during 1936–1963.  相似文献