Late Devensian palaeoenvironmental changes in the sea area adjacent to Islay, SW Scotland: implications for the deglacial history of the island

Abstract

Synopsis From a study of offshore borehole samples collected by the British Geological Survey in 1975, it is suggested that arctic marine or glaciomarine sediments of Dimlington Stadial (DS) age (>13 ka 14 C ka BP) in Loch Indaal, Islay, were laid down following the retreat of a glacier from the head of the loch, possibly only a few hundred radiocarbon years before the opening of the Windermere Interstadial (WI, 13–11 14 C ka bp). A reworked molluscan fauna in the DS sediments, which is identical to that living in the area today, is believed to be of last interglacial age or earlier. Sediments of WI age and Holocene age ( 4 C ka bp) have also been intersected in the boreholes. Deposits of Loch Lomond Stadial age (11–10 14 C ka bp) are absent from two boreholes investigated from Loch Indaal, but may be present in a borehole east of Islay. The proposal that ice of the Last Glacial Maximum reached only as far west as central Islay is unsupported by both this assessment and the published geomorphological evidence.