Lateglacial and Early Holocene glacier stages - New dating evidence from the Meiental in central Switzerland

Abstract

In order to improve our understanding of the glacier development in central Switzerland after the Last Glacial Maximum (LGM) we have investigated moraine sequences of the Meiental (“Meien Valley”). After detailed field mapping, 34 rock samples from different moraines were dated with cosmogenic 10Be. The results indicate that the investigated moraines were deposited mainly in multi-phased advances during the Younger Dryas and the Early Holocene. This is in contrast to previous studies suggesting that these moraines represent equivalents of the older Egesen and Daun stadials. Our research shows that factors like the moraine stratigraphy, geomorphologic characteristics and Equilibrium Line Altitudes (ELAs) can be highly variable at the local scale, which can make a stadial correlation of moraines between different valleys or regions within the Alps without age constraints ambiguous and unreliable. Against this background the interregional use of ΔELAs (ELA depressions) for the parallelization of paleo-glacier extents throughout the Alps according to traditional concepts of the Lateglacial deglaciation seems to produce erroneous results. Geomorphologic observations and relative age relationships in moraine successions based on stratigraphic principles remain the basis for this kind of studies. But as we show here it is necessary to base local-to-regional comparisons of moraine sequences additionally on exposure ages to gain a more reliable understanding of the Alpine glacier development after the LGM.