Weichselian Late Pleniglacial and Late-glacial depositional environments, Coleoptera and periglacial climatic records from central Poland (Bełchatów)

Abstract

Environmental conditions during the Weichselian have been studied at the Bełchatów brown coal pit in central Poland. Palaeoclimate has been reconstructed by a multiproxy approach based on sedimentary environments, periglacial structures and Coleoptera remains. The Weichselian Middle to Late Pleniglacial sequence reveals a change from lacustrine to fluvial deposition. During the Late Pleniglacial, deposition by ephemeral streams with relatively stable channels was abruptly replaced by braided-river deposition. An increased aridity and the disappearance of the vegetation are held reponsible for this change in river style. The increase of aridity in the second part of the Late Pleniglacial has been inferred from the absence of organic material in the braided deposits and the extension of aeolian environments at the expense of the braided environment. A return towards wetter conditions during the Late-glacial has been inferred from lake marl deposition and local fluvial reworking of dunes. Special attention has been given to the climate reconstruction of the early Late Pleniglacial (26–24 ka). Permafrost conditions during this period, in combination with local strong relief and intensive slope processes, resulted in rapid aggradation by ephemeral streams with relatively stable channels. The climate during the early Late Pleniglacial was extremely harsh. The habitat was in many ways analogous to the true tundra of the present-day Arctic. The periglacial features indicate a mean annual air temperature lower than −4°C. The coleopteran assemblage from Bełchatów is one of the most cold-adapted faunas so far recorded from Europe. The mean temperatures of the warmest and coldest months were respectively 8°C and −27°C. It is concluded that a strong temperature decline, especially of the winter temperature, occurred at the transition from the Middle to the Late Pleniglacial. At the onset of the Late-glacial Younger Dryas period a cooling of the climate has been inferred from the presence of small ice-wedge casts at the base of overlying dune sands. A mean annual air temperature between −2 and −5°C is postulated. © 1998 John Wiley & Sons, Ltd.