LIVE AND DEAD FORAMINIFERAL FAUNAS FROM SAINT-TROPEZ CANYON (BAY OF FREJUS): OBSERVATIONS BASED ON IN SITU AND INCUBATED CORES

Abstract

The impact of sedimentary processes on the live (rose- Bengal-stained) foraminiferal faunas and on the composition of dead assemblages was investigated at a 373-m-deep station in Saint-Tropez Canyon (Bay of Frejus, France). For the .150-mm fraction, biocoenoses and thanatocoenoses were investigated in two 10-cm-long cores collected with a classical Barnett multi-corer. In the 63- to 150-mm size fraction, living faunas were investigated in the first centimeter of the sediment. The first core was fixed with ethanol and rose- Bengal at the time of the sampling (the in situ core) whereas the second core was stored in a culture room during a 2.5- year-long incubation before its fauna was investigated. Both cores present similar thanatocoenoses (.150-mm size fraction) that are substantially contaminated by neritic foraminifera presumably transported from adjacent shelves. The sedimentological analysis of a third core reveals neither graded sediments nor erosional surfaces. Abundant organic remains are detected downcore in the muddy silt sediment. All these observations preclude the idea of deposition by a recent turbidite. Therefore, our canyon environment seems to behave at present as a depocenter for a rather continuous flux of fine sediment and resuspended organic matter originating from shallower areas.