The Late Quaternary glacial history of the Trotternish Escarpment, Isle of Skye, Scotland, and its implications for ice-sheet reconstruction

Geomorphological mapping indicates that the last (Late Devensian) Scottish ice sheet moved northwards across the Trotternish Peninsula. A periglacial trimline inferred to represent the maximum altitude of the last ice sheet descends northwards from 580–610 m to 440–470 m over 24 km. Retreat of the ice sheet appears to have been uninterrupted by Stillstands or readvances, but two small corrie glaciers developed east of the escarpment during the Loch Lomond Stadial of c. 11–10 ka B.P. Most of the extensive landslipping east of the escarpment predates the last ice sheet maximum, though some landslip blocks adjacent to the scarp represent slope failure since ice-sheet retreat. Calculations based on the altitude and gradient of the inferred upper limit of the last ice sheet suggest that its margin extended 25–40 km north of Trofternish and was confluent with an independent Outer Hebridean ice cap. Calculated basal shear stresses of only 30–39 kPa suggest that the form of the ice sheet over Trotternish was influenced by adjacent low-gradient ice streams flowing over deforming sediments. If so, this illustrates the invalidity of assuming parabolic profiles characteristic of glacier flow over a rigid bed in reconstructions of the form of the last Scottish ice sheet.