Trough-Mouth Fans: Crary Fan, Eastern Weddell Sea, Antarctica

The “trough-mouth fan (TMF)” concept was introduced by Vorren et al. [1989] when describing the large cone-shaped glaciogenic depocentre on the Barents Sea continental margin, located near Bear Island at the mouth of a transverse shelf trough of glacial origin. Such TMF’s are composed of glacial debris deposited on the outer shelf and upper slope at the grounding line of ice streams when these extend out to the shelf edge. This glacial debris forms prograding-slope strata that pinch out in basinward direction. A comparative MCS study has allowed Vanneste [1995] to identify three basic types of TMF’s: 1. mostly stable TMF’s characterised by absence of large-scale mass-wasting deposits (e.g. Scoresby Sund TMF off East Greenland); 2. unstable TMF’s characterised by the presence of large-scale mass-wasting deposits (e.g. Bear Island TMF in Barents Sea); and 3. TMF’s associated with deep-sea fan systems in their distal parts (e.g. Crary Fan in Weddell Sea).