Late Holocene sedimentation and palaeoagronomy in a carbonate dry valley system using OSL, sedaDNA and geochemistry:Implications for understanding anthropogenic slope-sediment transfer in fluvial headwaters

The understanding of landscape stability and erosional regimes from carbonate geological areas has traditionally been limited to fluvial areas due to the lack of lakes and the predominance of clastic-dominated valley fills. The combination of novel Optically Stimulated Luminescence (OSL) dating and sediment ancient DNA opens up new possibilities to study these geomorphological, ecological and agrarian changes in clastic‑carbonate landscapes. Here, we use OSL dating and sedaDNA analyses alongside traditional geoarchaeological techniques to examine potential anthropogenic and palaeoclimatic drivers of sediment transfer within a loessic-dominated dry valley with agricultural lynchets at Sint Martens-Voeren, eastern Belgium, through the late Holocene. Cultivation of loess-dominated sediments across the dry-valley hilltop occurred from the Bronze Age (1900–700 BCE), with lynchet formation on the steep valley sides occurring from later prehistory (Iron Age 700–50 BCE). Major erosion and valley bottom sedimentation began in the early medieval period (450–1000 CE) and accelerated in the medieval and post medieval periods (1000–1750 CE) in line with an intensification of arable cultivation, particularly beet and hops, the development of open three-field agrarian diversity, landscape connectivity and increased climatic variability. This pattern of late Holocene slope-sediment erosion, transfer and storage mirrors other dry valley sites in the Voer catchments, especially in relation to lynchets, and accelerations in sedimentation in other eastern Belgian fluvial catchments, driven by high-intensity palaeoagronomic systems.