Conceptualizing catchment storage dynamics and nonlinearities          下载免费PDF全文

Marco P. Maneta  Chris Soulsby  Sylvain Kuppel  Doerthe Tetzlaff 《水文研究》2018,32(21):3299-3303

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Formation of decollement upwarps during thrusting     

Ashok Kumar Dubey 《地学学报》2004,16(3):91-94

Geometric and kinematic models reveal that rotation of layers during thrusting or development of drag folds produced by movement along listric thrust faults results in the formation of dilation space at the junction of the thrust ramp with the basal decollement. This is accompanied by upwarping of the basement to occupy the available space thereby producing an antiformal structure, which restricts the thrust displacement. The structure is termed a decollement upwarp and examples are cited from the foothill belt of the Himalaya.  相似文献   

Geochemical and hydrodynamic constraints on the distribution of trace metal concentrations in the lagoon of Nouméa, New Caledonia   总被引：1，自引：0，他引：1  

Christophe Migon  Sylvain Ouillon  Xavier Mari  Emmanuel Nicolas 《Estuarine, Coastal and Shelf Science》2007,74(4):756

Seawater samples were collected in the lagoon of Nouméa (southwest New Caledonia) along two transects from eutrophic coastal bays to the oligotrophic barrier reef. Land-based emissions to the lagoon were measured with dissolved and particulate concentrations of chromium (Cr) and nickel (Ni), used as tracers of both terrigenous and industrial (Ni ore treatment) activities, as well as dissolved and particulate concentrations of zinc (Zn), used as a tracer of urban effluents. The spatial variability of metal concentrations was related to geochemical and hydrodynamic conditions, i.e., respectively: (1) natural and anthropogenic emission sources, and chemical processes occurring in the water column; and (2) water residence times. The parameter used to describe the residence time of water masses was the local e-flushing time, i.e. the time required for a tracer mass contained within a given station to be reduced by a factor 1/e. High metal concentrations were found in coastal areas (up to 9000 ng dissolved Ni L⁻¹), and steeply decreased with distance from the coast (down to 101 ng dissolved Ni L⁻¹ near the barrier reef) to reach levels similar to those found in remote Pacific waters, suggesting a rapid renewal of waters close to the barrier. Distributions of metals in the lagoon are controlled upstream by land-based emission sources and later chemical processes. Then hydrodynamics constrain metal distributions, as shown by the observed relationship between local e-flushing times and the spatial variability of metal concentrations. In addition, a change in the direction of prevailing winds yielded a decrease of dissolved metal concentrations at the same site by a factor of 2.5 (Cr and Ni) and 2.9 (Zn). It is suggested that the residence time is a key parameter in the control of elemental concentrations in the lagoon waters, as much as land-based emission sources.  相似文献   

The GeoForschungsZentrum Potsdam/Groupe de Recherche de Gèodésie Spatiale satellite-only and combined gravity field models: EIGEN-GL04S1 and EIGEN-GL04C   总被引：2，自引：1，他引：1  

Christoph Förste  Roland Schmidt  Richard Stubenvoll  Frank Flechtner  Ulrich Meyer  Rolf König  Hans Neumayer  Richard Biancale  Jean-Michel Lemoine  Sean Bruinsma  Sylvain Loyer  Franz Barthelmes  Saskia Esselborn 《Journal of Geodesy》2008,82(6):331-346

The recent improvements in the Gravity Recovery And Climate Experiment (GRACE) tracking data processing at GeoForschungsZentrum Potsdam (GFZ) and Groupe de Recherche de Géodésie Spatiale (GRGS) Toulouse, the availability of newer surface gravity data sets in the Arctic, Antarctica and North-America, and the availability of a new mean sea surface height model from altimetry processing at GFZ gave rise to the generation of two new global gravity field models. The first, EIGEN-GL04S1, a satellite-only model complete to degree and order 150 in terms of spherical harmonics, was derived by combination of the latest GFZ Potsdam GRACE-only (EIGEN-GRACE04S) and GRGS Toulouse GRACE/LAGEOS (EIGEN-GL04S) mean field solutions. The second, EIGEN-GL04S1 was combined with surface gravity data from altimetry over the oceans and gravimetry over the continents to derive a new high-resolution global gravity field model called EIGEN-GL04C. This model is complete to degree and order 360 and thus resolves geoid and gravity anomalies at half- wavelengths of 55 km at the equator. A degree-dependent combination method has been applied in order to preserve the high accuracy from the GRACE satellite data in the lower frequency band of the geopotential and to form a smooth transition to the high-frequency information coming from the surface data. Compared to pre-CHAMP global high-resolution models, the accuracy was improved at a spatial resolution of 200 km (half-wavelength) by one order of magnitude to 3 cm in terms of geoid heights. The accuracy of this model (i.e. the commission error) at its full spatial resolution is estimated to be 15 cm. The model shows a reduced artificial meridional striping and an increased correlation of EIGEN-GL04C-derived geostrophic meridional currents with World Ocean Atlas 2001 (WOA01) data. These improvements have led to select EIGEN-GL04C for JASON-1 satellite altimeter data reprocessing. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Quality Assessment of Cartographic Generalisation   总被引：2，自引：1，他引：2  

Sylvain Bard 《Transactions in GIS》2004,8(1):63-81

This paper proposes a methodology to assess the quality of cartographic generalisa‐tion, which consists of representing geographic space in a simplified way according to the scale and the objectives of the intended map. The automation of this process makes the derivation of data easier, but the quality of the results is often not evaluated. This paper proposes an assessment model based on: (1) characterisation of the data in their initial and final states at different levels of analysis; (2) a data quality assessment by comparison of the two characterisations; and (3) aggregation of the various assessment results to summarise data quality. The assessment algorithm has been implemented and the method has been tested to assess the generalisation of a small urban area. A visualisation tool for assessment of the results has been developed to validate the generalisation evaluation. The results of the research are presented and discussed at the end of the paper.  相似文献   

Late Miocene movement within the Himalayan Main Central Thrust shear zone, Sikkim, north-east India   总被引：7，自引：0，他引：7  

E. J. Catlos  C. S. Dubey  T. M. Harrison  M. A. Edwards 《Journal of Metamorphic Geology》2004,22(3):207-226

In the Sikkim region of north‐east India, the Main Central Thrust (MCT) juxtaposes high‐grade gneisses of the Greater Himalayan Crystallines over lower‐grade slates, phyllites and schists of the Lesser Himalaya Formation. Inverted metamorphism characterizes rocks that immediately underlie the thrust, and the large‐scale South Tibet Detachment System (STDS) bounds the northern side of the Greater Himalayan Crystallines. In situ Th–Pb monazite ages indicate that the MCT shear zone in the Sikkim region was active at c. 22, 14–15 and 12–10 Ma, whereas zircon and monazite ages from a slightly deformed horizon of a High Himalayan leucogranite within the STDS suggest normal slip activity at c. 17 and 14–15 Ma. Although average monazite ages decrease towards structurally lower levels of the MCT shear zone, individual results do not follow a progressive younging pattern. Lesser Himalaya sample KBP1062A records monazite crystallization from 11.5 ± 0.2 to 12.2 ± 0.1 Ma and peak conditions of 610 ± 25 °C and 7.5 ± 0.5 kbar, whereas, in the MCT shear zone rock CHG14103, monazite crystallized from 13.8 ± 0.5 to 11.9 ± 0.3 Ma at lower grade conditions of 525 ± 25 °C and 6 ± 1 kbar. The P–T–t results indicate that the shear zone experienced a complicated slip history, and have implications for the understanding of mid‐crustal extrusion and the role of out‐of‐sequence thrusts in convergent plate tectonic settings.  相似文献   

Geotechnical Susceptibility Constraints on Seismicity of Karewa Group and Its Implication in Quaternary Earthquakes Around Kashmir Valley,India     

R. K. Dubey  Javid Ahmad Dar 《Geotechnical and Geological Engineering》2015,33(3):609-620

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A methodology for regionalizing 3‐D effective porosity at watershed scale in crystalline aquifers          下载免费PDF全文

Benoît Dewandel  Yvan Caballero  Jérôme Perrin  Alexandre Boisson  Fabrice Dazin  Sylvain Ferrant  Subash Chandra  Jean‐Christophe Maréchal 《水文研究》2017,31(12):2277-2295

An innovative approach for regionalizing the 3‐D effective porosity field is presented and applied to two large, overexploited, and deeply weathered crystalline aquifers located in southern India. The method derives from earlier work on regionalizing a 2‐D effective porosity field in that part of an aquifer where the water table fluctuates, which is now extended over the entire aquifer using a 3‐D approach. A method based on geological and geophysical surveys has also been developed for mapping the weathering profile layers (saprolite and fractured layers). The method for regionalizing 3‐D effective porosity combines water table fluctuation and groundwater budget techniques at various cell sizes with the use of satellite‐based data (for groundwater abstraction), the structure of the weathering profile, and geostatistical techniques. The approach is presented in detail for the Kudaliar watershed (983 km²) and tested on the 730 km² Anantapur watershed. At watershed scale, the effective porosity of the aquifer ranges from 0.5% to 2% in Kudaliar and between 0.3% and 1% in Anantapur, which agrees with earlier works. Results show that (a) depending on the geology and on the structure of the weathering profile, the vertical distribution of effective porosity can be very different and that the fractured layers in crystalline aquifers are not necessarily characterized by a rapid decrease in effective porosity and (b) that the lateral variations in effective porosity can be larger than the vertical ones. These variations suggest that within a same weathering profile, the density of open fractures and/or degree of weathering in the fractured zone may significantly vary from a place to another. The proposed method provides information on the spatial distribution of effective porosity that is of prime interest in terms of flux and contaminant transport in crystalline aquifers. Implications for mapping groundwater storage and scarcity are also discussed, which should help in improving groundwater resource management strategies.  相似文献   

An insight into subterranean flow proposition around Alleppey mudbank coastal sector,Kerala, India: inferences from the subsurface profiles of Ground Penetrating Radar     

V. J. Loveson  R. Dubey  Dinesh Kumar  R. Nigam  S. W. A. Naqvi 《Environmental Earth Sciences》2016,75(20):1361

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Provenance and Palaeoweathering Attributes of Proterozoic Rock Formations from the Son Valley,Central India     

R. K. Dubey  Ravi Shankar 《Journal of the Geological Society of India》2018,91(3):307-314

The characteristics of source rocks and weathering of Palaeoproterozoic phyllitic rock of Mahakoshal Group and Mesoproterozoic shales and siliciclastics of Vindhyan Supergroup exposed in Son Valley, Central India have been investigated by analyzing their chemical compositions. The investigations pertaining to the relationship between major-elements were carried out along Parshoi, Chitrangi, and Markundi areas of Son valley, Central, India. The studied rock strata have been classified into three categories namely phyllitic rocks, shales and sandstone.The A-CN-K ternary diagram, CIW, CIA, MIA, and ICV values indicate about the similar provenance or source rocks subjected to severe chemical weathering, under dry and hot-humid climates in a basic and acidic environment with changing lower to higher PCO₂ of continental flora. Various geochemical discriminantts diagrams, elemental ratios suggest that rocks are derived from post-Archaean-Proterozoic igneous source. The igneous source was mainly granite with a minor contribution of granodioritic rock, in a passive margin setting. The sediments responsible for formation of shale and sandstones were most likely deposited in the interglacial period in between the Mesoproterozoic and Neoproterozoic glacial times. Compositionally the sandstones is distinctive of cratonic environments with their passive continental margin setting. However, the phyllities of Mahakoshal Group suggests their formation under lower weathering conditions in dry climatic conditions which were operating on more intermediate to basic igneous rocks with abundance of mafic minerals.  相似文献