MAXIMUM ALTITUDE OF DEVENSIAN GLACIATION ON THE ISLE-OF-SKYE

A high-level periglacial trimline occurs on the mountains of Skye at a ltitudes of 750-870 m in the Cuillins, c. 850 m on Bla Bheinn, c. 760 m on Glamaig, 440-610 m on Trotternish and at c. 480 m on Macleod's Ta bles in Duirinish. Widespread survival of gibbsite in soils above the trimline indicates significantly more advanced weathering than in soil s at lower altitudes, implying that the trimline marks the upper level of Devensian glacial erosion and thus defines the maximum altitude of the ice dome that developed on Skye during the Devensian glacial maxi mum. Three-dimensional reconstruction of the form of the ice surface s uggests that glaciers descended steeply from west-facing corries in th e Cuillins, whilst east-facing corries nourished an ice mass that esca ped north via Glen Sligachan and SE over cols and around the southern end of the Cuillin ridge. Across central and northern Skye the ice sur face descended more gently at gradients of 7.5-9.0 m km(-1), declining to an altitude of c. 450 m across Duirinish, Waternish and the northe rn tip of Trotternish. Implied basal shear stresses are consistent wit h those of an ice mass moving across a rigid bed, and the dimensions o f the former ice dome indicate confluence of Skye ice and Outer Hebrid ean ice in the Minches.