Environment and Climate in Southwestern Switzerland during the Last Termination, 15-10 ka BP

• Various records from sites ranging in altitude between 372 and 2290 m along a NW-SE transect through SW Switzerland were compiled and correlated within well defined chrono- and biostratigraphic units. Deglaciation of lowland areas is estimated at ca. 15,000-14,000 BP (minimum age), while the lower part of the Rhone valley and the Jura Mountains may have become ice free later. A significant climatic warming is clearly indicated by several palaeoecological records at ca. 12,600 BP. The compiled data give no clear evidence of a cooler phase between 12,200-12,000 BP. Oxygen isotope data point to a slight and progressive decrease in the deltaO-18 values between ca. 12,500-11,000 BP, which is followed by a marked drop at 11,000 BP. A very distinct change in lithology, rock glacier development and in mollusc and vegetation records characterises many low and high altitude sites ca. 300 years later, at 10,700 BP. Between 11,000 and 10,000 BP oxygen isotope records seem to respond more rapidly to the climatic shifts than the biostratigraphical records. Possible explanations for these time-lags are discussed. Our compilation shows that further multidisciplinary research in key sites would provide more precise palaeoclimatological information, both qualitatively and quantitatively. Higher time resolution and quantitative estimates of climatic parameters are needed to evaluate in detail the mechanisms and consequences of these rapid climatic changes in SW Switzerland.

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Paleoecology

Paleoekologi

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