Middle Pleistocene interglacial peat deposits from Northern Germany investigated by 230Th/U and palynology: Case studies from Wedel and Schöningen

Interstadial and interglacial deposits including peat layers are widespread in Northern Europe and enable us to reconstruct the past climate and vegetation history. Such reconstructions require a reliable and precise chronological framework. Uranium series dating, sedimentological and palynological investigations were performed on a peat deposit at Wedel in Schleswig-Holstein. Previous palynological studies suggested a Middle Pleistocene age for these interglacial deposits. The sediment sequence including a fen peat of 130 cm thickness at a depth of 14-15 m below surface was drilled and cored. Palynological results correlate well to the late Holsteinian Interglacial, but the radiometric age determination failed due to U-series open system behaviour. Comparison of results obtained at Wedel with those from Holsteinian Interglacial deposits in Northern Germany reveals the weakness of numerical age determinations. Furthermore, a brief discussion on radiometric data available of the Middle Pleistocene Reinsdorf Interglacial peat deposits at Schöningen is given, as the laboratory has performed further quality assurance processes. A spike calibration led to new calculations on isotope activities, resulting in higher values shifted by 5-7 % and corrections on published data of the same order. The age of the Reinsdorf Interglacial peat deposit 13 II-2c5 cannot be maintained as the assigned errors inhibit the calculation of reasonable mean ages nearby the methodological age limits.