A high-resolution record of soil erosion based on portable luminescence reader derived colluvium chronologies from the Lower Rhine Area

Anthropogenic soil erosion has shaped European agricultural landscapes since thousands of years. Reconstructing their past dynamics is crucial for understanding associated driving and feedback mechanisms as a basis for numerical models that predict future trends. While colluvial deposits provide abundant records of Holocene soil erosion, their use for reconstructing spatial and temporal patterns is limited by poorly-resolved and low-resolution chronologies. For colluvial deposits from a loess landscape at the southeastern rim of the Lower Rhine Area, we show how unprecedented high-resolution chronologies can be constructed using a portable optically stimulated luminescence (pOSL) reader in combination with conventional OSL dating and Bayesian age modelling. The resulting cm-scale chronologies for the past ~3500 years reveal unique insights into colluvium formation by capturing variations in deposition rates over several orders of magnitude. These variations include phases with virtually absent erosion and several hundred years duration in the Early Middle Ages, but also short episodes or even single events with drastically accelerated erosion during Roman Times and the Late Middle Ages. Within the loess-derived colluvium of our study site the pOSL-based dating approach also offers huge possibilities for upscaling, since additional colluvium cores can be dated with little effort once a robust relation between pOSL and conventional OSL has been established. This approach sets the foundation for reconstructing not only temporal but also spatial patterns of local soil erosion dynamics with exceptional resolution.