LAUSR

Abstract On the Swiss Plateau, glacial and glaciofluvial sediments deposited during MIS 2 are widespread. They are generally overlain by younger sediments of different origin, mainly related to periglacial and slope wash processes. Depending on their genesis and composition, 3 types of slope deposits can be distinguished, which are classified as units 1, 2a and 2b. Unit 1 is characterized by its wide spatial occurrence and a constant thickness of 40–60 cm, high silt contents, and a sharp lithological discontinuity to the lying sediments, generally forming the parent material for the Ah- and Al-horizons of the Luvisols. Unit 2 represents erosion rills, filled up with loess loam and some gravel ( Based on stratigraphic assumptions, the formation of unit 1 has been tentatively attributed to the Younger Dryas. Optical Stimulated Luminescence and radiocarbon dating of unit 2 indicate morphodynamic activity during the Early Holocene up to 7.5 ka, suggesting an open landscape. This scenario is in conflict with the established notion that reforestation in Middle Europe took place during the Bolling-Allerod warm period. In order to explain this apparent contradiction for the Younger Dryas to Early Holocene environment, we suggest a continental climate with dry summers and drought stress on the vegetation, in combination with very cold winters and deep soil frost at the Pleistocene/Holocene transition, caused by the orbital precession maximum. After 7.5 ka, with the spread of oceanic woodland and reduced seasonal contrasts, the landscape stabilized and soils developed.