The terrestrial Eemian to late Weichselian sediment record at Beckentin (NE-Germany): First results from lithostratigraphic, palynological and geochronological analyses

摘要

Over recent decades a growing number of well-documented records from terrestrial last interglacial sites across central Europe have substantially improved our understanding of Eemian climate and landscape dynamics. Despite this progress, there are also large areas from which little information is available, thus constituting significant paleo-geographic gaps in the last interglacial record. Among the regions with still inadequate paleo-environmental information is the maritime-influenced area of NE-Germany at the southern margin of the Eemian (Baltic) Sea. Here we present first results from a geological investigation of a new last interglacial site, recently discovered during archaeological excavations near Beckentin (SW-Mecklenburg). The study area is located approximately 25 km to the south of the maximum MIS-2 ice limit of the Scandinavian Ice Sheet in NE-Germany, and thus lies outside the Weichselian belt of glaciation. Based on lithostratigraphic and sedimentological logging, complemented by geochemical (XRF) and palynological investigations, we divide the local succession into three sections: (1) a basal facies comprising Saalian till and associated glaciofluvial sand, overlain by section (2) consisting of a fen peat which grades into laminated organic to minerogenic mud. The organic deposits of section (2) preserve a near complete Eemian pollen inventory, encompassing pollen zones (PZ) I to VI (Menke and Tynni 1984). Above this rest poorly sorted periglacial sands (section 3) with ventifacts and evidence for cryogenic deformation. Geochronological results from Th-230/U dating of the buried organic-rich deposits at Beckentin, show that these units accumulated in a former dead ice depression between 118 +/- 7/6 ka and 114 +/- 6/5 ka during the Eemian Interglacial. High-resolution optically stimulated luminescence (OSL) profiling, undertaken with a portable luminescence reader, reveals a significant hiatus between the lacustrine fines and overlying periglacial cover sand. Five OSL ages obtained from these cover sediments and the sand-filling of an ice-wedge cast show that these strata formed between during the last glacial interglacial transition. (C) 2017 Elsevier Ltd and INQUA. All rights reserved.