Cold-Climate Aeolian Sand-Sheet Formation in North-Western Europe (c. 14–12.4 ka); a Response to Permafrost Degradation and Increased Aridity

During the late Weichselian (c. 14–12.4 ka BP) an extensive aeolian sand sheet formed in north-western Europe. Factors that favoured formation were: (i) thick, unconsolidated, fluvial and fluvioglacial, sandy Quaternary deposits that acted as a sand source; (ii) a sparse vegetation cover; (iii) generally low relief (lower than 200 m) and absence of major topographic barriers; (iv) periodically low sand availability due to the wet, frozen or cemented state of the surface; and, of particular importance, (v) permafrost degradation and increased aridity. Permafrost degradation resulted from climate warming after the Last Glacial Maximum. Increased infiltration and enhanced water storage capacity of the unconsolidated sandy soil resulted in a drier soil surface and an increase in aeolian processes. The absence of overland flow favoured the preservation of aeolian deposits. Increased aridity during the sand-sheet phase is inferred from a decreased drainage density and floodplain width. This arid phase is attributed to a major deglacial meltwater event and southward flow of cold waters in the North Atlantic Ocean between 14.2 and 13.2 ka.