Late-glacial fossil midge stratigraphies (Insecta: Diptera: Chironomidae) from the Swiss Alps

Chironomid midges (Insecta: Diptera: Chironomidae) are sensitive indicators of environmental change, but relatively few studies have been made of the response of European midge faunas to the high amplitude climatic oscillations of the late-glacial. In this study, late-glacial assemblages of chironomid midges from four Swiss lakes, or former lakes, [Gerzensee (603 m), Leysin (1230 m), Regenmoos (1260 m) and Heremence (2300 m)] were compared and contrasted. The study focused on the response of chironomid assemblages to the beginning and end of the Younger Dryas cold interval (c. 12690-11485 cal. yr BP) and to minor cold climatic fluctuations (Gerzensee Oscillation, c.13200-12800 cal. yr BP, and Preboreal Oscillation, c. 11365-11100 cal. yr BP). The durations of these climatic fluctuations were defined climato-stratigraphically based on oxygen isotope boundaries and the chronology was derived by correlation with GRIP oxygen isotope records. Major differences in the composition of the four lakes' chironomid assemblages reflected differences in altitude and local environmental conditions. Nevertheless, each lake fauna showed a marked response to the major and minor climatic oscillations, demonstrating that large-scale temperature change had an overriding influence on the distribution of chironomid midges. (C) 2000 Elsevier Science B.V. All rights reserved.