High-energy sedimentation, Creag Aoil, Spean Bridge, Scotland: implications for meltwater movement and storage during Loch Lomond Stadial (Younger Dryas) ice retreat

This paper examines the origin and significance of Loch Lomond Stadial (Younger Dryas) gravel deposits at Creag Aoil, Spean Bridge, Scotland. Sedimentation into ice-dammed lakes in Glen Roy and Glen Spean associated with shorelines at 260 m, 325 m and 350 m is well-documented, yet little is known about later, lower level lakes near Spean Bridge. Excavations on the northern flanks of the Lundy Channel revealed exposures into a 35–40 m thickness of sand and gravel. These sediments reflect deposition in a subaqueous environment experiencing repeated short-lived periods of high-energy subaerial deposition. Deformation structures within subaqueous deposits are associated with at least two ice-push events. This study presents new evidence for the existence of ice-dammed lakes at elevations between 260 m and 113 m and for periodic jökulhlaups draining southwest via the Lundy Channel. Active glacier ice associated with the deposits flowed northwest to southeast, driving meltwater across the Great Glen to the Lundy Channel. Glacier retreat was punctuated by periodic minor readvances. Progressive ice retreat was accompanied by ice thinning, and changes in ice-flow direction and subglacial meltwater routing. These findings add to knowledge of Loch Lomond Stadial deglaciation around Spean Bridge and have implications for our understanding of lacustrine glacier margins during deglaciation. Copyright © 2003 John Wiley & Sons, Ltd.

Keywords:

ice-dammed lake;
subaqueous outwash;
jökulhlaups;
ice-push structures;
Scotland