Sediment export in marly badland catchments controlled by frost cracking intensity, Draix-Bléone CZO, SE France

At the interface between the lithosphere and the atmosphere, the critical zone records the complex interactions between erosion, climate, geologic substrate and life, and can be directly monitored. The sparsely vegetated, steep marly badland catchments of the Draix-Bléone Critical Zone Observatory (CZO), SE France are characterised by high quantities of exported sediment and rapid morphologic changes. Characterizing and understanding the physical weathering processes in this area are key to predict the temporal variability of regolith production and sediment flux, as well as their evolution under changing climate conditions.

Long data records collected in the Draix-Bléone CZO allow analysing long-term regolith dynamics and climatic control on sediment export. Although widely accepted as the first order control, rainfall variability does not fully explain the observed yearly variability in sediment export, suggesting that regolith production and its controls may contribute to the observed pattern of sediment export. Within the several factors that can influence marls weathering (soil moisture, density, chemical weathering), this study focuses on continuous temperature data, recorded at different locations over multiple years, and aims to highlight the role of frost cracking in regolith production. Several proxies for frost cracking intensity have been calculated from these data and compared to the sediment export anomalies, with careful consideration of field data quality. Our initial results suggest that frost-cracking processes have a significant impact on catchment sediment response and should be taken into account when building a predictive model of sediment export from these catchments under a changing climate.