Heavy metal in surface sediments from three embayments of central-south Chile     

Marco A. Salamanca  Lisandro Chuecas  Franklin Carrasco 《Marine pollution bulletin》1986,17(12):567-568

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Multivariate Analysis of Incomplete Mapped Data     

Stéphane Dray  Nathalie Pettorelli  Daniel Chessel 《Transactions in GIS》2003,7(3):411-422

Classical multivariate analyses are based on matrix algebra and enable the analysis of a table containing measurements of a set of variables for a set of sites. Incomplete mapped data consist of measurements of a set of variables recorded for the same geographical region but for different zonal systems and with only a partial sampling of this zone. This kind of data cannot be analysed with usual multivariate methods because there is no common system of sites for all variables. We propose a new approach using GIS technology and NIPALS, an iterative multivariate method, to analyse the spatial patterns of this kind of data. Moreover, an extension of our method is that it can be used for areal interpolation purposes. We illustrate the method in analysing data concerning the distribution of roe deer weights over several years in a reserve.  相似文献   

PP amplitude bias caused by interface scattering: are diffracted waves guilty?     

Nathalie Favretto-Cristini  Eric de Bazelaire 《Geophysical Prospecting》2003,51(2):99-116

This paper is concerned with the problem of interpretation of anomalous seismic amplitudes, induced by the amplitude‐scattering phenomenon. This phenomenon occurs in the vicinity of a crack distribution at the interface between elastic layers. The purpose of this work is to obtain a better understanding of the physics of this distinctive phenomenon, in order to interpret correctly the amplitudes of the reflected events. By analogy with studies in optics and in acoustics, we suggest that diffraction is widely involved in the amplitude‐scattering phenomenon. Analytical evaluation of the amount of energy carried by the reflected and the diffracted waves shows that neglecting diffraction in numerical models leads to local underestimation of the amplitude of waves reflected at interfaces with gas‐filled crack distribution.  相似文献   

Découverte de niveaux phosphatés associés à des restes de vertébrés dans les dépôts carbonatés du Coniacien–Santonien du Jabal Abtar : épisode précoce de la phosphatogenèse sénonienne des Palmyrides (Syrie centrale)     

A Khaled Al Maleh  Nathalie Bardet 《Comptes Rendus Geoscience》2003,335(4):391-400

Sedimentologic study of carbonated sediments of the Rmah-I member (Coniacian–Santonian) of Jabal Abtar, central southern Palmyrides (Central Syria), uncovers phosphatic levels, associated with marine vertebrate remains, that give evidence of an early episode of the Senonian phosphatogenesis in the Palmyrides. Sedimentary sequence analysis reveals a gradual marine transgression during the Senonian. Phosphatic sedimentation occurred in a shallow neritic marine environment almost connected with the open sea. Condensed sedimentation could have contributed to the phosphatogenesis. To cite this article: A.K. Al Maleh, N. Bardet, C. R. Geoscience 335 (2003).  相似文献   

Influence of neutral transport on ion chemistry uncertainties in Titan ionosphere     

N. Carrasco  E. Hbrard  M. Banaszkiewicz  M. Dobrijevic  P. Pernot 《Icarus》2007,192(2):519-526

Models of Titan ionospheric chemistry have shown that ion densities depend strongly on the neutral composition. The turbulent diffusion transport conditions, as modeled by eddy coefficients, can spectacularly affect the uncertainty on predicted neutral densities. In order to evaluate the error budget on ion densities predicted by photochemical models, we perform uncertainty propagation of neutral densities by Monte Carlo sampling and assess their sensitivity to two turbulent diffusion profiles, corresponding to the extreme profiles at high altitudes described in the literature. A strong sensitivity of the ion density uncertainties to transport is observed, generally more important than to ion–molecule reaction parameters themselves. This highlights the necessity to constrain eddy diffusion profiles for Titan ionosphere, which should progressively be done thanks to the present and future measurements of the orbiter Cassini.  相似文献   

Tectonic shortening and gravitational spreading in the Gulf of Cadiz accretionary wedge: Observations from multi-beam bathymetry and seismic profiling     

Marc-André Gutscher  Stephane Dominguez  Graham K. Westbrook  Pascal Gente  Nathalie Babonneau  Thierry Mulder  Eliane Gonthier  Rafael Bartolome  Joaquim Luis  Filipe Rosas  Pedro Terrinha 《Marine and Petroleum Geology》2009,26(5):647-659

The Gulf of Cadiz lies astride the complex plate boundary between Africa and Eurasia west of the Betic-Rif mountain belt. We report on the results of recent bathymetric swathmapping and multi-channel seismic surveys carried out here. The seafloor is marked by contrasting morphological provinces, spanning the SW Iberian and NW Moroccan continental margins, abyssal plains and an elongate, arcuate, accretionary wedge. A wide variety of tectonic and gravitational processes appear to have shaped these structures. Active compressional deformation of the wedge is suggested by folding and thrusting of the frontal sedimentary layers as well as basal duplexing in deeper internal units. There is evidence for simultaneous gravitational spreading occurring upslope. The very shallow mean surface and basal slopes of the accretionary wedge (1° each) indicate a very weak decollement layer, geometrically similar to the Mediterranean Ridge accretionary complex. Locally steep slopes (up to 10°) indicate strongly focused, active deformation and potential gravitational instabilities. The unusual surface morphology of the upper accretionary wedge includes “raft-tectonics” type fissures and abundant sub-circular depressions. Dissolution and/or diapiric processes are proposed to be involved in the formation of these depressions.  相似文献   

Holocene seasonal sea‐surface temperature variations in the southern Adriatic Sea inferred from a multiproxy approach     

Francesca Sangiorgi  Lucilla Capotondi  Nathalie Combourieu Nebout  Luigi Vigliotti  Henk Brinkhuis  Simona Giunta  Andr F. Lotter  Caterina Morigi  Alessandra Negri  Gert‐Jan Reichart 《第四纪科学杂志》2003,18(8):723-732

Holocene cooling events have been reconstructed for the southern Adriatic Sea (central Mediterranean) by means of analyses of organic walled dinoflagellate cysts, planktonic foraminifera, oxygen isotopes, calcareous nanoplankton, alkenones and pollen from a sediment core. Two cooling events have been detected, during which sea‐surface temperatures (SSTs) were ca. 2°C lower. Unravelling the SST signal into dominant seasonal components suggests maximum winter cooling of 2°C at around 6.0 ka, whereas the cooling at ca. 3.0 ka might be the result of a spring temperature cooling of 2–3°C. The events, lasting several hundred years, are apparently synchronous with those in the Aegean Sea, where they have been related to known cooling events from the Greenland ice‐core record. A distinct interruption in Adriatic Sea sapropel S1 is not clearly accompanied by a local drop in winter temperatures, but seems to be forced by ventilation, which probably occurred earlier in the Aegean Sea and was subsequently transmitted to the Adriatic Sea. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Three Secondary Reference Materials for Lithium Isotope Measurements: Li7-N, Li6-N and LiCl-N Solutions     

Jean Carignan  Nathalie Vigier  Romain Millot 《Geostandards and Geoanalytical Research》2007,31(1):7-12

The CRPG (Nancy, France) has prepared secondary reference materials for Li isotope measurements by mixing ⁷Li or ⁶Li spikes and either L-SVEC or IRMM-016 certified reference materials to produce solutions having a known Li concentration and isotopic composition. The Li7-N and Li6-N solution samples (1.5 mol l⁻¹ HNO₃) have nominal δ⁷Li isotopic compositions of 30.1‰ and -9.7‰ respectively relative to L-SVEC and concentrations of 100 mg l⁻¹. Repeated measurement of these samples using the QUAD-ICP-MS at the CRPG yielded δ⁷Li of 30.4 ± 1.1‰ (n = 13) and -8.9 ± 0.9‰ (n = 9) at the 2s level of confidence. An additional LiCl-N solution was measured and yielded a delta value of 9.5 ± 0.6‰ (n = 3). Identical results were obtained at the BRGM (Orléans, France) from determinations performed with a Neptune MC-ICP-MS (30.2 ± 0.3‰, n = 89 for the Li7-N, -8.0 ± 0.3‰, n = 38 for the Li6-N and 10.1 ± 0.2‰, n = 46 for LiCl-N at the 2s level of confidence). The deviation of measured composition relative to the nominal value for the Li6-N solution might be explained by either contamination during preparation or an error during sample weighing. These secondary reference materials, previously passed through ion exchange resin or directly analysed, may be used for checking the accuracy of Li isotopic measurements over a range of almost 40‰ and will be available to the scientific community upon request to J. Carignan or N. Vigier, CRPG.  相似文献   

Contribution of stable isotopes to the understanding of the unsaturated zone of a carbonate aquifer (Nerja Cave, southern Spain)     

Francisco Carrasco  Bartolom Andreo  Cristina Lin  Jacques Mudry 《Comptes Rendus Geoscience》2006,338(16):1203-1212

We analysed the stable isotopes (¹⁸O and ²H) of rainwater and drip water within a cave (Nerja Cave) located in the unsaturated zone of a carbonate aquifer. Rainfall is more abundant and presents lower isotopic content in winter, while the volume of drip water is greater and its isotopic content is lower in summer. The flow analysis of ¹⁸O through the unsaturated zone confirms the seasonal lag between rainfall and the appearance of drip water in the cave and reveals that the unsaturated zone of the aquifer, in the sector of the cave, behaves like an inertial system with a strong capability to modulate the input signal. To cite this article: F. Carrasco et al., C. R. Geoscience 338 (2006).  相似文献   

Hydraulic Conductivities of Low Permeability Sediments Inferred from a Triple Pumping Test and Observed Vertical Gradients   总被引：2，自引：0，他引：2  

Luc Lebbe  Nathalie Van  Meir 《Ground water》2000,38(1):76-88

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