Rodent palaeofaunas from Bisnik Cave (Krakow-Czestochowa Upland, Poland): Palaeoecological, palaeoclimatic and biostratigraphic reconstruction

摘要

A unique record of faunal changes from the late Middle Pleistocene until the end of the late Pleistocene was provided by rodent assemblages from Bisnik Cave in Poland. The 17 rodent assemblages, of different qualitative and quantitative composition, included a total of 25 species of various ecological requirements and associated with five types of climate, represented by over 8500 individuals. For biostratigraphic analysis, the following indices were used: the ratio of enamel thickness on anterior and posterior edges of tooth loops in the genus Arvicola (SDQ), and morphological teeth changeability of Microtus oeconomus and Dicrostonyx. All three biostratigraphic methods are consistent, and made it possible to determine the stratigraphic position of the rodent assemblages. The layers from 19 to 14 were deposited in Middle Pleistocene, and the layers from 13 to 1 were deposited in the Late Pleistocene. The layers 14 and 13 constitute the border between the Middle and Late Pleistocene. Climatic and environmental conditions (temperature and humidity, duration of vegetation season) during the deposition were reconstructed, based on the assemblages representing the late Middle Pleistocene (layers 19-14; MIS 7-6), the Eemian interglacial (layers 14,13; MIS 5e), and the Vistulian (Weichselian) glaciation (layers 12-1; MIS 5d-2). The analysis of bioclimatic indices made it possible to determine the most probable climate during the deposition of the respective assemblages. The environmental preferences allowed reconstruction of the prevailing biomes in the environments of Bisnik Cave. The results of quantitative bioclimatic analysis indicate that the deposition of same of the assemblages may be associated with cold temperature climate. The values of 11 climatic indices show the oscillations of two types of climate, temperate and boreal, with oceanic and continental influence. Reconstruction values of 11 climatic parameters shows an interesting pattern of relative stability in almost all the climatic parameters. Only drought length shows a remarkable change across Middle and Late Pleistocene sediment sequences from Bisnik Cave.