High-resolution reconstruction of the last ice sheet in NW Scotland

Reconstructions of the last (late Devensian) British ice sheet have hithert o been based on assumptions regarding its extent and form. Here we employ o bservational evidence for the maximum altitude of glacial erosion (trimline s) on mountains that protruded through the ice (palaeonunataks) to reconstr uct the form of the ice sheet over approximate to 10 000 km(2) of NW Scotla nd, Contrasts in the clay mineralogy of soils and exposure ages of rock sur faces above and below these trimlines confirm that they represent the upper limit of late Devensian glacial erosion. The reconstruction yields realist ic values of basal shear stress and is consistent with independent evidence of ice movement directions. The ice sheet reached approximate to 950 m alt itude over the present N-S watershed, descended northwards and north-westwa rds, was deflected around an ice dome on Skye and an independent Outer Hebr ides ice cap, and probably extended across the adjacent shelf on a bed of d eforming sediments.