A coleopteran fauna from the middle Wurm (Weichselian) of Switzerland and its bearing on palaeobiogeography, palaeoeclimate and palaeoecology

Recent exposures of the upper lignite layer from the Gossau section on the Swiss plateau (near Zurich) have shown that it contains a rich fauna of fossil coleopteran remains (beetles). These deposits have been radiocarbon dated to 28 500 yr BP. Up to now the environ ment of the middle Wurm period has not been well documented in Switzerland so this exposure provides a rare opportunity to investigate the palaeobiogeography, local environment and palaeoclimate of this episode. A coleopteran assemblage was obtained from the upper lignite in which 30 taxa were identified of which 26 could be determined to the species level. All the species are still living today though ten of them are no longer found in Switzerland. Their modern geographical ranges are boreal or boreo-montane and, on the whole, the fauna is typical of lower alpine or northern tundras of the present day. The MCR (Mutual Climatic Range) method was used here to estimate the mean temperatures of the warmest month (9 degreesC) and of the coldest months (-21 degreesC). Comparing these estimated palaeotemperatures with modern values from the nearest meteorological station (Zurich Airport), middle Wurm mean July palaeotemperatures were about 10 degreesC lower and mean January/February palaeotemperatures were about 20 degreesC lower than today. Copyright (C) 2001 John Wiley & Sons, Ltd.