A glaciological approach for the discrimination of Loch Lomond Stadial glacial landforms in the Brecon Beacons, South Wales

Abstract

The interpretation of small ridge systems observed within cirques is often ambiguous and glacial, periglacial and mass-movement origins have been proposed. Much of this ambiguity centres around the interpretation of purely geomorphological data, with little consideration of the glaciological constraints upon the dimensions of small snowpatches and niche glaciers. Application of a glaciological approach to reconstruction, using an estimation of former glacier ablation gradient and the temperature at the reconstructed equilibrium line allows the calculation of glacier mass-balance, total velocity and basal slippage, which may be compared with observed data from contemporary glaciers. The approach outlined is applied to five sites in the Brecon Beacons, South Wales and suggests that four sites reflect upland glaciation during the Loch Lomond Stadial. A fifth site is rejected as being of glacial origin at this time and is suggested to reflect earlier glaciation during different environmental conditions, probably during final wastage of the Last Glacial Maximum Welsh ice cap.