Éditeur(s) : HAL CCSD International Phycological Society
Résumé : International audience
We studied a group of monoraphid diatom species (Bacillariophyceae, Achnanthidiaceae) found in the marine coastal environment of tropical islands of the Caribbean Sea, western Atlantic Ocean, Indian Ocean, South Pacific Ocean, the Adriatic Sea and the Black Sea. Based on light and electron microscope examination, Madinithidium was formally described as a genus new to science with the generitype defined as Madinithidium undulatum. The characteristic features of the valve structure are a strongly developed sternum and raphe sternum, transapical striae formed by a single areola (macroareolae) positioned in small depressions, elevated virgae and coaxial internal central raphe endings. Furthermore, the striae of both raphe and sternum valves are closed by finely perforated hymenes. Madinithidium and Achnanthidium species are difficult to identify correctly with light microscopy since their valves are small and finely structured. Four species recently described from the western Indian Ocean and assigned to Achnanthidium sensu lato – Achnanthidium capitatum, A. flexuistriatum, A. pseudodelicatissimum and A. scalariforme – possessed morphological features permitting their placement into Madinithidium gen. nov. The above-mentioned species were formally transferred to the new genus.
ISSN: 2330-2968

hal-01333391
https://hal-univ-perp.archives-ouvertes.fr/hal-01333391
DOI : 10.2216/14-21R2

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Climatic changes result in an increased in mean temperature and in a higher incidence of extreme weather events such as heat and cold waves. For ectotherms, such as insect parasitoids, the ability to remain active under extreme climatic conditions is a significant key to fitness. The body size of individuals, and in particular their surface to volume ratio, may play a role in their resistance to thermal conditions. The thermal tolerances are investigated of two closely-related sympatric parasitoid species [Aphidius avenae Haliday and Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Aphidiinae)] that have a similar ecology but differ in body size and phenologies. The critical thermal limits of individuals are assessed in both sexes of each parasitoid species and the influence of surface-volume ratios on their thermal tolerances. Aphidius avenae is less resistant to low temperatures and more resistant to high temperatures than A. rhopalosiphi. The lower surface to volume ratio of A. avenae individuals may help them to remain active in summer when experiencing heat waves. However, body size is not the sole factor that plays a role in differences of thermal tolerance between species and body size may not be an adaptation to extreme temperatures but rather a by-product of developmental regulation. Closely related sympatric species from the same ecological guild can have different thermal tolerances that may allow them to occur within the same habitat. The present study also highlights the importance of clearly defining how to measure critical thermal limits to determine the thermal tolerance of a species.
ISSN: 0307-6962

hal-00589094
https://hal.archives-ouvertes.fr/hal-00589094
DOI : 10.1111/j.1365-3032.2010.00758.x

Éditeur(s) : HAL CCSD
Résumé : International audience
Continental erosion and weathering destroy parts of the stratigraphic record. Analyses of the sedimentary filling of paleokarsts help completing the geological record of regions that have been submitted to post-depositional, long-term, continental evolution. Jurassic carbonate platform of Languedoc (South of France) has undergone several karstification phases from Cretaceous to Neogene. Later incision of canyons through the carbonate massifs allows to observe paleokarsts over 400m depth, within the massifs. Paleokarsts are partly filled with sediments. Some have yielded marine bioclasts (echinoderms, radiolars), foraminifera and nannofossils; others are composed of polygenic detrital sediments, including sources from the upstream Paleozoic basement (Cevennes). The age of the filling of successive paleokarsts can be constrained by structural relationships and by biostratigraphy. These findings suggests 1) the marine elements of the karstic filling relate to a Late Cretaceous to Early Paleocene interval, while 2) the Paleozoic basement-sourced-sediments were trapped in the karst during Miocene to Present. Karstic sediment containing Early Paleocene foraminifera and nannofossils are found in paleokarsts cavities distributed across the entire thickness of the carbonate massif (≥350m). This requires base-level lowering and associated karstification, followed by base-level rise and karst filling of at least 350 m amplitude, respectively. The time interval corresponding to the occurrence of foraminifera and nannofossils in karsts covers 10 Myrs ; surprisingly, no equivalent marine sediments are preserved on the surface. In addition, analyses of the different forams species suggests several (up to 3) distinct karstification and marine filling cycles. Finally, sedimentological facies analysis of the karst filling reveals the following succession of processes: low energy settling of mudstone, high energy reworking, transport and deposition of silts and sandstones within the karst system. Integration of geological, paleontological and sedimentological data, leads to a polyphase scenario in response to repeated base-level variations, more than 350m amplitude. Such an amplitude excludes eustacy, and the improbable repeated sequence of uplift and subsidence rules out tectonics, as driving forces for base-level change, respectively. We propose that the high-amplitude base-level changes results from a succession of desiccation-flooding events of an endorheic, silled, basin during Early Paleogene. The later detrital assemblage sourced in the Cevennes occurs on perched paleosurfaces and in karst cavities across the whole 350m-deep canyon walls. When found on paleosurfaces, they correspond to the south-flowing Early Miocene fluvial drainage, and can be correlated downstream with the marine, well dated, Early Miocene, sediments. When found within the karst cavities, they correspond to successive base-level surfaces connected to the progressive incision of the canyon. This canyon incision is coeval with a Late Miocene uplift of the hinterland.
24th International Karstological School "Classical karst" : Paleokarst
Postojna, Slovenia

hal-01306683
https://hal-brgm.archives-ouvertes.fr/hal-01306683
https://hal-brgm.archives-ouvertes.fr/hal-01306683/document
https://hal-brgm.archives-ouvertes.fr/hal-01306683/file/Abstract_IKS.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A dense, local network of 30 geodetic markers covering a 50 × 60 km2 area in the southwestern European Alps (Briançon region) has been temporarily surveyed in 1996, 2006 and 2011 by GPS. The aim is to measure the current deformation in this seismically active area. The study zone is characterized by a majority of extensional and dextral focal mechanisms, along north–south to N160 oriented faults. The combined analysis of the three measurement campaigns over 15 years and up to 16 years of permanent GPS data from the French RENAG network now enables to assess horizontal velocities below 1 mm/year within the local network. The long observation interval and the redundancy of the dense campaign network measurement help to constrain a significant local deformation pattern in the Briançon region, yielding an average E–W extension of 16 ± 11 nanostrain/year. We compare the geodetic deformation field to the seismic deformation rate cumulated over 37 years, and obtain good coherencies both in amplitude and direction. Moreover, the horizontal deformation localized in the Briançon region represents a major part of the Adriatic-European relative plate motion. However, the average uplift of the network in an extensional setting needs the presence of buoyancy forces in addition to plate tectonics.
ISSN: 0264-3707

hal-01119724
https://hal.archives-ouvertes.fr/hal-01119724
DOI : 10.1016/j.jog.2015.02.001

Éditeur(s) : HAL CCSD
Résumé : The sandy coasts of Languedoc-Roussillon are a zone vulnerable to erosion and flooding. These hazards are generally associated with a combination of natural factors such as waves, wind, rising sea levels and the importance of sediment supply, and are therefore worsened during storms. For the management of such risks, a better knowledge of the hydrodynamic phenomena occuring from the surf zone through to the coastal scale is essential. This need led to the development of a numerical modelling platform consisting of the 3D ocean circulation model Symphonie, usually dedicated to regional and coastal scales, which was modified to include the wave forcing, modeled by the WaveWatch III or Swan models. Using this platform the entire littoral and coastal regions can be accurately represented. The model was tested in several academic cases. Measurements on the barred beach of Sète during the winter of 2008-2009 served to refine the model, which is able to successfully reproduce the characteristics of the currents in coastal areas, drifts or rip currents over more complex bathymetries and also the vertical profiles of currents. To validate the model on the inner-shelf, we compared the simulations with measurements taken during a winter storm in 2004 around the mouth of the Têt river, as well as during storms in 2007 and 2008 in the Gulf of Aigues-Mortes. Currents are generally well reproduced. However, the scope of wave action seems limited to a depth of 30m. The characteristics of our model allow a good reproduction of the currents at all scales and the 3D nature of the model permits a more precise calculation of the shear stress and bottom current responsible, respectively, for the suspension and advection of sediments.
Le littoral sableux du Languedoc-Roussillon est un système vulnérable aux risques d'érosion et de submersion. Ces aléas sont liés à la conjonction des facteurs naturels que sont les vagues, vent, élévation du niveau de la mer et apports sédimentaires et sont donc aggravés en période de tempête. En vue d'une gestion des risques, une meilleure connaissance des phénomènes hydrodynamiques de l'échelle littorale à l'échelle côtière est essentielle. Ce travail a conduit à la réalisation d'une plateforme de modélisation numérique composée du modèle de circulation océanique 3D Symphonie, traditionnellement dédié aux échelles régionales et côtières, qui a été modifié pour inclure le forçage par les vagues, modélisées par les modèles Wavewatch III ou Swan, et ainsi étendre sa validité au littoral. Le modèle a été testé sur des cas académiques littoraux. Des mesures sur la plage à double barres de Sète pendant l'hiver 2008-2009, ont également servi à parfaire le modèle qui reproduit ainsi avec succès les caractéristiques des courants en zone littorale : la dérive, les courants sagittaux sur des bathymétries plus complexes et les profils verticaux des courants. Pour valider le modèle à des échelles plus côtières, nous avons confronté ses résultats à des mesures réalisées pendant une tempête hivernale en 2004 aux alentours de l'embouchure de la Têt, mais également sur des tempêtes de 2007 et 2008 dans le Golfe d'Aigues-Mortes. Les courants sont globalement bien reproduits. Les zones d'action des vagues semblent limitées aux zones de profondeur inférieure à 30 m. Notre modèle autorise une reproduction correcte des courants à toutes les échelles et sa nature 3D permet un calcul plus précis de la tension de cisaillement de fond et du courant près du fond, responsables respectivement de la mise en suspension et de l'advection des sédiments.
https://tel.archives-ouvertes.fr/tel-00680405

tel-00680405
https://tel.archives-ouvertes.fr/tel-00680405
https://tel.archives-ouvertes.fr/tel-00680405v2/document
https://tel.archives-ouvertes.fr/tel-00680405/file/2011_MICHAUD.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
ISSN: 0169-1368

hal-00329701
https://hal.archives-ouvertes.fr/hal-00329701
DOI : 10.1016/j.oregeorev.2008.03.003

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : The Latest Cretaceous/Paleocene paleokarsts from Bas-Languedoc (South of France) are characterized by : 1) exokarstic paleosurfaces (sink holes, pinnacles, canyons) which are mostly superimposed onto the Late Jurassic limestones and partly filled up with breccias and sandy clays containing Paleocene planktonic foraminifera; 2) endokarstic cavities filled up by sandy pelites and laminated mudstones with similar micropaleontological assemblage. All these cavities constitute three cut-and-filled paleokarstic systems. A general model of formation for this polyphase system is proposed. These paleosurfaces are generated by a Latest Cretaceous tectonic phase and Paleocene movements associated with eustatic rises inducing rapid floodings. During Upper Danian-Lower Selandian times three successive base levels drops, whose cumulated duration could be as long as 3 Ma, have induced several hundred metres of incisions within the exposed Jurassic carbonate series. A paleogeographic reconstruction shows three main marine gulfs which extend towards NE the EW Pyrenean thrust belt ("Pyrenean Paleocene Trough", PPT) located on the axis of the future Pyrenees. The similarity of the facies and micropaleontological content in the two domains suggests connexions between the marine Paleocene deposits of Bas-Languedoc and the PPT. It could thus explain the succession of the same tectono-eustatic events. We propose, as an hypothesis, that the rapid sea-level changes, as recorded by the imbricated karstic paleomorphologies, could be induced by the closing and the opening of a strait in the Eastern part of the PPT acting as a sill. This would be controlled by tectonic movements along the active orogenic axis of the Pyrenean Range and eustatic variations of the Paleocene World Ocean. The karstic systems developed during these low-stand episodes may have been later reactivated after the Early Selandian and more specifically during the Messinian desiccation event. This late evolution may have generated deep flooded karsts, now situated below the present sea level. Such karsts, partly inherited from Paleocene, could be important aquifers of economic interest.
ISSN: 0985-3111

hal-00407601
https://hal.archives-ouvertes.fr/hal-00407601
DOI : 10.3166/ga.20.301-326

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Generation and emplacement of felsic magmas in the Paleoproterozoic Baoulé-Mossi domain, West African Craton does not match the apparent peaks of global crust generation identified between ca. 2900–2600, 1900–1600 and 1200–900 Ma. In contrast, across the Baoulé-Mossi domain, the emplacement of felsic intrusions ranges from ca. 2300 to 2000 Ma. It has proven difficult to place this magmatism within a robust geodynamic framework due to the lack of accurate geochronological data from across the West African Craton. The present study addresses this issue by presenting eighty-four new felsic intrusions zircon ion microprobe and LA-ICP-MS U-Pb ages from areas that up until now have not been targeted for geochronology. The new dataset, when fully integrated with existing age data, reveals a craton-wide diachronous geochronological pattern characterized by a magmatic front that migrated westward. This migration proceeded at a rate of 35 km per million years, with an apparent offset of the initiation and cessation of felsic magmatic activity between the east and west of approximately 50 million years. The new data also show that although the entire Baoulé-Mossi domain was subject to continuous magmatic activity for at least 150 million years, this magmatic activity displays a rather different record in the eastern and western portions of the domain. The differences are expressed as a westward migration of the magmatic activity, cessation of activity around ca. 2100 Ma (easternmost portion) and ca. 2050 Ma (westernmost portion) and a higher incidence of inherited ages in the westernmost portion when compared to the easternmost region. In addition, the new U-Pb data identify some of the oldest felsic intrusions in the region, including a granite from Burkina Faso (2265 ± 17 Ma) and a diorite porphyry (2216 ± 5 Ma) in southern Mali. This study also reveals inherited Archean zircon cores from across southern Mali. The combination of the new data presented here, along with previously published data, suggests that the Baoulé-Mossi domain formed from the accretion of two major crustal blocks. The Archean inherited ages open a window for further investigation of the interaction between the Archean Kénéma-Man and the Paleoproterozoic Baoulé-Mossi domains.
ISSN: 0301-9268

hal-01623272
https://hal.archives-ouvertes.fr/hal-01623272
DOI : 10.1016/j.precamres.2017.07.036

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Chelonanthus alatus is a bat-pollinated, pioneer Gentianaceae that clusters in patches where still-standing, dried-out stems are interspersed among live individuals. Flowers bear circum-floral nectaries (CFNs) that are attractive to ants, and seed dispersal is both barochorous and anemochorous. Although, in this study, live individuals never sheltered ant colonies, dried-out hollow stems--that can remain standing for 2 years--did. Workers from species nesting in dried-out stems as well as from ground-nesting species exploited the CFNs of live C. alatus individuals in the same patches during the daytime, but were absent at night (when bat pollination occurs) on 60.5% of the plants. By visiting the CFNs, the ants indirectly protect the flowers--but not the plant foliage--from herbivorous insects. We show that this protection is provided mostly by species nesting in dried-out stems, predominantly Pseudomyrmex gracilis. That dried-out stems remain standing for years and are regularly replaced results in an opportunistic, but stable association where colonies are sheltered by one generation of dead C. alatus while the live individuals nearby, belonging to the next generation, provide them with nectar; in turn, the ants protect their flowers from herbivores. We suggest that the investment in wood by C. alatus individuals permitting still-standing, dried-out stems to shelter ant colonies constitutes an extended phenotype because foraging workers protect the flowers of live individuals in the same patch. Also, through this process these dried-out stems indirectly favor the reproduction (and so the fitness) of the next generation including both their own offspring and that of their siblings, all adding up to a potential case of inclusive fitness in plants.
ISSN: 1932-6203

hal-00825845
https://hal.archives-ouvertes.fr/hal-00825845
https://hal.archives-ouvertes.fr/hal-00825845/document
https://hal.archives-ouvertes.fr/hal-00825845/file/Dejean2011_Inherited.pdf
DOI : 10.1371/journal.pone.0018071

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
ISSN: 0028-646X

hal-00480370
https://hal.archives-ouvertes.fr/hal-00480370

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Volumetrically minor microsyenites, alkali microgranite and related trachytic dykes intrude early Pliocene OIB-like alkali basaltic and basanitic flows of the Meseta del Lago Buenos Aires in Central Patagonia (47 degrees S-71 degrees 30'W), and occur together with scarce trachytic lava flows. Whole-rock K-Ar ages between 3.98 and 3.08 Ma indicate that the emplacement of these felsic rocks occurred more or less synchronously with that of the post-plateau basaltic sequence that they intrude, during a bimodal mafic-felsic magmatic episode devoid of intermediate compositions. Chemically, these rocks have A(1)-type granitoid affinities and are characterized by high silica and alkali contents (60-68 wt.% SiO2; 8.7-10.8 wt.% Na2O+K2O), major and trace elements patterns evidencing evolution by low-pressure fractional crystallization, and Sr and Nd isotopic signatures similar to those of coeval basalts ((Sr-87/Sr-86)o=0.70488-0.70571; (Nd-143/Nd-144)(o)=0.512603-0.512645). Nevertheless, some of them have the most radiogenic Sr values ever reported for a magmatic rock in the Meseta and even in the whole Neogene Patagonian Plateau Lavas province ((Sr-17/Sr-86)(o)= 0.70556-0.70571; (Nd-143/Nd-144)(o)=0.512603-0.512608). In addition, very high contents of strongly incompatible elements in the most evolved rocks, together with Sr isotopic ratios higher than those of coeval basalts, suggest the occurrence of open-system magmatic processes. Continuous fractional crystallization from a primitive basaltic source, similar to post-plateau coeval basalts, towards alkali granites combined with small rates of assimilation of host Jurassic tuffs (AFC) in a shallow magmatic reservoir, best explains the geochemical and petrographic features of the felsic rocks. Therefore, A(1)-type magmatic rocks can be generated by open-system crystallization of deep asthenospheric melts in back-are tectonic settings. In Central Patagonia, these similar to 3-4 Ma old alkaline intrusions occur aligned along a similar to N160-170 trending lineament, the Zeballos Fault Zone, stacking the morphotectonic front of one segment of the Patagonian Cordillera. Intrusion along this fault zone
ISSN: 0024-4937

hal-00412030
https://hal.archives-ouvertes.fr/hal-00412030
DOI : 10.1016/j.lithos.2007.07.002

Éditeur(s) : HAL CCSD Ecole nationale du génie rural
Résumé :  
La télédétection aérienne et spatiale a été, dès ses origines, un outil irremplaçable pour l'étude et la gestion des milieux forestiers. Pourtant, les méthodes d'exploitation des images, souvent conçues pour des forêts tempérées ou boréales, sont partiellement mises en échec par l'hétérogénéité de la forêt tropicale humide, la mangrove étant un cas beaucoup plus favorable en raison de son homogénéité. Ayant précisé l'apport des principaux capteurs et constaté les limites des possibilités de modélisation radiométrique, nous passons en revue les méthodes empiriques ou plus rigoureuses qui font actuellement l'objet de recherches.
ISSN: 0035-2829

hal-01032113
https://hal.archives-ouvertes.fr/hal-01032113

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We analyze in this study a new set of marine data including 3D local tomography, 1992-2008 relocated earthquakes and two recent multichannel seismic lines to characterize the deformation style in the collision area offshore east Taiwan. We have mapped in detail the Mohos of the converging plates as well as the subduction interface with a resolution never reached before. We show that the sharp continental subduction of the Eurasia plate, beneath the middle part of the Central Range, indents the Philippine Sea plate (PSP) as attested by intra-oceanic slicing and incipient subduction of the PSP beneath the east coast of Taiwan. The westernmost part of the PSP slab is probably experiencing a beginning of break-off as attested by NW-trending en-échelon shear zones beneath the southern slope of the southern Ryukyu arc (SRA). These en-échelon shear zones have a sinistral component favored by the "collision-free" subduction of the PSP north of 24°30′N. The down-faulting of the subduction interface forms ramps along which earthquakes clusterize. Three M7 subduction earthquakes occurred offshore Suao city along these ramps with a recurrence interval of about 40 years: 1920 Mw7.7, 1963 Mw7.2 and 2002 Mw7.1 events. The 1966 Mw6.0-7.5 earthquakes sequence likely outlines a WNW-ESE left-lateral intra-slab shear zone. The SRA upper plate accommodates the complex geometry and deformation of the subducting PSP through seismic deformation. Shallow high velocities fringing the Luzon volcanic arc (LVA) beneath the Longitudinal Valley and north of the southernmost Ryukyu forearc basins are interpreted as relics of the LVA forearc basement squeezed in the collision zone. Based on the accommodation of a large part of the convergence through shortening within the PSP and the subsequent segmentation of the shallow subduction interface, we consider that the nucleation of a Mw ≥ 8 earthquake along the southernmost Ryukyu megathrust is unlikely.
ISSN: 0040-1951

hal-00853365
https://hal.archives-ouvertes.fr/hal-00853365
https://hal.archives-ouvertes.fr/hal-00853365/document
https://hal.archives-ouvertes.fr/hal-00853365/file/publallemandifremer.pdf
DOI : 10.1016/j.tecto.2013.03.020

Éditeur(s) : HAL CCSD Wiley-VCH Verlag
Résumé : International audience
Deciphering the assembly history of the Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps of the Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with a well-defined view of the current chemo-kinematical structure of the Milky Way, but will only enable a blurred view on the temporal sequence that led to the present-day Galaxy. As demonstrated by the (ongoing) exploitation of data from the pioneering photometric missions CoRoT, Kepler, and K2, asteroseismology provides the way forward: solar-like oscillating giants are excellent evolutionary clocks thanks to the availability of seismic constraints on their mass and to the tight age-initial-mass relation they adhere to. In this paper we identify five key outstanding questions relating to the formation and evolution of the Milky Way that will need precise and accurate ages for large samples of stars to be addressed, and we identify the requirements in terms of number of targets and the precision on the stellar properties that are needed to tackle such questions. By quantifying the asteroseismic yields expected from PLATO for red-giant stars, we demonstrate that these requirements are within the capabilities of the current instrument design, provided that observations are sufficiently long to identify the evolutionary state and allow robust and precise determination of acoustic-mode frequencies. This will allow us to harvest data of sufficient quality to reach a 10% precision in age. This is a fundamental pre-requisite to then reach the more ambitious goal of a similar level of accuracy, which will only be possible if we have to hand a careful appraisal of systematic uncertainties on age deriving from our limited understanding of stellar physics, a goal which conveniently falls within the main aims of PLATO's core science.
ISSN: 0004-6337

hal-01541393
https://hal.archives-ouvertes.fr/hal-01541393
ARXIV : 1706.3778
BIBCODE : 2017AN....338..644M
DOI : 10.1002/asna.201713385

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
In the mid-afternoon of 15 July 2007, during the Convective and Orographically induced Precipitation Study (COPS), in a very warm and dry environment, an isolated, short-lived, deep convective system developed over the southern Black Forest. Most of the high-resolution, convection-permitting models involved in COPS were unable to capture this event whereas the Meso-NH forecast was quite skilful. To assess the Meso-NH performance further, the model results were carefully checked against the various and numerous COPS observations. In full agreement with clear-air radar observations, model results underlined the triggering role of a low-level convergence line that developed in the lee of the Feldberg. The main departure from the observations was found to be in the low-level moisture fields, which appeared significantly moister in the model than in the observations and also slightly moister than in the other models. Sensitivity studies showed that this departure from the observations was strongly controlled by the initial surface moisture conditions. When the surface moisture was reduced by 20% or replaced by the value derived from a different analysis, the evolution of the planetary boundary layer was more accurately represented while the storm evolution was still correctly captured. These results demonstrate that the quality of the initial forecast cannot be ascribed to the moist bias of the model. It could therefore be hypothesized that the key parameters for a satisfactory forecast of this event lie more in the ability of the model to reproduce the dynamical forcing accurately than in the characteristics of the air-mass instability.
ISSN: 0035-9009

hal-00554400
https://hal.archives-ouvertes.fr/hal-00554400
DOI : 10.1002/qj.710

Éditeur(s) : HAL CCSD
Résumé : National audience
Un ensemble de données sur l’environnement géologique despéridotites de la Zone Nord-Pyrénéenne a été obtenu dans lecadre des programmes ANR Pyramid et RGF-BRGM consacrésà l’évolution géodynamique des Pyrénées. Ces données représententdes contraintes indispensables pour l’étude des processus del’exhumation du manteau, de l’amincissement de la croûte continentaleet de sa disparition complète lors de l’ouverture desbassins transtensifs albo-cénomaniens. On y trouve : (1) de nouveauxlevés géologiques de détail autour des lherzolites de Lherz-Freychinède-Vicdessos-Bestiac-Prades et d’Urdach-Les Pernes et(2) des analyses multi-méthodes des métasédiments de la couvertureprérift et du socle paléozoïque adhérent au manteau :composition des assemblages du métamorphisme HT, températuresmaximales par spectrométrie RAMAN sur la m.o., fabriquede la calcite par EBSD, inclusions fluides et isotopes stables dansles marbres et veines associées, datations U-Th-Pb in situ. Cesdonnées permettent d’estimer les conditions thermiques lors de laremontée du manteau et de sa mise à l’affleurement. Nous montronsune variabilité remarquable de l’Ouest vers l’Est.A l’Ouest, le manteau est exhumé à l’Albien sup. - Cénomanieninf. en perçant une couverture mésozoïque prérift qui n’a pas étéchauffée à plus de 250C. La croûte continentale supérieure y estréduite en lames ductiles extrêmement amincies puis cataclaséeset remaniées sur le fond ultrabasique avec des fragments de manteauet de la couverture prérift, durant le dépôt du flysch noir. Latempérature augmente au cours du Cénomanien (480C) dans leszones où le manteau n’a pas été mis à l’affleurement. Le Triassupérieur se transforme profondément (talc-chlorites) et perd sacomposante évaporitique. La couverture prérift décollée joue unrôle majeur comme couvercle isotherme, suivi en cela par les flyschsalbiens puis cénomaniens.A l’Est, le manteau perce à travers une couverture chauffée localementà plus de 600C. Le Keuper y est réduit à quelquesdécimètres de grès et brèches riches en saphirine. La croûtesupérieure a été presque totalement éliminée tectoniquement, maisdes granulites sont remaniées à côté des péridotites et des marbresdans les brèches recouvrant le manteau exhumé.Ces données de terrain représentent les contraintes de base pourconstruire les modèles d’amincissement crustal. La variabilitémise en évidence (gradient thermique et présence ou absence decroûte profonde remaniée) ne permet pas de proposer un modèled’amincissement simple et unique. Cependant, toutes ces donnéesindiquent que la croûte moyenne à supérieure se comporteductilement sous les écrans thermiques de la couverture prériftet synrift, mobiles sur le Keuper. Un modèle de marge passivedistale faisant appel à des blocs continentaux rigides de type ”extensional allochthons ” ne peut s’appliquer ici. Sur la base deces données géologiques, nous mettons donc en avant un nouveaumodèle de type marge distale chaude plus ou moins transtensive.
RST 2016, livre des résumés
Caen, France

insu-01388463
https://hal-insu.archives-ouvertes.fr/insu-01388463

Éditeur(s) : HAL CCSD International Frequency Sensor Association (IFSA)
Résumé : International audience
This paper introduces an approach illustrating how the Open Geospatial Consortium (OGC) Sensor Web Enablement (SWE) framework can be used in order to build a franco-lebanese observatory. We present the practical application of SWE services as a source of real-time observation data and the associated technical architecture for making near real-time observations available to end users on the Web. We discuss the question of crossing sensor data with other data sources, e.g., data provided by human observations. We illustrate our approach by describing the methodology to integrate a first illustration case to monitor snow weather stations in the Lebanese Mountains.
ISSN: 1726-5479

lirmm-01381092
https://hal-lirmm.ccsd.cnrs.fr/lirmm-01381092

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
We investigate upper mantle anisotropy beneath the Pyrenean range along three N-S profiles across the mountain belt. The results of a first profile that operated in 1993 in the central part of the belt have been presented elsewhere. We present the results of two other profiles that ran in 1995-1996 and 1996-1997 in the eastern and western part of the belt, respectively and propose an interpretation of the whole results. Teleseismic shear waves (SKS, SKKS, and PKS) are used to determine splitting parameters: the fast polarization direction φ and the delay time δt. Teleseismic shear wave splitting in the eastern Pyrenees displays homogeneous φ values trending N100°E and δt values in the range 1.1 to 1.5 s. A station located in the southern Massif Central, 100 km north of the range, is characterized by different splitting parameters (φ = N70°E, δt = 0.7 s). In the western part of the belt, anisotropy parameters are similar across the whole belt (φ = N110°E and δt = 1.3 to 1.5 s). Most of the measured delay times, including those obtained in the central part of the range, are above the global average of the SKS splitting (around 1 s). At the belt scale, φ is generally poorly correlated with recent estimations of the absolute plate motion, which predicts a fast direction ranging between N50°E and N80°E. Instead, the orientation of φ (N100°E) is parallel to the trend of the Pyrenean belt but also to Hercynian preexisting structures. This parallelism supports an anisotropy primarily related to frozen or active lithospheric structures. We show that a signature related to the Pyrenean orogeny is likely for the stations located in the internal domains of the belt. By contrast, the anisotropy measured at the stations located on the external parts of the belt could reflect a pre-Pyrenean (Hercynian) deformation. We suggest that a late Hercynian strike-slip deformation is responsible for this frozen upper mantle anisotropy and that the Pyrenean tectonic fabric developped parallel to this preexisting fabric. Finally, no particularly strong splitting is related to the North Pyrenean Fault, commonly believed to represent the plate boundary between Iberia and Eurasia.
ISSN: 2169-9313

hal-01388841
http://hal.univ-reunion.fr/hal-01388841
http://hal.univ-reunion.fr/hal-01388841/document
http://hal.univ-reunion.fr/hal-01388841/file/Barruol_Aniso_Pyr_JGR1998.pdf
DOI : 10.1029/98JB02790

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The Convective and Orographically-driven Precipitation Study (COPS) carried out in summer 2007 over northeastern France and southwestern Germany provided a fairly comprehensive description of the low-troposphere water-vapour field, thanks in particular to the deployment of two airborne differential absorption lidar systems. These lidar observations were assimilated using the 3D-Var assimilation system of the Application of Research to Operations at MEsoscale (AROME) numerical weather prediction mesoscale model. The assimilation was carried out for the period 4 July-3 August by running a three-hour forward intermittent assimilation cycle. First, the impact of the lidar observations was assessed by comparing the analyses with a set of more than 200 independent soundings. The lidar observations were found to have a positive impact on the analyses by reducing the dry bias in the first 500 m above ground level and by diminishing the root-mean-square error by roughly 15% in the first km. Then the impact of the lidar observations was assessed by comparing the precipitation forecasts (obtained with and without the lidar observations for the period 15 July-2 August) with the gridded precipitation observations provided by the Vienna Enhanced Resolution Analysis. In general, the impact was found to be positive but not significant for the 24 h precipitation and positive and significant for the 6 h precipitation, with an improvement lasting up to 24 h. Some selected case studies show that the improvement was obtained through a better depiction of convection initiation or through a more accurate positioning of the precipitation systems
ISSN: 0035-9009

hal-00659497
https://hal.archives-ouvertes.fr/hal-00659497
DOI : 10.1002/qj.1864

Éditeur(s) : HAL CCSD Météo et Climat
Résumé : International audience
Le premier volet du projet Cyprim vise à mieux identifier les précurseurs des cyclogenèses et des précipitations intenses en région méditerranéenne. Cet article en présente les principaux résultats. Il est question des ingrédients météorologiques à l'origine de ces systèmes, de la grande à la mésoéchelle, des causes des fortes intensités, localisations et parfois stationnarité des récipitations associées. Le coeur de l'article présente des méthodes d'identification des anomalies de tourbillon potentiel liées à l'occurrence d'événements précipitants intenses et dresse une climatologie de ces anomalies. Les perspectives d'exploitation de cette information pour améliorer la qualité des prévisions sont évoquées. ENGLISH VERSION: The first part of the CYPRIM project (Cyclogenesis and intense precipitations in the Mediterranean region) aims at a better identification of the precursor structures of cyclogenesis and heavy precipitation in the Mediterranean region. This article presents the main results. It mentions the meteorological ingredients from which these systems originate from the large to themesoscale, the reasons for large intensities, the localization and sometimes stationarity of the associated precipitations. The heart of the article shows methods for identifiying potential vorticity anomalies involved in the occurrence of heavy precipitation events and sets up a climatology of these anomalies.The perspectives of the usefulness of this information for improving forecast quality are discussed.
ISSN: 0026-1181

insu-00448250
https://hal-insu.archives-ouvertes.fr/insu-00448250
DOI : 10.4267/2042/28828