We report new LA-ICP-MS U-Pb zircon ages of varied crystalline rocks occurring in the Serre Chevalier crystalline terrain, an allochtonous basement unit located at the top of the Briançonnais nappes ...stack ∼5 km west of Briançon city. Mapped as an undifferentiated metasedimentary basement on the geological map at 1/50,000 scale, this unit actually displays varied lithologies including alternating micaschist, paragneiss, quartzite, coarse-grained conglomerate and felsic (leptynite) to mafic (amphibolite) gneiss of magmatic origin. All rocks were metamorphosed in response to a dominant pre-Alpine event under amphibolite facies conditions. Partial recrystallization under low-grade amphibolite to greenschist facies conditions was associated with alpine events. Zircon ages were obtained on four types of rocks: (i) a micaceous quartzite from the core of the metasedimentary unit displays a dominant age population around 610 Ma, with a minimal age of 580 Ma, and subordinated age populations at c. 940 Ma, 1825 Ma and 2100-2560 Ma ; (ii) a granite boulder from a coarse-grained conglomerate yields a well-defined age of 582 ± 5 Ma and subordinated inherited ages between 1800 and 2200 Ma. Zircon rims of probable metamorphic origin provide a concordant age of 492 ± 4 Ma ; (iii) a gneissic band in the vicinity of the conglomerate is dated at 597 ± 4 Ma ; (iv) a coarse-grained garnet amphibolite yields an age of 517 ± 3 Ma interpreted as the emplacement age of the protolith, either as intrusive unit cutting accross the sedimentary succession or lava intercalated within the sediments. The mainly Ediacarian record in the metasediments (quartzite and granite boulder in conglomerate) lead us to conclude that this material resulted from the erosion of a nearby Ediacarian (Cadomian ?) basement. The age of 517 Ma obtained on the amphibolite provides a minimum age for the sedimentary succession which deposition is therefore bracketed between 582 Ma and 517 Ma. This interval is comparable to that of the metasedimentary units of the Brioverian group of the Armorican Massif. Based on their low Th/U ratio, the 492 Ma-old zircon rims in the granite boulder are attributed to an Upper Cambrian metamorphic event.
Nous présentons de nouveaux âges U-Pb sur zircon (LA-ICP-MS) sur des roches cristallines variées localisées à Serre Chevalier au sein d’une unité de socle allochtone située au sommet de l’empilement de nappes de la zone briançonnaise ∼ 5 km à l’ouest de la localité de Briançon. Cartographiée comme une unité métasédimentaire indifférenciée sur la carte géologique au 1/50 000 e , cet ensemble présente en fait une grande diversité lithologique, associant des micaschistes, des paragneiss, des quartzites, des conglomérats parfois très grossiers et des gneiss felsiques (leptynites) et mafiques (amphibolites) d’origine magmatique. Toutes les roches sont métamorphisées en lien avec un événement pré-alpin dans les conditions du faciès amphibolite et plus ou moins recristallisées dans les conditions du faciès amphibolite de bas degré à schiste vert lors d’un événement alpin. Les âges U/Pb sur zircon ont été obtenus sur 4 types de roches : (i) un quartzite micacé prélevé au cœur de l’unité métasédimentaire montre une population d’âges dominante vers 610 Ma, avec un âge minimal de 580 Ma, et des âges subordonnés à ∼ 940 Ma, 1825 Ma et 2100-2560 Ma ; (ii) un bloc de granite extrait d’un conglomérat très grossier montre un âge bien défini à 582 ± 5 Ma et des âges subordonnés dans l’intervalle 1800-2200 Ma. Des surcroissances à la périphérie des zircons fournissent des âges à 492 ± 4 Ma ; (iii) une bande gneissique voisine du conglomérat fournit un âge à 597 ± 4 Ma ; (iv) un banc massif d’amphibolite à texture grossière est daté à 517 ± 3 Ma, âge interprété comme celui du protolithe, qui pouvait être un corps intrusif dans la série sédimentaire ou une lave intercalée dans les sédiments. L’enregistrement essentiellement édiacarien dans les métasédiments (quartzite et bloc de granite dans le conglomérat), sans indice d’âge plus jeune, indique que ce matériel dérive de l’érosion d’un socle d’âge édiacarien (Cadomien ?). L’âge à 517 Ma obtenu sur l’amphibolite permet d’encadrer la mise en place de la série entre 582 Ma et 517 Ma ; cet âge est comparable à celui des séries métasédimentaires du Briovérien armoricain. Du fait de leur faible rapport Th/U, les surcroissances de zircon dans le bloc de granite sont attribuées à un événement métamorphique d’âge cambrien supérieur.
•Primary producers in Cretaceous OAE1a to 1d were evaluated by triaromatic steroids.•A mid-polar column enables clearer separation of GC peaks of triaromatic steroids.•Triaromatic dinosteroid index ...is proposed as a dinoflagellate productivity indicator.•Biomarker record suggests predominance of dinoflagellates as producers during OAE1b.•Assemblages of primary producers in each OAE varied depending on marine conditions.
Desmethyl and A-ring methyl triaromatic (TA) steroids, including dinosteroids, were analyzed in the sediments deposited during the mid-Cretaceous oceanic anoxic events (OAEs) 1a (Goguel), 1b (Jacob, Kilian and Paquier) and 1d (Breistroffer) from the Vocontian Basin, SE France. These TA steroids were identified by GC–MS using non-polar (DB5-HT) and mid-polar (VF-200ms) columns; their peaks are more clearly separated by the mid-polar column. The triaromatic dinosteroid indices (TADS and TADS′) are defined as alternative indicators for reconstructing dinoflagellate production. In these relationships, the TADS′ values tend to increase in the samples that have higher abundances of the co-eluted 3-methyl TA steroids. The TADS values are lower in the Goguel, Jacob and Kilian samples but increase in the Paquier and Breistroffer samples, and are especially consistently higher in the Paquier. These results suggest that dinoflagellates flourished under the stratified and eutrophic conditions in surface waters during the Paquier deposition (OAE1b). Moreover, an inverse correlation between the TADS and C27 TA steroid (TAS) values is noticeable in the samples from the Kilian and Paquier deposits. Thus, the C27 TA steroids in these sediments, which originated from C28 sterols, may be primarily derived from an ecological competitor of dinoflagellates. We propose that their competitors are possibly coccolithophorids and/or prasinophyte algae. During the mid-Cretaceous hothouse period, coccolithophorids/prasinophytes had the potential to flourish under more oligotrophic conditions, whereas dinoflagellates were dominant as primary producers under eutrophic conditions.
The practice of recreational sports plays a part in the structuring of mountain regions with regard to several requirements. Following the golden age of winter sports, the challenge of sustaining the ...French ski resort economy in the 1980s was affected by a diversification of practices. Embodying this "fun" attitude, all-terrain cycling spread into the mountains. The representations and the values underlying it allow us to understand the appropriation of these new forms of practices as much as their co-transformations. The case of Oisans, a territory with mythical status thanks to the historical passage of the Tour de France, allows us to put the impact of these new methods into perspective. The events, the shaping of the territory, the professional transformations which are seeds of a sociocultural mutation, and the conflicts linked to integrating the practice determine the impact of this activity, which has now become an identity marker of mountain regions.
Lyme borreliosis is a zoonotic tick-borne infection representing the most frequent vector-borne disease in the northern hemisphere. The Mediterranean rim is generally described as unsuitable for the ...European vector, Ixodes ricinus. We conducted an epidemiological study to assess whether I. ricinus was present and study its infection status for tick-borne bacteria. Ticks originating from southeastern France were obtained from flagging sampling and removed from animals and tick-bitten patients. Species level identification used morphological keys and MALDI-TOF MS. Quantitative PCR and sequencing assays were used to detect and identify tick-associated bacteria (Borrelia, Rickettsia, Anaplasmataceae, Bartonella, Coxiella burnetii) in each specimen. A total of 1232 ticks were collected in several localities. Among these, 863 were identified as I. ricinus (70%). Bacterial screening allowed identification of Lyme group Borrelia among I. ricinus ticks originating from various regional areas. Other emerging tick-borne pathogens like Borrelia miyamotoi and Rickettsia species were also detected. The Alpes-Maritimes region, part of the French Riviera, harbours I. ricinus ticks infected with Lyme group Borrelia and several other tick-borne bacterial agents. Clinicians and outdoor activity participants should be aware of the local Lyme borreliosis transmission risk.
A key component of the environment in coastal territories, the sea also creates special geographical features and grounds social and cultural identities. At a time of rising concern and multiple ...projects for its exploitation as well as its protection, public policies need to consider the social representation of the marine environment and people’s visions of its future. Relying on the concept of maritimity, defined as all the relationships binding human societies to the sea and the resulting landscape, economy and culture, we assess the maritime character of a coastal region in southern France by analysing the local sea–related associations its population are engaged in. This is made possible through the supervised extraction of the relevant data from the national directory of associations, the official database of non-profit associations in France, which are then given appropriate statistical and cartographic treatments. Results provide an indication of the depth of the region’s maritime character, as well as the areas of activity and places in which maritimity is the most developed. These are consistent with the social and economic profile of the region, highly engaged in tourism and a residential economy. Further work is recommended, with a view to exploring the region’s maritimity more closely by comparing it with other regions and applying finer analysis to the stated objectives of the sea-related associations.
For many years now, several museums and heritage sites linked to the textile industries in the Rhône-Alpes region have been handicapped by the disappearance of the skills and savoir-faire associated ...with these industries, especially where the conservation, the repair and the mediation of textile making equipment is concerned. This awareness has led five museums to react and to try their best to preserve not only the technical, material heritage but also the immaterial heritage associated with it. Joined together in a federation, these museums are now thinking about the preservation, the promotion and the future of their collections. How must the museography of a place combine both the historical aspects of the site with a balanced presentation of the collection, so that everything seems coherent for the public ? How to respond to specific issues raised by welcoming the public and preserving the collections when the museum is part of a former industrial site or located in a traditional workshop? And finally, how to ensure the interpretation and mediation which are necessary for the proper understanding of the collections (especially of the textile equipment), when confronted with the decline and even the disappearance of technical know-how ? These are some of the questions to which the members of the federation are trying to find answers.
Probability maps of landslide reactivation are presented for the Pra Bellon landslide located in the southern French Alps based on results obtained with dendrogeomorphic analysis. Spatiotemporal ...patterns of past landslide activity was derived from tree-ring series of 403 disturbed mountain pine trees growing in the landslide body. In total, 704 growth disturbances were identified in the samples indicating 22 reactivation phases of the landslide body between 1910 and 2011. The mean return period was 4.5
years. Given the spatiotemporal completeness of the reconstruction, probabilities of landslide reactivation were computed and illustrated using a Poisson distribution model and for 5, 20, 50, and 100
years. Probability of landslide reactivation is highest in the central part of the landslide body and increases from 0.13 for a 5-year period to 0.94 for a 100-year period. Conversely, probabilities of reactivation are lower at its margins. The proposed method differs from conventional approaches based on statistical analyses or physical modeling that have demonstrated to have limitations in the prediction of spatiotemporal reactivation of landslides. Our approach is, in contrast, based on extensive data on past landslides and therefore allowed determination of quantitative probability maps of reactivation derived directly from the frequency of past events. This approach is considered a valuable tool for land managers in charge of protecting and forecasting people and their assets from the negative effects of landslides as well as for those responsible for land use planning and management. It demonstrates the reliability of dendrogeomorphic mapping that should be used systematically in forested shallow landslides.
► Probability maps of landslide reactivation are derived from tree-ring analysis. ► It demonstrates the reliability of dendrogeomorphic mapping in shallow landslides. ► This approach is a valuable tool for land managers in charge of protecting people.
Submarine groundwater discharge (SGD), the flow of fresh and saline groundwater from the seabed into the coastal ocean, has been intensively investigated in the recent years. This research has ...usually been restricted to shallow water and intertidal areas, whereas knowledge about groundwater seepage in deeper water is mainly limited to point sources from karstic aquifers. In this study we observed submarine groundwater seepage and a subterranean estuary in sediments at water depths of 20–44 m located within the Ligurian Margin, western Mediterranean Sea. Here, a catastrophic submarine landslide occurred near the Nice airport (French Ligurian coast) in the fall of 1979 after a period of heavy rainfall. During two research cruises, gravity cores were recovered in and around the area of the landslide scar. Pore water samples collected from sediment cores indicated sediments containing freshwater within the landslide scar. Pore water profiles of selected ions, such as chloride, ammonium, manganese, sulfate and barium were used to assess transport and reaction processes within the sediment. A 1-dimensional transport model indicates in most cores upward pore water velocities of 2.3–8.8 cm yr−1. This study shows that submarine groundwater seepage along the French Mediterranean coastline can occur at water depths reaching 44 m.
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