Zur Gletscher-, Vegetations- und Klimageschichte der Schweiz seit der Sp?teiszeit

摘要

A Statistical analysis of published and compilated snowlinedata for the late-glacial Stades of Gschnitz, Clavadel, Daunand Egesen is presented. The calculation of snowline andsnowline-depression (compared to the extent of 1850) isbased on the 2: 1 -equilibrium line method. The Interpretation does not show significant differences in snowline-depression between the Lower Engadin (Eastern Alps) and theMont Blanc area (Western Alps). The larger deviations fromthe averages can be explained by the glacier individuality(morphology, topography of the ice surfaces) and the rarelyconsidered 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 placeduring the Late-Glacial and Holocene and also provides aframework for biostratigraphical results. During the OldestDryas a heliophile Artemisia-Chenopodiceae-Helianthemum-Thalictrum-Ephedra-Juniperus-Betula nana pioneerVegetation covered the icefree areas in Switzerland. Theoldest pollen spectra found in clay gyttja Sediments are datedbetween 13,000 and 14,000 y BP by the radiocarbon method.The development of the Swiss Central Alpine wood belt sincethe Late-Glacial is shown in Fig. 11.Postglacial alterations of the geomorphological activity in theAlps can be reconstructed by radiocarbon dating of fossilsoils found in moraines. earth-flows and talus deposits. Theresults show that the geomorphological activity was veryslow up to 4500 y BP; but the second part of the postglacialperiod was marked by often changing phases of activity andstability.Differing qualities of the evidence relating to glacial history andthe absence of glacier advances within several periods of theHolocene make it impossible to reconstruct a complete curveof the glacier movements. With the aid of a graphical diagramwhich includes both evidence on glacier fluctuations and dendroclimatologicalanalysis, it will be shown that the Alpine glaciers probably oscillated inside different "levels".