Éditeur(s) : HAL CCSD
Résumé : International audience
The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Using laboratory experiments designed to study lithosphere-scale deformation, we show that the overall pattern of Aegean extension requires not only the combination of trench retreat and Anatolia escape since 15 Ma but also the presence of an inherited lithosphere-scale mechanical discontinuity: the Vardar Suture Zone (VSZ). The reactivation in dextral shear of the eastern branch of the VSZ accommodates both the trench retreat (NS stretching) and the westward escape of Anatolia (EW shortening) in the Cyclades area since 15 Ma. Additionally, our model shows that the North Anatolian Fault (NAF) is a late structure in the evolution of the Aegean, initiated 10 Ma after the onset of Anatolia escape. The model displays displacement sub-domains, which result from strain partitioning instead of being “rigid microplates”, directly comparable to the present-day displacement field (GPS) of the Aegean and western Anatolia. Our modelling provides a simple way to look at the dynamics of Aegean extension in two main stages. From middle Eocene to middle Miocene, extension was only driven by the southward retreat of the Hellenic trench at a rate lower than 1 cm.y-1. Since middle Miocene, the combination of slab rollback with Anatolia westward escape, resulted in a southwest direction of trench retreat, with an accelerating rate of up to 3 cm.y-1.
AGU Fall Meeting 2015
San Francisco, United States

insu-01242045
https://hal-insu.archives-ouvertes.fr/insu-01242045

Résumé : Les espaces naturels protégés sont aujourd’hui à l‘échelle mondiale l’une des principales politiques publiques mises en œuvre pour faire face à la destruction des écosystèmes. Leur nombre a beaucoup augmenté ces dernières années et les modes d’action qu’ils recouvrent se sont considérablement diversifiés. Pour autant, les écosystèmes continuent à se dégrader, et l’efficacité de ces dispositifs est souvent remise en cause. Cette thèse vise à analyser les facteurs influant sur l’efficacité des espaces protégés pour la conservation d’écosystèmes amazoniens encore peu dégradés. Elle étudie pour cela la mise en œuvre de dispositifs relevant de doctrines de gestion de l’environnement différentes, basées sur (i) la limitation réglementaire maximale des activités humaines impactantes pour les écosystèmes, (ii) la gestion des ressources par des populations locales ou traditionnelles ou (iii) la mise en place d’une gestion forestière durable sur des terres publiques. Nous nous plaçons dans une posture comparative entre la Guyane (France) et l’Amapá (Brésil), territoires partageant une frontière commune, principalement matérialisée par le fleuve Oyapock. La comparaison internationale entre ces deux régions présentant une couverture exceptionnelle en espaces protégés, dans des conditions écologiques et géographiques relativement similaires, nous permet d’observer l’influence du contexte historique et sociopolitique sur les modes de prise en charge de la gestion de l’environnement par les aires protégées. Nous nous sommes basés sur une approche constructiviste, appuyée sur une production de données principalement qualitatives (entretiens semi-directifs, analyse de documents, observation participante…). Nous avons ainsi procédé à une déconstruction critique des dispositifs « aires protégées », permettant de mettre en lisibilité les enjeux environnementaux qu’ils portent, et d’analyser l’efficacité environnementale des stratégies mises en œuvre. Cette analyse s’est articulée autour d’une lecture à la fois diachronique et multiscalaire des processus de gestion.Nous montrons que la mise en place des espaces protégés de Guyane et d’Amapá a été portée par des coalitions d’acteurs structurées autour de doctrines de gestion, c’est à dire de conceptions partagées des conditions de mise en œuvre d’une « bonne gestion environnementale ». Les dispositifs créés ont hérité des ressources stratégiques d’action et de la légitimité de ces coalitions. Les coalitions porteuses de la création des espaces protégés en Amapá sont fortement articulées aux mouvements sociaux et environnementaux plus généraux de l’Amazonie brésilienne, notamment pour les revendications socio-environnementales émergeant à la sortie de la période dictatoriale. En Guyane française, les espaces naturels protégés sont principalement la résultante de compromis entre d’une part une volonté d’exemplarité de l’action de la France en Amazonie, et d’autre part une recherche de minimisation des conflits avec les acteurs politiques locaux.
Nowadays, natural protected areas are one of the main public policies implemented at the international level in order to prevent the destruction of ecosystems. During the last decades, they became very numerous, and mobilized more and more diversified modes of action. However, natural ecosystems continue to deteriorate, and the effectiveness of protected areas is often questioned. The aim of this thesis was to analyse the factors influencing the effectiveness of protected areas in a context of Amazonian ecosystems that are still well preserved. We observed the implementation of environmental management arrangement (protected areas) that are based on various doctrines: (i) the strong limitation of all harmful human activities through legislation; (ii) the management of resources by local or traditional populations; and (iii) the implementation of sustainable forest management on public lands. We adopted a comparative approach between Guyana (France) and Amapá (Brazil), territories that share a common border, mainly identifiable by the Oyapock River. These two territories present quite similar ecological and geographical conditions, and both have an exceptional coverage of protected areas. Therefore this international comparison allowed us to observe the influence of the historical and socio-political context on the implementation of protected areas. We used a constructivist approach, mainly based on qualitative data (semi-structured interviews, document analysis, participant observation...). We effected a critical deconstruction of "protected areas" management arrangements in order to make their environmental objectives intelligible, and we analysed the environmental effectiveness of the strategies implemented. This analysis was based on a diachronic and multiscalar lecture of management processes. We show that the establishment of protected areas in Guiana and Amapá was led by coalitions of actors structured around management doctrines, i.e. shared conceptions of "good environmental management". Management arrangements created inherited the strategic resources of action and the legitimacy of these coalitions. In Amapá, coalitions were strongly articulated with wider social and environmental movements of the Brazilian Amazon, especially in the case of socio-environmental claims rising at the end of the dictatorship. In French Guiana, the natural protected areas are mainly the result of compromise between the French willingness to serve as an example in the Amazon region, and the minimisation of conflicts with local politicians.

http://www.theses.fr/2014AGUY0744/document

Éditeur(s) : HAL CCSD Erès
Résumé : International audience
This article tries to show how any action of change in Martinique and Guadelupian enterprises collides in resistances provoked by the racial structures and cleavages profoundly anchored in the culture, inherited from colonialism and slavery. They condition within the enterprise the identities, the hierarchical relationships, the modes of division of labour and individual and collective behaviours. In this difficult situation, the consultant is questioned in his personal and professional identity. To be able to maintain nevertheless the position of third party, he should lean on values and convictions of ethical order, but also on robust theoretical bases (theory of the intervention, analyses of the Martiniquian society and its history).
Cet article cherche à montrer comment toute action de changement dans des entreprises martiniquaises et guadeloupéennes se heurte aux résistances provoquées par les structures et les clivages de nature raciale profondément ancrés dans la culture antillaise, hérités du colonialisme et de l’esclavage, qui conditionnent dans l’entreprise les identités, les rapports hiérarchiques, les modes de division du travail, et les conduites individuelles et collectives. Dans cette situation difficile, le consultant est mis en question dans son identité personnelle et professionnelle. Afin de pouvoir maintenir néanmoins la position de tiers requise par la démarche d’intervention psychosociologique, il doit s’appuyer sur des valeurs et des convictions d’ordre éthique, mais aussi sur de solides bases théoriques (théorie de l’intervention, analyses de la société martiniquaise et de son histoire).
ISSN: 1951-9532

Droits : info:eu-repo/semantics/OpenAccess
hal-01664274
https://hal.univ-antilles.fr/hal-01664274
https://hal.univ-antilles.fr/hal-01664274/document
https://hal.univ-antilles.fr/hal-01664274/file/Nicolas%20Lamic%20Nouvelle%20Revue%20de%20Psychosociologie.pdf
DOI : 10.3917/nrp.003.0181

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) elements that participate to elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace element behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, < 20% serpentinization) to the paleo-Moho, composed of massive serpentinites (MS, 80% serpentinization), the trace elements mobility is reduced. The chemical composition of lizardite and antigorite is homogenized with the local degree of serpentinization: in SSP, serpentine veins composition is inherited from the host mineral while, in MS, their composition is homogenous between destabilized phases at the scale of the outcrop (~ 5 m). In the shallowest part of the oceanic lithosphere, from the paleo-Moho to the oceanic paleo-seafloor, the serpentinites are foliated (FS, > 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these elements are removed from slab to mantle wedge during subduction.
ISSN: 0009-2541

hal-00937661
https://hal.archives-ouvertes.fr/hal-00937661
DOI : 10.1016/j.chemgeo.2013.08.025

Éditeur(s) : HAL CCSD
Résumé : We introduce a general context involving a presheaf A and a subpresheaf B of A. We show that all previously considered cases of local analysis of generalized functions (defined from duality or algebraic techniques) can be interpretated as the B-local analysis of sections of A. But the microlocal analysis of the sections of sheaves or presheaves under consideration is dissociated into a "frequential microlocal analysis " and into a "microlocal asymptotic analysis". The frequential microlocal analysis based on the Fourier transform leads to the study of propagation of singularities under only linear (including pseudodifferential) operators in the theories described here, but has been extended to some non linear cases in classical theories involving Sobolev techniques. The microlocal asymptotic analysis can inherit from the algebraic structure of B some good properties with respect to nonlinear operations.
https://hal.archives-ouvertes.fr/hal-00190006

Droits : info:eu-repo/semantics/OpenAccess
hal-00190006
https://hal.archives-ouvertes.fr/hal-00190006
https://hal.archives-ouvertes.fr/hal-00190006/document
https://hal.archives-ouvertes.fr/hal-00190006/file/Regularity-Local-Microlocal-Analysis5.pdf
ARXIV : 0711.3688

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Standard microbial evolutionary ontology is organized according to a nested hierarchy of entities at various levels of biological organization. It typically detects and defines these entities in relation to the most stable aspects of evolutionary processes, by identifying lineages evolving by a process of vertical inheritance from an ancestral entity. However, recent advances in microbiology indicate that such an ontology has important limitations. The various dynamics detected within microbiological systems reveal that a focus on the most stable entities (or features of entities) over time inevitably underestimates the extent and nature of microbial diversity. These dynamics are not the outcome of the process of vertical descent alone. Other processes, often involving causal interactions between entities from distinct levels of biological organisation, or operating at different time scales, are responsible not only for the destabilisation of pre-existing entities, but also for the emergence and stabilisation of novel entities in the microbial world. In this article we consider microbial entities as more or less stabilised functional wholes, and sketch a network-based ontology that can represent a diverse set of processes including, for example, as well as phylogenetic relations, interactions that stabilise or destabilise the interacting entities, spatial relations, ecological connections, and genetic exchanges. We use this pluralistic framework for evaluating (i) the existing ontological assumptions in evolution (e.g. whether currently recognized entities are adequate for understanding the causes of change and stabilisation in the microbial world), and (ii) for identifying hidden ontological kinds, essentially invisible from within a more limited perspective. We propose to recognize additional classes of entities that provide new insights into the structure of the microbial world, namely ``processually equivalent'' entities, ``processually versatile'' entities, and ``stabilized'' entities.
ISSN: 0169-3867

hal-01544796
https://hal.archives-ouvertes.fr/hal-01544796
DOI : 10.1007/s10539-012-9350-2

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Synkinematic phyllosilicates in fault zones can be used to deduce the deformation mechanisms and the conditions of fault activity, as their chemical composition, crystal structure and texture can record the different stages of deformation and fluid-rock interactions. The Pic de Port Vieux, a second-order thrust related to the major Gavarnie thrust in the southern central part of the Pyrenees Axial Zone, juxtaposes Triassic pelites of the hanging wall and Cretaceous limestones of the footwall. In order to investigate the mineralogical and geochemical changes and constrain the deformation conditions of thrusting, characterization of phyllosilicates was performed along a transect in the fault hanging wall pelites. The Triassic pelites are mainly composed of quartz, calcite, phyllosilicates (chlorite and K-white mica) and ± hematite. The core fault zone thickness is estimated to be about one meter of intensively foliated green pelites, whereas the damage zone is composed of several meters of red pelites. XRD data demonstrated that the difference in color is related to hematite which is only present in the damage zone. Phyllosilicates of the damage zone are mainly inherited/diagenetic K-white mica and chlorite. In the core zone, newly formed chlorite is abundant and preferentially located in veins. It is enriched in Fe compared to the chlorite of the red pelites. The well-defined foliation in the core zone is overlaid by preferentially oriented muscovite grains which have homogeneous compositions, with less Na and relatively more Fe than mica from the red pelites. Newly formed chlorite and muscovite in the core zone are synkinematic to the fault activity. They are both related to deformation processes and fluid rock interactions. Kübler index measurements and chlorite thermometry show that synkinematic phyllosilicates have registered a temperature of 270°C ± 23°C for the damage zone and 285°C ± 28°C for the core zone which are corresponding to lower-anchizone/epizone grade conditions. Numerical modelling with the geochemical modelling program PhreeqC was performed to determine the favorable conditions for the mineralogical change between red and green pelites. It suggests that the main critical parameter favoring hematite dissolution and chlorite precipitation in the core zone, is the redox conditions. According to the model, the chemical changes in the core zone occurred due to interactions with highly reductive fluids. In addition, the hematite dissolution maybe the source of iron for newly formed phyllosilicates in the core zone that are more iron rich compared to those from the red pelites.
ISSN: 0169-1317

hal-01536006
https://hal.archives-ouvertes.fr/hal-01536006
DOI : 10.1016/j.clay.2017.05.008