Paraglacial sedimentation and denudation processes in an Alpine valley of Switzerland. An approach to the quantification of sediment budgets

As a result of recent drillings in the Walensee Valley (eastern Switzerland) a new facies model for the Quaternary filling of Alpine valleys has been developed. A detailed lithological model and some new radiocarbon dating allowed the calculation of regional sedimentation and denudation rates and their change during the Late- and Postglacial period. It is shown that these changes follow the paraglacial sedimentation model by Church and Ryder [1]. The absolute quantification of the sediment budgets between the Last Glaciation and today points to denudation rates in the order of 1.5 mm y−1 for the catchment of the Lake of Walenstadt. This is 50 % higher than suggested from current tectonic and isostatic estimates up to now. In that case present day uplift of the Alps would not be in balance with denudation.