Periglacial cover-beds on the Swiss Plateau: indicators of soil, climate and landscape evolution during the Late Quaternary

Soils and the stratification of their parent materials were studied on the central Swiss Plateau. This area is characterized by glacial deposits varyi ng from Late Glacial to pre-Wurmian in age. Soils of all studied sites are developed within colluvial layers, the so-called cover-beds. In relation to the underlying deposits, we find a regular spatial distribution of cover-b ed types. A surficial layer (Upper Layer) with relatively constant thicknes s (around 50 cin independent of relief position) covers Pleistocene sedimen ts of any age. Therefore, it was formed mainly by cryoturbation/solifluctio n after the final glacier retreat from the Swiss Plateau (Younger Dryas or Oldest Dryas age). Layers that originate mainly from aeolian processes (Int ermediate Layers) are restricted to areas outside the recessional moraines of the Berne-Stade (BS). Hence, they were formed merely up to the late Plen iglacial. They frequently consist of two distinct layers. Outside the glaci ation of the Last Glacial Maximum (LGM), cover-beds in places overlie pre-L GM palaeosol relics (probably of Eemian age or even older). These are prese rved even on higher relief positions, indicating that periglacial erosion d uring the Pleniglacial was only marginal. The palaeosol relics also occur o n till of the so-called Older Wangen-Stade, which is commonly believed to r epresent the LGM, whereas we consider it to be older at least partly. Event ually, the distribution of soil types and their ecological characteristics are influenced considerably by cover-beds. As these beds reflect distinct p hases of the Pleistocene, colluvial sediments provide a major tool for link ing modern landscape characteristics to the Late Quaternary climate evoluti on. (C) 2001 Elsevier Science BN. All rights reserved.