Late glacial sea-level changes and ice-limits in Islay, Jura and Scarba, Scottish Inner Hebrides

Abstract

Synopsis Ice-marginal landforms produced at the edge of the last (Late-Devensian) ice-sheet in Islay, Scottish Inner Hebrides are described. A glacial stillstand is indicated by the central Islay moraine and is associated with a fall in the marine limit of c. 12 m. Deglaciation occurred initially in western and central Islay and was associated with the formation of a series of raised coastal terrace fragments. Slightly later, western Jura was deglaciated. This was followed by the development of two prominent Lateglacial shorelines (LI and L2). The latter features decline in altitude SW from c. 40 m in NW Jura to c. 15 m in central Islay and possess regional gradients of 0.59 m/km and 0.56 m/km. The relative regression of the Lateglacial sea was accompanied in western Jura by the widespread development of beach ridges. Measurement of the ridge altitudes shows that in this area the relative retreat of the Lateglacial sea was uninterrupted by any major transgressions, relative stillstands or renewed periods of glacio-isostatic downwarping.