LATE QUATERNARY DELTAIC LOWSTAND WEDGES ON THE RHONE CONTINENTAL-SHELF, FRANCE

Shallow seismic profiles on the Rhône continental shelf have shown the existence of stacked progradational lowstand wedges on the outer shelf accumulated during late Quaternary glacioeustatic lowstands. The wedges are bounded by sharp to erosional sequence boundaries and onlap onto the middle shelf. The thickness of individual wedges attains 50 meters at the shelf edge, where they are sheared by slumping. The wedges exhibit well-developed progradational clinoforms, episodically interrupted by internal unconformities on which there is a downward shift of the succeeding clinoforms. These represent small-scale (in the order of a few meters) falls in sea-level. During the Quaternary eustatic cycles, the durations of the stable highstand conditions appear to have been too brief to permit the regressive highstand tract to prograde to the outer shelf. Therefore, the shelf edge builds up entirely with lowstand wedges. © 1990.