Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
During the GWADASEIS cruise (Lesser Antilles volcanic arc, February-March 2009) a very high resolution (VHR) seismic-reflection survey was performed in order to constrain Late Quaternary to Present faulting. The profiles we obtained evidence frequent "ponding" of reworked sediments in the deepest areas, similar to the deposition of Mediterranean "homogenites". These bodies are acoustically transparent (few ms t.w.t. thick) and are often deposited on the hanging walls of dominantly normal faults, at the base of scarps. Their thickness appears sufficient to compensate (i.e. bury) co-seismic scarps between successive earthquakes, resulting in a flat and horizontal sea floor through time. In a selected area (offshore Montserrat and Nevis islands), piston coring (4 to 7 m long) was dedicated to a sedimentological analysis of the most recent of these particular layers. It corresponds to non-stratified homogenous calcareous silty sand (reworked calcareous plankton and minor volcanoclastics). This layer can be up to 2 m thick, and overlies finegrained hemipelagites. The upper centimeters of the latter represent the normal RedOx water/sediment interface. 210Pb and 137Cs activities lack in the massive sands, while a normal profile of unsupported 210Pb decrease is observed in the hemipelagite below, together with a 137Cs peak correspond- ing to the Atmospheric Nuclear Experiments (1962). The RedOx level was thus capped by a recent instantaneous major sedimentary event considered as post-1970 AD; candidate seismic events to explain this sedimentary deposits are either the 16 March 1985 earthquake or the 8 October 1974 one (Mw=6.3 and Mw=7.4, respectively). This leads to consider that the syntectonic sedimentation in this area is not continuous but results from accumulation of thick homogenites deposited after the earthquakes (as observed in the following weeks after Haiti January 2010 event, McHugh et al., 2011). The existence of such deposits suggests that, in the area of study, vertical throw likely results from cumulated effects of separated earthquakes rather than from aseismic creep. Examination of VHR profiles shows that all major co-seismic offsets are recorded in the fault growth sequence and that co-seismic offsets can be precisely estimated. By using a sedimentation rate deduced from 210Pb decrease curve (0.5 mm yr−1) and taking into account minor reworking events detected in cores, we show that the Redonda system may have been responsible for five >M6 events during the last 34 000 yr. The approach presented in this work differs from fault activity analyses using displaced sets of isochronous surfaces and postulating co-seismic offsets. Combining VHR seismic imagery and coring we can decipher co-seismic vs. slow continuous displacement, and thus actually estimate the amplitude and the time distribution of major co-seismic offsets.
ISSN: 1561-8633

insu-00844581
https://hal-insu.archives-ouvertes.fr/insu-00844581
https://hal-insu.archives-ouvertes.fr/insu-00844581/document
https://hal-insu.archives-ouvertes.fr/insu-00844581/file/nhess-12-1755-2012.pdf
DOI : 10.5194/nhess-12-1755-2012

Éditeur(s) : HAL CCSD
Résumé : National audience
Objectives To define the different stages of spontaneous labour. To determine the indications, modalities of use and the effects of administering synthetic oxytocin. And to describe undesirable maternal and perinatal outcomes associated with the use of synthetic oxytocin. Method A systematic review was carried out by searching Medline database and websites of obstetrics learned societies until March 2016. Results The 1st stage of labor is divided in a latence phase and an active phase, which switch at 5 cm of cervical dilatation. Rate of cervical dilatation is considered as abnormal below 1 cm per 4 hour during the first part of the active phase, and blow 1 cm per 2 hours above 7 cm of dilatation. During the latent phase of the first stage of labor, i.e. before 5 cm of cervical dilatation, it is recommended that an amniotomy not be performed routinely and not to use oxytocin systematically. It is not recommended to expect the active phase of labor to start the epidural analgesia if patient requires it. If early epidural analgesia was performed, the administration of oxytocin must not be systematic. If dystocia during the active phase, an amniotomy is recommended in first-line treatment. In the absence of an improvement within an hour, oxytocin should be administrating. However, in the case of an extension of the second stage beyond 2 hours, it is recommended to administer oxytocin to correct a lack of progress of the presentation. If dynamic dystocia, it is recommended to start initial doses of oxytocin at 2 mUI/min, to respect at least 30 min intervals between increases in oxytocin doses delivered, and to increase oxytocin doses by 2 mUI/min intervals without surpassing a maximum IV flow rate of 20 mUI/min. The reported maternal adverse effects concern uterine hyper-stimulation, uterine rupture and postpartum haemorrhage, and those of neonatal adverse effects concern foetal heart rate anomalies associated with uterine hyper-stimulation, neonatal morbidity and mortality, neonatal jaundice, weak suck/poor breastfeeding latch and autism. Conclusion The widespread use of oxytocin during spontaneous labour must not be considered as simply another inoffensive prescription without any possible deleterious consequences for mother or foetus. Conditions for administering the oxytocin must therefore respect medical protocols. Indications and patient consent have to be report in the medical file. © 2016 Elsevier Masson SAS
Revue Sage - Femme

hal-01467543
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01467543
DOI : 10.1016/j.sagf.2016.11.006

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Multi-proxy analysis of two marine sediment cores (MS27PT and MD04-2726) from the Nile continental slope provides evidence of changes in Nile sediment discharge related to changes in Ethiopian African Monsoon (EAM) precipitation, and allows us to reconstruct changes in Nile River runoff, vegetation and erosion in the Nile headwaters. Sediment element composition and neodymium isotopic composition reveal significant changes in clastic sediment provenance, with sources oscillating between a Saharan aeolian contribution during the Last Glacial Maximum/deglacial transition and during the Late Holocene, and a Blue/Atbara Nile fluvial contribution during the African Humid Period (AHP). This study provides a new understanding of past environmental changes. Between 14.6 and 14.13 ka there was a major input of sediments from the Ethiopian Highlands, consistent with a stronger EAM at that time. Climate in the Nile basin was wetter between 14.8 and 8.4 ka, with a corresponding increase in Blue Nile water and sediment discharge via the main Nile into the Eastern Mediterranean. The gradual climatic transition from the AHP to the present-day dry climate was reflected in a decrease in Blue Nile sediment deposition and flood discharge between 8.4 and 3.7 ka, with aridity at a maximum between 3.7 and 2.6 ka. The onset of drier conditions in the Blue Nile basin seems to have begun before the 8.2 ka cooling event in the North Atlantic. We speculate that the climatic change from the wet AHP to the dry late Holocene may have been a result of a break in the low latitude dynamic equilibrium between climate, vegetation and erosion, which may in turn have affected the climate in higher latitudes. Reduced Nile flow may also have had an impact on Levantine Intermediate Water originating in the Eastern Mediterranean through an increase in intermediate water formation.
ISSN: 0277-3791

hal-01277950
https://hal.archives-ouvertes.fr/hal-01277950
DOI : 10.1016/j.quascirev.2015.10.030

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 Blackwell Publishing
Résumé : International audience
In the Causses platform (south-east France), Late Hettangian to Sinemurian deposits were interpreted previously as shallow-water carbonate ramp deposits. A new look at these deposits has shown a fault-controlled mosaic carbonate platform that is different from the carbonate ramp models. Within the platform mosaic, 15 lithofacies have been recognized, which are organized in four facies associations, including peritidal, restricted shallow sub-tidal, sand dunes and sub-tidal shelf facies associations. The rapid lateral and vertical facies changes, and the lack of consistent landward or seaward direction indicated by the pattern of facies changes, question the existence of a shoreline suggested by the traditional models for this region. Instead, the facies organization and cycle stacking pattern suggest deposition in a mosaic of intertidal islands between which sub-tidal restricted or open conditions could coexist in very close proximity. Such a platform mosaic would have been defined by tectonic activities along normal faults which segmented the shallow-water Causses platform. The facies and facies associations are arranged into metre-scale, peritidal and sub-tidal cycles that are also variable. Certain cycles show the same stacking pattern in all the sections and seem to be traceable over tens of kilometres. On the contrary, other cycles cannot be correlated; they are present only in specific sections and have a maximum lateral extension of 1 or 2 km. These metre-scale cycles stack to form four medium-scale cycles bounded by surfaces that display sub-aerial exposure features. Medium-scale cycles stack into two larger-scale cycles (tens of metres thick) and are bounded by well-defined karstic surfaces. Based on their lateral continuity and their stacking pattern, the metre-scale cycles are controlled probably by high frequency eustatic variations overprinting the topographic irregularities formed by differential subsidence of fault-bounded blocks. Episodic fault activities may reorganize the topography so that, even if eustatic changes may still be the major control of cycles, the expression and number of cycles could be different. Cycles of medium and large-scale are interpreted as being allogenic, controlled by changes in eustasy and/or subsidence rates as evidenced by their lateral continuity and the correlations of the large-scale cycles with third-order depositional sequences.
ISSN: 1469-3496

hal-00411940
https://hal.archives-ouvertes.fr/hal-00411940
DOI : 10.1111/j.1365-3091.2007.00896.x

Éditeur(s) : Edp Sciences S A
Résumé : The present work examines the usefulness of the combination of multivariate analyses and further one-way analysis of variance in the search for links between causes and effects in heterologous stimulation of spawning in fish. Stimulations with both 20 and 50 mu g . kg(-1) doses of [D Trp(6)] luteinizing hormone-releasing hormone analogue (LH-RHa) were effective in inducing and synchronizing spawning of red drum, Sciaenops ocellatus. Oocyte development monitoring using ovarian biopsy allowed treatment injections at different stages of maturation. The influence at stimulation time of female oocyte development state upon further development was shown. An interesting potential of second stimulation, leading to high quality spawns, was established and factors of success were identified. The best conditions for stimulation success were simultaneously late stage of oocyte development characterized by the beginning of oil droplet coalescence, high ovarian homogeneity quoted by the proportion of most developed oocytes in the biopsy sample, and low dose of hormone (20 mu g . kg(-1)) for both first and second stimulations.
Ce travail examine l’intérêt de la combinaison d’analyses multivariées et de l’analyse de variance à un facteur pour la recherche de liens au sein d’expérimentations aquacoles faisant intervenir une diversité de causes et d’effets. L’injection de l’analogue [D Trp6] de la gonado-libérine (LH-RHa) est efficace aux doses de 20 et 50 íg×kg–1 pour provoquer et synchroniser les pontes chez l’ombrine, Sciaenops ocellatus. Un suivi du développement ovocytaire par biopsie ovarienne permet en outre de réaliser des injections à différents stades de maturation et l’influence du stade ovocytaire de la femelle, au moment de la stimulation sur la qualité de la ponte, est ainsi mise en évidence. Un potentiel intéressant suite à une seconde stimulation aboutissant à des pontes de qualité, est établi et des facteurs de réussite sont identifiés. Les meilleures conditions pour le succès de la stimulation sont simultanément : le dernier stade de développement ovocytaire, caractérisé par le début de coalescence de la gouttelette lipidique, la forte homogénéité ovarienne représentant la proportion des ovocytes les plus développés au sein de l’échantillon obtenu par biopsie, la faible dose hormonale (20 íg×kg–1) à la fois pour les premières et les secondes stimulations.
Aquatic Living Resources (0990-7440) (Edp Sciences S A), 2000-01 , Vol. 13 , N. 1 , P. 19-27

Droits : 2000 Ifremer/Cnrs/Inra/Ird/Cemagref/Éditions scientifiques et médicales Elsevier SAS. All rights reserved
http://archimer.ifremer.fr/doc/00187/29875/28361.pdf
DOI:10.1016/S0990-7440(00)00137-6
http://archimer.ifremer.fr/doc/00187/29875/

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : International audience
The central part of the Gulf of Lions shoreline is characterized by many coastal wetlands that resulted from the interaction between a process of shoreline regularization by migrations of littoral barriers and a slow filling of the back-barrier areas by the riverine and marine inputs. Analyses of Late-Holocene deposits with a very high-resolution multi-proxy study of two sediment cores, allow us to reconstruct the evolution of this coastal system. Two main Holocene sediment units are identified overlying a Pliocene carbonate continental formation. The lower unit consists of sandy and pebbly marine sediments deposited around 7800 B.P., during the final stand of the last sea level rise. Just above, the upper unit displays lagoonal grey clay silts with shells and some intercalated layers of silty sands related to paleostorm events. The age model was established from radiocarbon dating, for the oldest part of the core. Over the last century, sedimentation rates were calculated using the CFCS Pb-210 model, together with Cs-137 data. Radiocarbon data show an increase in he accumulation rate from the base to the top of cores. Marine sand units related to the last transgressive deposit allow to refine the curve of Holocene post-glacial sea level rise. Sedimentological and faunal analyses associated with chronological data provide a means for reconstructing the Late-Holocene paleoenvironments along this part of the coast and suggest that the final closure of the coastal lagoon by the sandy barrier occurred at around 730 +/- 120 yr cal B.P. The beginning of this closure, together with the progradation of the coastal plain, could be responsible for the decline in economic activity of the Lattara harbour during the Roman period.
La partie centrale du littoral du golfe du Lion est caractérisée par de nombreuses lagunes qui résultent de l'interaction entre un processus de régularisation du trait de côte par migration de barrières littorales et d'un lent remplissage des zones situées en arrière des barrières par des apports continentaux et marins. Les analyses des dépôts tardi-holocènes avec une étude multi-traceurs à très haute résolution de deux carottes sédimentaires nous permettent de reconstruire l'évolution de ce système côtier. Deux unités sédimentaires holocènes sont identifiées recouvrant une formation pliocène carbonatée. L'unité inférieure est constituée de sables et de galets d'origine marine déposés vers 7800 B.P., durant les stades ultimes de la dernière remontée marine. Audessus, l'unité supérieure montre des dépôts d'argile et de silt gris coquilliers d'origine lagunaire, dans lesquels sont intercalés des niveaux de sable silteux révélant la présence d'événements de tempêtes. Le modèle d'âge est établi à partir de dates radiocarbones pour les parties les plus anciennes des archives sédimentaires, tandis que pour le dernier siècle, les taux de sédimentation sont calculés en utilisant le modèle CFCS pour le 210Pb, associé aux données de 137Cs. Les données 14C montrent une augmentation du taux d'accumulation depuis la base jusqu'en surface des carottes. Les unités de sables marins liées aux dépôts de la dernière transgression marine permettent de préciser la courbe post-glaciaire de remontée du niveau marin. Les analyses sédimentologiques et faunistiques associées aux données chronologiques fournissent une méthode permettant de reconstituer les paléoenvironnements littoraux tardi-holocènes dans la zone d'étude et suggèrent que la fermeture finale de ces lagunes par le cordon sableux survient autour de 730 ± 120 ans cal B.P. Le début de cette fermeture, associée à la une progradation deltaïque, pourrait être responsable du déclin des activités économiques du port de Lattara durant la période Romaine.
EISSN: 1777-5817

halshs-00740923
https://halshs.archives-ouvertes.fr/halshs-00740923
DOI : 10.2113/gssgfbull.181.1.27

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We use 3-D mechanical modeling representing faults as planar surfaces with frictional properties that obey Coulomb-failure process to explore the long-term slip rates of the Altyn Tagh fault and Kunlun faults in the north Tibetan plateau. Crustal theology is simplified as an elastoplastic upper crust and a viscoelastic lower crust. Far-field GPS velocities and late Quaternary fault slip rates are used to constrain the model results. Rheological tests show that effective fault friction lower than 0.1-0.08 leads to high slip rates that fit with geologically and geodetically determined slip rates of the Kunlun fault (10-11.7 +/- 1.5 mm/yr). Meanwhile, the modeled Altyn Tagh fault reaches slip rates similar to 13.7 mm/yr to similar to 7.8 mm/yr in its central portion, between ranges of the geological slip rates. Associated with high slip rates, our model predicts that central Tibet (similar to 84 degrees E-95 degrees E) from the Altyn Tagh fault to the north of the Himalayan arc accommodates north-south shortening and east-west extension rates of similar to 10-12 mm/yr and similar to 8-10 mm/yr, respectively. We also question the widely accepted idea that interseismic strain is driven at the base of the seismogenic zone by a screw dislocation. If this assumption fails, the presented model implies that interseismic strain around large strike-slip faults could be distributed in a much broader way if the lithosphere deforms as a thin elastic plate rather than an elastic half-space with an embedded dislocation. If this distributed deformation is ignored, and the instantaneous surface deformation field modeled as that resulting from slip on a dislocation below a specified depth embedded in an elastic half-space, the estimated slip rate will inevitably be lower than the true long-term slip rate. This appears to explain why geodetic slip rates proposed for the Altyn Tagh fault (510 mm/yr) are lower than some of the geological slip rates. (C) 2008 Elsevier B.V. All rights reserved.
ISSN: 0012-821X

hal-00411926
https://hal.archives-ouvertes.fr/hal-00411926
DOI : 10.1016/j.epsl.2008.06.049

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Iranian plateau is a flat ~ 1.5–2 km high plateau thought to result from the collision between the Arabian and Eurasian plates since ~ 30 ± 5 Ma, and may represent a young analogue to the so far better studied Tibetan plateau. In order to constrain the exhumation history of the internal Zagros and of the Iranian plateau, we herein present apatite (U-Th)/He (AHe) and apatite (AFT) and zircon fission-track (ZFT) data on plutonic rocks from the Sanandaj–Sirjan Zone (SSZ), Urumieh–Dokhtar magmatic arc (UDMA), Central Iran and Kopet Dagh. Thermochronologic data show that the SSZ was exhumed early in the collision process (essentially before 25–20 Ma), with a likely acceleration of cooling during the late Eocene, from 0.04 to 0.3 mm/year. Results suggest that cooling of the internal Zagros migrated from the SSZ to the UDMA during a more mature stage of the continental collision, after ~ 17 Ma (i.e., coeval with the outward propagation of deformation and topography fronts in the external Zagros). Constant exhumation rates in the UDMA (~ 0.3 mm/year) suggest that no significant variation of erosion rates occurred since the onset of continental collision. In Central Iran, the overlap of ZFT, AFT and AHe ages from gneissic samples points to rapid cooling during the late Eocene (~ 42 °C/Myr), which is consistent with previous reports on the formation of Eocene metamorphic core-complexes.
ISSN: 0024-4937

hal-01115691
https://hal.archives-ouvertes.fr/hal-01115691
DOI : 10.1016/j.lithos.2014.07.021

Éditeur(s) : HAL CCSD
Résumé : National audience
This note present the results of a test pits archaeological operation conducted in 2001 on the Anse Couleuvre multi-componant pre-Columbian site located in north Martinique. This site for a major part destroyed by natural erosion is composed by component linked to Middle/Late Cedrosan Saladoid and Suazan Troumassoid sub-series.
Cette note présente le bilan d'une opération de sondage menée en 2001 sur le site précolombien à occupations multiples de l'Anse Couleuvre à l'extrémité nord de la Martinique. Ce gisement largement détruit par l'érosion naturelle présente des composantes rattachées au Saladoïde cedrosan moyen/récent et au Troumassoïde suazan.
Bilan scientifique de la région Martinique

hal-00967576
https://hal.univ-antilles.fr/hal-00967576
https://hal.univ-antilles.fr/hal-00967576/document
https://hal.univ-antilles.fr/hal-00967576/file/bilancoul2001.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Understanding long-term variability in the frequency of intense storm activity is important for assessing whether changes are controlled by climate evolution. Understanding this variability is also important for predicting present and future community vulnerability and economic loss. Our ability to make these assessments has been limited by the short (less than 50 years) instrument record of storm activity. Storm-induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and storm activity on longer timescales. In this study, we present a record of these extreme climatic events that have occurred in the French Mediterrannean coast over the past 1500 years. The identification of these extreme events is based on the analysis of sediment cores from Gulf of Aigues-Mortes lagoons that contain a specific sedimentary and geochemical signature associated with intense storms.;Overwash deposits do not show any evidence of intense storm landfalls in the region for several hundred years prior to the late 17th century A.D. The apparent increase in intense storms around 250 years ago occurs during the latter half of the Little Ice Age, a time of lower continental surface temperatures. Comparison of the sediment record with palaeoclimate records indicates that this variability was probably modulated by atmospheric dynamics. The apparent increase of the superstorm activity during the latter half of the Little Ice Age was probably due to the thermal gradient increase leading to enhanced lower tropospheric baroclinicity over a large Central Atlantic/European domain and leading to a modification of the occurrence of extreme wind events along the French Mediterranean coast. A complete understanding of the relationship between climate fluctuations, storm activity, and the coastal response will be crucial to predicting the impacts of future climate change.
ISSN: 0031-0182

hal-00617525
https://hal.archives-ouvertes.fr/hal-00617525
DOI : 10.1016/j.palaeo.2010.11.009

Éditeur(s) : HAL CCSD
Résumé : IODP Hole U1309D (IODP Exp. 304-305, 30°N) and ODP Site 1275 (ODP Lag 209, 15°45?N) sampled two oceanic core complexes, at the Mid-Atlantic Ridge. The recovered rocks are mostly gabbroic with some very primitive and olivine rich (Ol>70%). In Hole U1309D, trace element compositions of clinopyroxene and plagioclase poikiloblasts from olivine-rich rocks ndicate that they crystallized from the same melt in all lithologies. Olivine trace element compositions are in disequilibrium with the two other minerals. Olivine crystallographic preferred orientations are weak, with a relatively strong uncommon [001] concentration but consistent with deformation by dislocation creep with activation of the high temperature (010) [100] slip system, commonly described in asthenospheric mantle. The joint study of geochemical processes and microstructures in these rocks suggest a complex crystallization history in an open system with percolation of large volume of MORBtype melt and interaction with the depleted shallow mantle. Olivine-rich rocks are interpreted as the ultimate residue of these melt-mantle reaction processes. At Site 1275, the formation of the more evolved rocks of the gabbroic series is not related to the impregnation event creating olivine-rich rocks.
These rocks represent late magmatic injections, which are completely crystallized at depth as intrusivegabbroic bodies. The results presented in this thesis are consistent with the formation of oceanic core complexes associated with relatively strong magmatic activity, and with the crystallization of most of melt in the lithosphere without basaltic counterpart erupted on the seafloor.
Le puits IODP U1309D (Exp. IODP 304-305, 30°N) et le Site ODP 1275 (Leg ODP 209, 15°45'N) ont permis d'échantillonner deux core complexes océaniques de la dorsale Médio-Atlantique. Les roches récupérées sont principalement gabbroïques dont certaines très primitives et riches en olivine (ol >70%). Dans le puits U1309D, les compositions en éléments en trace des poeciloblastes de clinopyroxène et de plagioclase des roches riches en olivine indiquent qu'ils précipitent depuis le même magma dans toutes les lithologies. La composition en éléments en trace des olivines est en déséquilibre avec ces deux minéraux. Les fabriques cristallographiques de l'olivine sont faibles avec une concentration sur [001] inhabituelle, néanmoins compatibles avec une déformation plastique de haute température, avec l'activation du système de glissement (010) [100] communément décrit dans le manteau asthénosphérique. L'étude conjointe des caractéristiques géochimiques et microstructurales de ces roches met en lumière une histoire complexe de cristallisation dans un système ouvert où de larges volumes de magma de type MORB ont percolé et interagi avec le manteau appauvri superficiel. Ces roches riches en olivine représenteraient le résidu ultime de ces réactions liquide-manteau. Au site 1275, la formation des roches les plus évoluées de la série n'apparaît pas liée à l'événement d'imprégnation formant les roches riches en olivine. Ces roches correspondent à des injections tardives de magma qui ont entièrement cristallisé en profondeur sous forme de plutons intrusifs. Les résultats présentés dans ce mémoire sont compatibles avec une formation des core complexes océaniques associée à une activité magmatique relativement importante, et à une cristallisation complète de tout ou partie de ces magmas dans la lithosphère sans contre-partie volcanique en surface.
https://tel.archives-ouvertes.fr/tel-00354807

tel-00354807
https://tel.archives-ouvertes.fr/tel-00354807
https://tel.archives-ouvertes.fr/tel-00354807/document
https://tel.archives-ouvertes.fr/tel-00354807/file/these_MD.pdf

Éditeur(s) : Gauthier-Villars
Résumé : Marine muds deposited on the French Guiana coast mostly originate in the Amazon. Recent sediments are composed of (a) illite (33 %) and chlorite (13 %) of Andean mountain origin; and (b) kaolinite (28 %) and smectite (26 %), principally from the Amazonian lowlands but also from the Guiana Shield. In the coastal mud prism, high-resolution seismic profiles, together with sedimentological, micropaleontological and soil engineering studies, supplemented by C-14 dates, permitted a stratigraphic interpretation of eight cores. Three episodes have been determined on the basis of clay-mineral variations related to Amazonian lowland, Andean and Guiana shield sources. The older episodes 3 (3000-1700 y BP) and 2 (1700-1000 y BP) are predominantly characterized by lowland-derived clays (smectite = 43 %, kaolinite = 26 %) from Amazonian and local sources. The most important event is a reduction of the Andean source, due to successive dry phases which occurred in western Amazonia about 2200 and 1200 y BP, confirming that regional decreases in rainfall, water discharge and erosion were associated with climatic fluctuations. It is suggested that these dry phases (within the last 3000 years) are the consequence of several protracted (10-100 years) periods, during which atmospheric conditions mimicked the present-day ''El Nino Southern Oscillation'' (ENSO) phenomenon. As a result, particulate flux from the ocean decreased, leading to reduced silting of the Guiana coast, In the past 1000 years (episode 1), illite and chlorite have increased, indicating a stronger Andean contribution to the Amazonian continental flux that reaches the ocean. This is the first demonstration that the nature of the coastal marine muds of northern South America reflects climatic changes in the Amazon basin.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1996 , Vol. 19 , N. 5 , P. 477-487

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00094/20506/18175.pdf
http://archimer.ifremer.fr/doc/00094/20506/

Éditeur(s) : HAL CCSD
Résumé : 1 p.
International audience
The Patagonian plateau basalts are a sequence of flat-lying Late Cretaceous through Tertiary basaltic and andesitic rocks exposed east of the Andes in dissected mesetas of Chilean and Argentine Patagonia. The plateau basalts cover a total area of 120,000 km2 between 40°S and 52°S. These igneous rocks rest on generally flatlying older Mesozoic silicic volcanic or sedimentary rocks. Of major importance to the paleomagnetic investigation is the lack of significant tectonic disturbance of this portion of Patagonia from Late Cretaceous to present. 12 sites (107 cores) have been sampled in the Tertiary (Paleocene to Miocene) volcanic rocks between 43°S and 46°S in latitude and between 68°W and 70°W in longitude. Rocks are usually very fresh but, as they outcrop generally on top of the mesas, few hundred meters above the Plateau, remagnetization by lightning strikes is a major problem of the paleomagnetic analysis. Paleomagnetic, rock magnetic and paleointensity results will be presented.
Eos, Transactions, American Geophysical Union
Acapulco, Mexico

insu-00266820
https://hal-insu.archives-ouvertes.fr/insu-00266820

Éditeur(s) : HAL CCSD American Association for the Advancement of Science
Résumé : International audience
Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics.
ISSN: 0036-8075

hal-01054316
https://hal.archives-ouvertes.fr/hal-01054316
DOI : 10.1126/science.1251306

Éditeur(s) : HAL CCSD
Résumé : This historical perspective provides an overall view of the main steps that led to the acceptance of the concept of mantle exhumation accompanying lithosphere stretching and extreme crustal thinning. We first remember that the presence of exposures of mantle rocks along oceanic spreading ridges was early reported in the 60's due to the results of sediment cores and dredge hauls collected along the Mid-Atlantic Ridge. In the meantime, detailed analysis of the relationships between oceanic sediments of Late Jurassic age and their primary basement in the Apennine ophiolites led many authors to point to the importance of exhumation of mantle rocks on ancient seafloors. By contrast to the thick sections of classical ophiolites (e.g. Oman), the Alpine-Corsican-Appennine ophiolites are characterized by a relatively small amount of mafic rocks (gabbros and basalts), by the absence of any sheeted dyke complex and by the frequent occurrence of oceanic sediments stratigraphically overlying mantle-derived peridotites and associated gabbroic intrusions. They display some of the characteristics of slow-spreading ridge systems, but, due to their highly tectonized character, they have been interpreted successively either as remnants of oceanic fracture zones of normal ocean or as remnants of very-poorly organized, abnormal oceanic basement. This review shows how the concept of mantle exhumation has been elaborated more or less in the same period both by marine geoscientists and by geologists conducting investigations in ophiolitic units of the Alps-Apennines mountain belt. Dredging and diving results from the Gorringe Bank, the Iberia margin, the Thyrrenian Sea and the Central Atlantic in the 1980's and 1990's provided additional proofs that the mantle is currently exhumed in various oceanic environments, including distal continental margins, back-arc basins and slow-spreading ridges of wide oceans. It is shown finally how renewed cross-information from mountain belts and the oceans, multiplying the examples of sedimentary reworking of mantle material, help better constrain the mechanisms of mantle exhumation. This mechanism progressively appeared as a fundamental step during the processes of extension of both continental and oceanic lithospheres in numerous geological situations worldwide.
Bollettino della Società Geologica Italiana

hal-00475653
https://hal.archives-ouvertes.fr/hal-00475653
DOI : 10.3301/IJG.2009.128.2.279

Éditeur(s) : HAL CCSD Springer
Résumé : The analysis of three different regions of the South- Pyrenean fold-and-thrust belt reveals that during the Tertiary compression the hydrological system was compartmentalised in time and space. During the early-middle Eocene, when the thrust front affected marine soft-sediments in the Ainsa basin, the thrust fault zones were dominated by formation fluids derived from Eocene marine waters trapped in the underlying Eocene marls, although influences of meteoric waters were also present. During the middle-late Eocene, when the thrust front emplaced marine rocks over continental redbeds in the eastern Catalan basin (L'Escala thrust), the thrust fault zones were dominated by meteoric fluids. These fluids flowed preferentially along these faults, draining laterally the meteoric fluids and acting as barriers hindering their flowing towards more external parts of the belt. During the Oligocene, the most external part of the fold-and-thrust belt in the eastern Catalan basin developed on top of a salt detachment horizon. The thrust front affected continental materials of late Eocene-Oligocene age. At this moment, the thrusts were conduits for meteoric fluids arriving from the surface and also for evolved meteoric fluids migrating over short distance upwards after being in contact with the underlying evaporitic beds. Most of the fractures show a similar sequence of microfractures. Microfractures of stage 1 formed when the sediment was poorly lithified. Microfractures of stage 2 represent the main episode of vein formation which developed when a progressive induration of the host sediment occurred. During microfracture stage 3, formed in an extensional regime, the host sediment was more indurated. The repetition of this sequence of microfractures in different fracture generations of the same outcrop indicates that the sediment induration was restricted to the vicinity of the vein. Away from the veins, the sediment remained poorly lithified during the entire deformation cycle. Calcite cement within the host rock precipitated later than the syn-compressive veins, when the sediment was more indurated. Elemental geochemistry and stable isotopes of the calcite veins indicates that early generation of microfractures is infilled by local fluids (either marine or meteoric), whereas external fluids (meteoric or evolved meteoric) infilled the main compressive stage of microfractures. The hot temperature of these fluids (157°C to 183°C in the Atiart-Arro example) indicates their circulation through deep parts of the thrust belt. The progressive increase of the 87Sr/86Sr ratio through time is due to the progressive uplift, exposure and erosion of the internal Pyrenean Axial Zone.
Thrust belts and foreland basins, from fold kinematics to hydrocarbon systems

hal-00408001
https://hal.archives-ouvertes.fr/hal-00408001
DOI : 10.1007/978-3-540-69426-7_5

Éditeur(s) : HAL CCSD
Résumé : International audience
The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Using laboratory experiments designed to study lithosphere-scale deformation, we show that the overall pattern of Aegean extension requires not only the combination of trench retreat and Anatolia escape since 15 Ma but also the presence of an inherited lithosphere-scale mechanical discontinuity: the Vardar Suture Zone (VSZ). The reactivation in dextral shear of the eastern branch of the VSZ accommodates both the trench retreat (NS stretching) and the westward escape of Anatolia (EW shortening) in the Cyclades area since 15 Ma. Additionally, our model shows that the North Anatolian Fault (NAF) is a late structure in the evolution of the Aegean, initiated 10 Ma after the onset of Anatolia escape. The model displays displacement sub-domains, which result from strain partitioning instead of being “rigid microplates”, directly comparable to the present-day displacement field (GPS) of the Aegean and western Anatolia. Our modelling provides a simple way to look at the dynamics of Aegean extension in two main stages. From middle Eocene to middle Miocene, extension was only driven by the southward retreat of the Hellenic trench at a rate lower than 1 cm.y-1. Since middle Miocene, the combination of slab rollback with Anatolia westward escape, resulted in a southwest direction of trench retreat, with an accelerating rate of up to 3 cm.y-1.
AGU Fall Meeting 2015
San Francisco, United States

insu-01242045
https://hal-insu.archives-ouvertes.fr/insu-01242045

Éditeur(s) : HAL CCSD Geological Society
Résumé : Xenoliths from Hawk's Nib (Bute, SW Scotland), entrained in alkali basalt of late Carboniferous–early Permian age, generally possess unrecrystallized igneous cumulate textures. Most are inferred to derive from lower crustal (20–30 km) depths, with a small minority from the underlying restitic mantle. Compositions range from ultramafic cumulates (dunite, wehrlite, websterite, clinopyroxenite) to gabbros and anorthosites. The suite is unique in being dominated by poikilitic wehrlites and olivine clinopyroxenites. Major element variation in the cumulates is controlled by modal mineral variations. The ultramafic cumulates all have high REE contents and light REE (LREE)-enriched patterns, with websterites being the least enriched. Gabbroic xenoliths have uniform patterns in which both LREE and heavy REE are depleted relative to the middle REE, with small positive Eu anomalies. Present-day Sr–Nd isotopic data for the suite are the most depleted among Scottish xenoliths. The xenoliths are inferred to be products of young replenishments of the lower crust by basaltic magmas during continental underplating. Orthopyroxene-bearing lithologies crystallized from tholeiitic magmas whereas alkali basalts formed the clinopyroxene-rich samples; both parental magma-types were derived from similar mantle sources.
ISSN: 0016-7649

hal-00407203
https://hal.archives-ouvertes.fr/hal-00407203
DOI : 10.1144/0016-76492006-177

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
During the last decade, the interaction of deep processes in the lithosphere and mantle with surface processes (erosion, climate, sea-level, subsidence, glacio-isostatic readjustment) has been the subject of heated discussion. The use of a multidisciplinary approach linking geology, geophysics, geodesy, modelling, and geotechnology has led to the awareness of coupled deep and surface processes. Deep earth dynamics (topography, erosion, tectonics) are strongly connected to natural hazards such as earthquakes, landslides, and tsunamis; sedimentary mass transfers have important consequences on isostatic movements and on georesources, geothermal energy repartitions. The ability to read and understand the link between deep Earth dynamics and surface processes has therefore important societal impacts. Ground-truthing at carefully-selected sites of investigation is imperative to better understand these connections.Due to its youth (<30 Ma) and its subsidence history, the almost land-locked Gulf of Lion–Sardinia continental margins system provides a unique record of sedimentary deposition from the Miocene to present. Due to its high subsidence rate, palaeoclimatic variations, tectonic events and vertical evolution are all recorded here at very high resolution. The late Miocene isolation and desiccation of the Mediterranean, the youngest and most catastrophic event, the Messinian Salinity Crisis (MSC), induced drastic changes in marine environments: widespread deposition of evaporite (gypsum, anhydrite and halite) in the central basin, and intense subaerial erosion along its periphery. These extraordinary mass transfers from land to sea induced strong isostatic re-adjustments that are archived in the sedimentary record and represent a window to the lithospheric rheology and the deep processes.The GOLD (Gulf of Lion Drilling) project, proposes to explore this unique sedimentary record as well as the nature of the deep crustal structure, providing valuable information about the mechanisms underlying vertical motions in basins and their margins.
ISSN: 0264-8172

insu-01197393
https://hal-insu.archives-ouvertes.fr/insu-01197393
https://hal-insu.archives-ouvertes.fr/insu-01197393/document
https://hal-insu.archives-ouvertes.fr/insu-01197393/file/Rabineau%20et%20al.-final-MPG2014_REVISED-FINAL-No-Marked_FINAL%2BFigures.pdf
DOI : 10.1016/j.marpetgeo.2015.03.018