Denudation rates and Holocene sediment storage dynamics inferred from in situ 14 C concentrations in the Feshie basin, Scotland

Towers, Anya H.; Mudd, Simon M.; Attal, Mikael; Clubb, Fiona J.; Binnie, Steve A.; Dunai, Tibor J.; Haghipour, Negar

Abstract

Summary: Scotland's Highlands are tectonically quiescent but have experienced high rates of isostatic uplift in response to deglaciation. To understand the effects of both deglaciation and regional uplift on landscape evolution, we measured the concentration of cosmogenic in situ 14C in river sands collected in Glen Feshie (Cairngorms). Like other terrestrial cosmogenic radionuclides, in situ 14C can be used to calculate basin‐wide denudation rates over millennial timescales. 14C has a short half‐life relative to other in situ cosmogenic radionuclides, giving it an advantage in post‐glacial landscapes: Very little 14C will be inherited from exposure before glaciation of the landscape, meaning that concentrations will reflect sediment production and transport dominantly in the Holocene. When we calculate denudation rates based on the common assumption of basin‐wide homogeneity of erosion, we find no correlation between topographic metrics such as the normalised channel steepness index and inferred denudation rates, which range between 0.175 and 1.356 mm/year. Based on field and remote sensing observations, we suggest that 14C becomes diluted downstream due to sediment supply from paraglacial terrace material, and develop a mixing model to test this hypothesis. We identify the terraces that are likely to contribute sediment to the channels through flood modelling, geomorphic mapping and remote sensing observations. Our mixing model indicates that the observed distribution of 14C concentrations can be explained if terrace escarpments have basin‐averaged migration distances of 8 to 30 cm during large flood events. This interpretation is consistent with remotely sensed images of channel activity and terrace bank retreat within the catchment. Our results show that paraglacial sediment stores contribute to sediment fluxes in the late Holocene and highlight the on‐going glacial legacy on landscape evolution.

Citation

Towers, A. H., Mudd, S. M., Attal, M., Clubb, F. J., Binnie, S. A., Dunai, T. J., & Haghipour, N. (2025). Denudation rates and Holocene sediment storage dynamics inferred from in situ 14 C concentrations in the Feshie basin, Scotland. Earth Surface Processes and Landforms, 50(4), Article e70043. https://doi.org/10.1002/esp.70043

• Journal Article Type: Article
• Acceptance Date: Mar 5, 2025
• Online Publication Date: Mar 25, 2025
• Publication Date: Mar 30, 2025
• Deposit Date: Mar 31, 2025
• Publicly Available Date: Mar 31, 2025
• Journal: Earth Surface Processes and Landforms
• Print ISSN: 0197-9337
• Electronic ISSN: 1096-9837
• Publisher: British Society for Geomorphology
• Peer Reviewed: Peer Reviewed
• Volume: 50
• Issue: 4
• Article Number: e70043
• DOI: https://doi.org/10.1002/esp.70043
• Keywords: catchment averaged erosion rates, sediment transport, sediment sources, post‐glacial landscapes
• Public URL: https://durham-repository.worktribe.com/output/3745408