Overbank silt-clay deposition and intensive Neolithic land use in a Central European catchment - Coupled or decoupled?

Hydro-sedimentary processes such as soil erosion, sediment transport, deposition, and re-deposition influence the environmental evolution of floodplains, especially in loess-covered catchments. Holocene floodplain deposits are thus a source of information on previous hydro-sedimentary dynamics and land use in the catchment. Resulting from forest clearings in the catchment, the onset of overbank silt-clay deposition is considered as an initial and significant human-induced process affecting Central European floodplain evolution and ecosystems. However, it is difficult to separate climate-related from anthropogenic forces on depositional environments, and the complexity of the hydro-sedimentary responses is part of an ongoing debate in geoscientific, ecological, and archaeological communities. This study focuses on the Central European Weiße Elster river system, where humans have been influencing hydro-sedimentary processes since the Early Neolithic due to land-use-induced soil erosion predominantly in the loess-covered sub-basin of the middle course. A catchment-scale XRF element record of fluvial sediment sources combined with the geochemical characterisation of Holocene floodplain deposits aim for a better understanding of the interplay between past soil erosion, overbank deposition in the floodplain, and potential changes in sediment provenances. The Weiße Elster floodplain chronosequences show a geochemical differentiation into a lower (Neolithic) and an upper (post-Neolithic) overbank silt-clay deposition. The construction of a sediment source fingerprinting mixing model yields the significant finding that the Neolithic overbank silt-clay deposition reveals a remote provenance signal from the upper catchment and less from the proximal loess-covered sub-catchment. According to a systematic archaeological data survey, the upper catchment was not permanently settled and used for agriculture in the Neolithic period. This contradicts the previous assumption that Neolithic overbank silt-clay deposition primarily originates from forest clearings and subsequent farming-induced soil erosion in the catchment. From a more general perspective, further examination of existing hypotheses concerning overbank silt-clay deposition in Central European floodplains is thus in order.