Extent, style and timing of former glaciation in the Gaick, Central Grampians, Scotland, and implications for palaeoclimate

Abstract

The well-preserved record of glacial sediment-landform assemblages in Scotland provides an excellent opportunity to reconstruct the extent and style of former glaciation. Despite a concerted research effort, there remain areas where glacial events are poorly constrained. This is exemplified by the Gaick, a dissected plateau in the Central Grampians, which has proven to be an enigmatic and controversial area. Previously-proposed models fail to adequately explain glacial events in the area, partly due to a paucity of detailed geomorphological, chronological and sedimentological investigations. This thesis presents the results of systematic studies of the sediment-landform record in the Gaick. These investigations, combined with the application of morphostratigraphic principles, have elucidated sediment-landform signatures indicative of multiple glacier fluctuations, specifically (i) interactions of local and regional ice lobes following unzipping during ice sheet deglaciation, (ii) a major stillstand of an extensive pre-Younger Dryas plateau icefield, and (iii) spatiallyrestricted plateau icefield glaciation during the Younger Dryas. The sediment-landform record also suggests a two-phased Younger Dryas advance, as has been found elsewhere in Scotland. The sediment-landform evidence was used to produce palaeoglaciological reconstructions for the three glacial phases. The clarity and completeness of the geomorphological record relating to the Younger Dryas, combined with ice surface profile modelling, allowed the three-dimensional reconstruction of a ~42 km2 plateau icefield. This reconstruction yielded an equilibrium line altitude value of 751 ± 46 m, which was used to derive a sea-level equivalent precipitation estimate of 826 ± 331 mm a-1. Taken together with glacier-derived precipitation estimates from across Scotland, this indicates a strong west–east precipitation gradient during the Younger Dryas. This thesis arrives at a more nuanced understanding of former glaciation in the Gaick, resolving discrepancies with previous conceptual models. In particular, this thesis demonstrates that the Gaick was an important ice dispersal centre throughout the Last Glacial-Interglacial Transition.