Découverte d’un chevauchement d’âge quaternaire au sud de la Grande Kabylie (Algérie)     

Azzedine Boudiaf  Hervé Philip  Alain Coutelle  Jean-François Ritz 《Geodinamica Acta》2013,26(2):71-80

Résumé

À l’échelle du Maghreb, la Kabylie (Algérie) est considérée comme une région asismique. L’étude détaillée des données de la sismicité historique et instrumentale de cette région montre une activité sismique modérée depuis au moins un siècle et demi (M₁ = 5,0). Les observations géomorphologiques faites sur le versant sud du massif kabyle, s’appuyant sur l’analyse d’images satellites, de photos aériennes et de la topographie, nous ont permis de démontrer la présence d’une activité tectonique quaternaire le long de la rupture de pente au sud de ces massifs. Elle correspond à la réactivation de chevauchements d’âge miocène qui se manifestent par des escarpements d’au moins 10 m affectant le glacis d’âge quaternaire ainsi que les cônes de déjection. Ces escarpements sont interprétés comme des ruptures probablement associées à une succession de séismes de forte magnitude. Les observations que nous décrivons se situent dans la région de Tazmalt et de Boüira où ces déformations sont les plus spectaculaires. L’ampleur des déformations quaternaires qui affectent l’ensemble de cette région considérée jusqu’à l’heure actuelle comme asismique ou faiblement sismique pose, comme dans la plupart des régions intracontinentales, le problème de la période de retour des séismes de forte magnitude. © Elsevier, Paris  相似文献   

The Effects of the Velocity Filtration Mechanism on the Minor Ions of the Corona     

Pierrard  Viviane  Lamy  Hervé 《Solar physics》2003,216(1-2):47-58

Due to their different mass and varying charge states, heavy solar ions provide invaluable information on the physical mechanisms responsible for the heating of the corona and the solar wind acceleration. It is shown in the present work that some key characteristics observed in the corona are straightforward features predicted by the velocity filtration effect. This mechanism originally proposed by Scudder (1992a,b) accounts for the heating of the corona by just assuming that the velocity distribution functions have enhanced supra-thermal tails. The apparent `heating' is then a natural consequence of the increasing ratio of supra thermal over thermal particles as a function of altitude. Applied to the minor ions, it offers a natural explanation for the high temperatures of the heavy ions compared to the protons. The kinetic filtration theory predicts temperatures more than proportional to the mass of the ions, with a small correction for the charge state. With sufficiently high temperatures, the ions flow faster than the protons. These characteristics are in good agreement with the most recent spectroscopic and in-situ solar wind observations.  相似文献   

4. Building of a Habitable Planet     

Hervé Martin  Francis Albarède  Philippe Claeys  Muriel Gargaud  Bernard Marty  Alessandro Morbidelli  Daniele L. Pinti 《Earth, Moon, and Planets》2006,98(1-4):97-151

Except the old Jack Hills zircon crystals, it does not exit direct record of the first 500 Ma of the Earth history. Consequently, the succession of events that took place during this period is only indirectly known through geochemistry, comparison with other telluric planets, and numerical modelling. Just after planetary accretion several episodes were necessary in order to make life apparition and development possible and to make the Earth surface habitable. Among these stages are: the core differentiation, the formation of a magma ocean, the apparition of the first atmosphere, oceans and continents as well as the development of magnetic field and of plate tectonics. In the same time, Earth has been subject to extraterrestrial events such as the Late Heavy Bombardment (LHB) between 3.95 and 3.8 Ga. Since 4.4–4.3 Ga, the conditions for pre-biotic chemistry and appearance of life were already met (liquid water, continental crust, no strong meteoritic bombardment, etc...). This does not mean that life existed as early, but this demonstrates that all necessary conditions assumed for life development were already present on Earth.  相似文献   

Neogene exhumation history of the Bergell massif (southeast Central Alps)     

Gweltaz Mahéo  Cécile Gautheron  Philippe‐Hervé Leloup  Matthew Fox  Laurent Tassant‐Got  Eric Douville 《地学学报》2013,25(2):110-118

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Advanced insights into sources of vertical velocity in the ocean     

Hervé Giordani  Louis Prieur  Guy Caniaux 《Ocean Dynamics》2006,56(5-6):513-524

Estimating vertical velocity in the oceanic upper layers is a key issue for understanding ocean dynamics and the transport of biogeochemical elements. This paper aims to identify the physical sources of vertical velocity associated with sub-mesoscale dynamics (fronts, eddies) and mixed-layer depth (MLD) structures, using (a) an ocean adaptation of the generalized Q-vector form of the ω-equation deduced from a primitive equation system which takes into account the turbulent buoyancy and momentum fluxes and (b) an application of this diagnostic method for an ocean simulation of the Programme Océan Multidisciplinaire Méso Echelle (POMME) field experiment in the North-Eastern Atlantic. The approach indicates that w-sources can play a significant role in the ocean dynamics and strongly depend on the dynamical structure (anticyclonic eddy, front, MLD, etc.). Our results stress the important contribution of the ageostrophic forcing, even under quasi-geostrophic conditions. The turbulent w-forcing was split into two components associated with the spatial variability of (a) the buoyancy and momentum (Ekman pumping) surface fluxes and (b) the MLD. Process (b) represents the trapping of the buoyancy and momentum surface energy into the MLD structure and is identified as an atmosphere/oceanic mixed-layer coupling. The momentum-trapping process is 10 to 100 times stronger than the Ekman pumping and is at least 1,000 times stronger than the buoyancy w-sources. When this decomposition is applied to a filamentary mixed-layer structure simulated during the POMME experiment, we find that the associated vertical velocity is created by trapping the surface wind-stress energy into this structure and not by Ekman pumping.  相似文献   

Discovery of two ophiolite complexes of different ages in the Khoy area (NW Iran)     

Morteza Khalatbari-Jafari  Thierry Juteau  Hervé Bellon  Hashem Emami 《Comptes Rendus Geoscience》2003,335(12):917-929

New field and laboratory studies on the ophiolite of Khoy (northwestern corner of Iran) lead to the discovery that there are not one, but two ophiolitic complexes in the Khoy area: (1) an old, poly-metamorphic ophiolite, whose oldest metamorphic amphiboles yielded a Lower Jurassic apparent ⁴⁰K–⁴⁰Ar age, and whose primary magmatic age should logically be pre-Jurassic (Upper-Triassic?); (2) a younger non metamorphic ophiolite of well dated Upper Cretaceous age. To cite this article: M. Khalatbari-Jafari et al., C. R. Geoscience 335 (2003).  相似文献   

La stratigraphie oligo-miocène et la surface d'érosion messinienne en mer Noire,stratigraphie sismique haute résolution     

Hervé Gillet  Gilles Lericolais  Jean-Pierre Rehault  Corneliu Dinu 《Comptes Rendus Geoscience》2003,335(12):907-916

The stratigraphy of the Black Sea western margin is revisited through seismic data acquired during two French-Romanian surveys. These data are calibrated by industrial and DSDP drillings; they display several major discontinuities regarded as Tertiary erosional surfaces. The major seismic discontinuity underlines the base of Miocene formations and corresponds to a composite surface including at least three erosional phases ranging from Oligocene to Pontian times. Moreover, a Messinian erosional surface is clearly identified. This is in agreement with the Hsü's proposition [Palaeogeogr. Palaeoclimatol. Palaeoecol. 29 (1979) 75–93] suggesting a Messinian sea-level drop of Black Sea related to the Messinian Salinity Crisis described in the Mediterranean Sea. To cite this article: H. Gillet et al., C. R. Geoscience 335 (2003).  相似文献   

Nouvelles données structurales et datations 40K–40Ar sur les roches métamorphiques de la région de Neyriz (zone de Sanandaj–Sirjan,Iran méridional). Leur intérêt dans le cadre du domaine néo-téthysien du Moyen-Orient     

Reza Sheikholeslami  Hervé Bellon  Hachem Emami  Mossaı̈eb Sabzehei  Alain Piqué 《Comptes Rendus Geoscience》2003,335(13):981-991

The metamorphic rocks of the Neyriz area (Sanandaj–Sirjan zone) represent a Palaeozoic sequence, the upper part of which being palaeontologically dated from the Carboniferous and the Permian. Field structural analysis of the whole sequence, detailed in laboratory by microstructural one and ⁴⁰K–⁴⁰Ar dating carried on separated minerals, lead to establish that the whole sequence, from gneisses to Permian rocks, has suffered a unique synmetamorphic deformation, of variable intensity, marked by a foliation. Isotopic ages measured on extracted amphiboles and micas, clustered in four groups between 300 and 60 Ma, show the successive stages of their slow exhumation, which ended by the end of the Cretaceous. To cite this article: R. Sheikholeslami et al., C. R. Geoscience 335 (2003).  相似文献   

Premiers résultats d'une étude géophysique sur le flanc nord des glissements de Storegga (Norvège)     

Hervé Nouzé  Isabelle Contrucci  Jean-Paul Foucher  Bruno Marsset  Yannick Thomas  Estelle Thereau  Alain Normand  Éliane Le Drezen  Stéphane Didailler  Jean-Pierre Regnault  Sandie Le Conte  Stéphanie Guidart  Wim Lekens  Simon Dean  Alexandre Throo 《Comptes Rendus Geoscience》2004,336(13):1181-1189

The Storegga slides, off Norway, are among the largest submarine slides ever known on a continental slope. The HYDRATECH cruise on N/O Le Suroît aimed at a high-resolution survey of an area at the northern boundary of the slides. This survey images in great detail the bottom simulating reflector (BSR) extent and properties, the various fluid escape structures and the sediment deformations. The combination and the quality of the data help to understand the still poorly constrained relationships between fluid escapes, gas hydrates and slope stability in the survey area. To cite this article: H. Nouzé et al., C. R. Geoscience 336 (2004).  相似文献   

Early Palaeozoic orogenic events north of the Rheic suture (Brabant,Ardenne): A review     

Manuel Sintubin  Timothy Nick Debacker  Hervé Van Baelen 《Comptes Rendus Geoscience》2009,341(2-3):156-173

The Lower Palaeozoic rocks exposed in the Brabant-Ardenne region (Belgium, France) recorded the Early Palaeozoic history on the southern margin of the perigondwanan microcontinent of Avalonia, north of the Rheic suture. These rocks crop out in the Brabant basement and in the Ardenne basement inliers within the Variscan Ardenne allochthon. The two main unconformities are classically associated with distinct orogenic episodes, the Late Ordovician “Ardennian” event and the Early Devonian “Brabantian” event. A review of the current state-of-knowledge with respect to the reconstruction of Early Palaeozoic geodynamics in the Brabant-Ardenne region is presented. It is demonstrated that an unconformity does not necessarily represent an orogenic event, and that the hiatus related to an unconformity does not necessarily coincide with tectonic activity, especially when tectonism is diachronous in nature. The former applies to the Ardennian unconformity, while the latter applies to the Brabantian unconformity. Finally, the well-constrained Brabantian orogeny, as well as the Ardenne-Eifel basin development, is tentatively framed within the Early Palaeozoic geodynamic context of the northern margin of the Rheic realm. By doing so, it is shown that the Brabant-Ardenne region links, both in space and time, the Rheic and Rhenohercynian ocean.  相似文献