A first attempt to date the original “Deckenschotter” of Penck and Brückner with cosmogenic nuclides

In the classical area of Alpine Quaternary stratigraphy, Bavaria, Germany, a succession of four gravel spreads that are separated from each other by valley incision, was recognized by Penck and Brückner [1909. Die Alpen im Eiszeitalter. Tauchnitz, Leipzig, 1199p.]. The two older gravel terraces, attributed to glaciations named “Günzian” and “Mindelian”, have so far not been dated. Recent advances in the use of cosmogenic nuclides allow the burial age determination of sediments. The method uses the different decay of the two nuclides 26Al and 10Be to date the time since a deposit was shielded from further radiation. A depth profile makes it possible to model ages for surface sediments that are not shielded completely. This paper discusses the various constraints that must be addressed in order to date surface sediments and it presents the ages obtained (2.35 Ma for Günzian, 0.68 Ma for Mindelian). These dates are in good agreement with measurements of tectonic displacement and development of catchments. The results confirm that the burial age determination method is basically feasible for such terraces.