Éditeur(s) : HAL CCSD
Résumé : Sand intrusions (or injectites) are most often the product of post-depositional remobilization of sand leading to its injection into the surrounding rocks. While injectites were recognized for the first time nearly 200 years ago, their emplacement process has been studied for a couple of decades only, since the concepts of deep sea depositional environments have allowed us to better understand their emplacement processes. However, these processes are still relatively poorly understood. Our approach is based on the study of injectites in the Lower Congo Basin from seismic and well data, which we compare to a fossil system in the SE France basin. We have shown that: (1) In buried turbidite channel systems draping deposits on the channel flanks and terraces of channels have the same geophysical signature as 'wing-like' injectites. Finally, the only criterion for identifying seismic injectites is the presence of bedding-discordant seismic reflections, and in the best case the associated uplift of the overlying seismic reflectors. (2) Seismic-scale conical and saucer-shaped sand injectites have been identified in the Lower Congo Basin. The remobilization is likely due to overpressuring induced by the buoyancy effect of hydrocarbons trapped in the margins of a lobe buried underneath 160 m of sediment, followed by the sudden injection of fluidized sand associated with fault reactivation of faults (with a possible role of nearby salt diapirs). (3) A network of injectites (dykes, sills/wings and laccoliths) was formed in the Vocontian basin during the late Albian and/or early Cenomanian, from a lower-middle Albian turbidite channel. The emplacement is probably due to the early compartmentalization of the channel during its burial and the increase of the sedimentation rate generating overpressure; and the subsequent large influx of deep fluids triggering injection. The injection of sand was polyphased: a first episode formed the sills and another emplaced the dykes. Sills/wings and dykes propagated about 2 km laterally away from the parent sand body and about 200 m up to the surface, revealing a much more extended lateral than vertical reach, contrary to the classically accepted idea from the interpretation of seismic data. (4) The emplacement of this large network of injectites was governed by hydrofracturing. Therefore, its morphology is dependent on the host rock heterogeneity (isotropy, fractures), the paleo-stress orientation (ó3 = NW-SE) and the burial depth of the source (300-600 m) at the time of injection. The study of this fossil network allows us to define the relationship between morphology of the injected network and stress state at the time of injection. This relationship can be extrapolated to constrain the morphology of subsurface networks beyond seismicvisibility. (5) Sands injected into low permeability lithologies bear evidence to a major event of fluid escape in the studied basin, but also channeled fluids long after their formation. In this way, injectites both attest to specific episodes of fluid migration in sedimentary basins and contribute to long-lived re-routing of migrating fluids once emplaced. The injection of sand is associated with the sudden escape of fluids, probably resulting from a significant tectonic and/or sedimentary event; in addition, the architecture of injectite networks is governed by the local paleo-stress and heterogeneity in the host rock. Consequently, characterizing injectite networks is an important step in understanding the plumbing systems of continental margins, i.e. the post-depositional evolution of sedimentary basins.
Les intrusions sableuses (ou injectites) sont le plus souvent le produit de la remobilisation post-dépositionnelle des sédiments et de l'injection du sable dans les roches environnantes. Bien que reconnues pour la première fois il y a près de 200 ans, elles ne sont réellement étudiées que depuis quelques dizaines d'années, depuis que les concepts sur les environnements de dépôt dans les domaines marins profonds nous permettent de mieux comprendre les processus de mise en place. Cependant, ces processus restent encore aujourd'hui relativement mal compris. Notre approche repose sur l'étude d'injectites dans le bassin du Bas-Congo a partir de données de sismique et de puits que nous comparerons a un système fossile dans le bassin du SE de la France. Nous avons montre que : (1) Dans des systèmes de chenaux turbiditiques enfouis, les dépôts de drapage sur les marges et terrasses de chenaux présentent la même signature géophysique que les injectites de type "wing". Finalement, le seul critère sismique d'identification des injectites est la présence de réflexions sismiques sécantes vis-a-vis de la stratigraphie associée dans le meilleur des cas au soulèvement des réflecteurs sismiques sus-jacents. (2) Des injectites d'échelle sismique en forme de cône et d'assiette ont été identifiées dans le bassin du Bas-Congo. La remobilisation résulte probablement des pressions anormales induites par l'effet de flottabilité des hydrocarbures piégés dans les marges d'un lobe enfoui sous 160 m de sédiment, puis de l'injection soudaine du sable fluidise associée a la réactivation de failles (possible rôle des diapirs de sel a proximité). (3) Un réseau d'injectites (dykes, sills/wings et laccolites) s'est formé dans le bassin Vocontien entre la fin de l'Albien supérieur et/ou le début du Cénomanien, depuis un chenal turbiditique de l'Albien inférieur-moyen. La mise en place résulte probablement de la compartimentalisation précoce du chenal au cours de son enfouissement et de l'augmentation du taux de sédimentation générant la surpression et de l'apport ulterieur d'importante quantité de fluides profonds déclenchant l'injection. L'injection du sable a été polyphasée : une première injection a formé des sills et une suivante des dykes. Les sills/wings et les dykes se sont propagés latéralement au chenal source sur environ 2 km et vers la surface sur environ 200 m, mettant en évidence une forte remobilisation latérale plutôt que verticale, contrairement a l'idée classiquement admise a partir de l'interprétation des données sismiques. (4) La formation de ce large réseau d'injectites a été gouvernée par des mécanismes d'hydrofracturation. Par conséquent, sa morphologie a été dépendante des hétérogenéités de la roche hôte (milieu isotrope, fracture), des directions de paléo-contraintes (ƒÐ3 = NWSE) et de la profondeur d'enfouissement de la source (300-600 m) au moment de l'injection. L'étude de ce réseau fossile permet de définir les relations entre morphologie du réseau injecté et état de contraintes au moment de l'injection. Cette relation peut être extrapolée de façon à contraindre la morphologie des réseaux de subsurface au-delà de la visibilité sismique. (5) Les sables injectés dans des lithologies de faible perméabilité témoignent d'un épisode d'échappement de fluide important dans les bassins étudiés mais ont aussi guide les fluides longtemps après leur formation. Les injectites contribuent ainsi a l'initiation épisodique et la pérennisation de migrations de fluides dans les bassins sedimentaires. Le processus d'injection est associé a l'échappement brutal de fluides, résultant vraisemblablement d'un évènement tectonique et/ou sédimentaire important, et l'architecture des réseaux d'injectites est gouverné par les paléo-contraintes locales et les hétérogénéités de la roche hôte. Par conséquent, la caractérisation des réseaux d'injectites est une étape importante dans la compréhension de la plomberie des marges, c'est-a-dire l'évolution post-dépôt des bassins sédimentaires.
https://tel.archives-ouvertes.fr/tel-01011486

tel-01011486
https://tel.archives-ouvertes.fr/tel-01011486
https://tel.archives-ouvertes.fr/tel-01011486/document
https://tel.archives-ouvertes.fr/tel-01011486/file/These_Monnier_2013_banalisee.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We have discovered in a marine core, located 20 km east of the Coastal Range of Taiwan at the top of a 1200 m deep submarine high, sheltered from rivers discharges and gravitational flows, a 23 cm-thick anomalous sequence topped with broken bivalves and wood fragments. Based on radiocarbon dating, we distinguish five sub-events within ∼ 100 yrs, about 3000 years ago. The oldest four sub-events are interpreted as the record of local submarine landslides, likely triggered by clustered earthquakes that are common in this tectonically active area. The last event including shells and wood has a different origin. Despite the high level of climatic and tectonic recent activity, no comparable event has been observed at the same site since that time, making it unique during the last 3.75 ka. Hydrodynamical modeling stimulated with a set of submarine landslide-triggered tsunami sources and combined with the regional oceanic circulation dominated by the Kuroshio Current, allow us to better constrain the transport paths of the suspended material, the expected run-up at the coast, and ultimately the trigger and source that best fit our observations. The Kuroshio Current appears as a strong constraint that generally prevents cross-shore transport of suspended material even during a major tsunami. Since the largest aerial debris flow observed along the east coast of Taiwan during the last 4 ka was synchronous with the marine deposit, our preferred scenario starts with the occurrence of four distinct large earthquakes within less than a century, triggering both submarine and aerial landslides in the study area. Then, a giant typhoon reworked the nearshore material as well as the slided material stored upstream resulting in a debris flow. It deeply modified the surface current, allowing the wood debris and shells to fastly reach the core site.
ISSN: 0040-1951

hal-01467640
https://hal.archives-ouvertes.fr/hal-01467640
DOI : 10.1016/j.tecto.2015.11.001

Éditeur(s) : HAL CCSD l'Harmattan
Résumé : International audience
La Martinique constitue l'un des trois départements français d'outre-mer de la zone Caraïbe-Amérique. Cette société est marquée dans sa période contemporaine, par le dynamisme de ses formes culturelles et par un essor notable des médias de masse. Les mutations rapides qui la travaillent en profondeur sous l'effet des activités d'information et des phénomènes de communication invitent au renouvellement de l'approche des cultures et des identités. Comment envisager la place de la médiatisation dans la discussion publique sur l'identité martiniquaise? On observe les représentations de l'identité dans l'espace public martiniquais à partir de la sphère médiatique. On s'intéresse ici aux modalités de circulation des messages relatifs aux cultures quant à leur rôle dans les processus de construction identitaire. Cette approche permet d'interroger les relations qui existent entre journalistes, personnel politique et opinion publique ; elle ouvre la réflexion sur le sens que les acteurs donnent au message médiatisé et, l'usage qu'ils en font dans un espace social donné. Un contexte sociopolitique pesant L'espace public martiniquais reste encore marqué actuellement, par le contexte sociopolitique local fortement politisé des années 1960. Les discours politiques de l'époque s'articulent d'abord sur la nature des relations à la Métropole et posent la question du changement de statut pour le département d'outre-mer. Ils se structurent aussi autour de préoccupations culturelles et visent la conservation du patrimoine.
Paroles d'outre-mer. Identités linguistiques, expressions littéraires, espaces médiatiques
Saint-Denis (La Réunion), France

hal-01152955
https://hal.archives-ouvertes.fr/hal-01152955
https://hal.archives-ouvertes.fr/hal-01152955/document
https://hal.archives-ouvertes.fr/hal-01152955/file/Identites_et_medias.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Estrogens are known as steroid hormones affecting the brain in many different ways and a wealth of data now document effects on neurogenesis. Estrogens are provided by the periphery but can also be locally produced within the brain itself due to local aromatization of circulating androgens. Adult neurogenesis is described in all vertebrate species examined so far, but comparative investigations have brought to light differences between vertebrate groups. In teleost fishes, the neurogenic activity is spectacular and adult stem cells maintain their mitogenic activity in many proliferative areas within the brain. Fish are also quite unique because brain aromatase expression is limited to radial glia cells, the progenitor cells of adult fish brain. The zebrafish has emerged as an interesting vertebrate model to elucidate the cellular and molecular mechanisms of adult neurogenesis, and notably its modulation by steroids. The main objective of this review is to summarize data related to the functional link between estrogens production in the brain and neurogenesis in fish. First, we will demonstrate that the brain of zebrafish is an endogenous source of steroids and is directly targeted by local and/or peripheral steroids. Then, we will present data demonstrating the progenitor nature of radial glial cells in the brain of adult fish. Next, we will emphasize the role of estrogens in constitutive neurogenesis and its potential contribution to the regenerative neurogenesis. Finally, the negative impacts on neurogenesis of synthetic hormones used in contraceptive pills production and released in the aquatic environment will be discussed
ISSN: 0960-0760

hal-01174214
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01174214
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01174214/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01174214/file/Steroid%20modulation%20of%20neurogenesis.pdf
DOI : 10.1016/j.jsbmb.2015.06.011

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Demerara plateau, located offshore French Guiana and Suriname, is part of a passive transform continental margin particularly prone to develop slope instabilities, probably in relation to the presence of a free distal border along its steep continental slope. Slope failure occurred at different periods (Cretaceous to Neogene) and shows an overall retrogressive evolution through time. Upslope these failure headscarp, an enigmatic regional Mio-Pliocene unconformity has been discovered through the interpretation of new academic and industrial datasets. The aim of this work is to describe and understand the origin of this surface. Our analysis shows that this unconformity is made of a series of valleys that cross-cut sedimentary strata. Each one of these valleys has a short lateral extent and is closed along two perpendicular directions, which suggests that it could correspond to a highly meandering system, or to some sub-circular depressions. The infill of these features is equivalent to the regional stratigraphic strata found outside the structures, but in a subdued position. This seems to imply that the structures have originated by a local loss of sediments at their base or by sliding processes. Furthermore, these depressions intersect each other through time, while migrating progressively downslope.We discuss a series of hypotheses that try to explain the onset and evolution of these depressions forming the Mio-Pliocene unconformity (Canyons? Slope failures? Contourite moats? Hydrate pockmarks?). Having established that these structures are depressions formed by collapse, and have many similarities with structures recently described in the literature as pockmarks associated with gas hydrate dissolution, we favor this hypothesis.We propose that these hydrate pockmarks form with a mass failure that was triggered by fluid-overpressure development at the base of the hydrate stability zone.
ISSN: 0025-3227

hal-01365920
https://hal.archives-ouvertes.fr/hal-01365920
DOI : 10.1016/j.margeo.2015.04.001

Éditeur(s) : HAL CCSD IODP
Résumé : Integrated Ocean Drilling Program (IODP) Expedition 335 (14 April–4 June 2011) will be the fourth ocean cruise of the "Superfast" campaign to drill a deep hole into intact oceanic basement and will return to Ocean Drilling Program (ODP) Hole 1256D to deepen this scientific reference penetration a significant distance into cumulate gabbros. Cores and data recovered during the Superfast 4 expedition will provide hitherto unavailable observations that will test models of the accretion and evolution of the oceanic crust. Site 1256 was specifically located on oceanic crust that formed at a superfast spreading rate (>200 mm/y) to exploit the observed relationship between spreading rate and depth to axial low velocity zones, thought to be magma chambers, seismically imaged at active mid-ocean ridges. This was a deliberate strategy to reduce the drilling distance to gabbroic rocks because thick sequences of lavas and dikes have proved difficult to penetrate in past. ODP Leg 206 (2002) initiated operations at Site 1256, including the installation in Hole 1256D of a reentry cone with 16 inch casing inserted through the 250 m thick sedimentary cover and cemented into basement to facilitate deep drilling. The hole was then cored ~500 m into basement. IODP Expeditions 309 and 312 (2005) successfully completed the first sampling of an intact section of upper oceanic crust from lavas, through the sheeted dikes, and into the upper gabbros. Hole 1256D now penetrates >1500 meters below seafloor (mbsf) and >1250 m subbasement and currently resides in the dike–gabbro transition zone. The first gabbroic rocks were encountered at 1407 mbsf. Below this lies a ~100 m complex zone of fractionated gabbros intruded into contact metamorphosed dikes. Although previous cruises achieved the benchmark objective of reaching gabbro in intact ocean crust, critical scientific questions remain. These include the following: 1. Does the lower crust form by the recrystallization and subsidence of a high-level magma chamber (gabbro glacier), crustal accretion by intrusion of sills throughout the lower crust, or some other mechanism? 2. Is the plutonic crust cooled by conduction or hydrothermal circulation? 3. What is the geological nature of Layer 3 and the Layer 2/3 boundary at Site 1256? 4. What is the magnetic contribution of the lower crust to marine magnetic anomalies? Hole 1256D is poised at a depth where samples that should conclusively address these questions can be obtained, possibly with only a few hundred meters of drilling. Importantly, as of the end of Expedition 312, the hole was clear of debris and open to its full depth. Increased rates of penetration (1.2 m/h) and enhanced core recovery (>35%) in the gabbros indicate that this return to Hole 1256D could deepen the hole >300 m into plutonic rocks, past the transition from dikes to gabbro, and into a region of solely cumulate gabbroic rocks.
https://hal.archives-ouvertes.fr/hal-00564953

hal-00564953
https://hal.archives-ouvertes.fr/hal-00564953
DOI : 10.2204/iodp.sp.335.2010

Éditeur(s) : HAL CCSD Université des Antilles
Résumé : International audience
Political declarations and manuals to combat poverty occur while poverty is sustainable within our society. Then, economic and political leaders consider tourism as a tool for poverty reduction. Policies that judiciously use tourism must allow a catch-up in favor of the poorest.The article emphasizes the complexity of tourism and the need to take into account the tourism project in its entirety. The host territory is the support for tourist consumption which require specific improvements. But the distribution of revenues from tourism, the international movement and the final distribution of the profits must be considered across all local, national and international actors involved in the field of tourism.
Les déclarations politiques et les modes d’emploi destinés à combattre la pauvreté se succèdent tandis que la pauvreté s’inscrit durablement dans notre société. Désormais, les leaders politiques et économiques du moment considèrent le tourisme comme un outil privilégié pour réduire la pauvreté. Des politiques touristiques judicieuses doivent permettre un rattrapage économique en faveur des plus pauvres.L’article insiste sur la complexité du tourisme et la nécessité de prendre en compte le projet touristique dans sa globalité. Le territoire d’accueil est le support de consommations touristiques qui nécessitent des aménagements spécifiques. Mais la répartition des revenus du tourisme, la circulation internationale et la distribution finale des bénéfices doivent être considérées à l’échelle de tous les acteurs locaux, nationaux et internationaux qui interviennent dans le champ du tourisme.
ISSN: 1779-0980

Droits : http://creativecommons.org/licenses/by-nc/
hal-01368478
https://hal.univ-antilles.fr/hal-01368478
https://hal.univ-antilles.fr/hal-01368478/document
https://hal.univ-antilles.fr/hal-01368478/file/lorsque-le-tourisme-se-preoccupe-de-la-pauvrete.pdf

Éditeur(s) : HAL CCSD
Résumé : Time-series bathymetric data acquired between 1991 and 2011 have been used to evaluate the recent morphological evolution of the Nice upper continental slope (SE France, Ligurian Sea). Small-scale landslides lead to a retrogressive evolution of the continental shelf/upper slope transition but their frequency, size and impact are not well known. Mapping was undertaken to identify the morphology of landslide scarps and the location of the shelfbreak. Map comparisons were performed using ArcGIS “raster calculator”. Sediment remobilization on the upper slope (up to depths of 200 m) is fast and significant; landslide scars with volumes greater than 25,000 m3 can appear with a frequency less than 8 years. Shelfbreak migration toward the coastline can reach rates of 60 m over 7–8 years where the continental shelf is over 200 m wide. Furthermore, this quantitative analysis highlights alternations between periods of strongly erosive events and sedimentation periods. On the upper slope, eroded volumes can be multiplied by 10 during periods of enhanced landslide patterns (1999–2006). Such cycle-like landslide activity raises the issue of the triggering processes. On the Nice continental slope thick poorly consolidated beds rapidly deposited on a steep slope, earthquakes and rainfall leading to fresh water circulation below the shelf were identified as potential triggers. Our 4D bathymetric study suggests that over the last 20 years the greatest impacting factor may be freshwater outflows.
Engineering Geology for Society and Territory - Volume 4

hal-01218436
https://hal.archives-ouvertes.fr/hal-01218436
DOI : 10.1007/978-3-319-08660-6_42

Éditeur(s) : HAL CCSD Geological Society
Résumé : International audience
Palaeoclimate and sea-level studies commonly rely on interpretations based on depth. The location and quantity of core recovered during a drilling expedition has direct implications for subsequent applications of core measurements. A key objective of Integrated Ocean Drilling Program (IODP) Expedition 3 10 is to establish the course of postglacial sea-level rise for Tahiti in the South Pacific, for which assigning the correct depth to recovered core is fundamental. By convention, core is placed at the top of the core barrel run from which it was collected. Unless core recovery is 100%, this results in depth errors that are inversely proportional to the recovery. The difficulties of locating core are compounded for the Tahiti boreholes, where primary cavities in the carbonate reef successions are frequently present. Only through the integration of core with continuous geophysical measurements of the borehole can accurate depth positioning be achieved. High-resolution optical and acoustic images of the borehole wall allow effective visual correlation of the core and logging datasets. The final integrated depths form the underlying framework for all subsequent scientific analyses of recovered core employing evaluations that rely on depth. Furthermore, the integration process allows true core recoveries to be accurately estimated.
ISSN: 0016-7649

hal-00411915
https://hal.archives-ouvertes.fr/hal-00411915
DOI : 10.1144/0016-76492007-041

Éditeur(s) : Springer
Résumé : Series of sensitivity tests were performed with a z-coordinate, global eddy-permitting (1/4 degrees) ocean/sea-ice model (the ORCA-R025 model configuration developed for the DRAKKAR project) to carefully evaluate the impact of recent state-of-the-art numerical schemes on model solutions. The combination of an energy-enstrophy conserving (EEN) scheme for momentum advection with a partial step (PS) representation of the bottom topography yields significant improvements in the mean circulation. Well known biases in the representation of western boundary currents, such as in the Atlantic the detachment of the Gulf Stream, the path of the North Atlantic Current, the location of the Confluence, and the strength of the Zapiola Eddy in the south Atlantic, are partly corrected. Similar improvements are found in the Pacific, Indian, and Southern Oceans, and characteristics of the mean flow are generally much closer to observations. Comparisons with other state-of-the-art models show that the ORCA-R025 configuration generally performs better at similar resolution. In addition, the model solution is often comparable to solutions obtained at 1/6 or 1/10 degrees resolution in some aspects concerning mean flow patterns and distribution of eddy kinetic energy. Although the reasons for these improvements are not analyzed in detail in this paper, evidence is shown that the combination of EEN with PS reduces numerical noise near the bottom, which is likely to affect current-topography interactions in a systematic way. We conclude that significant corrections of the mean biases presently seen in general circulation model solutions at eddy-permitting resolution can still be expected from the development of numerical methods, which represent an alternative to increasing resolution.
Ocean Dynamics (1616-7341) (Springer), 2006-12 , Vol. 56 , N. 5-6 , P. 543-567

Droits : © Springer 2006. Part of Springer Science+Business Media
http://archimer.ifremer.fr/doc/2006/publication-3514.pdf
DOI:10.1007/s10236-006-0082-1
http://archimer.ifremer.fr/doc/00000/3514/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
ODP (Ocean Drilling Program)/IODP (Integrated Ocean Drilling Program) Site 1256 is located on the Cocos Plate in the Eastern Equatorial Pacific Ocean, in a 15 Ma old oceanic lithosphere formed at the EPR during a period of superfast spreading (>200 mm/yr). ODP/IODP Hole 1256D reached for the first time the contact between sheeted dikes and underlying gabbros. It consequently offers a unique opportunity to study in situ, in present-day oceanic crust, the root zone of the sheeted dike complex. This root zone is a thin, 100 m thick boundary layer between the magmatic system (i.e., the axial melt lens, similar to 1100 degrees C), and the overlying high temperature hydrothermal system (<= 450 degrees C). The understanding of interactions within this boundary layer is critical to that of crustal processes along mid-ocean ridges.;This work focuses on the petrophysical characterization of the root zone of the sheeted dike complex in order to further constrain the hydrothermal circulation system in the vicinity of the axial melt lens, as recorded in non-granoblastic dikes, granoblastic dikes, and varitextured gabbros. The petrophysical properties were determined from sample measurements in the laboratory and were compared to in situ downhole geophysical probing. The porosity structure is bipolar, depending on lithology, resulting in a layered system. Non-granoblastic dikes are generally altered in the greenschist fades (similar to>250 degrees C) with relatively high and interconnected (cementation index m similar to 1.72, electrical tortuosity tau similar to 28.3) porosity (1.5%). In contrast, gabbros are retrogressively metamorphosed in the amphibolite (similar to>450 degrees C) and greenschist facies, with lower porosity (1.3%) that involves numerous fissures and cracks, resulting in a more connected medium (m similar to 1.58, tau similar to 11.8) than non-granoblastic dikes. These cracks are more abundant but also tend to close with increasing depth as indicated in downhole geophysical data. Porosity and alteration, as viewed from surface electrical conductivity, appear to be directly correlated.
ISSN: 0040-1951

hal-00544556
https://hal.archives-ouvertes.fr/hal-00544556
DOI : 10.1016/j.tecto.2010.07.013

Éditeur(s) : HAL CCSD SpringerOpen
Résumé : The Karakorum Fault zone (KFZ) plays an important role in understanding the formation, evolvement and deformation of the Tibetan Plateau. The high-T dextral shearing metamorphic rocks, e.g., mylonites or mylonitized gneisses-granites, locally crop out along the southeastern part of the KFZ in the Ayila Ri'gyü Range area. The SHRIMP U-Pb dating of the syn-kinematic crystallized zircons indicates that the initial age of the KFZ is ∼27 Ma, ∼10 Ma older than previous results. The extensive high-T dextral shearing along the KFZ started at least at 27–20 Ma, accompanied by the syn-kinematic emplacement of leuco-granites. Deformation and concomitant fluid circulation during shearing most likely occurred as early as at 25–13 Ma. The KFZ probably grew from southeast to northwest along the fault as a result of continuous convergence between the India plate and Eurasia plate.
ISSN: 1001-6538

hal-00406402
https://hal.archives-ouvertes.fr/hal-00406402
DOI : 10.1007/s11434-007-0164-6

Éditeur(s) : Amer Meteorological Soc
Résumé : The Congo River has the second largest rate of flow in the world and is mainly responsible for the broad tongue of low-salinity water that is observed in the Gulf of Guinea. Despite their importance, near-equatorial river plumes have not been studied as thoroughly as midlatitude plumes and their dynamics remain unclear. Using both theory and idealized numerical experiments that reproduce the major characteristics of the region, the authors have investigated the dynamics of the Congo River plume and examine its sensitivity to different forcing mechanisms. It is found that near-equatorial plumes are more likely to be surface trapped than midlatitude plumes, and the importance of the effect in describing the strong offshore extent of the low-salinity tongue during most of the year is demonstrated. It is shown that the buoyant plume constrained by the geomorphology is subject to the pulling of nonlinear structures and wavelike equatorial dynamics. The wind is found to strengthen the intrinsic buoyancy-driven dynamics and impede the development of the coastal southward current, in coherence with observations.
Journal Of Physical Oceanography (0022-3670) (Amer Meteorological Soc), 2014-03 , Vol. 44 , N. 3 , P. 980-994

Droits : 2014 American Meteorological Society
http://archimer.ifremer.fr/doc/00187/29850/28298.pdf
DOI:10.1175/JPO-D-13-0132.1
http://archimer.ifremer.fr/doc/00187/29850/

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
We analyse the fluid flow regime within sediments on the Eastern levee of the modern Mississippi Canyon using 3D seismic data and downhole logging data acquired at Sites U1322 and U1324 during the 2005 Integrated Ocean Drilling Program (IODP) Expedition 308 in the Gulf of Mexico. Sulphate and methane concentrations in pore water show that sulphate-methane transition zone, at 74 and 94 m below seafloor, are amongst the deepest ever found in a sedimentary basin. This is in part due to a basinward fluid flow in a buried turbiditic channel (Blue Unit, 1000 mbsf), which separates sedimentary compartments located below and above this unit, preventing normal upward methane flux to the seafloor. Overpressure in the lower compartment leads to episodic and focused fluid migration through deep conduits that bypass the upper compartment, forming mud volcanoes at the seabed. This may also favour seawater circulation and we interpret the deep sulphate-methane transition zones as a result of high downward sulphate fluxes coming from seawater that are about 5-10 times above those measured in other basins. The results show that geochemical reactions within shallow sediments are dominated by seawater downwelling in the Mars-Ursa basin, compared to other basins in which the upward fluid flux is controlling methane-related reactions. This has implications for the occurrence of gas hydrates in the subsurface and is evidence of the active connection between buried sediments and the water column.
ISSN: 1468-8115

hal-00590501
https://hal.archives-ouvertes.fr/hal-00590501
DOI : 10.1111/j.1468-8123.2010.00304.x

Éditeur(s) : HAL CCSD Presses universitaires du sport
Résumé : International audience
The institutional changes interrogate the structuration of the collective organisation modalities in particular in the development of sports practices for disabled people. The phenomenon of circularity between global and local logics has to be taken into account in the analysis of institutions and gives to these ones a multidimensional character (Fossier & Monet, 2009). This work studies various local modalities of organization to enlighten foreground institutional stakes which are in process. For that purpose, we made a compared historical monograph of two Guadeloupians associations which develop sports practices for the physical disabled people. The hypothesis would be that these various Handisport organizations do not aim the same object to be established. The characteristics of these associations show that through the modalities of organization deceive underground divergent institutional stakes in particular about the definition of social places of physical disabled people.
Les transformations institutionnelles questionnent la structuration des modes d’organisation collective notamment dans le développement des pratiques sportives pour les personnes handicapées. Le phénomène de circularité entre des logiques globales et des logiques locales est à prendre en compte dans l’analyse des institutions et donne à ces dernières un caractère multidimensionnel (Fossier & Monet, 2009). Ce travail se propose d’étudier différents modes d’organisation locaux afin de faire émerger les enjeux institutionnels sous-jacents qui sont à l’oeuvre. Pour cela, nous avons effectué une monographie historique comparée de deux associations guadeloupéennes qui développent les pratiques sportives à l’intention des personnes déficientes physiques. L’hypothèse de travail est que ces différentes organisations Handisport ne visent pas le même objet à instituer. Les caractéristiques de ces associations montrent qu’à travers les modes d’organisation se dévoilent des enjeux institutionnels divergents qui portent notamment sur la définition des places sociales des personnes handicapées physiques.
ISSN: 1297-8019

hal-01681887
https://hal.archives-ouvertes.fr/hal-01681887

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Most of the Mediterranean coastal porous aquifers are intensively exploited. Because of climatic and anthropogenic effects, understanding the physical and geological controls on groundwater distribution and flow dynamics in such aquifers is crucial. This study presents the results of a structural investigation of a system located along the coastline of the Gulf of Lions (NW Mediterranean). A key aspect of this study relies on an onshore-offshore integrated approach combining outcrops, seismic profiles, and borehole data analysis. This multidisciplinary approach provides constraints on pore-fluid salinity distribution and stratigraphic organization, which are crucial in assessing the modes of groundwater/seawater exchanges. Onshore, Lower Pliocene deposits dip gently seaward. They are unconformably overlain by Holocene clays in the lagoons. Offshore the Pliocene deposits either outcrop at the seabed or are buried below nonconsolidated sands infilling paleo-valleys. Beneath the lido, the groundwater salinity distribution consists of salty pore water, overlying fresher pore water. Active circulation of groundwater masses is inferred from the geophysical results. In particular, offshore outcrops and paleo-valleys may play an important role in salt water intrusion.
ISSN: 0017-467X

halsde-00866825
https://hal.archives-ouvertes.fr/halsde-00866825
DOI : 10.1111/j.1745-6584.2012.01011.x

Éditeur(s) : HAL CCSD Frontiers Media
Résumé : The disease, Heartwater, caused by the Anaplasmataceae E. ruminantium, represents a major problem for tropical livestock and wild ruminants. Up to now, no effective vaccine has been available due to a limited cross protection of vaccinal strains on field strains and a high genetic diversity of Ehrlichia ruminantium within geographical locations. To address this issue, we inferred the genetic diversity and population structure of 194 E. ruminantium isolates circulating worldwide using Multilocus Sequence Typing based on lipA, lipB, secY, sodB, and sucA genes. Phylogenetic trees and networks were generated using BEAST and SplitsTree, respectively, and recombination between the different genetic groups was tested using the PHI test for recombination. Our study reveals the repeated occurrence of recombination between E. ruminantium strains, suggesting that it may occur frequently in the genome and has likely played an important role in the maintenance of genetic diversity and the evolution of E. ruminantium. Despite the unclear phylogeny and phylogeography, E. ruminantium isolates are clustered into two main groups: Group 1 (West Africa) and a Group 2 (worldwide) which is represented by West, East, and Southern Africa, Indian Ocean, and Caribbean strains. Some sequence types are common between West Africa and Caribbean and between Southern Africa and Indian Ocean strains. These common sequence types highlight two main introduction events due to the movement of cattle: from West Africa to Caribbean and from Southern Africa to the Indian Ocean islands. Due to the long branch lengths between Group 1 and Group 2, and the propensity for recombination between these groups, it seems that the West African clusters of Subgroup 2 arrived there more recently than the original divergence of the two groups, possibly with the original waves of domesticated ruminants that spread across the African continent several thousand years ago.
ISSN: 2235-2988

hal-01594501
https://hal.archives-ouvertes.fr/hal-01594501
https://hal.archives-ouvertes.fr/hal-01594501/document
https://hal.archives-ouvertes.fr/hal-01594501/file/paper_MLST_ER_2016_%7B51027B58-C2C7-41C8-9746-BD8A9F387C87%7D.pdf
DOI : 10.3389/fcimb.2016.00111

Éditeur(s) : Elsevier Sci Ltd
Résumé : The eastern Demerara Plateau offshore French Guiana was surveyed in 2003 during the GUYAPLAC cruise (multibeam bathymetry and acoustic imagery, 6-channel seismic reflection and 3.5 kHz echo-sounding). The data show the "post-transform" Cenozoic that the series located on the outer part of the plateau (below c. 2000 m) contain at least twelve stacked mass transport deposits (MTDs) that have recorded a history of large-scale slope failure, as well as two main normal fault sets that provide possible pathways for upward fluid migration through the series, reaching at high as the uppermost MTDs. Seabed data show that the area above the failures is characterized by circular-to-elongate (slope-parallel) depressions interpreted as fluid seeps (pockmarks), some of them have been modified by along slope currents. We suggest that the development of the MTDs to results from the combinaiton of the presence of fluid overpressure at depth the geometry of the margin's deep structure, in particular the existence of a 'free borderlateral border' on the outermost plateau. Our results also emphasise the role of stratigraphic decollements within the Cenozoic series.
Marine And Petroleum Geology (0264-8172) (Elsevier Sci Ltd), 2013-09 , Vol. 46 , P. 287-303

Droits : 2013 Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00157/26850/25316.pdf
DOI:10.1016/j.marpetgeo.2013.06.010
http://archimer.ifremer.fr/doc/00157/26850/

Éditeur(s) : Amer Geophysical Union
Résumé : Hydrographic (0-1000 dbar) and direct current measurements (0-600 dbar) along 165-degrees-E (20-degrees-S-10-degrees-N) between January 1984 and July 1991 are used to investigate the mean circulation and its relationships with the distributions of salinity and potential vorticity on isopycnal surfaces. Less well documented mean sections along 142-degrees-E and 137-degrees-E are used to complement the 165-degrees-E analysis. The Equatorial Undercurrent is centered on the equator at 165-degrees-E and on 0.5-degrees-N at 142-degrees-E. No variation in its transport (15.0 x 10(6) m3 s-1) is found between those longitudes. We find indication of the Equatorial Undercurrent at 137-degrees-E-0.75-degrees-N in the geostrophic field. The northern and southern Subsurface Countercurrents are clearly identified by extrema of eastward velocity at 165-degrees-E around 3-degrees-N and 3-degrees-S (250 dbar). No evidence of a southern Subsurface Countercurrent is found at 142-degrees-E. At 137-degrees-E the northern Subsurface Countercurrent is not characterized by a local extrema of eastward velocity: the North Equatorial Countercurrent seems to extend from the surface to 400 dbar with a southward shift of its core. Analysis of the seasonal variability at 165-degrees-E indicates that the Equatorial Undercurrent transport increases by a factor 2 between January (10.7 x 10(6) m3 s-1) and July (21.5 x 10(6) m3 s-1) and the Equatorial Intermediate Current transport is halved (6.3 x 10(6) m3 s-1 in January, 3.5 x 10(6) m3 s-1 in July). hi contrast, the transport of the Subsurface Countercurrents does not vary substantially between those two months. The meridional distributions of salinity and potential vorticity show that the axes of the main eastward currents are associated with strong meridional property gradients, not with property extrema. The eastward currents thus represent a barrier to the northward extension of the high salinity Tropical Water. Relatively weak meridional gradients of salinity and potential vorticity are observed in the westward directed South Equatorial Current and Equatorial Intermediate Current.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 1993-12 , Vol. 98 , N. C12 , P. 22495-22520

Droits : 1993 by the American Geophysical Union.
http://archimer.ifremer.fr/doc/00192/30346/29190.pdf
DOI:10.1029/93JC02513
http://archimer.ifremer.fr/doc/00192/30346/

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : We report rare earth element (REE) and neodymium (Nd) isotope data for the organic fraction of sediments collected from various depositional environments, i.e. rivers (n=25), estuaries (n=18), open-ocean settings (n=15), and cold seeps (n=12). Sedimentary Organic Matter (SOM) was extracted using a mixed hydrogen peroxide/nitric acid solution (20%-H2O2 – 0.02M-HNO3), after removal of carbonate and oxy-hydroxide phases with dilute hydrochloric acid (0.25M-HCl). A series of experimental tests indicate that extraction of sedimentary organic compounds using H202 may be complicated occasionally by partial dissolution of sulphide minerals and residual carbonates. However, this contamination is expected to be minor for REE because measured concentrations in H2O2 leachates are about two-orders of magnitude higher than in the above mentioned phases. The mean REE concentrations determined in the H2O2 leachates for samples from rivers, estuaries, coastal seas and open-ocean settings yield relatively similar levels, with ΣREE = 109 ± 86 ppm (mean ± s; n=58). The organic fractions leached from cold seep sediments display even higher concentration levels (285 ± 150 ppm; mean ± s; n=12). The H2O2 leachates for most sediments exhibit remarkably similar shale-normalized REE patterns, all characterized by a mid-REE enrichment compared to the other REE. This suggests that the distribution of REE in leached sedimentary organic phases is controlled primarily by biogeochemical processes, rather than by the composition of the source from which they derive (e.g. pore, river or sea- water). The Nd isotopic compositions for organic phases leached from river sediments are very similar to those for the corresponding detrital fractions. In contrast, the SOM extracted from marine sediments display εNd values that typically range between the εNd signatures for terrestrial organic matter (inferred from the analysis of the sedimentary detrital fractions) and marine organic matter (inferred from the analysis of local surface seawater). A notable exception is the case of organic matter (OM) fractions leached from cold seep sediment samples, which sometimes exhibit εNd values markedly different from both terrigenous and surface seawater signatures. This suggests that a significant fraction of organic compounds in these sediments may be derived from chemosynthetic processes, recycling pore water REE characterized by a distinct isotopic composition. Overall, our results confirm that organic matter probably plays an important role in the oceanic REE budget, through direct scavenging and remineralization within the water column. Both the high REE abundances and the shape of shale-normalized patterns for leached SOM also suggest that OM degradation in sub-surface marine sediments during early diagenesis could control, to a large extent, the distribution of REE in pore waters. Benthic fluxes of organic-bound REE could hence substantially contribute to the exchange processes between particulates and seawater that take place at ocean margins. Neodymium isotopes could provide useful information for tracing the origin (terrestrial versus marine) and geographical provenance of organic matter, with potential applications in paleoceanography. In particular, future studies should further investigate the potential of Nd isotopes in organic compounds preserved in sedimentary records for reconstructing past variations of surface ocean circulation.
Geochimica Et Cosmochimica Acta (0016-7037) (Pergamon-elsevier Science Ltd), 2014-09 , Vol. 140 , P. 177-198

Droits : 2014 Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00191/30250/28682.pdf
DOI:10.1016/j.gca.2014.05.016
http://archimer.ifremer.fr/doc/00191/30250/