Éditeur(s) : Gauthier-Villars
Résumé : The mangroves of Senegal are limited to the inlet of the Casamance - a river with very low discharge - and to the Sine-Saloum. The mineralogical and geochemical analysis of sediments (derived from 30 deep bore-holes) shows the thickness of the mangrove substrate, which overlies the continental terminal formation. Kaolinite and smectite account for over 90% of the clay fraction. The former is derived from the continental terminal whereas the latter is of marine origin. The chemical composition of the mangrove sediments is remarkably stable and clays play an overwhelming role in the preservation of organic matter and pyrite. Since 1968, a drought in Senegal has caused an important increase in the salinity levels of streams and water-tables; a considerable modification of vegetation zones in the Casamance, especially manifest in the extension of bare flats locally known as "tannes" at the expense of mangroves and marked changes in the morphology and geochemistry of mangrove soils. Compared to most mangrove areas in the humid tropics, mangroves in Senegal are characterized by a very fragile equilibrium.
Oceanologica Acta, Special issue (0399-1784) (Gauthier-Villars), 1982

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00246/35744/34252.pdf
http://archimer.ifremer.fr/doc/00246/35744/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Forest successional processes following disturbance take decades to play out, even in tropical forests. Nonetheless, records of vegetation change in this ecosystem are scarce, increasing the importance of the chronosequence approach to study forest recovery. However, this approach requires accurate dating of secondary forests, which until now was a difficult and/or expensive task. Cecropia is a widespread and abundant pioneer tree genus of the Neotropics. Here we propose and validate a rapid and straightforward method to estimate the age of secondary forest patches based on morphological observations of Cecropia trees. We found that Cecropia-inferred ages were highly correlated with known ages of the forest. We also demonstrate that Cecropia can be used to accurately date disturbances and propose twenty-one species distributed all over the geographical range of the genus as potential secondary forest chronometer species. Our method is limited in applicability by the maximal longevity of Cecropia individuals. Although the oldest chronosequence used in this study was 20 years old, we argue that at least for the first four decades after disturbance, the method described in this study provides very accurate estimations of secondary forest ages. The age of pioneer trees provides not only information needed to calculate the recovery of carbon stocks that would help to improve forest management, but also provides information needed to characterize the initial floristic composition and the rates of species remigration into secondary forest. Our contribution shows how successional studies can be reliably and inexpensively extended without the need to obtain forest ages based on expensive or potentially inaccurate data across the Neotropics.
ISSN: 1932-6203

halsde-00757518
https://hal.archives-ouvertes.fr/halsde-00757518
DOI : 10.1371/journal.pone.0042643
PUBMED : 22916144

Éditeur(s) : HAL CCSD
Résumé : International audience
In the context of climate change, this study presents the ability of major/trace elements together with strontiumisotopes to trace back water paths at small scale and to deconvolve the geochemical signal of a small watershedsubject to intense flash floods episodes (Peyne, Hérault, France). Two small sub-basins draining distinct lithologiesin their heads (Plio-Villafranchian conglomerate versus Triassic gypsum-rich marls and dolomites) and the sameMiocene lithology downstream are investigated.Major elements and Ca/Na vs. Mg/Na ratios classically applied at large scale to distinguish carbonate from silicateweathering, allow here discriminating the three main lithologies from the two sub-basins. Trace elements Rband Sr coupled to calcium, also allow this lithological discrimination but in addition the Ca/Rb vs. Sr/Rb tracersappear to be much more discriminant for the various hydrological conditions. Thus, in combination with detailedlithological descriptions, they allow identifying the different facies that imprint the water signature through water-rock interaction according to the hydrological conditions.Strontium isotopes and Rb/Sr ratio, discriminate more precisely the drained lithologies of the 2 sub-basins. Firstly,the 87Sr/86Sr ratios allow identifying the nature of the lithologies and their main component(s) contributing to theSr budget in water and thus imprint the isotopic signature. Secondly, Sr isotopes evidenced two distinct Miocenefacies: the detritric faction (sandy marls), and the marine carbonates.The geochemical signatures of the brook samples draining both compartments were compared to the signatureof the Peyne River outlet just before the confluence into the Hérault River. It appears that the signature of thePeyne River, integrating all the water draining the basin, is relatively stable whatever the hydrological conditionsand mainly marked by the Miocene formations. Sr isotopes further highlight that this signature seems to resultfrom the mixing of both Miocene facies present in the lower part of the Peyne watershed, i.e. the sandy marls andthe carbonates. The typical signatures of the Plio-Villafanchian conglomerates and Triassic gypsiferous marls anddolomites of the headwaters of each sub-basin are completely hidden by the Miocene signatures. This should berelated to the large drainage area of the Miocene compared to other lithologies, despite the high solubility of thegypsum formations releasing large quantities of dissolved elements in solution.Understanding water paths at small scale is even more efficient when the geochemical approach is coupled with adetailed geological description. Indeed, the geochemical tracers are extremely dependent on the facies sequences(morphology) and of the soil nature (mineralogical composition), this is particularly sensitive at small scale.In the context of climate change increasing the intensity of rain events in the Mediterranean region, and resultingin catastrophic floods events (flash floods), tracing the origin of water contributing to the runoff is of primaryimportance and this must be investigated at small scale. Geochemical and isotopic fingerprinting thus constituteexcellent tools which can help to define the area of interest to be monitored in the framework of flood forecast andwarning networks
EGU General Assembly 2015
Vienne, Austria

hal-01118622
https://hal-brgm.archives-ouvertes.fr/hal-01118622

Éditeur(s) : Academic Press Ltd- Elsevier Science Ltd
Résumé : Extracellular products (ECPs) of the pathogenic Vibrio aestuarianus 01/32 were previously reported to display lethality in Crassostrea gigas oysters and to cause morphological changes and immunosuppression in oyster hemocytes. To identify the source of this toxicity, biochemical and genetic approaches were developed. ECP protease activity and lethality were shown to be significantly reduced following incubation with metal chelators, suggesting the involvement of a zinc metalloprotease. An open reading frame of 1836 bp encoding a 611-aa metalloprotease (designated yam) was identified. The deduced protein sequence showed high homology to other Vibrio metalloproteases reported to be involved in pathogenicity. To further confirm the role of this enzyme in ECP toxicity, a plasmid carrying the yarn gene under the control of an araC-P-BAD expression cassette was transferred to a Vibrio splendidus related strain, LMC20012(T), previously characterized as non-pathogenic to oysters. Expression of Vam conferred a toxic phenotype to LMG20012(T) ECPs in vivo and cytotoxicity to oyster hemocytes in vitro. Collectively, these data suggest that the Vam metalloprotease is a major contributor to the toxicity induced by V aestuarianus ECPs and is involved in the impairment of oyster hemocyte functions. (C) 2010 Elsevier Ltd. All rights reserved.
Fish & Shellfish Immunology (1050-4648) (Academic Press Ltd- Elsevier Science Ltd), 2010-11 , Vol. 29 , N. 5 , P. 753-758

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00015/12649/9588.pdf
DOI:10.1016/j.fsi.2010.07.007
http://archimer.ifremer.fr/doc/00015/12649/

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
We present new results on the long-term throw rates of active normal faults in the North Baikal Rift (NBR), eastern Siberia, based on a statistical analysis of triangular faceted scarps. Fault-bounded ridges in the NBR display typical morphologies with several contiguous facets separated by fault-perpendicular catchments. Over a range of 20 fault segments analyzed, triangular facet heights vary from similar to 200 to >900 m. As fault scarps have been developing under similar long-term climatic conditions, we infer that the scatter in mean facet height arises from long-term differences in fault throw rate. We compare the morphology of NBR facets with results obtained in a previously published numerical model of facet growth. Using facet height as an input, model results provide estimates of the long-term fault throw rate. NBR throw rates vary between 0.2 and 1.2 mm yr(-1). The throw rates are then compared with the cumulated throw, which has been constrained by geophysical and stratigraphic data in the basins. This provides an estimate of the age of fault and basin initiation. We show that the modern stage of basin development started circa 3 Myr ago, except for the North Baikal basin (similar to 8Ma). Our results also suggest that a proportion of the observed throw is inherited from an earlier tectonic stage.
ISSN: 0278-7407

hal-00455985
https://hal.archives-ouvertes.fr/hal-00455985
DOI : 10.1029/2009TC002555

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Vertebrate genomes contain around 20,000 protein-encoding genes, of which a large fraction is still not associated with specific functions. A major task in future genomics will thus be to assign physiological roles to all open reading frames revealed by genome sequencing. Here we show that C2orf62, a highly conserved protein with little homology to characterized proteins, is strongly expressed in testis in zebrafish and mammals, and in various types of ciliated cells during zebrafish development. By yeast two hybrid and GST pull-down, C2orf62 was shown to interact with TTC17, another uncharacterized protein. Depletion of either C2orf62 or TTC17 in human ciliated cells interferes with actin polymerization and reduces the number of primary cilia without changing their length. Zebrafish embryos injected with morpholinos against C2orf62 or TTC17, or with mRNA coding for the C2orf62 C-terminal part containing a RII dimerization/docking (R2D2) - like domain show morphological defects consistent with imperfect ciliogenesis. We provide here the first evidence for a C2orf62-TTC17 axis that would regulate actin polymerization and ciliogenesis.
ISSN: 1932-6203

hal-00955242
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00955242
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00955242/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00955242/file/C2orf62_and_TTC17-accepted.pdf
DOI : 10.1371/journal.pone.0086476

Éditeur(s) : HAL CCSD Kasetsart University
Résumé : http://www.ceropath.org/references/rodent_protocols_book
Technical book
"Protocols for field and laboratory rodent studies" present the best practices for the studies of rodents and rodent-borne pathogens and parasites from the field to the laboratory. It aims at covering the different steps of rodent studies: 1) Trapping, 2) Dissection and preparation of tissue samples for pathogens screening, 3) Identification of species, 4) Isolation of helminths, 5) Preparing rodent specimens for collections. This book gathers accurate recommendations and techniques, based on those generally accepted in the literature and adapted from the experience of the different authors during rodent surveys and laboratory work. Its presentation is designed to work in the fields with a clear and colorful organization of each chapter, with: inserts providing definitions and recommendations, protocols detailed step by step, and an emphasis on illustrations with several photographs. This book is a publication generated by the CERoPath project (Community Ecology of Rodents and their Pathogens in a changing environment, www.ceropath.org) funded by the French Ministry of Research from 2008 to 2011.
http://hal.ird.fr/ird-00714514

ird-00714514
http://hal.ird.fr/ird-00714514
http://hal.ird.fr/ird-00714514/document
IRD : fdi:010056183

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Previous estimates of the geodetic and geologic slip rates of the 1500 km long Altyn Tagh fault bordering the northern edge of the Tibetan plateau vary by a factor of five. Proposed reasons for these discrepancies include poor GPS geometry, interpretative errors in terrace morphology, and changes in fault slip rate over time. Here we present results from a new dense GPS array orthogonal to the fault at ~86.2°E that indicates a velocity of 9.0−3.2/+4.4 mm/yr, in close agreement with geomorphologic estimates at the same location. Our estimated geodetic slip rate is consistent with recent geological slip rates based on terrace offsets. The resulting mean combined geological and geodetic slip rate (9.0 ± 4.0 mm/yr) is remarkably uniform for the central ~800 km of the Altyn Tagh fault, significantly lower than early kinematic estimates and consistent with deformation elsewhere in Tibet and central Asia.
ISSN: 0094-8276

hal-00963568
https://hal.archives-ouvertes.fr/hal-00963568
DOI : 10.1002/2013GL057497

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Gravitropism is necessary for plants to control the orientation of their axes while they grow in height. In woody plants, stem re-orientations are costly because they are achieved through diameter growth. The functional diversity of gravitropism was studied to check if the mechanisms involved and their efficiency may contribute to the differentiation of height growth strategies between forest tree species at the seedling stage. Seedlings of eight tropical species were grown tilted in a greenhouse, and their up-righting movement and diameter growth were measured during three months. Morphological, anatomical and biomechanical traits were measured at the end of the survey. Curvature analysis was used to analyse the up-righting response along the stems. Variations in stem curvature depend on diameter growth, size effects, the increase in self-weight, and the efficiency of the gravitropic reaction. A biomechanical model was used to separate these contributions. Results showed that (1) gravitropic movements were based on a common mechanism associated to similar dynamic patterns, (2) clear differences in efficiency (defined as the change in curvature achieved during an elementary diameter increment for a given stem diameter) existed between species, (3) the equilibrium angle of the stem and the anatomical characters associated to the efficiency of the reaction also differed between species, (4) the differences in gravitropic reaction were related to the light requirements: heliophilic species, compared to more shade-tolerant species, had a larger efficiency and an equilibrium angle closer to vertical. This suggests that traits determining the gravitropic reaction are related to the strategy of light interception and may contribute to the differentiation of ecological strategies promoting the maintenance of biodiversity in tropical rain forests.
ISSN: 0022-0957

hal-00797023
https://hal.archives-ouvertes.fr/hal-00797023
https://hal.archives-ouvertes.fr/hal-00797023/document
https://hal.archives-ouvertes.fr/hal-00797023/file/Functional_diversity_gravitropic_Almeras_al.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We developed a new granular material (MatIV) to study experimentally landscape evolution in active mountain belt piedmonts. Its composition and related physical properties have been determined using empirical criteria derived from the scaling of deformation, erosion-transport and sedimentation natural processes. MatIV is a water-saturated composite material made up with 4 granular components (silica powder, glass microbeads, plastic powder and graphite) whose physical, mechanical and erosion-related properties were measured with different laboratory tests. Mechanical measurements were made on a modified Hubbert-type direct shear apparatus. Erosion-related properties were determined using an experimental set-up that allows quantifying the erosion/sedimentation budget from tilted relaxation topographies. For MatIV, we also investigated the evolution of mean erosion rates and stream power erosion law exponents in 1D as a function of slope.;Our results indicate that MatIV satisfies most of the defined criteria. It deforms brittlely according to the linear Mohr-Coulomb failure criterion and localizes deformation along discrete faults. Its erosion pattern is characterized by realistic hillslope and channelized processes (slope diffusion, mass wasting, channel incision). During transport, eroded particles are sorted depending on their density and shape, which results in stratified alluvial deposits displaying lateral fades variations. To evaluate the degree of similitude between model and nature, we used a new experimental device that combines accretionary wedge deformation mechanisms and surface runoff erosion processes. Results indicate that MatIV succeeded in producing detailed morphological and sedi-mentological features (drainage basin, channel network, terrace, syntectonic alluvial fan). Geometric, kinematic and dynamic similarity criteria have been investigated to compare precisely model to nature. Although scaling is incomplete, it yields particularly informative orders of magnitude. With all these characteristics, MatIV appears as a very promising material to investigate experimentally a wide range of scientific questions dealing with relief dynamics and interactions between tectonics, erosion and sedimentation processes.
ISSN: 0040-1951

hal-00669904
https://hal.archives-ouvertes.fr/hal-00669904
DOI : 10.1016/j.tecto.2011.09.029

Éditeur(s) : HAL CCSD
Résumé : Guadeloupe Island (West French Indies) is one of the twenty islands that compose the Lesser Antilles Arc, which results from the subduction of the Atlantic Ocean plate beneath the Caribbean one. The island lies in a complex volcano-tectonic system and the need to understand its geological context has led to numerous on- and offshore geophysical investigations. This work presents the compilation and processing of available, on-land, airborne and marine, gravity and magnetic data acquired during the last 40 years on Guadeloupe Islands and at the scale of the Lesser Antilles Arc. The overall dataset provides new Bouguer and reduced to the pole magnetic anomaly maps at the highest achievable resolution. Regionally, the main central negative gravity trend of the arc allows defining two subsident areas. The first one is parallel to the arc direction (~N160°E) to the north, whereas the second unexpected southern one is oriented parallel to oceanic ridges (N130°E). Along the Outer Arc, the long wavelength positive anomaly is interpreted, at least along the Karukera Spur, as an up-rise of the volcanic basement in agreement with the seismic studies. To the NE of Guadeloupe, the detailed analysis of the geophysical anomalies outlines a series of structural discontinuities consistent with the main bathymetric morphologies, and in continuity of the main fault systems already reported in this area. Based on geophysical evidences, this large scale deformation and faulting of the Outer Arc presumably primarily affects the Atlantic subducting plate and secondarily deforms the upper Caribbean plate and the accretion prism. At the scale of Guadeloupe Island, joined gravity and magnetic modeling has been initiated based on existing interpretation of old seismic refraction profiles, with a general structure in three main layers. According to our geophysical anomalies, additional local structures are also modeled in agreement with geological observations: i) the gravity and magnetic signals confirm an up-rise of the volcanic basement below the limestone platforms outcropping on Grande-Terre Island ; ii) the ancient volcanic complexes of Basse-Terre Island are modeled with high density and reverse magnetized formations; iii) the recent volcanic centre is associated with formations consistent with the low measured density and the underlying hydrothermal system. The EW models coherently image a NNW-SSE depression structure in half-graben beneath Basse-Terre Island, its western scarp following the arc direction in agreement with bathymetric and seismic studies to the north of the island. The so-defined depressed area, and particularly its opening in half-graben toward the SW, is interpreted as the present-day front of deformation of the upper plate associated with the recent volcanic activity on and around Guadeloupe. Based on this regional deformation model, perspectives are given for further integrated investigation of key targets to address the internal structure and evolution of the Lesser Antilles Arc and Guadeloupe volcanic system.
Colloque 2012 du Comité National Français de Géodésie et Géophysique (CNFGG)
Clermont-Ferrand, France

hal-00742653
https://hal-brgm.archives-ouvertes.fr/hal-00742653
https://hal-brgm.archives-ouvertes.fr/hal-00742653/document
https://hal-brgm.archives-ouvertes.fr/hal-00742653/file/CNFGG_Caraibes.pdf

Éditeur(s) : HAL CCSD Editions Paralia CFL
Résumé : Les lagunes du Golfe du Lion constituent un patrimoine naturel reconnu ainsi qu'un enjeu essentiel pour les activités économiques locales. Leur évolution morphologique est donc une question importante dans le contexte actuel de changements climatiques et environnementaux. L'analyse de données topo-bathymétriques du système des étangs Palavasiens a permis de mieux cerner son évolution depuis le XVIIIème siècle. Les actions anthropiques et les apports du bassin versant apparaissent comme les facteurs principaux de l'évolution du système. Au cours des 40 dernières années, le système montre une tendance à se combler lentement avec une accumulation moyenne de 1,3 mm/an. Des différences de fonctionnement sur chacun des étangs sont mises en lumière en fonction des forçages naturels et anthropiques locaux. Lagoons of the Gulf of Lion, recognized for their natural heritage, are a key challenge for local economic activities. Their morphological evolution is an important issue in the current context of climate and environmental changes. Analysis of topo-bathymetric data of the Palavasian lakes system has helped to clarify its evolution since the XVIII th century. Human impacts and contributions from the watershed appear to be the main drivers governing the evolutionof the system. Over the past40 years, the system shows a tendency to slowly fill at an accumulation rate of 1.3 mm/year. Differences between lagoons are highlighted according to local natural and anthropogenic forcings.
ISSN: 1760-8716

hal-00854075
https://hal.archives-ouvertes.fr/hal-00854075
DOI : 10.5150/revue-paralia.2011.007

Éditeur(s) : HAL CCSD
Résumé : Patagonia is well known for spectacular occurrences of a variety of glacial-derived landforms and deposits and for a long history of ancient glaciations. In this paper, we first review the diverse evidence that demonstrates the development of glacial-related sedimentary units within the Central Patagonian Cordillera since 7 Ma. Well preserved glacial landforrns at the top surface of mesetas on both sides of the Lago General Carrera-Buenos Aires are described: the Meseta Guenguel to the north, and the volcanic Meseta del Lago Buenos Aires to the south. The latter meseta corresponds to a 3 Ma old, morphologically inverted paleo-piedmont, based on Ar/Ar dates of the uppermost lava flows. It shows evidence of glacier advances to the NE direction. Over a distance of 20 km, glacial landforms observed by remote sensing data and digital elevation model define glacial tongues that were fed by the Cordillera reliefs to the west. These lobes are now beheaded from their westward sources along a morpho-structural corridor that bounds the Meseta del Lago Buenos Aires to the west. These remnants can be correlated with the oldest glacial landforms recognized north of Lago General Carrera-Buenos Aires, on the Meseta Guenguel that form the Chipanque moraine system. From these features it is concluded that the glacial drainage network of Central Patagonia has been strongly modified following relief inversion in response to erosion processes and to tectonic causes. Changes occurred after 3 Ma, from a smooth piedmont surface covered by an extensive ice mantle ending with ample glacial lobes, to the current series of deeply incised glacial valleys such as the Lago General Carrera-Buenos Aires depression. These new data bear important constraints on the history and development of the first glaciations in southern South America.
ANDEAN GEOLOGY

hal-00512682
https://hal.archives-ouvertes.fr/hal-00512682

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
The Taleghan fault (TF) is a major active fault of the Central Alborz mountain range in Iran. Located 50 km northwestwards of Tehran, this 80-km-long fault represents one of the major structures threatening 15 million people living in the capital of Iran and the surrounding cities (e.g. Karaj). The TF could be the source of some of the strongest historical earthquakes recorded in the Tehran region, notably the 958 AD event (estimated magnitude M 7.7). To characterize the kinematics and activity of the fault, we carried out a detailed morphological and palaeoseismological study combining aerial photographs, digital elevation models and fieldwork. We show that, unliked described so far, the TF is not a reverse fault but a left-lateral strike-slip fault with a normal component. Its strike, dip and rake within its eastern part are 105, 60 and -20/-40, respectively. Our palaeoseismological analysis shows that a sequence of 2-3 events with magnitudes M-w >= 7 occurred during the past 5300 years. If we consider a three-event scenario, the average recurrence interval is similar to 2000 years, and the most recent event is younger than 80 AD. If we consider a two-event scenario, the time interval between the second and the first events ranges between 3760 and 830 years, and the elapsed time since the last event ranges between 3529 and 1599 years. Combined with morphotectonics data, our palaeoseismological analysis allows estimating a minimum horizontal slip rate of 0.6-1.6 mm yr(-1) and a minimum vertical slip rate of similar to 0.5 mm yr(-1). Taking the similar to 450-m total vertical displacement observed across the fault, we conclude that the kinematical change along the TF (from reverse to left-lateral + normal) occurred similar to 1 Ma.
ISSN: 0956-540X

hal-00420896
https://hal.archives-ouvertes.fr/hal-00420896
https://hal.archives-ouvertes.fr/hal-00420896v2/document
https://hal.archives-ouvertes.fr/hal-00420896/file/narariGJI2009.pdf
DOI : 10.1111/j.1365-246X.2009.04173.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We present results of a geomorphological and morphotectonic analysis of the northeastern part of the Rif. We show that the present day kinematics of the Rif is characterized by active deformation along the Trougout and Nekor faults in the North-East. Digital Elevation Models of offset drainage features (streams, fluvial terraces) allow determining a normal-left-lateral motion along the Trougout fault and a left-lateral strike-slip motion along the Nekor fault. Preliminary 3He cosmogenic dates of tectonic markers yield vertical and horizontal slip rates of ∼0.9 mm/yr and ∼0.5 mm/yr, respectively along the Trougout fault. The present-day localized transtension seen in the north-eastern Rif morphology (Ras Tarf) is coeval with uplifted marine terraces near the Al Hoceima Bay. U/Th dating of shells yield an average uplift rate of ∼0.2 mm/yr during the past 500 ka. These data show that active transtension in the northeastern Rif is also associated with uplift. These new morphotectonic constraints are consistent with the GPS measurements showing southwestward overall motion of most of the Rif belt with respect to stable Africa.
ISSN: 0264-3707

hal-01053492
https://hal.archives-ouvertes.fr/hal-01053492
DOI : 10.1016/j.jog.2014.01.004

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
This study examines the response of the Central Patagonian Cordillera to the subduction of the active South Chile Ridge and the development of the asthenospheric slab window beneath Patagonia since the Pliocene. We investigated the eastern part of the Cordillera where the glacio-volcanic piedmont is topographically inverted. Glacial morphology and associated deposits capping the top of these piedmonts reveal that during the Pliocene (after 3 Ma), glaciers were flowing to the east over a regional surface connecting the western Cordillera and the palaeo-piedmont. N160-trending normal faulting along the western edge of the inverted plateau disrupted the geomorphic surface after 3 Ma. At a regional scale, extensional tectonics is responsible for a relief inversion with a minimum value of 800 m. The timing of extensional tectonics is contemporaneous with the subduction of the spreading axis and the development of the slab window beneath Central Patagonia.
ISSN: 0954-4879

hal-00595547
https://hal.archives-ouvertes.fr/hal-00595547
DOI : 10.1111/j.1365-3121.2010.00981.x

Éditeur(s) : Wiley-blackwell
Résumé : Managing fisheries resources to maintain healthy ecosystems is one of the main goals of the ecosystem approach to fisheries (EAF). While a number of international treaties call for the implementation of EAF, there are still gaps in the underlying methodology. One aspect that has received substantial scientific attention recently is fisheries-induced evolution (FIE). Increasing evidence indicates that intensive fishing has the potential to exert strong directional selection on life-history traits, behaviour, physiology, and morphology of exploited fish. Of particular concern is that reversing evolutionary responses to fishing can be much more difficult than reversing demographic or phenotypically plastic responses. Furthermore, like climate change, multiple agents cause FIE, with effects accumulating over time. Consequently, FIE may alter the utility derived from fish stocks, which in turn can modify the monetary value living aquatic resources provide to society. Quantifying and predicting the evolutionary effects of fishing is therefore important for both ecological and economic reasons. An important reason this is not happening is the lack of an appropriate assessment framework. We therefore describe the evolutionary impact assessment (EvoIA) as a structured approach for assessing the evolutionary consequences of fishing and evaluating the predicted evolutionary outcomes of alternative management options. EvoIA can contribute to EAF by clarifying how evolution may alter stock properties and ecological relations, support the precautionary approach to fisheries management by addressing a previously overlooked source of uncertainty and risk, and thus contribute to sustainable fisheries.
Fish And Fisheries (1467-2960) (Wiley-blackwell), 2014-03 , Vol. 15 , N. 1 , P. 65-96

Droits : 2012 John Wiley & Sons Ltd
http://archimer.ifremer.fr/doc/00124/23522/21409.pdf
DOI:10.1111/faf.12007
http://archimer.ifremer.fr/doc/00124/23522/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The barrier reef tract of New Caledonia is the second largest in the world enclosing lagoons of variable width. The Late Quaternary evolution of these barrier reefs and lagoons is poorly known. A recent high resolution seismic and multibeam bathymetry survey was carried out in the south-western lagoon from shoreline to open ocean across the barrier reef pass systems to perform sequence stratigraphy and to better understand the Quaternary evolution of the lagoon. Two depositional sequences bounded by type-1 erosional surfaces can be identified. The bounding surfaces delineate the bottom of two generations of incised valleys. System tracts comprising a complete succession of regressive, lowstand, transgressive and highstand tracts were observed only in the upper sequence. Chronostratigraphic and sedimentological interpretations of the seismic data are based on correlations with the chronology defined in the nearby cores drilled through the reefs and in the gravity cores previously recovered in the inner lagoon. Interpretation of seismic data is also carried out on the basis of correlation with multibeam bathymetric data. Our results indicate that the history of the New Caledonian lagoon probably does not exceed 200ka marked by two or three brief episodes each of immersion of about ten thousand years. The bathymetric data reveal that during successive low sea level stands, the lagoon was dependent upon erosional fluvial networks. The deep fluvial valleys were connected to the continental slope through the passes. Seismic records reveal that upstream palaeo-channels are not connected to the modern coastal rivers. In contrast, many aggrading deposits, including numerous stacking channels, and extending across the proximal part of the outer lagoon, can be identified. Examination of drainage network morphology suggests a progressive tilt of the outer lagoon. Such evolution reveals that the Nouméa lagoon which is one of the widest in the world is an exceptional modern example of a rimmed shelf providing data to analyze the past counterparts.
ISSN: 0031-0182

insu-00338953
https://hal-insu.archives-ouvertes.fr/insu-00338953
DOI : 10.1016/j.palaeo.2008.08.012

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : The Maguelone shore extends along the northern coast of the Gulf of Lions margin, West of the Rhone delta and East of some high gradient coastal streams that have been providing most of the elastic sediments to the Gulf of Lions margin since the early Miocene. This 10 km wide area comprises an onshore small coastal watershed (15 km long) in low-lying carbonate hills, kilometer wide marshes, sandy beach and shoreface featuring local low sedimentation. Deposit architecture in such a coastal zone records dynamics of incised valley fill under the influence of rivers and wave/current hydrodynamics in a microtidal environment during an eustatic cycle.;A detailed analysis of about 250 km of very high resolution seismic profiles, tens of cores and outcrops data revealed the evolution of the Maguelone coastal system from Late-Quaternary to present-day. It highlighted also dominant denudation processes in the upstream catchments associated to the formation of incised valley seaward during Quaternary. Combination of this inherited morphology together with hydrodynamics controlled the lagoonal environment evolution since the last transgression. In particular, the Maguelone shore is characterized by the formation of built-over-rias lagoonal systems and records an evolution from partially protected lagoon to isolated lagoon environment. These two stages of lagoon evolution correspond to distinct deposit environments. Correlation of fauna contents with deposit geometry improves lagoonal environment models.
EISSN: 1777-5817

hal-00486370
https://hal.archives-ouvertes.fr/hal-00486370
DOI : 10.2113/gssgfbull.181.2.211

Éditeur(s) : HAL CCSD
Résumé : International audience
The history of the peneplain in East Sayan was studied using apatite fission-track analysis (AFTA). This method is suitable for determining the formation time of the erosional surface and estimating its denudation rate. The largest known relic of the peneplanation surface in this area is the Oka Plateau, separated from the Kropotkin Ridge by the Oka-Jombolok fault. The AFTA shows that the peneplain on the Oka Plateau formed in the Late Jurassic-Early Cretaceous. This peneplain is much younger than the erosional surfaces that persist today in the Tien Shan, Gobi Altai, and Mongolian Altai (Early Jurassic). However, it is older than the peneplain on the Chulyshman Plateau, Altai (Late Cretaceous), suggesting asynchronous formation of the ancient peneplain in Central Asia. The similar exhumation histories of samples from the Oka Plateau and Kropotkin Ridge indicate that these morphotectonic structures developed from Jurassic to late Miocene as a single block, which underwent continuous slow denudation at an average rate of 0.0175 mm/yr. Active tectonic processes in the Late Miocene caused the destruction of the peneplanation surface and its partial uplifting to different altitudes. The rate of Pliocene-Quaternary vertical movements along the Oka-Jombolok fault is roughly estimated at 0.046-0.080 mm/yr, which is several times higher than the denudation rate in this area. During the Pliocene-Quaternary, the Oka Plateau has not undergone any significant morphologic changes owing to its intermediate position between the summit plain and datum surface of East Sayan and to its partial shielding by basaltic lavas.
Russian Geology and Geophysics

insu-00839215
https://hal-insu.archives-ouvertes.fr/insu-00839215
DOI : 10.1016/j.rgg.2013.06.004