Deep-sea sediments texture and magnetic fabric, indicators of bottom currents regime

Critical speeds for erosion, transport and deposition of sedimentary particles and prevailing bottom currents intensities are in such a range that the textural properties of the sediment silt fraction may be correlated to the intensity of the deep circulation. On the other hand, the long axis of the sediment magnetic susceptibility ellipsoid, should be aligned according to the current flow. These hypotheses have been positively tested in five abyssal areas. The authors then apply textural studies to the study of Cenozoic deep water circulation in two continental margin areas (Bay of Biscay and Western mediterranean, DSDP Site 400 and Site 372). The results are in good agreement with informations provided by micropaleontological and geochemical indicators. [NOT CONTROLLED OCR]Les conditions d'érosion, de transport et de dépôt des particules sédimentaires et la gamme des vitesses des courants de fond susceptibles de prévaloir en milieu abyssal sont telles que les propriétés texturales de la fraction silteuse des sédiments paraissent pouvoir être corrélées a l'intensité de la circulation profonde. D'autre part, le grand axe de l'ellipsoïde des indices de susceptibilité magnétique des sédiments paraît s'aligner selon la direction du courant prévalant a l'interface. Un test de ces hypothèses dans cinq secteurs de la zone abyssale apparaît positif. Les auteurs appliquent la première de ces techniques (texture) a l'étude de l'évolution de la circulation profonde au cours du Tertiaire dans deux sites des marges continentales (golfe de Gascogne et Méditerranée occidentale, DSDP sites 400 et 372). L'évolution mise en évidence est en accord avec les informations fournies par les indicateurs géochimiques et micropaléontologiques. [OCR NON CONTRÔLE

Campagne Precyad: Preparation du projet de plongees Cyaden dans le golfe d'Aden

In December 83, R.V. Jean Charcot left Djibouti harbor for Leg 2 of the Seamewe 1 cruise devoted to the survey of the projected track of a telecommunication cable between Djibouti and Suez. During this cruise, two days have been devoted to the preparation of the Cyaden diving Cruise, Precyad Cruise. Three maps have been realized

Sedimentation in the southern Cape Verde Basin: seismic and sediment facies

International audienc

Campagne Hydrofast: Etudes quantitatives de l'activite hydrothermale sur la ride-est pacifique a 13 degree Nord

Hydrofast Cruise of the R.V. Jean Charcot addressed the important problem of the variation of hydrothermal activity along the strike of the Ridge over a distance of 100 km with respect to the structure of the ridge axis. This cruise was conducted along the East Pacific Rise between the OSC at 11 degree 45'N and the topographic high at 13 degree N. To reach that objective, a new tool, the dynamic hydrocast, was used. This technique obtains average samples mile per mile, horizontally, at 4 different depths above the bottom. Temperature is recorded at the same time. In addition, the side-scan sonar SAR gave a continuous picture of the fissures along the strike and of the different facies within the 300 to 400 m width of the axial graben. A magnetometer and a thermistance array towed with the SAR completed the set of data

Sediments tertiaires et quaternaires du plateau abyssal du Cap Vert

International audienc