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

Éditeur(s) : Elsevier Science Bv
Résumé : Mechanisms controlling the transfer and retention of silicon (Si) along continental margins are poorly understood, but play a major role in the functioning of coastal ecosystems and the oceanic biological pump of carbon. Deep-sea fans are well recognized as carbon sink spots, but we lack knowledge about the importance of the fans in the global Si cycle. Here, we provide a first estimate of the role played by the Congo deep-sea fan, one of the biggest in the world, in the Si cycle. Sediment cores sampled in the deep-sea fan were analyzed to build a Si mass balance. An exceptionally high accumulation rate of amorphous silica aSiO(2) (2.29 +/- 0.58 mol Si m(-2) y(-1)) was found, due to a high sedimentation rate and the presence of aluminum in the sediments. Although favored by bioirrigation, recycling fluxes remained low (0.3 mol Si m(-2) y(-1)) and reconstructed input fluxes could only be explained by lateral inputs coming from the canyon. Preliminary calculations show that the rapid transport of aSiO(2) through the canyon and the excellent preservation efficiency in the sediments imply that 50% of aSiO(2) river inputs from the Congo River accumulate annually in the deep-sea fan. Si:C ratios in deep-sea fan sediments were very low (0.2) and only three times as high as those measured in the river itself, which suggests that material from the river and the continental shelf was delivered directly through the canyon, with very little time for Si and C cycle decoupling to take place.
Journal Of Marine Systems (0924-7963) (Elsevier Science Bv), 2015-01 , Vol. 141 , P. 71-79

Droits : 2014 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00251/36242/35797.pdf
DOI:10.1016/j.jmarsys.2014.07.010
http://archimer.ifremer.fr/doc/00251/36242/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
We show here that the Amalaoulaou complex, in the Pan-African belt of West Africa (Gourma, Mali), corresponds to the lower and middle sections of a Neoproterozoic intra-oceanic arc. This complex records a 90-130-Ma-long evolution of magmatic inputs and differentiation above a subducting oceanic slab. Early c. 793 Ma-old metagabbros crystallised at lower crustal or uppermost mantle depths (25-30 km) and have geochemical characteristic of high-alumina basalts extracted from a depleted mantle source slightly enriched by slab-derived sedimentary components ((La/Sm)(N) < 1; epsilon(Nd): +5.4-6.2; Sr-87/Sr-86: 0.7027-0.7029). In response to crustal thickening, these mafic rocks were recrystallised into garnet-granulites (850-1,000A degrees C; 10-12 kbar) and subject to local dehydration-melting reactions, forming trondhjemititic leucosomes with garnet-clinopyroxene-rutile residues. Slightly after the granulitic event, the arc root was subject to strong HT shearing during partial exhumation (detachment faults/rifting or thrusting), coeval with the emplacement of spinel- and garnet-pyroxenite dykes crystallised from a high-Mg andesitic parental magma. Quartz and hornblende-gabbros (700-660 Ma) with composition typical of hydrous volcanic rocks from mature arcs ((La/Sm)(N): 0.9-1.8; epsilon(Nd): +4.6 to +5.2; Sr-87/Sr-86: 0.7028-0.7031) were subsequently emplaced at mid-arc crust levels (similar to 15 km). Trace element and isotopic data indicate that magmas tapped a depleted mantle source significantly more enriched in oceanic sedimentary components (0.2%). Exhumation occurred either in two stages (700-660 and 623 Ma) or in one stage (623 Ma) with a final exhumation of the arc root along cold P-T path (550A degrees C, 6-9 kbar; epidote-amphibolite and greenschist facies conditions) during the main Pan-African collision event (620-580 Ma). The composition of magmas forming the Cryogenian Amalaoulaou arc and the processes leading to intra-arc differentiation are strikingly comparable to those observed in the deep section of exposed Mezosoic oceanic arcs, namely the Kohistan and Talkeetna complex. This evolution of the Amalaoulaou oceanic arc and its accretion towards the West African craton belong to the life and closure of the Pharusian Ocean that eventually led to the formation of the Greater Gondwana supercontinent, a similar story having occurred on the other side of the Sahara with the Mozambique Ocean.
ISSN: 0010-7999

hal-00639447
https://hal.archives-ouvertes.fr/hal-00639447
DOI : 10.1007/s00410-011-0624-5

Éditeur(s) : HAL CCSD
Résumé : The present study addresses the question of increasing need in water supply. One line of research consists in investigating karst aquifers that represent significant water supplies for the areas around the Mediterranean. This work aims at developing a methodology of predictive evaluation of karst distribution and karst thickness within the carbonate massifs. It is based on the study of the Tethysian carbonate platform from the area of Montpellier, South of France. This area underwent a polyphased, complex, tectonic evolution, involving successive karst forming events. The approach is based on the relationships between eustacy and geodynamics, on one hand, and base-level variation recorded within palaeokarsts, on the other hand. Sedimentary fill of palaeokarsts allows to identify distinct karstification phases and sometimes to date them. It is a marker of base-level variations, which we attempt to quantify, that is responsible for karst formation and karst filling and sealing. For three palaeokarsts of regional extent, we analyze : karst sedimentary-fill, the distribution along upstream-downstream profile, the vertical extension of palaeokarsts, indicative of the base-level lowering. - The " Bauxite palaeokarst " results from the two-stage evolution of the " Isthme Durancien " : i) Bauxitic weathering of the Neocomian cover over the southern Massif Central , related to an inversion during Barremian ; ii) ≥1600 m uplift and exhumation during Aptian-Albian, inducing erosion of alterites, upstream, and deposition of detrital bauxites, downstream. - The " Early Paleocene palaeokarsts with marine sedimentary-fill " indicate base level variations of more than 350m in the upstream area. It is suggested here that such base-level variations, exceeding eustacy and recorded in tabular undeformed series, result from desiccation-flooding events in an endoreic silled basin. - The " Miocene palaeokarst with Cevennes-sourced sediment-fill " records a Serravalian-Tortonian base-level drop, depicted by canyon incision in the hinterland of the Gulf of Lion Margin. Uplift values of ≥ 400m upstream, about 250m in an intermediate area and 10's of m downstream, are measured. The present 3D geometry and distribution of carbonate massifs (exposed and covered) are modeled in the study area, from the Cevennes to the Mediterranean. The 3D geological model integrates seismic reflection, borehole and gravimetric data. Tectonic restoration of a N-S section, extracted from the 3D model, allows to reconstruct paleo-base-levels with respect with the carbonate massifs, at different stages of deformation and successive phases of karstification. The 3D paleo-flows through carbonates across the study area, are thus constrained, especially during the Messinian desiccation stage. Application of the results to hydrogeology leads to the following : - Uplift of upstream hinterland (Cretaceous, Miocene) produces large amplitude karsts, but they do not make significant reservoirs. - Karstification responsible for the development of important and deep karst reservoirs is related to desiccation of endoreic basins (early Paleocene and Messinian). - Theses two events have produced two main deep karst reservoirs, with a gravimetric signature : (1) Upstream of Montpellier Thrust, between Pic St Loup, Les Matelles Fault and Hérault Basin, a deep karsts developed over 900m thickness in the Malm limestone, during Paleocene. (2) Downstream (south) of Montpellier Thrust, the coastal karsts extend offshore over more than 10km, they are sealed by a thick Miocene to Quaternary cover, and they result from the Messinian event.
Cette étude s'inscrit dans un contexte de demande croissante en ressources en eau, conduisant à mieux contraindre et estimer la distribution des aquifères karstifiés qui représentent une ressource importante, notamment sur le pourtour méditerranéen. Le but de ce travail est d'élaborer une méthode prédictive de la distribution de la karstification et de l'épaisseur de massifs carbonatés karstifiés, notamment pour les karsts profonds. La méthodologie est développée à partir de l'étude des karsts de la plateforme carbonatée téthysienne du Languedoc montpelliérain; région qui a subi une histoire tectonique complexe et polyphasée, entrainant des phases de karstification successives. Elle est basée sur la compréhension des relations entre eustatisme, géodynamique et niveau de base, enregistrées par les paléokarsts de la région. Le remplissage sédimentaire des paléokarsts permet d'identifier les épisodes de karstification et de les dater ; c'est un marqueur des variations -que l'on cherche à quantifier- du niveau de base local responsable de la formation et du comblement des karsts. On analyse 3 paléokarsts d'extension régionale dont on peut étudier : le remplissage karstique, la distribution le long de profils amont-aval et l'extension verticale indicatrice de l'amplitude de l'abaissement du niveau de base dont il est issu. On en déduit les causes géodynamiques à l'origine de leur formation: - Le " paléokarst des bauxites " à remplissage caractéristique, résulte de l'évolution en 2 phases de " l'Isthme Durancien " : altération bauxitique de la couverture néocomienne sur le sud du Massif Central, liée à une inversion au Barrémien, suivi d'une surrection ≥ 1600m à l'Aptien-Albien, causant l'érosion des altérites en amont et le dépôt des bauxites détritiques en aval. - Le " paléokarst à remplissage marin paléocène inférieur " indique des variations du niveau de base local ≥350m dans la zone amont sud-cévenole. On propose que ces variations de niveau de base d'amplitude très supérieures aux variations eustatiques et dans une zone faiblement déformée, résultent d'assèchements et d'ennoiements d'un bassin endoréique à seuil. - Le " paléokarst à remplissage détritique d'origine cévenole ", enregistre la chute du niveau de base au Serravalien-Tortonien, qui se traduit par l'incision de canyons dans l'arrière-pays de la marge du Golfe du Lion. On détermine une surrection de plus de 400 mètres à l'amont, près de 250m dans les blocs faillés intermédiaires et quelques dizaines de mètres dans la zone avale. En parallèle, on établit la géométrie et la distribution actuelles des massifs carbonatés dans la zone d'étude (y compris sous couverture), en construisant un modèle géologique 3D, des Cévennes à la Méditerranée. On intègre les données de sismique réflexion, de forages et les données gravimétriques. La restauration tectonique séquentielle d'une coupe Nord-Sud extraite du modèle géologique permet d'appréhender la position des paléo-niveaux de base par rapport aux massifs carbonatés, pour chaque époque de karstification. On déduit l'organisation 3D des paléo-écoulements à travers la géométrie complexe des massifs carbonatés languedociens, notamment pendant l'évènement messinien. En terme d'évaluation de la ressource en eau, on déduit que: - Les surrections de l'arrière-pays (Crétacé " moyen ", Miocène) produisent des karsts de grande amplitude, mais ne constituent pas de réservoirs significatifs. - La karstification à l'origine de réservoirs exploitables importants et profonds est créée par l'assèchement de bassins endoréiques, qui ont affecté la région au Paléocène inférieur et au Messinien . - Ces deux évènements sont à l'origine de deux principaux réservoirs karstiques profonds qui ont une signature gravimétrique : (1) En amont du chevauchement de Montpellier, entre le Pic Saint Loup, la faille des Matelles et le bassin de l'Hérault, le karst profond se développe sur une épaisseur atteignant 900m, et est attribuée à l'événement du Paléocène. (2) Au Sud du chevauchement de Montpellier les karsts côtiers s'étendent jusqu'à plus de 10 km au large, scellés par une épaisse couverture Miocène et Plio-Quaternaire, et résultent de l'événement Messinien.
https://tel.archives-ouvertes.fr/tel-00936257

tel-00936257
https://tel.archives-ouvertes.fr/tel-00936257
https://tel.archives-ouvertes.fr/tel-00936257/document
https://tel.archives-ouvertes.fr/tel-00936257/file/thA_se_husson_couleurs.pdf

Éditeur(s) : Nature
Résumé : Mud volcanism is an important natural source of the greenhouse gas methane to the hydrosphere and atmosphere(1,2). Recent investigations show that the number of active submarine mud volcanoes might be much higher than anticipated ( for example, see refs 3 - 5), and that gas emitted from deep-sea seeps might reach the upper mixed ocean(6-8). Unfortunately, global methane emission from active submarine mud volcanoes cannot be quantified because their number and gas release are unknown(9). It is also unclear how efficiently methane-oxidizing microorganisms remove methane. Here we investigate the methane-emitting Haakon Mosby Mud Volcano (HMMV, Barents Sea, 72 degrees N, 14 degrees 44' E; 1,250 m water depth) to provide quantitative estimates of the in situ composition, distribution and activity of methanotrophs in relation to gas emission. The HMMV hosts three key communities: aerobic methanotrophic bacteria (Methylococcales), anaerobic methanotrophic archaea (ANME-2) thriving below siboglinid tubeworms, and a previously undescribed clade of archaea (ANME-3) associated with bacterial mats. We found that the upward flow of sulphate- and oxygen-free mud volcano fluids restricts the availability of these electron acceptors for methane oxidation, and hence the habitat range of methanotrophs. This mechanism limits the capacity of the microbial methane filter at active marine mud volcanoes to <40% of the total flux.
Nature (depuis 1997) (0028-0836) (Nature), 2006-10 , Vol. 443 , N. 7113 , P. 854-858

Droits : 2006 Nature Publishing Group
http://archimer.ifremer.fr/doc/2006/publication-4514.pdf
DOI:10.1038/nature05227
http://archimer.ifremer.fr/doc/00000/4514/

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : Deep-sea bivalves found at hydrothermal vents, cold seeps and organic falls are sustained by chemosynthetic bacteria which ensure part or all of their carbon nutrition. These symbioses are of prime importance for the functioning of the ecosystems. Similar symbioses occur in other bivalve species living in shallow and coastal reduced habitats worldwide. In recent years, several deep-sea species have been investigated from continental margins around Europe, West Africa, East America, the Gulf of Mexico, and from hydrothermal vents on the Mid-Atlantic Ridge. In parallel, numerous more easily accessible shallow marine species were studied. We here provide a summary of the current knowledge available on chemosymbiotic bivalves in the area ranging west-to-east from the Gulf of Mexico to Marmara Sea, and north-to-south from the Arctic to the Gulf of Guinea. Characteristics of symbioses in 51 species from the area are summarized for each of the five bivalve families documented to harbor chemosynthetic symbionts (Mytilidae, Vesicomyidae, Solemyidae, Thyasiridae and Lucinidae), and compared among families with special emphasis on ecology, life cycle, and connectivity. Chemosynthetic symbioses are a major adaptation to ecosystems and habitats exposed to reducing conditions, yet relatively little is known regarding their diversity and functioning apart from a few "model species" on which effort has focused over the last 30 yr. In the context of increasing concern about biodiversity and ecosystems, and increasing anthropogenic pressure on Oceans, we advocate for a better assessment of bivalve symbioses diversity in order to evaluate the capacities of these remarkable ecological and evolutionary units to withstand environmental change
Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2013 , Vol. 10 , N. 5 , P. 3241-3267

Droits : Author(s) 2012. CC Attribution 3.0 License.
http://archimer.ifremer.fr/doc/00133/24417/22431.pdf
DOI:10.5194/bg-10-3241-2013
http://archimer.ifremer.fr/doc/00133/24417/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The current interpretation of the Messinian Salinity Crisis (MSC) involves the deposition of peripheral or marginal evaporites in onshore basins as well as the erosion of the margin and the deposition of thick evaporites in deep basins. The so-called intermediate basins are formed in domains between the onland outcrops and the deep basins. The Balearic Promontory is a bathymetric high located between the deep Algerian and Liguro-Provençal basins and the onland Spanish basin. The SIMBAD project aims to investigate the spatial variability of the MSC-related deposits and to assess the extent of post-MSC reactivation over the Balearic Promontory. We present here the first results of the SIMBAD high-resolution seismic survey (January 2013) which imaged for the first time a thin MSC-related unit widely distributed in small sub-basins over the Balearic Promontory.Borehole analyses have shown that this unit could be correlated with primary gypsum formations linked to the peripheral evaporites. Locally, in the Central Depression between Mallorca and Ibiza islands, a thicker MSC unit is observed whose lowermost transparent part could correspond to a salt layer. Geometrical relationships suggest that the MSC in the Central Depression could postdate the primary gypsum. The occurrence of a halite layer in the Central Depression, at depths of 1000 to 1500 m, favours the hypothesis that the evaporites precipitated passively in closed or partially closed perched sub-basins, possibly as a result of evaporative drawdown at different depths and possibly diachronously, at least with respect to the deep-basin evaporites.
ISSN: 0264-8172

hal-01364255
https://hal.archives-ouvertes.fr/hal-01364255
DOI : 10.1016/j.marpetgeo.2014.09.008

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Cet article traite de la spécificité de l’activité touristique à Bali, fondée sur une identité locale forte et un riche patrimoine naturel et culturel mais aussi troublante en raison de l’importance et la complexité des jeux d’acteurs, ou encore des contextes sociaux, religieux et géopolitiques propres à ce territoire insulaire. Nous analyserons les liens pérennes ou non entre patrimoine et développement en focalisant sur ce qui fait l’image de marque de Bali sur les plans touristique et politique : le tourisme culturel. Cette étude de cas illustre les dynamiques d’acteurs dans le cadre de l’île de Bali où l’on constate une forte imbrication entre tourisme international, protection de l’environnement et promotion du patrimoine culturel. Vendue comme un paradis tropical, perçue comme l'île des Dieux, Bali se voit contrainte de mesurer les risques d'un tourisme culturel qui se transformerait trop rapidement en culture touristique. Des pistes seront proposées afin d’encourager l’ensemble des acteurs à œuvrer pour que le « dernier paradis » (last paradise) ne devienne pas un « paradis perdu » (lost paradise).
Since the 1930s, Bali has been generally seen as a traditional tourism destination quite fashionable. Nowadays, a new kind of tourism, rather esoteric if not totally spiritual, is emerging on this small “paradise” often referred as a natural untouched and cultural preserved island. To attire more international tourists, the “Island of Gods”, as the tourism promoters still name this tropical holiday paradise, is now also targeting on the industry of “well-being”. This article deals about the specificity of the local tourism activity which is based on a strong cultural identity and a rich natural and also religious heritage. Uncontrolled development of this predatory industry brings also a lot of new problems, such as pollution or acculturation. Here, our aim is to focus and analyse the real and false ties between heritage, development and tourism, always by keeping in mind that the regional motto about tourism policy still is to encourage “cultural tourism” as a real model (a “brand”, in fact) of success. We especially try to explain, in this current work (still in progress), the touristic situation in the main cultural site located on the island: Ubud. This small city, really boosting during the last decade, is worldwide reputed for the rich cultural performances and seen as “the” artistic capital of Bali. Ubud offers also a perfect example of an intense and dynamic bond between cultural heritage and economic development. Often for the best and sometimes also for the worse. In this rural but international spot, it seems that tourism business allows the local population to live in better ways and, sometimes, even to reborn, culturally speaking! Our case study shows also the big threats behind the current tourism policy: the large scale business occurred by globalization and all the tourism opportunities thus provided cannot hide the real weakness that for sure also concern the balinese way of thinking and living. Cultural tourism could rapidly be transformed in a dangerous kind of tourism of the culture, with all the big (and bad) changes the Balinese don’t want to see happening on their lovely and holy island. So, the present reflection conducts us to think more deeply on some new and alternative ways of developing tourism in Bali. Finally, our aim is to think, first by listening to the desire of the Balinese themselves, in which best manner this “last paradise” will not become a “lost paradise”.
Bali

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.5385
http://journals.openedition.org/etudescaribeennes/5385

Éditeur(s) : Elsevier
Résumé : The main feature of the Congo-Angola margin in the Gulf of Guinea is the Congo (ex-Zaire) deep-sea fan composed of a submarine canyon directly connected to the Congo River, a channel and a [sediment] lobe area. During the multi-disciplinary programme called BIOZAIRE conducted by Ifremer from 2000 to 2005, two CTD-O2 sections with discrete water column samples were performed (BIOZAIRE3 cruise: 2003-2004) to study the influence of the Congo River discharges, both in the surface layer and in the deep and near-bottom layers. The surface layer water is greatly diluted with river water that has a heavy particle load. The deep layer is affected by episodic turbidity currents that flow in the deep Congo channel and reach deep areas far from the coast. Previous studies revealed deep anomalies in oxygen (deficit) and nutrient (excess) concentrations at not, vert, similar4000 m depth and assumed that they resulted from mineralisation of the particulate organic matter from the Congo River. The BIOZAIRE3 sections were designed to explore these phenomena in more detail near the Congo channel. Oxygen and nutrients were measured as well as additional parameters, including stable isotopes of oxygen and carbon, dissolved inorganic carbon and pH. For the surface layer, the effect of the Congo River was studied with reference to salinity. Deviations from the theoretical dilution of various inorganic solutes suggested the occurrence of mineralisation and consumption processes. For the deep layer, the network of CTD-O2 stations gave a more detailed description of the deep anomalies than in previous studies. From the east-west section, anomalies appeared on the bottom at 4000 m depth and became slightly shallower when they spread to the west. They were also present north and south on the bottom along the 4000 m isobath. In these deep waters, the decrease in the o13C values of dissolved inorganic carbon confirmed that the mineralisation of organic matter plays a role in generating these anomalies. The location of the origin of this deep anomaly is debated. Here, arguments are given in favour of mineralisation of the particulate organic matter input that overflows from the Congo channel at not, vert, similar4000 m depth during turbidity current events. Other authors suggest that this input comes from downslope particle transport. Anomalies of the same origin, but weaker, also occurred deeper on the Congo lobe, where the Congo channel ends, but with a significant pH decrease on the bottom which was not seen at 4000 m depth.
Deep Sea Research Part II: Topical Studies in Oceanography (0967-0645) (Elsevier), 2009-11 , Vol. 56 , N. 23 , P. 2183-2196

Droits : 2009 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/2009/publication-6737.pdf
DOI:10.1016/j.dsr2.2009.04.002
http://archimer.ifremer.fr/doc/00000/6737/

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Society's needs for a network of in situ ocean observing systems cross many areas of earth and marine science. Here we review the science themes that benefit from data supplied from ocean observatories. Understanding from existing studies is fragmented to the extent that it lacks the coherent long-term monitoring needed to address questions at the scales essential to understand climate change and improve geo-hazard early warning. Data sets from the deep sea are particularly rare with long-term data available from only a few locations worldwide. These science areas have impacts on societal health and well-being and our awareness of ocean function in a shifting climate. Substantial efforts are underway to realise a network of open-ocean observatories around European Seas that will operate over multiple decades. Some systems are already collecting high-resolution data from surface, water column, seafloor, and sub-seafloor sensors linked to shore by satellite or cable connection in real or near-real time, along with samples and other data collected in a delayed mode. We expect that such observatories will contribute to answering major ocean science questions including: How can monitoring of factors such as seismic activity, pore fluid chemistry and pressure, and gas hydrate stability improve seismic, slope failure, and tsunami warning? What aspects of physical oceanography, biogeochemical cycling, and ecosystems will be most sensitive to climatic and anthropogenic change? What are natural versus anthropogenic changes? Most fundamentally, how are marine processes that occur at differing scales related? The development of ocean observatories provides a substantial opportunity for ocean science to evolve in Europe. Here we also describe some basic attributes of network design. Observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in European Seas adding needed certainty to estimates of future oceanic conditions. Observatory data can be analysed along with other data such as those from satellites, drifting floats, autonomous underwater vehicles, model analysis, and the known distribution and abundances of marine fauna in order to address some of the questions posed above. Standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit. The connection of ocean observatory effort into larger frameworks including the Global Earth Observation System of Systems (GEOSS) and the Global Monitoring of Environment and Security (GMES) is integral to its success. It is in a greater integrated framework that the full potential of the component systems will be realised. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2011-10 , Vol. 91 , N. 1 , P. 1-33

Droits : 2011 Published by Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00044/15557/15923.pdf
DOI:10.1016/j.pocean.2011.05.001
http://archimer.ifremer.fr/doc/00044/15557/

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Sur l'île de Bali, en Indonésie, paradis touristique et culturel, aujourd'hui en proie à un développement trop rapide, les rizières en terrasses constituent une véritable marque de fabrique du paysage local. La campagne autour de Jatiluwih est désormais le site naturel phare récemment reconnu par l'Unesco. Ses fameuses rizières représentent aussi un parfait exemple du fonctionnement des subak balinais, ces systèmes d’irrigation et de gestion de l’eau qui sont traditionnellement ancrés dans la culture balinaise. Ici, culture et agriculture sont intrinsèquement liées, et de plus en plus menacées. Cet article traite du présent et du devenir de la riziculture, patrimonialisée ou non, face à un essor du tourisme qui tous les jours s'affirme plus massif que culturel. Un défi majeur pour les Balinais qui souhaiteraient que leur paradis ne soit pas perdu mais préservé.
On the island of Bali, in Indonesia, a touristic and cultural heaven, nowadays confronted with a too fast development, the typical rice fields form a real distinguishable brand of the local landscape. The countryside around Jatiluwih become now the main natural site recently approved by UNESCO. Its famous rice fields also represent a perfect case of the Balinese system named Subak, a traditional water network deeply rooted in the local culture. Here, culture and agriculture are strongly tied together, but always more threatened these days. This contribution discuss the present and the future of the rice culture, whether put in heritage or not, in the context of a tourism growth which everyday looks more mass than cultural oriented. A major challenge for the Balinese who would prefer to see their paradise not lost but better preserved.
Bali
Indonésie

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.6957
http://journals.openedition.org/etudescaribeennes/6957

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Carbon is transported from Earth's surface into its interior at subduction zones. Carbonates in sediments overlying hydrothermally altered rocks (including serpentinites) within the subducted slab are the main carriers of this carbon1. Part of the carbon is recycled back to the surface by volcanism, but some is transferred to the deep Earth1, 2. Redox transformations during shallow subduction control the transfer and long-term fate of carbon, but are poorly explored1, 3. Here we use carbon stable isotopes and Raman spectroscopy to analyse the reduction of carbonate in an exhumed serpentinite-sediment contact in Alpine Corsica, France. We find that highly crystalline graphite was formed during subduction metamorphism and was concentrated in the sediment, within a reaction zone in direct contact with the serpentinite. The graphite in this reaction zone has a carbon isotopic signature (δ13C) of up to 0.8±0.1‰, similar to that of the original calcite that composed the sediments, and is texturally associated with the calcium-bearing mineral wollastonite that is also formed in the process. We use mass-balance calculations to show that about 9% of the total carbonaceous matter in the sedimentary unit results from complete calcite reduction in the reaction zone. We conclude that graphite formation, under reducing and low-temperature conditions, provides a mechanism to retain carbon in a subducting slab, aiding transport of carbon into the deeper Earth.
ISSN: 1752-0894

hal-00903464
https://hal.archives-ouvertes.fr/hal-00903464
DOI : 10.1038/NGEO1827

Éditeur(s) : Société Française d’Ichtyologie
Résumé : Following the volcanic eruption of April 2007 at Reunion Island, 12 specimens of the pomacentrid genus Chromis were collected at sea surface. One of these fishes was a C. chrysura known from the reef Island fauna. The others have enlarged eyes. Among them were one C. axillaris (Bennett, 1831), new for the Island fauna, and ten specimens of a new Chromis species, described here under the name C. durvillei. This new species of deep dwelling Chromis is distinguishable by large sized eyes 1.9 to 2.4 in the head length, D. XIII, 12-13, 25 to 26 gill-rakers on the first gill arch, three spiniform procurrent caudal rays, without black or dark brown spot or band on the body, pectorals or caudal peduncle. C. axillaris, C. woodsi, C. unipa, C. okamurai, C. struhsakeri and generally C. mirationis have 14 spinous dorsal rays. C. abyssicola and rarely C. mirationis have 13 spinous dorsal rays but two spiniform procurrent caudal rays and a dark axillary spot on pectorals.
Parmi les poissons récoltés en surface à l’île de la Réunion (océan Indien sud-ouest), après l’éruption volcanique d’avril 2007, se trouvaient 12 exemplaires du genre Chromis. Un C. chrysura connu de la faune récifale de l’île et 11 exemplaires présentant des yeux de grande taille : un C. axillaris (Bennett, 1831), nouveau pour la faune de l’île de La Réunion et 10 Chromis distinguables des autres espèces du genre par des yeux de grande taille (1,9 à 2,4 fois dans la longueur de la tête), D. XIII , 12-13, 25 à 26 branchicténies sur le premier arc branchial, trois rayons caudaux procurrents épineux et l’absence de tache ou de bande de couleur foncée sur le corps, les pectorales ou le pédoncule caudal. C. axillaris, C. woodsi, C. unipa, C. okamurai, C. struhsakeri et C. mirationis ont 14 rayons épineux à la dorsale, alors que C. abyssicola et rarement C. mirationis n’en ont que 13, mais deux rayons caudaux procurrents et une tache axillaire noire sur les pectorales. Cette espèce nouvelle de Chromis est décrite sous le nom de C. durvillei.
Cybium (0399-0974) (Société Française d’Ichtyologie), 2009-12 , Vol. 33 , N. 4 , P. 321-326

Droits : 2009 Société Française d’Ichtyologie
http://archimer.ifremer.fr/doc/00003/11382/8006.pdf
http://archimer.ifremer.fr/doc/00003/11382/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Mid-ocean ridge basalt (MORB) is the most abundant magma on Earth, and provides a geochemical window into the mantle. Deriving mantle composition and melting processes from the erupted lavas requires correction to be made for their evolution as they pass through and generate the oceanic crust. This is typically done by assuming that modification of melts in crustal magma chambers occurs exclusively by fractional crystallisation. However, extensive mineral major- and trace element data from a full section of fast-spread lower crustal rocks exposed in Hess Deep (equatorial Pacific Ocean) demonstrate that their evolution is instead controlled by reactive porous flow. These reactions lead to a strong enrichment in, and fractionation of, incompatible trace elements in the melt (as recorded by clinopyroxene compositions), leading to melt compositions far outside of the compositional realm of MORB both in terms of trace element abundances and ratios. The reactive signature increases in strength up section, peaking in varitextured gabbros interpreted to represent the fossilised axial melt lens, indicating that reactive porous flow occurred on the scale of the entire lower crust. The enrichment of the melt is coupled with a strong trace element depletion of plagioclase, olivine, and, to a lesser extent, clinopyroxene cores, suggesting that these phases represent the residues of the reactions from which trace elements have been removed. The dominant role of reactive porous flow, and the resulting deviations from fractional crystallisation predictions, suggest that the lower oceanic crust plays a much more complex and significant role in modifying the compositions of MORB than previously expected, with consequent implications for models of mantle processes.
ISSN: 0012-821X

hal-00814075
https://hal.archives-ouvertes.fr/hal-00814075
DOI : 10.1016/j.epsl.2012.11.012

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Assessing seismic hazards remains one of the most challenging scientific issues in Earthsciences. Deep tectonic processes are classically considered as the only persistentmechanism driving the stress loading of active faults over a seismic cycle. Here we show via amechanical model that erosion also significantly influences the stress loading of thrust faultsat the timescale of a seismic cycle. Indeed, erosion rates of about B0.1–20mmyr1, asdocumented in Taiwan and in other active compressional orogens, can raise the Coulombstress by B0.1–10 bar on the nearby thrust faults over the inter-seismic phase. Masstransfers induced by surface processes in general, during continuous or short-lived andintense events, represent a prominent mechanism for inter-seismic stress loading offaults near the surface. Such stresses are probably sufficient to trigger shallow seismicity orpromote the rupture of deep continental earthquakes up to the surface.
ISSN: 2041-1723

insu-01087103
https://hal-insu.archives-ouvertes.fr/insu-01087103
https://hal-insu.archives-ouvertes.fr/insu-01087103/document
https://hal-insu.archives-ouvertes.fr/insu-01087103/file/Steer2014_NatureComm_accepted.pdf
DOI : 10.1038/ncomms6564

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
Rainbow is a dome-shaped massif at the 36°14′N nontransform offset along the Mid-Atlantic Ridge. It hosts three ultramafic-hosted hydrothermal sites: Rainbow is active and high temperature; Clamstone and Ghost City are fossil and low temperature. The MoMARDREAM cruises (2007, 2008) presented here provided extensive rock sampling throughout the massif that constrains the geological setting of hydrothermal activity. The lithology is heterogeneous with abundant serpentinites surrounding gabbros, troctolites, chromitites, plagiogranites, and basalts. We propose that a W dipping detachment fault, now inactive, uplifted the massif and exhumed these deep-seated rocks. Present-day deformation is accommodated by SSW-NNE faults and fissures, consistent with oblique teleseismic focal mechanisms and stress rotation across the discontinuity. Faults localize fluid flow and control the location of fossil and active hydrothermal fields that appear to be ephemeral and lacking in spatiotemporal progression. Markers of high-temperature hydrothermal activity (∼350°C) are restricted to some samples from the active field while a more diffuse, lower temperature hydrothermal activity (<220°C) is inferred at various locations through anomalously high As, Sb, and Pb contents, attributed to element incorporation in serpentines or microscale-sulfide precipitation. Petrographic and geochemical analyses show that the dominant basement alteration is pervasive peridotite serpentinization at ∼160–260°C, attributed to fluids chemically similar to those venting at Rainbow, and controlled by concomitant alteration of mafic-ultramafic units at depth. Rainbow provides a model for fluid circulation, possibly applicable to hydrothermalism at oceanic detachments elsewhere, where both low-temperature serpentinization and magmatic-driven high-temperature outflow develop contemporaneously, channeled by faults in the footwall and not along the detachment fault.
ISSN: 1525-2027

hal-01115281
https://hal.archives-ouvertes.fr/hal-01115281
https://hal.archives-ouvertes.fr/hal-01115281/document
https://hal.archives-ouvertes.fr/hal-01115281/file/Andreani_et_al-2014-Geochemistry%2C_Geophysics%2C_Geosystems.pdf
DOI : 10.1002/2014GC005269

Éditeur(s) : The Oceanography Society
Résumé : Submarine hydrocarbon seeps are geologically driven "hotspots" of increased biological activity on the seabed. As part of the HERMES project, several sites of natural hydrocarbon seepage in the European seas were investigated in detail, including mud volcanoes and pockmarks, in study areas extending from the Nordic margin, to the Gulf of Cadiz, to the Mediterranean and Black seas. High-resolution seabed maps and the main properties of key seep sites are presented here. Individual seeps show ecosystem zonation related to the strength of the methane flux and distinct biogeochemical processes in surface sediments. A feature common to many seeps is the formation of authigenic carbonate constructions. These constructions exhibit various morphologies ranging from large pavements and fragmented slabs to chimneys and mushroom-shaped mounds, and they form hard substrates colonized by fixed fauna. Gas hydrate dissociation could contribute to sustain seep chemosynthetic communities over several thousand years following large gas-release events.
Oceanography (1042-8275) (The Oceanography Society), 2009-03 , Vol. 22 , N. 1 , P. 92-109

Droits : 2009 by The Oceanography Society. All rights reserved. Permission is granted to copy this article for use in teaching and research. Republication, systemmatic reproduction, or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The Oceanography Society. Send all correspondence to: info@tos.org or The Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA.
http://archimer.ifremer.fr/doc/2009/publication-6387.pdf
DOI:10.5670/oceanog.2009.11
http://archimer.ifremer.fr/doc/00000/6387/

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Lateral variations along the Himalayan arc are suggested by an increasing number of studies and carry important information about the orogen’s segmentation. Here we compile the hitherto most complete land gravity dataset in the region which enables the currently highest resolution plausible analysis. To study lateral variations in collisional structure we compute arc-parallel gravity anomalies (APaGA) by subtracting the average arc-perpendicular profile from our dataset; we compute likewise for topography (APaTA). We find no direct correlation between APaGA, APaTA and background seismicity, as suggested in oceanic subduction context. In the Himalayas APaTA mainly reflect relief and erosional effects, whereas APaGA reflect the deep structure of the orogen with clear lateral boundaries. Four segments are outlined and have disparate flexural geometry: NE India, Bhutan, Nepal & India until Dehradun, and NW India. The segment boundaries in the India plate are related to inherited structures, and the boundaries of the Shillong block are highlighted by seismic activity. We find that large earthquakes of the past millennium do not propagate across the segment boundaries defined by APaGA, therefore these seem to set limits for potential rupture of megathrust earthquakes.
ISSN: 2045-2322

hal-01420404
https://hal.archives-ouvertes.fr/hal-01420404
https://hal.archives-ouvertes.fr/hal-01420404/document
https://hal.archives-ouvertes.fr/hal-01420404/file/hetenyi2016.pdf
DOI : 10.1038/srep33866

Éditeur(s) : Amer Geophysical Union
Résumé : In the Atlantic Ocean, the northward export of warm surface water is compensated by a southward flow of cold North Atlantic Deep Water (NADW). The NADW is transported southward along the American continental margin within the Deep Western Boundary Current (DWBC). Some tracer and float observations have shown that part of the DWBC water flows eastward along the equator. Here we present three meridional velocity sections which give an instantaneous image of the top-to-bottom zonal circulation along the equatorial Atlantic. They reveal the presence of Equatorial Deep Jets (EDJs) between 1 degrees 30'N and 1 degrees 30'S, alternating eastward-westward currents with short vertical scale, surrounded by columns of eastward currents (the Extra Equatorial Jets or EEJs) at 2 degreesN and 2 degreesS. In addition to direct velocity measurements, tracer distributions give indications of water-mass feeding of the EDJs and EEJs by the DWBC.
Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2001-03 , Vol. 28 , N. 5 , P. 819-822

Droits : 2001 AGU
http://archimer.ifremer.fr/doc/00000/10369/9567.pdf
http://archimer.ifremer.fr/doc/00000/10369/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
To understand the deep cycle of water, upper mantle water content and distribution between nominally anhydrous minerals (NAMs) and hydrous minerals (e.g., amphibole) must be constrained. We need then to understand H behaviour during mantle melting and metasomatism. Major, minor and trace element compositions including water contents were obtained on ten xenoliths of spinel-bearing peridotites from the Ray Pic locality, in the Southern part of the Massif Central (France). The sample suite investigated here is composed of rather fertile lherzolites (89.4 ≤ Fo ≤ 90.8%; 11.3 ≤ cr# in spinel ≤ 21.1%; 0.942 ≤ [Yb]cpx ≤ 1.90 ppm; cpx: clinopyroxene), which can be best explained by batch melting, with degree of melting between 3 and 10%. These xenoliths contain up to 8% modal amphibole. Three groups are defined as a function of the amphibole modal abundance (above or below 1%) and equilibrium temperature (above or below 1000 °C). Results show no clear positive correlation between modal metasomatism (amphibole) and incompatible element enrichment in cpx. Trace element compositions in cpx show strong enrichments of the most incompatible elements (e.g., (La/Sm)PM as high as 15.7; PM: normalised to primitive mantle values), but strong negative anomalies of the high field strength elements (e.g., (Th/Nb)PM as high as ~ 680). Such trace element fractionations are usually ascribed to the so-called carbonatitic metasomatism involving the percolation of small volume melts which are enriched in volatiles. The hydrogen concentrations in cpx range from 203 to 330 ppm wt. H2O, in orthopyroxene from 66 to 160 ppm wt. H2O and in olivine from 2 to 6 ppm wt. H2O. These values are within the common concentration range of other spinel-bearing peridotites. Amphiboles contain 1.9 ± 0.5 wt.% of H2O.The effect of metasomatism on water abundances in NAMs is not straightforward. Hydrous metasomatism (i.e., leading to the crystallisation of OH-bearing amphibole) has no effect on the water content of the co-existing NAMs. This suggests thus that the occurrence of hydrous minerals, such as amphibole, does not systematically imply that the coexisting NAMs are water-rich (saturated). Further, the percolation of volatile-rich small volume melts, which is fingerprinted by the strong enrichment of the incompatible elements, has also no clear effect on the water content of the NAMs. These data are thus difficult to reconcile with the admitted highly incompatible behaviour of H in upper mantle minerals.
ISSN: 0024-4937

hal-01278062
https://hal.archives-ouvertes.fr/hal-01278062
DOI : 10.1016/j.lithos.2015.08.013