Assessment of seawater pollution by heavy metals in the neighbourhood of Algiers: use of the sea urchin, Paracentrotus lividus, as a bioindicator     

Soualili  Dina; Dubois  Philippe; Gosselin  Pol; Pernet  Philippe; Guillou  Monique 《ICES Journal of Marine Science》2008,65(2):132-139

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The <Emphasis Type="Italic">M</Emphasis> = 5.1 1980 Arudy earthquake sequence (western Pyrenees,France): a revisited multi-scale integrated seismologic,geomorphologic and tectonic investigation     

Pierre Courjault-Radé  José Darrozes  Philippe Gaillot 《International Journal of Earth Sciences》2009,98(7):1705-1719

This paper presents a combination of seismic imaging, geomorphologic, and tectonic data and an interpretation of the M = 5.1 1980 Arudy earthquake sequence putting in relation the seismicity, the inherited faults, and the geomorphologic (Würm and postwürm) markers in this region of the Pyrenees. Since the anticlockwise rotation of the regional compression axis in Oligocene time, western Pyrenees are under a dextral regime and the resulting motion is accommodated along major inherited E–W dextral strike-slip faults. The Arudy aftershocks sequence is controlled by antecedent horsetail splay faults built at the boundary between two shallow Mesozoic crustal blocks most probably due to their differing rheology. This boundary has played the role of a seismic barrier stopping the E–W slip motion. The Arudy earthquake has reactivated the eastern segment of the main E–W strike-slip fault, while the post-seismic aftershocks correspond to local relaxation processes in normal tectonic behavior.  相似文献   

CoFIS and TELog: New downhole tools for characterizing dispersion processes in aquifers by single-well injection-withdrawal tracer tests     

Philippe Gouze  Richard Leprovost  Thierry Poidras  Tanguy Le Borgne  Gérard Lods  Philippe A. Pezard 《Comptes Rendus Geoscience》2009,341(10-11):965-975

Contaminant migration in aquifers is one of the most debated issues in hydrogeology, as most experimental results display large deviations from the standard (asymptotic) Fickian dispersion theories. Multi-scale investigation and high-resolution sensors are required to determine the origin of non-asymptotic dispersion and validate models. For this, a set of multi-scale Single-Well Injection-Withdrawal (SWIW) tracer tests using a new dual-packer probe CoFIS, including a high resolution optical sensor TELog, are presented. When compared to standard techniques such as salinity measurements, it is shown that high-resolution optical measurements allow an improved characterization of the long-lasting non-asymptotic dispersion mechanisms.  相似文献   

Earth curvature effects on subduction morphology: Modeling subduction in a spherical setting   总被引：1，自引：0，他引：1  

Gabriele Morra  Philippe Chatelain  Paul Tackley  Petros Koumoutsakos 《Acta Geotechnica》2009,4(2):95-105

We present the first application in geodynamics of a (Fast Multipole) Accelerated Boundary Element Method (Accelerated-BEM) for Stokes flow. The approach offers the advantages of a reduced number of computational elements and linear scaling with the problem size. We show that this numerical method can be fruitfully applied for the simulation of several geodynamic systems at the planetary scale in spherical coordinates, and we suggest a general approach for modeling combined mantle convection and plate tectonics. The first part of the paper is devoted to the technical exposition of the new approach, while the second part focuses on the effect played by Earth curvature on the subduction of a very wide oceanic lithosphere (W = 6,000 km and W = 9,000 km), comparing the effects of two different planetary radii (ER = 6,371 km, 2ER = 2 × 6,371 km), corresponding to an "Earth-like" model (ER) and to a "flat Earth" one (2ER). The results show a distinct difference between the two models: while the slab on a "flat Earth" shows a slight undulation, the same subducting plate on the "Earth-like" setting presents a dual behavior characterized by concave curvature at the edges and by a folding with wavelength of the order of magnitude of 1,000 km at the center of the slab.  相似文献   

A pollen-based record of late glacial–Holocene climatic variability in the southern lake district, Chile     

Lourdes Vargas-Ramirez  Emile Roche  Philippe Gerrienne  Henry Hooghiemstra 《Journal of Paleolimnology》2008,39(2):197-217

A pollen record from Puyehue area (40°S; 72°W) in the southern Lake District, Chile, indicates that prior to 13,410 ¹⁴C yr BP (ca. 16,500–15,200 cal yr BP), cold resistant and hygrophilous vegetation, particularly Nothofagus forest and myricaceous vegetation, covered the area. From ca. 15,000 cal yr BP onward, the forest became increasingly dense. Between 10,010 and 7450 ¹⁴C yr BP (ca. 11,000–8000 cal yr BP), the expansion of Nothofagus obliqua and the spread of grasses suggests the climate became warmer and semi-arid. Lowland deciduous forest (Nothofagus obliqua, Aextoxicon punctatum, Laurelia sempervirens) and Valdivian rainforest (Nothofagus dombeyi, Eucryphia cordifolia, Caldcluvia paniculata, Aextoxicon punctatum, Laureliopsis philippiana) were abundant. During the next two thousand years, stable warm climatic conditions prevailed, and the diversity of the vegetation increased. From 5760 to 1040 ¹⁴C yr BP (ca. 6500–900 cal yr BP), the North Patagonian rainforest expanded. The presence of Pilgerodendron/Fitzroya, together with Nothofagus forest, suggests that humid conditions prevailed. During the last millennium, human impact intensified and regional vegetation was disturbed, particularly the lowland deciduous forest and Valdivian rainforest. North-Patagonian and subantartic taxa, such as Podocarpus nubigena, Pilgerodendron/Fitzroya, Nothofagus dombeyi type, Austrocedrus chilensis and Drimys winteri, occupied the low and high-altitude parts of the Cordillera. Five hundred years ago, shrub and grasses expanded in the Nothofagus forest, suggesting that forest became more open under cool–cold, and humid climatic conditions. These conditions prevail to the present day. This is the fourth in a series of eight papers published in this special issue dedicated to the 17,900 year multi-proxy lacustrine record of Lago Puyehue, Chilean Lake District. The papers in this special issue were collected by M. De Batist, N. Fagel, M.-F. Loutre and E. Chapron.  相似文献   

Preface     

Philippe Gourbesville 《Physics and Chemistry of the Earth》2008,33(5):277

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The Planeterrella,a pedagogic experiment in planetology and plasma physics     

Jean Lilensten  Mathieu Barthélemy  Cyril Simon  Philippe Jeanjacquot  Guillaume Gronoff 《Acta Geophysica》2009,57(1):220-235

We present here a plasma physics experiment which makes it possible to simulate, in a naive yet useful way, the formation of polar lights. It involves shooting electrons at a magnetized sphere placed in a vacuum chamber. This experiment, inspired by K. Birkeland’s Terrella, built at the turn of 19th century, allows the visualization of very many geophysical and astrophysical situations. Although delicate, it is feasible at undergraduate level.  相似文献   

The present-day atmosphere of Mars: Where does it come from?     

Cédric Gillmann  Philippe Lognonné  Eric Chassefière  Manuel Moreira 《Earth and Planetary Science Letters》2009,277(3-4):384-393

Recent observations and missions to Mars have provided us with new insight into the past habitability of Mars and its history. At the same time they have raised many questions on the planet evolution. We show that even with the few data available we can propose a scenario for the evolution of the Martian atmosphere in the last three billion years. Our model is obtained with a back integration of the Martian atmosphere, and takes into account the effects of volcanic degassing, which constitutes an input of volatiles, and atmospheric escape into space. We focus on CO₂, the predominant Martian atmospheric gas.Volcanic CO₂ degassing rates are obtained for different models of numerical model crust production rates [Breuer, D., Spohn, T. 2003. Early plate tectonics versus single-plate tectonics on Mars: Evidence from magnetic field history and crust evolution. J. Geophys. Res. - Planets, 108, E7, 5072, Breuer, D., Spohn, T., 2006. Viscosity of the Martian mantle and its initial temperature: Constraints from crust formation history and the evolution of the magnetic field. Planet. Space Sci. 54 (2006) 153–169; Manga, M., Wenzel, M., Zaranek, S.E., 2006. Mantle Plumes and Long-lived Volcanism on Mars as Result of a Layered Mantle. American Geophysical Union Fall Meeting 2006, Abstract #P31C-0149.] and constrained on observation. By estimating the volatile contents of the lavas, the amount of volatiles released in the atmosphere is estimated for different scenarios. Both non-thermal processes (related to the solar activity) and thermal processes are studied and non-thermal processes are incorporated in our modelling of the escape [Chassefière, E., Leblanc, F., Langlais, B., 2006, The combined effects of escape and magnetic field history at Mars. Planet. Space Sci. Volume 55, Issue 3, Pages 343–357.]. We used measurements from ASPERA and Mars Express and these models to estimate the amount of lost atmosphere.An evolution of the CO₂ pressure consistent with its present state is then obtained. A crustal production rate of at least 0.01 km³/year is needed for the atmosphere to be at steady state. Moreover, we show that for most of the scenarios a rapid loss of the primary (and primordial) atmosphere due to atmospheric escape is required in the first 2 Gyr in order to obtain the present-day atmosphere. When CO₂ concentration in the mantle is high enough (i.e. more than 800 ppm), our results imply that present-day atmosphere would have a volcanic origin and would have been created between 1 Gyr and 2 Gyr ago even for models with low volcanic activity. If the volcanic activity and the degassing are intense enough, then the atmosphere can even be entirely secondary and as young as 1 Gyr. However, with low activity and low CO₂ concentration (less than 600 ppm), the present-day atmosphere is likely to be for the major part primordial.  相似文献   

Field observations of an evolving rip current on a meso-macrotidal well-developed inner bar and rip morphology   总被引：1，自引：0，他引：1  

Nicolas Bruneau  Bruno Castelle  Philippe Bonneton  Rodrigo Pedreros  Rafael Almar  Natalie Bonneton  Patrice Bretel  Jean-Paul Parisot  Nadia Snchal 《Continental Shelf Research》2009,29(14):1650-1662

The Aquitanian Coast (France) is a high-energy meso-macrotidal environment exhibiting a highly variable double sandbar system. The inner and the outer bar generally exhibit a bar and rip morphology and persistent crescentic patterns, respectively. In June 2007, an intense five-day field experiment was carried out at Biscarrosse Beach. A large array of sensors was deployed on a well-developed southward-oriented bar and rip morphology. Daily topographic surveys were carried out together with video imaging to investigate beach morphodynamic evolution. During the experiment, offshore significant wave height ranged from 0.5 to 3 m, with a persistent shore-normal angle. This paper identifies two types of behavior of an observed rip current: (1) for low-energy waves, the rip current is active only between low and mid tide with maximum mean rip current velocity reaching 0.8 m/s for an offshore significant wave height (H_s) lower than 1 m; (2) for high-energy waves (H_s≈ 2.5–3 m), the rip current was active over the whole tide cycle with the presence of persistent intense offshore-directed flows between mid and high tide. For both low and high-energy waves, very low-frequency pulsations (15–30 min) of the mean currents are observed on both feeder and rip channels.A persistent slow shoreward migration of the sandbar was observed during the experiment while no significant alongshore migration of the system was measured. Onshore migration during the high-energy waves can be explained by different sediment transport processes such as flow velocity skewness, wave asymmetry or bed ventilation. High-frequency local measurements of the bed evolution show the presence of significant (in the order of 10 cm) fluctuations (in the order of 1 h). These fluctuations, observed for both low- and high-energy waves, are thought to be ripples and megaripples, respectively and may play an important but still poorly understood role in the larger scale morphodynamics. The present dataset improves the knowledge of rip dynamics as well as the morphological response of strongly alongshore non-uniform meso-macrotidal beaches.  相似文献   

Distributed hydrologic and hydraulic modelling with radar rainfall input: Reconstruction of the 8–9 September 2002 catastrophic flood event in the Gard region,France     

Laurent Bonnifait  Guy Delrieu  Matthieu Le Lay  Brice Boudevillain  Arielle Masson  Philippe Belleudy  Eric Gaume  Georges-Marie Saulnier 《Advances in water resources》2009

On 8–9 September 2002, an extreme rainfall event caused by a stationary mesoscale convective system (MCS) occurred in the Gard region, France. Distributed hydrologic and hydraulic modelling has been carried out to assess and compare the various sources of data collected operationally and during the post-event field surveys. Distributed hydrological modelling was performed with n-TOPMODELs and assessed for ungauged basins with the discharge estimates of the post-event surveys. A careful examination of the occurrence in time and space of the flash floods over the head watersheds indicates that flooding was controlled by the trajectory of the convective part of the MCS. Stationarity of the MCS over the Gardon watershed (1858 km² at Remoulins) for 28 h was responsible for the exceptional magnitude of the flood at this scale. The flood dynamics were characterized by an extensive inundation of the Gardonnenque plain upstream of the Gardon Gorges resulting in a significant peak flow reduction downstream. One-dimensional unsteady-flow hydraulic modelling was found to be required to reproduce these dynamics. Hydraulic modelling also proved to be potentially useful for the critical analysis and extrapolation of operational discharge rating curves.  相似文献