A late Devensian ice-free area and possible interglacial site on the Isle of Lewis, Scotland

Abstract

At the time of the last glacial maximum the last Scottish ice sheet has been considered by some1,2 to have extended to the continental shelf edge (Fig. 1a) whilst others3,4 have suggested that there were ice-free areas in northern Scotland. No radiocarbon-dated strati-graphical evidence has been published to support either interpretation. We present here data from the Isle of Lewis establishing that the shelly deposits from the north of that island are of late Devensian age but which also show that a late Devensian ice margin lay across northern Lewis leaving part of the island ice-free. A peat, possibly of interglacial status, has been found in the ice-free area. The last Scottish ice sheet therefore did not pass beyond the Outer Hebrides and may not even have reached the north of the island chain. This evidence is also of interest to the debate on the relative expansions of the northern and southern margins of the Laurentide and Scandinavian ice sheets at the last glacial maximum5,6, for it suggests a restricted glacial expansion of the northern margin of the last British ice sheet at the time of its greatest southerly extent.