Trough mouth fans - Palaeoclimate and ice-sheet monitors

Trough mouth fans are fans at the mouth of transverse troughs/channels on glaciated continental shelves. On the northwest European glaciated continental margin, eight trough mouth fans, varying in size between 2700 and 215,000 km(2), have been identified. The trough mouth fans are depocentres dominated by debris flows accumulated in front of ice streams draining the former large northwest European ice sheets. The debris flow units are separated by hemipelagic interglacial/interstadial sediments. It is inferred that the number of debris-flow units record the number of shelfbreak-positions of the ice sheet margins: the number found varies between three in the south and eight in the north. Typical trough mouth fans and related debris-flow units seem to have been formed later than the early mid-Pleistocene, thus the north European ice sheets did not form ice streams extending to the shelfbreak in any appreciable length before the mid-Pleistocene. Besides being loci for sediment deposition, the trough mouth fans were also the main sites of fresh water supply to the ocean (in the form of icebergs) during the mid/late Pleistocene ice ages. Copyright (C) 1997 published by Elsevier Science Ltd.