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1 British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK
2 Université de Caen, Laboratoire de Géologie, BP 5186, 14032 Caen Cédex, France
This paper describes the various debris-flow processes which have occurred on the Sula Sgeir Fan, a well-documented feature situated on the Hebrides Slope, NW of Scotland. The Sula Sgeir Fan covers an area 65 km in length and 28 km in width, between the 400 m and 1200 m bathymetric contours. The fan appears as a build-up of stacked debrisflow packages with transparent acoustic facies. These are termed glacigenic debris flows, as they are derived from sediment deposited by ice at the shelfbreak. However, on the southwestern edge of the Sula Sgeir Fan, and on its northeastern flank, there are different acoustic features which are described here as ‘classic’ debris flows. They are larger than the glacigenic type, and a scarp or a sliding scour characterizes their heads; they are thought to have been triggered by seismic events. Associated with these ‘classic’ debris flows are features on the seismic profiles interpreted as gas- or liquid-escape structures.
