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 Elsevier Masson
Résumé : International audience
We provide new constraints on the modes of mantle exhumation and denudation in the pre-orogenic Pyrenees by investigating the poorly known peridotites located east of the Lherz body, in eastern Ariè ge (Vicdessos, Urs, Bestiac, Caussou and Prades main peridotitic bodies). We show that: (1) numerous peridotite bodies, not described so far, are constituted by decametric to sub-metric outcrops scattered between and around the main outcrops identified by Monchoux (1970); (2) most of the peridotites form blocks and lenses of various sizes, from millimetric monocrystalline grains to hectometric olistoliths, embedded in debris flows involving mainly Mesozoic metasediments; these peridotites can therefore be linked to the S-type peridotites of Lagabrielle et al. (2010), and share similarities with the peridotites of Lherz region (Clerc et al., 2012). All originated from tectono-sedimentary processes associated with mantle exhumation in relation with extreme thinning and breakoff of the continental basement; (3) the various petrographic characters of these peridotites and their heterogeneity in serpentinisation degree imply a peculiar mode of exhumation, which merges mantle fragments inherited from different structural levels; (4) the lack of tectonic structures such as faults and shear planes associated with the ultramafic-rich breccia formation and the presence of neoformation of metamorphic minerals within the matrix preclude their origin as cataclasites related to the Latest Cretaceous and Tertiary Pyrenean contractional deformation. The peridotites of eastern Ariè ge are indisputable witnesses of the presence of an inverted hyper-extended Cretaceous passive margin forming the current North Pyrenean zone. The geometry of the extensional system was complex and probably associated with strike-slip faults and transcurrent motion. ß 2016 The Authors. Published by Elsevier Masson SAS on behalf of Acadé mie des sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/).
ISSN: 1631-0713

Droits : http://creativecommons.org/licenses/by-nc-nd/
insu-01280502
https://hal-insu.archives-ouvertes.fr/insu-01280502
https://hal-insu.archives-ouvertes.fr/insu-01280502/document
https://hal-insu.archives-ouvertes.fr/insu-01280502/file/1-s2.0-S1631071316000043-main.pdf
DOI : 10.1016/j.crte.2015.12.003

Éditeur(s) : HAL CCSD
Résumé : International audience
The geology of the North Pyrenean Zone in the central Pyrenees allows for the observation in the field of theentire section of the Pyrenean rift, from the mantle to the crust and the Mesozoic cover (pre, syn and post rift).The good knowledge we have of the pre-Alpine history of the Pyrenees allows us to properly constrain the Alpinegeological evolution of the pre-Triassic rocks which record both Variscan and Alpine orogenic cycles.The mantle outcrop as kilometric to centimetric fragments of peridotite dispersed within a carbonate metamorphicbreccia. The study of peridotite serpentinisation shows several events of low-temperature serpentinisation, incontact with seawater. In some locallities, we can observe a mixture of fragments of variously serpentinizedperidotites. This suggests a tectonic context where fragments of peridotites from different structural levels weresampled more or less synchronously.The granulitic basement is characterized by a Variscan syndeformational HT event (300-280 Ma). So farwe have not found any trace of a Cretaceous HT event (> 500C). On the other hand, the basement is affectedby a regional metasomatism that began during the Jurassic and became more spatially focused with time until itwas restricted to the Pyrenean rift during the Aptien, Albian and Cenomanian. The talc-chlorite metasomatism(120-95 Ma) shows an evolution from a static toward a syn-deformation hydrothermal event, under a more or lessnormal geothermal gradient. Extensional deformation is recorded by the reworking of several inherited low-angleVariscan tectonic contacts, but also by dispersed high-angle extensional shear zones formed under greenshistconditions.The metamorphic Mesozoic cover of the basement massifs, which constitute the so-called Internal MetamorphicZone, is an allochtonous unit made of lenses of Mesozoic rocks enclosed into the breccia, whichlocally contains peridotite and basement clasts. The Mesozoic metamorphic carbonates show a first phase ofsyn-metamorphic (450-600C, P < 2 kb) ductile deformation, and subsequent phases of folding and fracturing.The datation of neoformed minerals give a 108-85 Ma time span for the metamorphism. We interpret this brecciaas an abandonment breccia which marks the emergence of the main detachment. The basal contact of the Mesozoiccover has a complex 3D geometry traced by Triassic evaporites. It corresponds to a major pre- and synorogenicpolyphased tectonic contact.All these data show a geometrically complex hyper-extended rift where the crust was not stretched under ahigh geothermal gradient but thinned by the tectonic extraction of relatively thin lenses and perhaps cut by highangle low-grade shear zones. The 3D geometry, as well as the strain records and the breccia lithologies stronglysuggest a non-cylindricity for the exhumation process, probably within a transtentional system
Geophysical Research Abstracts
Vienne, Austria

insu-01510371
https://hal-insu.archives-ouvertes.fr/insu-01510371

Éditeur(s) : HAL CCSD
Résumé : National audience
Dans la région de Bestiac, en haute-Ariège, une coupe nord-sud d’àpeine plus d’un kilomètre de long centrée sur la zone nord-pyrénéennemétamorphique montre les relations entre le socle anté-alpin (gneissgranulitiques et série paléozoïque) du massif nord-pyrénéen du St Barthélémyet de la zone axiale, et la série mésozoïque constituée principalementde marbres et de brèches carbonatées à éléments de lherzolite,mais aussi du flysch crétacé supérieur.A partir de nouvelles données cartographiques, structurales, métamorphiqueset géochronologiques, nous montrons les modalités de l’extensiondans le socle varisque (comment ’escamoter’ la croûte sans ’trop’l’étirer ?), et comment celle-ci a précédé la mise à la surface du manteauet la formation du complexe bréchique. Ces données nous permettentde caractériser l’importance de l’héritage varisque dans la structurationalpine, mais aussi de poser la question de l’impact des déformations alpinesdans ce qui est considéré comme varisque. Enfin, la restaurationde la coupe nous permet d’aborder la question de la géométrie 3D dusystème au Crétacé, et des rôles respectifs des composantes extensiveset décrochantes.
24 ème Réunion des sciences de la Terre 2014
Pau, France

insu-01080833
https://hal-insu.archives-ouvertes.fr/insu-01080833