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 fos sil coleopteran remains (beetles). These deposits have been radiocarbon dat ed to 28 500 yr BP. Up to now the environ ment of the middle Wurm period ha s not been well documented in Switzerland so this exposure provides a rare opportunity to investigate the palaeobiogeography, local environment and pa laeoclimate of this episode. A coleopteran assemblage was obtained from the upper lignite in which 30 taxa were identified of which 26 could be determ ined to the species level. All the species are still living today though te n of them are no longer found in Switzerland. Their modern geographical ran ges 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 t emperatures of the warmest month (9 degreesC) and of the coldest months (-2 1 degreesC). Comparing these estimated palaeotemperatures with modern value s from the nearest meteorological station (Zurich Airport), middle Wurm mea n July palaeotemperatures were about 10 degreesC lower and mean January/Feb ruary palaeotemperatures were about 20 degreesC lower than today. Copyright (C) 2001 John Wiley & Sons, Ltd.