Geochronology of Betula extensions in pollen diagrams of Alpine Late-glacial lake deposits: A case study of the Late-glacial deposits of the Gasserplatz soil archives (Vorarlberg, Austria)

摘要

Pollen diagrams of Alpine Late-glacial calcareous lake deposits show several extensions of Betula. The geochronology of these extensions cannot be based on radiocarbon dating due to reservoir effects of such lakes on the radiocarbon ages. A robust geochronology can be based on the oxygen isotope stratigraphy. Additionally, recognition of 12,920 calBP LST in the sediment cores provides a secure time marker. The combined results of pollen, macro-remains and stable isotope analyses of the Gasserplatz cores point to a correlation of the Betula extensions with the oscillations in the oxygen isotope curve and are related to global climatic oscillations. This is sustained by the correlation of the Gasserplatz isotope oscillations with the oscillations as registered in the Greenland ice cores. Comparison of the results of the Gasserplatz cores with the results of similar Alpine lake deposits makes clear that the fluctuations in the Betula curve are not a local but a regional phenomenon.