Plongées en submersible dans les canyons méditerranéens : principaux résultats de la campagne Cyaligure

The observations carried out during the "Cyaligure" submersible cruise emphasize the shaping action of the submarine currents and slidings during the Quaternary. The canyons located off the french Riviera (Provence), cut in late Oligocene detrital formations, have been the locus of several phases of in-filling, lithification and cutting phenomena throughout the Messinian epoch up to now. Consequently they can be considered as complex polygenetic structures. The canyons located off SW Corsica appear to be directly cut, in their upper course either in the cristalline basement or in volcanic lava formations. In their median part, they are cut in quaternary sediments and in their lower part in middle or late Miocene sedimentary units. The strong linear NW-SE magnetic anomalies, lying on the south-western corsican margin, correspond with dredged metamorphic basalts whose the "greenschist facies" appears to be very significant of a typical oceanic crust. Observations and sampling show that, in the explored corsican canyons, the Quaternary sedimentation is purely of hemipelagic nature, whereas the Provence canyons are in-filled with terrigeneous turbidites (s.l.) assumed to be principally deposited during the ice epochs. So, these two opposite margins appear to be very asymmetrical both from structural and sedimentary points of view. [NOT CONTROLLED OCR]