Characteristics and origin of a Saalian glaciolacustrine to glaciofluvial succession in the Hümmling region, NW Germany

Abstract

In the lowlands of northwest Germany, glaciofluvial plateaus (German: Geestplatten), and pushmoraines built up by the Saalian ice sheet are surrounded by flat and low-lying country. In the study area in the Hümmling, the Geestplatte consists o f mainly sandy meltwater deposits with a capping of groundmoraine or till residue. This outwash plain was built up during the Main Drenthe Advance of the Saalian glaciation and subsequently overridden by the expanding ice sheet. The meltwater deposits form coarsening- upward sequences exposed in three sandpits in the study area. From base to top in the exposures, three waterlaid fades are distinguished: a basal glaciolacustrine fades, a transitional fades and an upper glaciofluvial fades. Unless erosion has interfered, the upward change from one fades to the next is markedly gradational. The paper gives arguments for the distal-lake origin of the basal fades. It supposedly formed as the fill of drainless depressions in the distant foreland of the ice-sheet margin. By this process, the terrain was levelled and prepared for a gradual change from glaciolacustrine to glaciofluvial depositional regime.