Optically stimulated luminescence (OSL) dating of coastal aeolian sand accumulation in Sanday, Orkney Islands, Scotland

Abstract

Optically stimulated luminescence (OSL) dating of sand has been used to identify periods of enhanced aeolian activity at two coastal archaeological sites in Orkney that coincide with periods of Holocene climatic deterioration recorded elsewhere in both Scotland and W Europe. Areas of Tofts Ness, Sanday were settled from the Neolithic, abandoned in the late Neolithic/early Bronze Age, reoccupied and permanently abandoned in the Iron Age. Sand layers above the Neolithic soils have been OSL dated to about 4000 BP, correlating well with a period of increased aeolian activity elsewhere in W Europe. OSL dating of aeolian sands above midden deposits and a Bronze Age burial at Lopness on Sanday suggest dune development by 3000 BP, although both sites also contain sand that was deposited during the `Little Ice Age'. Several possible mechanisms may have contributed to an increase in aeolian activity during the Holocene that led to the abandonment of these sites. Although volcanic eruptions in Iceland cannot be discounted as a contributory factor, a more likely driver of change in sand dune systems is the enhanced N Atlantic storminess suggested by ice core records from Greenland. During periods of climatic deterioration the declining productivity of other agricultural land places enhanced demands on agriculturally marginal sand dunes, leading to further destabilization and the potential for enhanced sand transport events.