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Temperate and Cold Climate Continental Dunes |
Department of Physical Geography, University of Utrecht, PO Box 80.115, 3508 TC Utrecht, The Netherlands
In northwest Europe local resedimentation of terrestrial deposits by wind from the Neolithic to the present has resulted in widespread accumulation of (aeolian) drift sands. These deposits consist mainly of fine, well-sorted and well-rounded unimodal sands; their mineralogical composition usually reflects local provenance. Palynological studies combined with radiocarbon analyses of the topmost part of buried peat sections reveal no distinct regional phases in drift sand accumulation: ages mainly vary from AD 500 to 1700. Small remnants of current actively moving drift sands provide evidence of sub-recent deflation and accumulation processes in relation to relief, topsoil and aerodynamic conditions. These are reflected in the sedimentary structures. Principal structures show dune foreset cross-bedding as well as even or wavy sub-horizontal lamination, while occasional strings of granules or small pebbles represent deflation phases. Primary structures resulting from tractional deposition (mainly sub-critical climbing ripple migration) and grainfall deposition, secondary structures (mainly slump, scour-fill and adhesion structures) and non-aeolian structures (mainly caused by rain impact, convolution structures, wetted sand crusts, and foot- or hoof-imprints) have a distinct appearance in lacquer peels and in SEM micrographs. Transport and accumulation of these temperate aeolian sands appear to have occurred under dry, moist and wet conditions.
