Zur Gletscher-, Vegetations- und Klimageschichte der Schweiz seit der Späteiszeit
Abstract. A Statistical analysis of published and compilated snowline data for the late-glacial Stades of Gschnitz, Clavadel, Daun and Egesen is presented. The calculation of snowline and snowline-depression (compared to the extent of 1850) is based on the 2: 1 -equilibrium line method. The Interpretation does not show significant differences in snowline-depression between the Lower Engadin (Eastern Alps) and the Mont Blanc area (Western Alps). The larger deviations from the averages can be explained by the glacier individuality (morphology, topography of the ice surfaces) and the rarely considered variations ot the "constant" 2 :1-ration. Geographical patterns, which could imply changes in paleo-precipitation, cannot be found in the investigated area.
The Quaternary Vegetation history provides evidence for climatic changes and timberline fluctuations which took place during the Late-Glacial and Holocene and also provides a framework for biostratigraphical results. During the Oldest Dryas a heliophile Artemisia-Chenopodiceae-Helianthemum- Thalictrum-Ephedra-Juniperus-Betula nana pioneer Vegetation covered the icefree areas in Switzerland. The oldest pollen spectra found in clay gyttja Sediments are dated between 13,000 and 14,000 y BP by the radiocarbon method. The development of the Swiss Central Alpine wood belt since the Late-Glacial is shown in Fig. 11.
Postglacial alterations of the geomorphological activity in the Alps can be reconstructed by radiocarbon dating of fossil soils found in moraines. earth-flows and talus deposits. The results show that the geomorphological activity was very slow up to 4500 y BP; but the second part of the postglacial period was marked by often changing phases of activity and stability.
Differing qualities of the evidence relating to glacial history and the absence of glacier advances within several periods of the Holocene make it impossible to reconstruct a complete curve of the glacier movements. With the aid of a graphical diagram which includes both evidence on glacier fluctuations and dendroclimatological analysis, it will be shown that the Alpine glaciers probably oscillated inside different "levels".