8. Uranium-series dating of peat from central and Northern Europe

Interstadial and interglacial peat layers are widespread in the Northern Hemisphere and enable us to reconstruct the vegetation history. Uranium-series dating methods can provide a reliable and precise chronological frame for peat of the past 500000 years. Uranium-series dating methods are based on the radioactive disequilibrium between ²³⁸U and its radioactive daughter elements and the re-establishment of equilibrium. The activity ratio [ ²³⁰Th/ ²³⁴U] is a measure of the time elapsed since the formation of the peat. In this study, uranium-series dating of peat in Central and Northern Europe is reviewed including new thermal ionisation mass spectrometry (TIMS) ²³⁰Th/U dating results from recently investigated interglacial peat horizons in Central Europe. The suitability of the peat layers for dating depends on two essential assumptions: a closed-system behaviour excluding uranium migration after deposition and the contamination of peat by varying amounts of detrital thorium, which has to be corrected owing to its essential effect on calculating ²³⁰Th/U ages. The radiometric and TIMS dating results are in good agreement for certain fen peat layers correlating with MIS 3 and 5, as confirmed by independent age control through radiocarbon and luminescence dating methods. There are only a few approaches dating pre-Eemian peat. Although the radiometric and TIMS dating results are less distinct, more reliable and precise absolute ages can be provided.