Sediment dynamics under the influence of dense shelf water flows and eastern storms, roses continental shelf, NW Mediterranean Sea

Abstract

Recently acquired high-resolution bathymetric and seismic data illustrate numerous current-generated bedforms on the continental shelf of Roses, mostly in the vicinity of the submarine canyons of Cap de Creus and La Fonera, which are deeply incised in the continental shelf. The set of bedforms includes oval and irregularly shaped depressions, lineations, obstacle marks and sediment waves. Bedform characteristics reveal that most of them are presently active under episodically strong (>60 cm s-1) near-bottom currents as part of a complex flow pattern on the shelf, influenced by the presence of submarine canyon heads. The strongest bottom currents flow from the north and are directed towards Cap de Creus canyon head. South of this canyon head, shelf bedforms are indicative of a diverging south-eastwards sediment transport pattern towards the shelf edge and southwards along the middle shelf. Farther south, bottom features are indicative of bottom current re-intensification close to La Fonera canyon head. The current regime deduced from bedforms is further confirmed by in situ current meter measurements in the Cap de Creus canyon and the adjacent continental shelf, and by previous numerical simulations. Current and sediment transport peaks result from high-energy episodic events, such as dense shelf water flows and major Eastern storms. Our findings show that shelf floor morphology provides valuable information about present-day sediment dynamics, the shelf bottom current regime and the physical processes governing erosion, transport and deposition of sediments in such temperate shelf environments.