Ice marginal ramps: An indicator of semi-arid piedmont glaciations

Ice marginal ramps are depositional landforms that often developed over several tens of kilometres along the ice margins of large piedmont glaciers in semi-arid environments. The ramps extend with a 7–15° gradient several kilometres or even tens of kilometres into the forelands. They have front slopes that are tens of metres to several hundred metres high and frame the former terminal basins. The front slopes and the underlying bed consist of till; in the latter case, the till thins out towards the periphery. The overlying beds contain ice contact stratified drift, which, with increasing distance from the former ice margin, is succeeded by clearly sorted glaciofluvial layers of gravel. Under semi-ari d environmental conditions, the syngenetic contribution oftwo agents of transport (glacial, glaciofluvial) in formingone accumulation complex produces stratigraphic and phenotypical features that are rare in the glacial morphology of the temperate/humid zones. For this reason, they are often misinterpreted. Being indicators of ice margins, ice marginal ramps permit the accurate reconstruction of extensive piedmont glaciations in the semi-arid highlands of subtropical latitudes. Because of their high radiation values these play a key part in the global energy balance and, thus, in the origin and the evolution of ice ages.The author gratefully acknowledges the translation of this paper rendered by Mrs. Anne Beck, Berlin.