The Glacial Geomorphology of the Loch Lomond (Younger Dryas) Stadial in Britain

Abstract

The Loch Lomond Stadial (LLS) refers to the abrupt return to severe cold conditions that occurred in Britain, between 12.9 and 11.7 ka, subsequent to the retreat of the last (Late Devensian) British-Irish Ice Sheet. This period has long been associated with the regrowth of glaciers in upland areas of Britain and left a wealth of geomorphological evidence in the landform record. However, previous research on these glaciers has largely comprised localised case studies, producing a fragmented and spatially inconsistent dataset. This thesis draws together the published geomorphological evidence for Loch Lomond Stadial glaciation to build a coherent picture of the extent, style and dynamics of glaciation during the stadial. Geomorphological mapping of glacial landforms associated with this period is compiled from the published literature to create a map and geographic information systems database of over 95,000 features. The evidence used to produce this map is critically assessed in the most comprehensive review of the Loch Lomond Stadial to date and is used to identify conceptual themes, common to the geomorphology in multiple sub-regions within Scotland, England and Wales. Persisting uncertainties, particularly regarding the extent and timing of Loch Lomond Stadial glaciation, are discussed and recommendations of future research to address these are made. Building on this review, the glacial geomorphological map is then used to construct five glacial landsystem models which reflect the style of Loch Lomond Stadial glaciation; the cirque/niche glacier landsystem, the alpine icefield landsystem, the lowland piedmont lobe landsystem, the plateau icefield landsystem and the ice cap landsystem. Use of these models to classify the Loch Lomond Stadial glacial geomorphology reveals the spatial distribution of each landsystem. Three styles of glacier retreat are represented by the glacial geomorphology. It is demonstrated that both landsystem and retreat style reflect the combined importance of pre-existing topography and palaeoclimate. Given the paucity of dating constraints on Loch Lomond Stadial landforms, the thesis pilots the use of a relative dating technique using soil chronosequences to differentiate between Loch Lomond Stadial and older moraines in the English Lake District. The results of this study highlight the potential of this technique to discriminate between Loch Lomond Stadial and pre-Loch Lomond Stadial moraines in Britain, although further work is required.