Samples for grain-size analyses from residual dune ridges were obtained using a vibracore system equipped with a window sampler (diameter 50 mm, probe length 100 cm). The spectrum of the sediment grain sizes was measured using a Sympatec Helos KF Magic laser particle-size analyser (measuring range 0.5/18-3500 µm). Prior to measurement, samples were treated with hydrogen peroxide and acetic acid to oxidize the organic fraction and to dissolve carbonate particles, respectively. For measurement, samples were suspended in water using tetra-sodium diphosphate decahydrate as dispersing agent. Grain-size statistics were calculated using Gradistat (Blott and Pye, 2001) and are based on the graphical method (Folk and Ward, 1957) as applied to the metrical scale (see Blott and Pye, 2001 for details and equations).