The Celtic Deep-Sea Fan located in the northwestern part of the Bay of Biscay is a middle sized fan with a surface area of more than 30,000 km2. The whole system is a mature mud/sand-rich submarine fan on a passive margin. Multi-beam echo sounder data, 3.5 kHz seismic and 12 Küllenberg cores were examined to define the fan morphology, the lithological characteristics, the sedimentary processes and the relationship between the evolution of the fan deposits and the environmental conditions on the Celtic continental shelf. The upper fan is characterised by the presence of two distinct tributary systems: (1) the Whittard system with a large, persistent, slightly sinuous channel, which is linked to the southern end of the Irish Sea River system; and (2) the Shamrock system, with a moderate sized channel, which is linked to the western end of the English Channel River system. The middle and lower fan corresponds to divergent braided secondary channels and associate lobes. Successive lobe elements, without important relief, were generated during periodic avulsions of middle fan channels. The lithological, palaeontological, and geochemical analyses on cores show the evolution of sedimentation since the last glaciation. During the last lowstand and rise of sea-level frequent low-density turbidity currents were predominant and deposited sediments throughout the whole fan system. They were initiated at the front of a deltaic environment on the Celtic outer-shelf. During the high sea-level conditions, occasional high-density turbidity currents and/or non-cohesive debris flows occur and were responsible for sand deposition in the middle-lower fan. They are derived from reworked sands due to the high-energy conditions on the outer shelf. Thus for the Celtic Fan, the variations of the hydrodynamic conditions on the outer Celtic Shelf seem to be the primary control on facies shift and fan growth.< Leer menos