Contribution of foraminifera to the study of Recent sedimentation in the Gulf of Lions (western Mediterranean Sea)

The spatio-temporal evolution of benthic and planktonic foraminiferal assemblages during the Holocene is studied on the margin of the Gulf of Lions, which is characterized by the indentation of several canyons. The analysis of modern thanatocenoses, sampled in various physiographical areas of four canyons (Lacaze-Duthiers, Petit-Rhoˆne, Marseille and Aude), reveals the importance of geomorphological and hydrologic factors on faunal composition. There is an evident link between the distribution of associations and the topography of the area: larger specimens ( Globorotalia inflata, G. truncatulinoides, Orbulina universa, Uvigerina mediterranea and Cibicidoides sp.) always decrease in abundance in the canyon axis, whereas smaller forms (such as globigerinids) follow the opposite trend, as a result of lateral transports. An increase of species diversity and the occurrence of littoral species in the canyon axis show evidence of channelled sedimentological transport; some littoral specimens with large and black or rusted tests originate from sediments reworked by progradation of the canyon. A comparative study of foraminiferal distribution in six box cores, obtained by Flucha box corers, contributes to the understanding of sedimentary processes in various parts of the Lacaze-Duthiers Canyon during the Holocene. The influence of geomorphological and hydrodynamic factors on planktonic foraminiferal distribution hides the climatic record in the upper canyon, whereas in the upper fan the climatic trend of the Holocene is clearly detectable.