Radiocarbon and optically stimulated luminescence dating based chronology of a polycyclic driftsand sequence at Weerterbergen (SE Netherlands)

The chronology of polycyclic driftsand sequences in cultural landscapes has mainly been based on the combination of radiocarbon (14C) dating of intercalated organic horizons and pollen analysis. This approach, however, yields indirect age information for the sediment units. Also, as soils are dynamic systems, the pedogenetical interpretation of the 14C ages is often quite difficult.To improve the results of radiocarbon dating, we applied fractionated 14C dating, sustained by soil micromorphology and pyrolysis-gas chromatography/mass spectrometry. The results indicate the complexity of the sources and decomposition processes of SOM, and, consequently, provide information as to why radiocarbon dates are not always reliable for the geochronology of driftsand deposits. We then performed an optically stimulated luminescence (OSL) dating study of the driftsand beds in the sequence. This approach yields direct sedimentation ages, and allows differentiating the instable (sand drifting) period from the stable (soil formation) period in each individual cycle of the sequence. Post-depositional mixing of the sands, however, may upset the reliability of the OSL chronology.