Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
3D seismic data located in the Gjallar Ridge (Vøring Basin, offshore Norway) reveals a closely-spaced polygonal fault system affecting more than 800 m of homogeneous mud-dominated Quaternary and Tertiary sequences. As some faults reach the modern seafloor, they represent an active polygonal fault system at present day. Even if the processes remain unclear and are still under debate, it is generally agreed that the initiation of polygonal faults is the result of shallow burial dewatering of fine-grained unconsolidated sediments by volumetric compaction. 3D seismic data are commonly interpreted by propagating horizons automatically and by picking faults manually. However, in the case of polygonal fault intervals, this approach is time consuming due to the huge number of faults and because automatic propagation can be misleading. In this study, we applied a new technique of 3D seismic interpretation based on a sequential stratigraphy analysis, using the new PaleoScan© software (Eliis Company). It allowed us to build a 3D geological model computing more than 300 horizons within the faulted intervals. We then used the coherency attribute, depicting anomalies in the shape of seismic waveform like faults, in order to constrain a possible link between fault distribution and stratigraphic levels. Our approach allows fault throws to be calculated in milliseconds on any polygonal fault plane. The result shows that fault segments have been reactivated by dip-linkage. Distribution of faults depends on mechanical units, intervals characterized by different petrophysical properties, which are independent from lithological and diagenetic changes. According to these results, we propose a model showing the evolution of polygonal fault intervals in which faulting stages are separated by a quiescence phase during burial. A first tier of polygonal faults is initiated at a specific depth, according to the Cam-clay model. Then, following a period of quiescence during which mud-rich sediments continued to accumulate, new fault segments are initiated above the first mechanical unit and within this undeformed interval. New nucleated faults then connect downward to pre-existing underlying polygonal fault system, thus progressively increasing the thickness of the faulted interval.
ISSN: 0025-3227

hal-00772470
https://hal.archives-ouvertes.fr/hal-00772470
DOI : 10.1016/j.margeo.2012.07.016

Éditeur(s) : HAL CCSD American Chemical Society
Résumé : International audience
The HIWATE (Health Impacts of long-term exposure to disinfection byproducts in drinking WATEr) project was a systematic analysis that combined the epidemiology on adverse pregnancy outcomes and other health effects with long-term exposure to low levels of drinking water disinfection byproducts (DBPs) in the European Union. The present study focused on the relationship of the occurrence and concentration of DBPs with in vitro mammalian cell toxicity. Eleven drinking water samples were collected from five European countries. Each sampling location corresponded with an epidemiological study for the HIWATE program. Over 90 DBPs were identified; the range in the number of DBPs and their levels reflected the diverse collection sites, different disinfection processes, and the different characteristics of the source waters. For each sampling site, chronic mammalian cell cytotoxicity correlated highly with the numbers of DBPs identified and the levels of DBP chemical classes. Although there was a clear difference in the genotoxic responses among the drinking waters, these data did not correlate as well with the chemical analyses. Thus, the agents responsible for the genomic DNA damage observed in the HIWATE samples may be due to unresolved associations of combinations of identified DBPs, unknown emerging DBPs that were not identified, or other toxic water contaminants. This study represents the first to integrate quantitative in vitro toxicological data with analytical chemistry and human epidemiologic outcomes for drinking water DBPs.
ISSN: 0013-936X

hal-00875923
https://hal.archives-ouvertes.fr/hal-00875923
DOI : 10.1021/es3024226
PUBMED : 22958121

Éditeur(s) : HAL CCSD Wiley Open Access
Résumé : Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species' threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project - and avert - future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups - including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems - ). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.
ISSN: 2045-7758

hal-01204216
https://hal.archives-ouvertes.fr/hal-01204216
DOI : 10.1002/ece3.1303
PRODINRA : 280886

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The Western Indian Ocean harbors one of theworld’s most diverse marine biota yet is threatened byexploitation with few conservation measures in place.Primary candidates for conservation in the region are theScattered Islands (Iles Eparses), a group of relativelypristine and uninhabited islands in the MozambiqueChannel. However, while optimal conservation strategiesdepend on the degree of population connectivity amongspatially isolated habitats, very few studies have beenconducted in the area. Here, we use highly variablemicrosatellite markers from two damselfishes (Amphiprionakallopisos and Dascyllus trimaculatus) with differing lifehistory traits [pelagic larval duration (PLD), adult habitat]to compare genetic structure and connectivity among theseislands using classic population structure indices as well asBayesian clustering methods. All classical fixation indexesFST, RST, G0ST, and Jost’s D show stronger genetic differentiationamong islands for A. akallopisos compared to D.trimaculatus, consistent with the former species’ shorterPLD and stronger adult site attachment, which may restrictlarval dispersal potential. In agreement with these results,the Bayesian analysis revealed clear genetic differentiationamong the islands in A. akallopisos, separating the southerngroup (Bassas da India and Europa) from the center(Juan de Nova) and northern (Iles Glorieuses) islands, butnot for D. trimaculatus. Local oceanographic patterns suchas eddies that occur along the Mozambique Channel appearto parallel the results reported for A. akallopisos, but suchfeatures seem to have little effect on the genetic differentiationof D. trimaculatus. The contrasting patterns ofgenetic differentiation between species within the samefamily highlight the importance of accounting for diverselife history traits when assessing community-wide connectivity,an increasingly common consideration in conservationplanning.
ISSN: 0722-4028

hal-01561992
https://hal-univ-perp.archives-ouvertes.fr/hal-01561992
DOI : 10.1007/s00338-016-1495-z

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We present new Sr-Nd-Pb isotope data of the western Alpujárride metamorphic basement and the pre-Miocene Flysch sediments of the Betic Cordillera (southern Spain). Nd model ages are consistent with an increasing detrital input from the Alborán domain to the Flysch Trough in the western Mediterranean during the late Oligocene. The Alpujárride metamorphic crustal rocks derived from Archean-Paleoproterozoic terranes located along the northern margin of Gondwana in the Neoproterozoic. The heterogeneous isotopic signatures of the Alpujárride units indicate that they have different sedimentary protoliths and underwent contrasted Variscan and pre-Variscan tectono-magmatic evolutions. Melts/fluids derived from the western Alpujárride gneisses contaminated the mantle source of the Ronda high-Mg pyroxenite dykes, implying that the Alpujárride lower crust underthrusted the subcontinental lithospheric mantle of the Alborán domain generating subduction-like magmatism in the late Oligocene. The western Alpujárride upper crust is involved in the Neogene volcanism of the Alborán Sea basin, but only contaminated some LREE-enriched calc-alkaline lavas erupted along the continental margins. On the other hand, tholeiitic lavas in the center of the basin show no isotopic evidence of crustal assimilation. This indicates that most of the crust in the central Alborán Sea accreted by Miocene tholeiitic magmatism and that Alpujárride lower crust is absent and likely foundered close to the continental margins of the basin.
ISSN: 0024-4937

hal-01526912
https://hal.archives-ouvertes.fr/hal-01526912
DOI : 10.1016/j.lithos.2016.10.003

Éditeur(s) : HAL CCSD PeerJ
Résumé : International audience
Coral reefs are in decline across the globe as a result of overexploitation, pollution, disease and, more recently, climate change. The impacts of changes in coral cover on associated fish communities can be difficult to predict because of the uneven dependence of reef fish species on corals for food, shelter or the three-dimensional structure they provide. We compared live coral cover, reef fish community metrics, and their associations in two surveys of the lagoon of the remote atoll of Mataiva (French Polynesia) carried out 31 years apart. In contrast to the general pattern of decreasing coral cover reported for many parts of the Indo-Pacific region, live coral cover increased 6–7 fold at Mataiva between 1981 and 2012, and fish density nearly doubled. The stable overall reef fish species richness belied a significant shift in community structure. There was little overlap in community composition across years, and fish assemblages in 2012 were more homogeneous in composition than they were in 1981. Changes in species abundance were not clearly related to species-specific reliance on corals. The strong positive relationships between live coral cover and fish diversity and abundance noted in 1981, when coral cover rarely exceeded 10%, were no longer present in 2012, when coral cover rarely fell below this value. The most parsimonious explanation for these contrasting relationships is that, over the combined range of coral cover observed in the 1981 and 2012 snapshots, there is a rapidly asymptotic relationship between coral and fish. Our results, and other data from the south and west Pacific, suggest that fish diversity and abundance might accumulate rapidly up to a threshold of approximately 10% live coral cover. Such a relationship would have implications for our expectations of resistance and recovery of reef fish communities facing an increasingly severe regime of coral reef disturbances.
ISSN: 2167-8359

Droits : http://creativecommons.org/licenses/by/
hal-01135589
https://hal.archives-ouvertes.fr/hal-01135589
https://hal.archives-ouvertes.fr/hal-01135589/document
https://hal.archives-ouvertes.fr/hal-01135589/file/2015_02_26_more_coral_more_fish.pdf
DOI : 10.7717/peerj.745

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Gibraltar arc, spans a complex portion of the Africa-Eurasia plate boundary marked by slow oblique convergence and intermediate and deep focus seismicity. The seemingly contradictory observations of a young extensional marine basin surrounded by an arcuate fold-and-thrust belt, have led to competing geodynamic models (delamination and subduction). Geophysical data acquired in the past decade provide a test for these models and support a narrow east-dipping, subduction zone. Seismic refraction studies indicate oceanic crust below the western Gulf of Cadiz. Tomography of the upper mantle reveals a steep, east-dipping high P-wave velocity body, beneath Gibraltar. The anisotropic mantle fabric from SKS splitting shows arc-parallel "fast directions", consistent with toroidal flow around a narrow, westward retreating subducting slab. The accompanying WSW advance of the Rif-Betic mountain belt has constructed a thick pile of deformed sediments, an accretionary wedge, characterized by west-vergent thrust anticlines. Bathymetric swath‐mapping images an asymmetric embayment at the deformation front where a 2 km high basement ridge has collided. Subduction has slowed significantly since 5 Ma, but deformation of recent sediments and abundant mud volcanoes suggest ongoing activity in the accretionary wedge. Three possible origins for this deformation are discussed; gravitational spreading, overall NW-SE convergence between Africa and Iberia and finally a WSW tectonic push from slow, but ongoing roll-back subduction. In the absence of arc volcanism and shallow dipping thrust type earthquakes, evidence in favor of present-day subduction can only be indirect and remains the object of debate. Continued activity of the subduction offers a possible explanation for great (M > 8.5) earthquakes known to affect the area, like the famous 1755 Great Lisbon earthquake. Recent GPS studies show SW motion of stations in N Morocco at velocities of 3-6 mm/yr indicating the presence of an independent block, a "Rif-Betic-Alboran" microplate, situated between Iberia and Africa.
ISSN: 0040-1951

insu-00769762
https://hal-insu.archives-ouvertes.fr/insu-00769762
DOI : 10.1016/j.tecto.2012.08.038

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
1. The use of targets to provide measurable objectives and benchmarks for management, conservation, andrestoration of ecosystems is commonplace. In the marine and coastal realms, targets have been successful insetting sustainable limits to fisheries harvests, thresholds for pollutants, and recommended amounts ofrepresentative habitat included in marine protected area (MPA) networks. Quantifiable targets can dissuadegovernments from making dubious claims about investments in ocean protection that sound impressive butcannot be verified. Examples are presented where protection targets have been used successfully for marinemanagement, and instances where measurable and meaningful benchmarks serve to allow tracking of true progress.2. However, the setting of targets can also be a double-edged sword. In some cases, targets have proven useful,but in many instances, interventions made to fulfil targets not only give a false illusion of progress or even success,they present opportunity costs that impede further conservation.3. Some of these issues were raised in the 2003 article ‘Dangerous Targets?: Unresolved issues and ideologicalclashes around marine protected areas’ that appeared in Aquatic Conservation: Marine and FreshwaterEcosystems. Since its publication, the article’s warnings about how targets can sometimes be dangerous andcounter-productive have led to intense debate among scientists and policy-makers alike, and the paper has beencited in more than 500 publications. Yet today, more than a dozen years after the first ‘Dangerous Targets’publication, new targets are driving more MPA designations and conservation strategies than ever before, andthe ‘dangerous’ aspects of target setting have been largely ignored.4. This paper discusses old ‘dangers’ in the context of new developments in marine conservation, including thelingering problem of having simplistic metrics drive marine policies, and the unintended result that can often occurwhen outputs (percentage of area under MPA designation) do not align with true outcomes of effectivemanagement and conservation. Newly emerging ‘dangers’ in letting areal targets (percentage of area underMPA designation) drive MPA designations are also discussed, including how the rush to fulfil obligations toprotect a certain proportion of area is taking place in planning, separate from broader level, and potentiallymore holistic, marine spatial planning (MSP).5. The paper suggests five recommendations that would allow policy-makers to use targets more effectively,including: (1) increase transparency in planning, especially around specific goals and objectives of MPAestablishment; (2) use time-based areal targets when representativity is a goal of the protected area strategy; (3)
ISSN: 1052-7613

hal-01380963
https://hal-univ-perp.archives-ouvertes.fr/hal-01380963
DOI : 10.1002/aqc.2675

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : International audience
ternational Ocean Discovery Program (IODP) Expedition 352 recovered a high-fidelity record of volcanism related to subduction initiation in the Bonin fore-arc. Two sites (U1440 and U1441) located in deep water nearer to the trench recovered basalts and related rocks; two sites (U1439 and U1442) located in shallower water further from the trench recovered boninites and related rocks. Drilling in both areas ended in dolerites inferred to be sheeted intrusive rocks. The basalts apparently erupted immediately after subduction initiation and have compositions similar to those of the most depleted basalts generated by rapid sea-floor spreading at mid-ocean ridges, with little or no slab input. Subsequent melting to generate boninites involved more depleted mantle and hotter and deeper subducted components as subduction progressed and volcanism migrated away from the trench. This volcanic sequence is akin to that recorded by many ophiolites, supporting a direct link between subduction initiation, fore-arc spreading, and ophiolite genesis.
ISSN: 0020-6814

hal-01685628
https://hal.archives-ouvertes.fr/hal-01685628
DOI : 10.1080/00206814.2016.1276482

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
A nested case-control association study was designed to investigate the influence of maternal and fetal copy number variants (CNVs) on reproductive outcomes. Genotypes of ten CNVs encompassing GST and CYP genes were assessed. Significant associations were only found for child CNV genotypes. In particular, the child GSTM1 insertion allele was associated with prematurity protection (odds ratio, 95% CI: 0.67, 0.51-0.89; P < 0.01), whereas the child GSTT2B insertion allele was associated with an increased risk of being small for gestational age (odds ratio, 95% CI: 1.33, 1.07-1.67; P = 0.01). The study highlights the role of the fetal genome in prenatal development and also the need to analyse CNVs in a systematic manner.
ISSN: 1470-0328

hal-00875955
https://hal.archives-ouvertes.fr/hal-00875955
DOI : 10.1111/j.1471-0528.2012.03400.x
PUBMED : 22676722

Éditeur(s) : HAL CCSD Oxford University Press
Résumé : International audience
The BioMart Community Portal (www.biomart.org) is a community-driven effort to provide a unified interface to biomedical databases that are distributed worldwide. The portal provides access to numerous database projects supported by 30 scientific organizations. It includes over 800 different biological datasets spanning genomics, proteomics, model organisms, cancer data, ontology information and more. All resources available through the portal are independently administered and funded by their host organizations. The BioMart data federation technology provides a unified interface to all the available data. The latest version of the portal comes with many new databases that have been created by our ever-growing community. It also comes with better support and extensibility for data analysis and visualization tools. A new addition to our toolbox, the enrichment analysis tool is now accessible through graphical and web service interface. The BioMart community portal averages over one million requests per day. Building on this level of service and the wealth of information that has become available, the BioMart Community Portal has introduced a new, more scalable and cheaper alternative to the large data stores maintained by specialized organizations.
ISSN: 0305-1048

hal-01146849
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01146849
DOI : 10.1093/nar/gkv350
PUBMED : 25897122

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
ISSN: 1932-6203

hal-01520195
https://hal.archives-ouvertes.fr/hal-01520195
DOI : 10.1371/journal.pone.0176862

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

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

Éditeur(s) : HAL CCSD
Résumé : International audience
Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, weconducted a meta-analysis of the relative extent of ITV within and among plant communities worldwide, using a data set encompassing 629 communities (plots) and 36 functional traits. Overall, ITV accounted for 25% of the total trait variation within communities and 32% of the totaltrait variation among communities on average. The relative extent of ITV tended to be greater for whole-plant (e.g. plant height) vs. organ-level traits and for leaf chemical (e.g. leaf N and P concentration) vs. leaf morphological (e.g. leaf area and thickness) traits. The relative amount of ITV decreased with increasing species richness and spatial extent, but did not vary with plant growth form or climate. These results highlight global patterns in the relative importance of ITV in plant communities, providing practical guidelines for when researchers should include ITV in trait-based community and ecosystem studies.
Ecology Letters

hal-01237101
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01237101
DOI : 10.1111/ele.12508
PUBMED : 26415616

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Correlations between major and minor transition elements in tectonically emplaced orogenic peridotites have been ascribed to variable degrees of melt extraction and melt–rock reaction processes, leading to depletion or refertilization. To elucidate how such processes are recorded in the subcontinental lithospheric mantle, we processed a large geochemical dataset for peridotites from the four tectono-metamorphic domains of the Beni Bousera orogenic massif (Rif Belt, northern Morocco). Our study reveals that variations in bulk-rock major and minor elements, Mg-number and modal mineralogy of lherzolites, as well as their clinopyroxene trace element compositions, are inconsistent with simple partial melting and mainly resulted from different reactions between melts and depleted peridotites. Up to 30% melting at < 3 GPa and cryptic metasomatism can account for the geochemical variations of most harzburgites. In Grt–Sp mylonites, melting and melt–rock reactions are masked by tectonic mixing with garnet pyroxenites and subsolidus re-equilibration. In the rest of the massif, lherzolites were mostly produced by refertilization of a refractory protolith (Mg-number ∼ 91, Ol ∼ 70%, Cpx/Opx = 0·4) via two distinct near-solidus, melt–rock reactions: (1) clinopyroxene and orthopyroxene precipitation and olivine consumption at melt/rock ratios <0·75 and variable mass ratio between crystallized minerals and infiltrated melt (R), which are recorded fairly homogeneously throughout the massif; (2) dissolution of orthopyroxene and precipitation of clinopyroxene and olivine at melt/rock ratios ≤1 and R = 0·2–0·3, which affected mainly the Ariègite–Seiland and Seiland domains. The distribution of secondary lherzolites in the massif suggests that the first refertilization reaction occurred prior to the differentiation of the Beni Bousera mantle section into petro-structural zones, whereas the second reaction was associated with the development of the tectono-metamorphic domains. Our data support a secondary, refertilization-related origin for most lherzolites in orogenic peridotite massifs.
ISSN: 0022-3530

hal-01526901
https://hal.archives-ouvertes.fr/hal-01526901
DOI : 10.1093/petrology/egx003

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : The environment is impacted by natural and anthropogenic disturbances that occur at different spatial and temporal scales, and that lead to major changes and even disequilibria when exceeding the resiliency capacities of the ecosystem. With an annual mean flow of 1700 m(3) s(-1), the Rhone River is the largest of the western Mediterranean basin. Its annual solid discharges vary between 2 and 20 Mt, with flood events responsible for more than 70% of these amounts. In the marine coastal area, close to the mouth, both flocculation and aggregation lead to the formation of fine-grained deposits, i.e. the prodelta. This area is characterized by sediment accumulation rates up to 20-50 cm yr(-1) and high accumulations of particle reactive contaminants such as various man-made radionuclides released into the river by nuclear facilities or arising form prior atmospheric nuclear tests (1954-1980) and the Chernobyl accident (April 1986). This prodelta, however, cannot be considered as a permanent repository for particle reactive pollutants since it is subjected to reworking processes. Sediment dynamics had to be linked to the influences of hydrodynamic and atmospheric events such as high flow rates or storms close to the Rhone River mouth. An experiment was carried out during the winter 2006 based on the deployment of two ADCPs and six altimeters at the Grand Rhone mouth for several months. This type of installation has never been used before in this area because of the hard meteorological conditions and the strong fishing activities. However, results showed pluricentimetric rises of the sedimentary level just after river flood events and decreases during storms, generated by southeast winds. Radiotracers and grain size depth profiles helped to characterise the studied events and to establish inventories of sediments and radionuclides. A cruise (CARMEX) was carried out during this same period to collect water samples, suspended particles and sediment cores. The results enabled us to link both river flow and wind characteristics to events recorded on the sea floor, i.e. resuspension, accumulation, consolidation, etc. Deposits of 11 cm of sediments were estimated during flood periods and bottom shear stresses up to 5 N m(-2) were calculated during sediment erosion phases. (C) 2010 Elsevier Ltd. All rights reserved.
Continental Shelf Research (0278-4343) (Pergamon-elsevier Science Ltd), 2010-05 , Vol. 30 , N. 9 , P. 1095-1107

Droits : 2010 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00006/11695/8479.pdf
DOI:10.1016/j.csr.2010.02.015
http://archimer.ifremer.fr/doc/00006/11695/

Éditeur(s) : HAL CCSD
Résumé : National audience
The Lesser Antilles subduction zone has produced no recent strong thrust earthquakes, making it difficult to quantify the seismic hazard from such events. The Lesser Antilles arc has a low subduction rate and an accretionary wedge that is very wide at its southern end. To investigate the effect of the wedge on seismogenesis, numerical models of forearc thermal structure were constructed along six transects perpendicular to the arc in order to determine the thermally predicted width of the seismogenic zone. The geometry of each section is constrained by published seismic profiles and crustal models derived from gravity and seismic data and by earthquake hypocenters at depth. A major constraint on the deep part of the model is that mantle temperature beneath the volcanic arc should achieve a temperature of 1,100°C to generate partial melts. Predicted surface heat flow is compared to the available heat flow observations. Thermal modeling results indicate a systematic southward increase in the width of the seismogenic zone, more than doubling in width from north to south and corresponding to a dramatic southward increase in forearc width (distance from the arc to the deformation front of the accretionary wedge). The minimum width of the seismogenic zone (distance between the intersections of the subduction interface with the 150°C and 350°C isotherms) increases from about 80 km, north of 16°N, to 230 km, at 13°N. The maximum width (between the 100°C and 450°C isotherms) ranges from about 150 km in the north to up to 320 km in the south. This large variation in the width of the seismogenic zone is a consequence of the increasing width of the accretionary wedge to the south, caused by the increased thickness of sediment on the subducting plate. There is good agreement between the thermally predicted seismogenic limits and the sparse distribution of recorded thrust earthquakes, which are observed only in the northern portion of the arc. Possible scenarios for mega-thrust earthquakes are discussed. Depending on the segment length (along-strike) of the rupture plane, the occurrence of an event of magnitude 8-9 cannot be excluded.
Bulletin Société Géologique de France

insu-00814056
https://hal-insu.archives-ouvertes.fr/insu-00814056
DOI : 10.2113/gssgfbull.184.1-2.47

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

hal-01092529
https://hal-agroparistech.archives-ouvertes.fr/hal-01092529

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Spinel (± plagioclase) peridotite xenoliths from the Tallante and Los Perez volcanic centres in the eastern Betics (SE Spain) range from depleted (clinopyroxene-poor) harzburgites to fertile (clinopyroxene-rich) lherzolites and orthopyroxene-free wehrlites. Significantly, only one harzburgite, which is depleted in heavy rare earth elements (HREE), retains the imprint of ca. 20% ancient melting of an original garnet lherzolite source. In contrast, REE abundances of other harzburgites and lherzolites from the eastern Betics have been increased by melt-rock reaction. The whole-rock and mineral compositions of these mantle rocks are largely controlled by three types of modal metasomatism: 1) common clinopyroxene-orthopyroxene addition and olivine consumption which increased FeOt, SiO2 and Al2O3, and decreased MgO compared to the refractory melting products; 2) subordinate orthopyroxene dissolution and precipitation of clinopyroxene and olivine, which led to higher FeOt and MgO and lower SiO2 than in common (orthopyroxene-rich) lherzolites; and 3) rare orthopyroxene consumption and olivine addition that caused higher FeOt and lower SiO2 compared to the original melting residues. These mineral modal and major element variations have been produced mostly by interactions with relatively FeOt-rich/SiO2-poor melts, likely derived from a peridotite-pyroxenite lithospheric mantle with a highly heterogeneous isotopic composition. Melting of the lithospheric mantle in the western Mediterranean was triggered by upwelling of the asthenosphere induced by back-arc extension in the Late Oligocene-Early Miocene. Trapping of small fractions of exotic melts in whole-rocks — likely the parental magmas of Miocene back-arc dykes that intruded the Betic crust — caused local disequilibrium between the trace element signatures and Pb isotopic compositions of clinopyroxene and whole-rock. Subsequent interaction with SiO2-undersaturated magmas, similar to the parental melts of the Pliocene alkali basalts that host the xenoliths, promoted orthopyroxene consumption and clinopyroxene-olivine enrichment at locations close to magma conduits, and finally generated orthopyroxene-free wehrlites. This event constitutes the last episode of the Cenozoic magmatic evolution of the westernmost Mediterranean which is recorded in the mantle xenoliths from the eastern Betics.
ISSN: 0024-4937

hal-01553092
https://hal.archives-ouvertes.fr/hal-01553092
DOI : 10.1016/j.lithos.2016.12.011

Éditeur(s) : Public Library Science
Résumé : Background: Resolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques - including site-based monitoring, genetic analyses, mark-recapture studies and telemetry - can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges. Methodology/Principal Findings: To address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including nesting sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for nesting sites, genetic stocks, and core distributions of population segments of all marine turtle species. We then spatially integrated this information from fine-to coarse-spatial scales to develop nested envelope models, or Regional Management Units (RMUs), for marine turtles globally. Conclusions/Significance: The RMU framework is a solution to the challenge of how to organize marine turtles into units of protection above the level of nesting populations, but below the level of species, within regional entities that might be on independent evolutionary trajectories. Among many potential applications, RMUs provide a framework for identifying data gaps, assessing high diversity areas for multiple species and genetic stocks, and evaluating conservation status of marine turtles. Furthermore, RMUs allow for identification of geographic barriers to gene flow, and can provide valuable guidance to marine spatial planning initiatives that integrate spatial distributions of protected species and human activities. In addition, the RMU framework - including maps and supporting metadata - will be an iterative, user-driven tool made publicly available in an online application for comments, improvements, download and analysis.
Plos One (1932-6203) (Public Library Science), 2010-12 , Vol. 5 , N. 12 , P. -

Droits : 2010 Plos One
http://archimer.ifremer.fr/doc/00028/13926/11308.pdf
DOI:10.1371/journal.pone.0015465
http://archimer.ifremer.fr/doc/00028/13926/