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Keywords:

  • plateau icefields;
  • Loch Lomond (Younger Dryas) Stadial;
  • ELA;
  • Lake District;
  • glacier reconstruction

Abstract

Detailed geomorphological mapping has revealed evidence for the development of plateau icefields in the central fells of the English Lake District during the Loch Lomond (Younger Dryas) Stadial (ca. 12.9–11.5 ka). The largest plateau icefield system, which covered an area of approximately 55 km2 (including outlet glaciers), was centred on High Raise. To the west, smaller plateau icefields developed on Grey Knotts/Brandreth and Dale Head, covering areas of 7 km2 and 3 km2 respectively. The geomorphological impact of these plateau icefields appears to have been minimal on the summits, where the survival of blockfields and other frost-weathered debris (mostly peat-covered) implies the existence of at least patches of protective, cold-based ice. Ice-moulded bedrock at some plateau edges, however, documents a transition to wet-based, erosive conditions. Prominent moraine systems were produced by outlet glaciers, which descended into the surrounding valleys where their margins became sediment traps for supraglacial debris and inwash. In some valleys, ice-marginal moraines record successive positions of outlet glaciers, which actively backwasted towards their plateau source. This interpretation differs from that of previous workers, who assumed an alpine style of glaciation, with reconstructed glaciers emanating from corries and valley heads. It is likely that plateau icefields were more common at this time in upland Britain than hitherto has been appreciated. Copyright © 2001 John Wiley & Sons, Ltd.