Dynamique sédimentaire dans les baies de Lancieux et de l'Arguenon (Côte-d'Armor)

ABSTRACT The Lancieux Bay and the Arguenon estuary are located in the Saint-Malo Gulf, along the southern part of the normand-breton Gulf, at places where coastal dynamics are conspicuously efficient. As being protected from the dominant eastward longshore currents by headlands such as cape Fréhel, these sheltered inlets are the site of a fine-grained sedimentation. At the mouth of Arguenon estuary, the mudsilty sedimentation is favoured by the presence of shellfish farming settings which enhance a natural tendancy for tidal-flat enrichment. Sediment deposition due to calm marine conditions and organic detrital excretion are both responsible for the mud intertidal accretion.RÉSUMÉ L'estuaire de l'Arguenon et la baie de Lancieux sont situés dans le Golfe de Saint-Malo, au sud du Golfe normand-breton dans une région où les agents dynamiques sont particulièrement efficaces. Cependant, la position d'abri qu'offre le cap Fréhel à ces baies les protège de la circulation dominante d'ouest, d'où une sédimentation essentiellement constituée de vase et de sables fins. Dans l'estuaire de l'Arguenon, la sédimentation fine est renforcée par la présence d'installations conchylicoles à son embouchure, ce qui, en freinant la propagation des agents hydrodynamiques, accentue la tendance à l'envasement déjà sensible dans la partie amont de l'estuaire ; à ce premier impact, purement mécanique, s'ajoute un impact biologique dû aux rejets des mollusques.Vaucourt C, Bonnot-Courtois C. Dynamique sédimentaire dans les baies de Lancieux et de l'Arguenon (Côte-d'Armor). In: Norois, n°153, Janvier-Mars 1992. pp. 29-44

Transformation and precipitation of phosphates during weathering: Characterization by REE distributions

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28. Mineralogy and geochemistry of alteration products in leg 81 basalts 1

International audienceAlteration products of basalts from the four holes drilled during Leg 81 were studied and found to be characterized by the widespread occurrence of trioctahedral clay minerals (Mg smectite to chlorite). In some cases zeolites (analcite, chabazite) are associated with the saponite. A more oxidizing stage is marked by a saponite-celadonite association, presenting the geochemical characteristics of hydrothermal processes. Later stages of alteration are represented by palagonitization and subaerial weathering at two sites. These different alteration processes of basalts from Leg 81 record the paleoenvironment during the first opening stages of the Northeast Atlantic Ocean in the Paleocene-Eocene periods

Fossil Polymetallic Concretions from Deep Sea Drilling Project Leg 81: Mineralogical, Geochemical, and Statistical Studies

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First pollen analyses combinated to foraminifera assemblages, a key to follow the climatic changes in a fjordic environment : the loch Sunart (NW Scotland).

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