WEICHSELIAN LATE PLENIGLACIAL AND LATE-GLACIAL DEPOSITIONAL-ENVIRONMENTS, COLEOPTERA AND PERIGLACIAL CLIMATIC RECORDS FROM CENTRAL POLAND (BETCHATOW)

Environmental conditions during the Weichselian have been studied at t he Betchatow brown coal pit in central Poland. Palaeoclimate has been reconstructed by a multiproxy approach based on sedimentary environmen ts, periglacial structures and Coleoptera remains. The Weichselian Mid dle to Late Pleniglacial sequence reveals a change from lacustrine to fluvial deposition. During the Late Pleniglacial, deposition by epheme ral streams with relatively stable channels was abruptly replaced by b raided-river deposition. An increased aridity and the disappearance of the vegetation are held reponsible for this change in river style. Th e increase of aridity in the second part of the Late Pleniglacial has been inferred from the absence of organic material in the braided depo sits and the extension of aeolian environments at the expense of the b raided 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 r econstruction of the early Late Pleniglacial (26-24 ka). Permafrost co nditions during this period, in combination with local strong relief a nd intensive slope processes, resulted in rapid aggradation by ephemer al streams with relatively stable channels. The climate during the ear ly Late Pleniglacial was extremely harsh. The habitat was in many ways analogous to the true tundra of the present-day Arctic. The periglaci al features indicate a mean annual air temperature lower than -4 degre es C. The coleopteran assemblage from Betchatow is one of the most col d-adapted faunas so far recorded from Europe. The mean temperatures of the warmest and coldest months were respectively 8 degrees C and -27 degrees C. it is concluded that a strong temperature decline, especial ly of the winter temperature, occurred at the transition from the Midd le to the Late Pleniglacial. At the onset of the Late-glacial Younger Dryas period a cooling of the climate has been inferred from the prese nce of small ice-wedge casts at the base of overlying dune sands. A me an annual air temperature between -2 and -5 degrees C is postulated. ( C) 1998 John Wiley & Sons, Ltd.