Éditeur(s) : HAL CCSD springer Link
Résumé : International audience
Experimental Astronomy

hal-01094521
https://hal.archives-ouvertes.fr/hal-01094521
BIBCODE : 2014ExA...tmp...41R
DOI : 10.1007/s10686-014-9383-4
ARXIV : 1310.0696

Éditeur(s) : HAL CCSD
International Conference on Mechanisms of Mesozoic Continental Extension in Eastern Eurasia
Orléans, France

insu-00610112
https://hal-insu.archives-ouvertes.fr/insu-00610112

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Coral reefs are among the most species-rich and threatened ecosystems on Earth, yet the extent to which human stressors determine species occurrences, compared with biogeography or environmental conditions, remains largely unknown. With ever-increasing human-mediated disturbances on these ecosystems, an important question is not only how many species can inhabit local communities, but also which biological traits determine species that can persist (or not) above particular disturbance thresholds. Here we show that human pressure and seasonal climate variability are disproportionately and negatively associated with the occurrence of large-bodied and geographically small-ranging fishes within local coral reef communities. These species are 67% less likely to occur where human impact and temperature seasonality exceed critical thresholds, such as in the marine biodiversity hotspot: the Coral Triangle. Our results identify the most sensitive species and critical thresholds of human and climatic stressors, providing opportunity for targeted conservation intervention to prevent local extinctions.
ISSN: 2041-1723

hal-01282870
https://hal-univ-perp.archives-ouvertes.fr/hal-01282870
https://hal-univ-perp.archives-ouvertes.fr/hal-01282870/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01282870/file/ncomms10491.pdf
DOI : 10.1038/ncomms10491

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Both oedometric and plane-strain tests were performed with parallelepipedic samples made of synthetic granular, cohesive, frictional and dilatant rock analogue material GRAM2. For the first time parallel sets of fractures that have all the characteristics of natural joints were reproduced in the laboratory. The fractures are regularly spaced, normal to σ3, and have plumose morphology very similar to that of natural joints. These fractures can form at tensile stress σ3 much smaller in magnitude than the tensile strength of material and even at slightly compressive σ3. When mean stress σ exceeds a certain value, the fractures become oblique to σ1 (the obliquity increases with σ), forming networks of conjugate shear bands/fractures. These results of plane-strain experiments are in good agreement with those of better controlled conventional axisymmetric tests on a similar material in Chemenda et al. (2011b) and are closer to real geological situations. Both types of experiments are complementary. Their results lead to the conclusion that at least certain categories of natural fractures (including joints, and conjugate shear fractures/bands) were initiated as deformation localization bands. The band orientation is defined by the constitutive properties/parameters (notably the dilatancy factor) that are sensitive to σ.
ISSN: 0040-1951

hal-00795555
https://hal.archives-ouvertes.fr/hal-00795555
DOI : 10.1016/j.tecto.2011.11.021

Éditeur(s) : HAL CCSD Elsevier
Résumé : Two peat sequences were sampled in the vicinity of the main mining districts of the Vosges Mountains: Sainte-Marie-aux-Mines and Plancher-les-Mines. Lead isotopic compositions and excess lead fluxes were calculated for each of these radiocarbon-dated sequences. Geochemical records are in very good agreement with the mining history of the area, well known over the last millennium. Except for an anomaly corresponding to the Middle Bronze Age which has not yet been resolved, there is no clear geochemical evidence of local metal production in the Vosges before the 10th century as excess lead deposition archived between 500 BC and 500 AD is attributed to long-range transport of polluted particulate matter. The approach described here can be applied to other mining districts where archaeological evidence is scarce or even lacking, but where past exploitation is suspected.
ISSN: 0375-6742

hal-00512409
https://hal.archives-ouvertes.fr/hal-00512409
DOI : 10.1016/j.gexplo.2010.05.004

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We report preliminary results of a seismological experiment, SEISMOTANZ'07, which consisted in the deployment of a local network (35 stations) in the East African Rift System (EARS), North Tanzania, during 6 months in 2007. We compare two earthquake sequences (Gelai and Manyara) occurring respectively in the southern end of the Kenya rift and in the North Tanzanian Divergence (NTD). Only distant of 150 km, their triggering mechanisms are different. None of the sequences depicts typical swarm or mainshock-aftershock patterns. They highlight the change in the magmatic/tectonic nature of the rift where the eastern branch of the EARS enters the Tanzanian craton. The similar shape and long-axis of the elongate sequences emphasize the preferred locus of active strain release along NE-SW discontinuities which probably root at depth into steep Proterozoic shear zones. At Gelai, the deformation is dominated by aseismic process involving slow slip on normal fault and dyke intrusion within the upper crust Calais_et_al_2008. The spatial and temporal earthquake distribution indicates a possible correlation between the Gelai crisis and the eruption of the nearby Oldoinyo Lengai volcano. At Manyara, the sequence is more uncommon, revealing a long-lasting seismic activity deepely rooted (20-35 km depth) possibly related to stress loading transmitted laterally. The yield stress envelope modelled from the depth frequency distribution of earthquakes in the NTD is consistent with the presence of a mafic lower crust and further supports the strength increase of the rifted crust from south Kenya to the NTD.
ISSN: 0899-5362

hal-00420599
https://hal.archives-ouvertes.fr/hal-00420599
DOI : 10.1016/j.jafrearsci.2009.09.005

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
o abstract
ISSN: 1043-4666

hal-01485264
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01485264

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Herbicides are generally the most extensively used of the pesticides applied to agricultural crops. However, the literature contains little evidence useful in assessing the potential sources of the general population's exposure to herbicides, including by residential proximity to crops.The objective of this study was to take advantage of data from the PELAGIE mother–child cohort to identify the main determinants of the body burden of exposure to the chloroacetanilide and triazine herbicides commonly used on corn crops in Brittany, France, before 2006. Urine samples from a randomly selected subcohort of women in the first trimester of pregnancy (n=579) were assayed for herbicide metabolites. The residential exposure resulting from proximity to corn crops was assessed with satellite-image-based scores combined with meteorological data. Data on diet, drinking tap water (from the public water supply), occupations, and household herbicide use were collected by questionnaires.Herbicides were quantified in 5.3% to 39.7% of urine samples. Alachlor and acetochlor were found most frequently in the urine of women living in rural areas. The presence of dealkylated triazine metabolites in urine samples was positively associated with residential proximity to corn crops (OR=1.38, 95% CI: 1.05–1.80). Urinary metabolites of both atrazine and dealkylated triazine were correlated with tap water consumption (OR=2.94, 1.09–7.90, and OR=1.82, 1.10–3.03, respectively); hydroxylated triazine metabolites were correlated with fish intake (OR=1.48, 1.09–1.99).This study reinforces previous results that suggest that environmental contamination resulting from agricultural activities may contribute to the general population's exposure to herbicides.
ISSN: 0160-4120

hal-01107546
https://hal.archives-ouvertes.fr/hal-01107546
DOI : 10.1016/j.envint.2013.10.010
PUBMED : 24246238

Éditeur(s) : HAL CCSD Wiley
Résumé : Genetic variation is generally considered a prerequisite for adaptation to new environmental conditions. Thus the discovery of genetically depauperate but geographically widespread species is unexpected. We used 12 paternally inherited chloroplast microsatellites to estimate population genetic variation across the full range of an emblematic circum-Mediterranean conifer, stone pine (Pinus pinea L.). The same chloroplast DNA haplotype is fixed in nearly all of the 34 investigated populations. Such a low level of variation is consistent with a previous report of very low levels of diversity at nuclear loci in this species. Stone pine appears to have passed through a severe and prolonged demographic bottleneck, followed by subsequent natural- and human-mediated dispersal across the Mediterranean Basin. No other abundant and widespread plant species has as little genetic diversity as P. pinea at both chloroplast and nuclear markers. However, the species harbors a nonnegligible amount of variation at adaptive traits. Thus a causal relationship between genetic diversity, as measured by marker loci, and the evolutionary precariousness of a species, cannot be taken for granted
ISSN: 0014-3820

hal-01032062
https://hal.archives-ouvertes.fr/hal-01032062
DOI : 10.1111/j.1558-5646.2007.00294.x

Éditeur(s) : HAL CCSD Wiley
Résumé : absent
ISSN: 0962-1083

hal-01032205
https://hal.archives-ouvertes.fr/hal-01032205

Éditeur(s) : HAL CCSD Geological Society
Résumé : Extensional basins often evolve both with the generation of normal faults at all scales, and with tilting in the hanging walls and footwalls of major structures. This paper examines the effect of regional tilting on the development of normal fault arrays in an anisotropic sequence, using the asymmetric Lodève Basin, France, as a case study. The orientation range of normal faults is found not to match that expected by continued symmetric generation of conjugate normal faults during tilting. Instead, continued generation of new faults preferentially occurred for faults dipping opposite to the direction of tilt, with propagation perpendicular to bedding. The presence of early bedding-perpendicular joints in the competent sandstone units aided propagation of these faults during tilting and this preferential asymmetric development. Bedding-parallel slip surfaces were activated as normal faults during the later stages of bedding tilting, showing complex interaction patterns with later faults downthrowing in the direction opposite to bedding tilting. Hence knowledge of the timing between tilting of the strata and deformation helps in evaluating the likely complexity of fault arrays at subseismic scales in extensional basins, and may also help in understanding the evolution of fault systems in tilted normal fault blocks at the reservoir scale.
ISSN: 0016-7649

hal-00404753
https://hal.archives-ouvertes.fr/hal-00404753
DOI : 10.1144/0016-76492006-047