Unique fan morphology in an entrenched thalweg channel on the Rhône Fan

Abstract

The elongate Rhône Fan is the largest turbidite system in the western Mediterranean and contains an elevated channel-levee system which constitutes the fan valley (Droz and Bellaiche 1985). Unique to modern submarine systems, both the Rhône fan-valley and an inner thalweg channel have arcuate, scallop- or cuspate-shaped morphology (Fig. 13.1), a morphology which is best developed in the modern thalweg channel (O’Connell et al. 1991). Between 1650 and 2200 m below sea level (mbs1) this channel and the surrounding fan-valley were investigated with a deep-towed, high-resolution side-looking sonar and a 4.5 kHz sub-bottom profiler (SeaMARC I; Fig. 13.2). Some of these images (Fig. 13.3), which provide information on the scale of a few tens of metres, are presented, and their implications for fan processes are discussed. Details of the acquisition of the data presented here are given in O’Connell et al. (1991).