The Bay of Skaill has a complex history which reflects sea level rise and the landward advance of dune systems (Vega Leinert et al., 2000). Freshwater ponds developed on glacial sediments ca. 6550 14C yr BP. Organic sediments accumulated in these ponds and the preserved pollen indicates that the surroundings supported a Betula, Corylus and Salix dominated woodland, with a rich under-storey of tall herbs and ferns. These sediments now lie below sea level, drowned by its subsequent rise, and probably relate to peat beds in the present intertidal zone, with abundant Phragmites remains. From ca. 6120 yr BP, the freshwater marsh was filled in by blown sand from the leading edge of a dune ridge migrating landwards from the west. Thereafter, a series of sand-blow events alternating with periods of calm occurred until ca. 4410 yr BP. Between 5240 and 4660 yr BP, pollen and charcoal records show evidence of anthropogenic activities, associated with the nearby Neolithic settlement of Skara Brae until its abandonment around 3800 years ago. Agriculture was probably affected by recurrent sand movement and widespread deposition of calcium carbonate in the hinterland of the bay. Machair development between ca. 6100 and 5000 yr BP corresponds to a mid-Holocene phase of dune formation recorded elsewhere in northwest Europe. The more recent and progressive formation of the bay has probably been related to increasing external forcing via storminess, long-term relative sea-level change and sediment starvation within this exposed environment.