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Barnaby Bedford (2012)

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Citation: a sophisticated, novel, multi-approach dissertation presented to a highly professional standard.

Title: To What Extent is Evidence from the Last Stadial a Proxy for the Long-Term Pattern of Glaciation in Scotland?

Quaternary glaciations have exerted a considerable erosive force across the Scottish landscape. Numerous studies have attempted to reconstruct the extent and dynamics of the most recent ice mass, that of the Loch Lomond Stadial (ca. 12.9-11.5ka BP) from a varied catalogue of geological and geomorphological data. This research aimed to assess the extent to which the ice cap that covered western Scotland at this time represents the long-term pattern of glaciation and more importantly erosion. A recent empirically-validated numerical reconstruction by Golledge and others (2009) provided ice thickness, basal temperature and basal velocity for the calculation of basal shear stress across Scotland which could broadly be used here to infer the likely distribution of erosion during the Loch Lomond Stadial. The modelled data was compared to data relating to valley morphology extracted from a DTM along Glen Lyon, Western Grampian Highlands. A long- profile allowed the assessment of longitudinal variations in basal shear stress relative to overdeepend rock basins – a direct result of increased erosion at a glacier bed. 25 valley cross- profiles were extracted and a general power law used to determine the shape and width-depth relationship at various stages along the glen that could then be compared to data from the ice sheet model. It was found that the macro-scale geomorphological evidence supports multiple styles of glaciation. These styles have variously occurred during entire stadials or at certain times during the growth and decay of larger ice sheets. The orientation of the preglacial topography appears to play an important role in determining ice flow conditions and hence the spatial and temporal pattern of erosion at the ice-bed interface. Future research could incorporate cosmogenic nuclide exposure dating and model data for the more expansive Main Late Devensian ice sheet to allow a more holistic approach to assessing the importance of a single style of glaciation on valley morphology.

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