THE EFFECTS OF LATE QUATERNARY SEA-LEVEL CHANGES ON THE RHONE SLOPE SEDIMENTATION (NORTHWESTERN MEDITERRANEAN), AS INDICATED BY SEISMIC STRATIGRAPHY

High-resolution, single-channel seismic profiles have been collected o n the shelf and slope off the present Rhone Delta (western Mediterrane an) using a 750 J Sparker. These profiles have been correlated with ea rlier high-resolution seismic work on the shelf that identified severa l superimposed wedge-shaped seismic units, interpreted to be Late Quat ernary shelf-perched lowstand wedges. These wedge-shaped seismic units are traced onto the slope in an intercanyon area between the Grand-Rh one and Petit-Rhone submarine canyons. Detailed analysis of the seismi c facies shows that Upper Quaternary slope deposits also define sedime ntary cycles, Each basic cycle is composed of a couplet of two differe nt subunits. The lowest one is mostly transparent, has a gentle seawar d-convergent geometry, and correlates with one complete perched lowsta nd wedge on the shelf, The upper subunit is well stratified, has a gen tle seaward-divergent geometry, and correlates with an erosional uncon formity on the shelf. C-14 dating of the youngest slope cycle indicate s that most of the deposition on the slope occurred during low sea-lev el periods and that the couplet of transparent and layered subunits ar e the result of the interaction between eustatic sea level, sediment f lux, and the geometry of the continental shelf and slope. Stratified e longated wedges on the slope are interpreted as deposition when the de pocenter moves out from the shelf to the upper slope and deep basin, T his model is compared to the Late Quaternary eustatic sea-level curve, Some cycles in this curve seem to be absent on the slope or completel y eroded on the shelf, indicating that caution is necessary in deducin g relative sea-level cycles from continental-margin stratigraphy.