The deep-sea Armorican depositional system (Bay of Biscay), a multiple source, ramp model

The deep-sea Armorican depositional system, located in the central part of the Bay of Biscay, is a medium-sized turbidite system with a surface area of more than 30,000 km2. The whole system is a mud/sand-rich submarine ramp on a passive margin. The medial ramp is characterised by the presence of six distinct tributary channels which form three systems: the Guilcher, Crozon and Cornouaille systems. The distal ramp corresponds to divergent braided secondary channels and associated lobes. Variations in hydrodynamic conditions on the outer Armorican Shelf during the last climatic cycle are the major factor controlling facies shifts and system growth. Thus, the Armorican depositional system is a delta-fed submarine ramp during low sea-level glacial conditions, and an outer shelffed submarine ramp at times of sea-level rise.