Aspects of the deglaciation of the Lochaber Glacial Lakes area, western Scottish Highlands

This paper examines the landforms and sediments in the area of the Lochaber Glacial Lakes in order to evaluate the process, pattern and timing of Late Devensian glaciation and ice wastage in that part of northwestern Scotland. Detailed evidence is provided for a number of critical areas including the Roy-Spey watershed region, the Allt Chonnal valley, the Glen Turret Fan and Moraine, the valley side fans of the upper and middle Roy valley and Glen Gloy. The work is based on field evidence and includes moraine ridges, fan landforms and sediments, along with the results of varve analyses from the Roy and Laggan valleys published elsewhere. The results suggest that, apart from some small corrie glaciers at the south side to the Roy-Spey watershed, much of the area was deglaciated following the Western Ross Readvance (c. 15.4–15.8 cal ka BP), prior to glaciers of the Loch Lomond Readvance (c. 12.9–11.7 cal ka BP) reaching the well-defined limits that held back the glacial lakes. The process of ice wastage within Glen Roy, from the Wester Ross Readvance, involved ice-marginal fluctuations, minor readvances and the formation of a pro-glacial lake related to the col at the Roy/Spey watershed. It is also proposed that many of the fans that occur along the sides of Glen Roy are of subaerial origin formed by paraglacial processes, rather than as subaquatic lake deltas.