North western Alps Holocene paleohydrology recorded by flooding activity in Lake Le Bourget, France and possible relations with Mont-Blanc glaciers fluctuations

International audienceA 14-m long piston core was retrieved from Lake Le Bourget, NWAlps (France), in order to provide a continuous record of flooding events of the Rhone River during the Holocene. The selection of the coring site was based on high resolution seismic profiling, in an area with limited mass wasting deposits and accumulated proximal Rhone River inter-and underflow deposits. The age-depth model of this core is based on (i) 14 AMS radiocarbon dates, (ii)radionuclide dating(137Cs) and (iii) the identification of historical data (flood events, eutrophication of the lake).The sedimentary record dates back to 9400 cal BP, and includes a thin mass wasting event deposited around 4500 cal BP. A multi-proxy approach was used to track the evolution and origin of clastic sedimentation during the Holocene, in order to identify periods of higher hydrologic al activity in the catchment area. Spectrophotometry was used to detect fluctuations in clastic supply and the study of clay minerals (especially the Illite crystallinity index) allowed locating the main source area of fine grained clastic particles settling at the lake after flood events. This dataset highlights up to 12 periods of more intense flooding events over the last 9400 years in Lake Le Bourget and shows that the main source area of clastic particles during this period is the upper part of the Arve River drainage basin. This part of the catchment area drains several large glaciers from the Mont-Blanc Massif, and fluctuations in Rhone River flood supply in Lake Le Bourget is interpreted as resulting essentially from Mont-Blanc Glacier activity during the Holocene.The comparison of clastic sedimentationin Lake Le Bourget with periods of increasing land use and periods of Alpine glacier and mid-European lake level fluctuations, suggest that the core LDB04 clastic record in Lake Le Bourget is a continuous proxy of the Holocene hydrologic al history of the NW Alps

Rapid volcanic ash entombment reveals the 3D anatomy of Cambrian trilobites

Knowledge of Cambrian animal anatomy is limited by preservational processes that result in compaction, size bias, and incompleteness. We document pristine three-dimensional anatomy of trilobites fossilized via rapid ash burial from a pyroclastic flow entering a shallow marine environment. Cambrian ellipsocephaloid trilobites from Morocco are articulated and undistorted, revealing exquisite details of the appendages and digestive system. Previously unknown anatomy includes a soft-tissue labrum attached to the hypostome, a slit-like mouth, and unique cephalic feeding appendages. Our findings resolve controversy over whether the trilobite hypostome is the labrum or incorporates it and establish crown-group euarthropod homologies in trilobites. This occurrence of moldic fossils with three-dimensional soft parts highlights volcanic ash deposits in marine settings as an underexplored source for exceptionally preserved organisms

Standards for Libraries in Higher Education

The Standards for Libraries in Higher Education are designed to guide academic libraries in advancing and sustaining their role as partners in educating students, achieving their institutions’ missions, and positioning libraries as leaders in assessment and continuous improvement on their campuses. Libraries must demonstrate their value and document their contributions to overall institutional effectiveness and be prepared to address changes in higher education. These Standards were developed through study and consideration of new and emerging issues and trends in libraries, higher education, and accrediting practices. These Standards differ from previous versions by articulating expectations for library contributions to institutional effectiveness. These Standards differ structurally by providing a comprehensive framework using an outcomes-based approach, with evidence collected in ways most appropriate for each institution

Marine Sandwave and River Dune Dynamics -1 & 2

Abstract As seen from the numerous works that were done in the past few years about dunes (this term follows the guidelines defined by Dune preservation Ripple and dune bedding is among the most common sedimentary figures encountered along outcrops or sub-surface records, especially when the sediments consist of siliciclastic shelf deposits. Nevertheless, the preservation of the dune itself including its shape is far from common. A nice example has been described by Preserved bedding Preservation potential The low probability of dune preservation may be due to the present-day high sea-level conditions and to the fact that most studies have been done in low sediment supply and slow subsidence rate areas. It seems easier to preserve shelf sand bodies in sea-level rise conditions. One the the nicest examples, even if bigger than dunes, consist in the so called 'tidal' sand bank

Enregistrement de processus sédimentaires pléistocènes<br />Exemples de plates-formes détritiques et de bassins profonds<br />Mer du Nord et mers de Chine

De leur source continentale à leur lieu de stockage ultime, les particules sédimentaires détritiques vont être produites en fonction de la nature et de l'intensité des processus continentaux : climat, contexte géodynamique. Sur les plates-formes, elles vont subir l'action des agents hydrodynamiques, vont se déplacer, constituer des corps sédimentaires qui seront préservés ou non selon la nature et l'intensité des processus : agitation s.l., apports sédimentaires, création d'espace par subsidence et variation du niveau marin... Enfin, dans les domaines océaniques profonds, elles vont se déposer.L'objectif des travaux présentés dans ce mémoire est, par une approche sédimentologique, de reconstituer les conditions environnementales, tant sur les continents que sur les plates-formes, ayant conduit aux dépôts étudiés. Sur cette base, nous avons entrepris des études sur des dépôts du Pléistocène en mer du Nord ainsi que dans les mers de Chine de l'Est et du Sud. Cette époque, par sa proximité, permet des études à très haute résolution temporelle tandis qu'elle est caractérisée par des oscillations climatiques et eustatiques importantes et rapides. De plus, les dépôts les plus récents portent la trace de l'Homme.Sur la plate-forme, l'étude des grands corps sableux, bancs et très grandes dunes, a permis de préciser les mécanismes de leur mise en place. A court terme, même dans les environnements dominés par la marée, l'importance de phénomènes sporadiques tels que les houles de tempêtes, a été démontrée. Ils impriment aux formes et à la structure des fonds marins leur marque tandis que les agents tidaux sont les pourvoyeurs du matériel sédimentaire. A plus long terme, ce ne sont plus les agents dynamiques qui conditionnent la préservation des corps sédimentaires mais la création d'espace disponible et l'importance des apports sédimentaires. Au niveau de l'estuaire de l'Authie, des séries de carottages nous ont aidé à mesurer les conséquences du mouvement vers le nord des divers ensembles sédimentaires sur le type de sédiment rencontré ainsi que sur les modifications d'un espace naturel convoité par l'Homme.Dans les bassins profonds, en mer de Chine du Sud, nos études ont permis de préciser les sources du matériel sédimentaire et son transport en faisant la part des contributions éolienne, fluviatile et marine. L'étude des caractères sédimentologiques de la fraction détritique a permis également d'étudier la balance ntre l'érosion et l'altération sur les zones émergées ainsi que de voir quelle est la réponse des marqueurs détritiques aux changements climatiques globaux depuis 2 millions d'années

Sedimentologic Analysis of Cores Recovered from the RV Marion Dufresne

International audienc

Sedimentologic Analysis of Cores Recovered from the RV Marion Dufresne

International audienc