Reduced sediment supply in a fast eroding landscape? A multi-proxy sediment budget of the upper Rhône basin, Central Alps

Stutenbecker, Laura Antonia; Delunel, Romain; Schlunegger, Fritz; Silva, Tiago Adrião; Šegvić, Branimir; Girardclos, Stéphanie; Bakker, Maarten; Costa, Anna; Lane, Stuart N.; Loizeau, Jean-Luc; Molnar, Peter; Akçar, Naki; Christl, Marcus (2018). Reduced sediment supply in a fast eroding landscape? A multi-proxy sediment budget of the upper Rhône basin, Central Alps. Sedimentary geology, 375, pp. 105-119. Elsevier 10.1016/j.sedgeo.2017.12.013

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Alpine water and sediment supply influence the sediment budget of many important European fluvial systems such as the Rhine, Rhône and Po rivers. In the light of human induced climate change and landscape modification, it becomes increasingly important to understand the mechanisms of sediment production and supply in Alpine sediment systems. This study aims to investigate the modern sediment budget of the upper Rhône basin, one of the largest Alpine intramontane watersheds, located in the Central Alps of southwestern Switzerland. Major areas of sediment generation are fingerprinted by framework petrography, heavy mineral concentrations and bulk geochemistry. The relative contributions of the three major sources to the sediment of the trunk Rhône river are identified by compositional mixing modelling. Concentrations of the terrestrial cosmogenic nuclide 10Be measured in quartz separated from fluvial sediments provide spatially averaged denudation rates for selected tributary basins. Results from sediment fingerprinting and mixing modelling suggest that tributaries located in the North and the East of the catchment are generating most of the sediment transported by the Rhône river to its primary sedimentary sink in Lake Geneva. Despite having some of the highest denudation rates within the basin, tributaries located in the southern area of the Rhône basin are relatively underrepresented in the sediment budget of the Rhône river. These tributaries are severely affected by human activities, for example through sediment mining as well as water and sediment abstraction in large hydropower reservoirs. Together, these processes reduce the basin-wide sediment discharge by about 50%, thereby explaining most of the observed compositional pattern. In addition, there is evidence suggesting that large amounts of glaciogenic sediments are currently supplied by retreating glaciers. Glaciogenic material with its low 10Be concentrations can lead to a significant overestimation of denudation rates and thus limit the applicability of cosmogenic nuclide analysis in such glaciated settings.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Stutenbecker, Laura Antonia; Delunel, Romain; Schlunegger, Fritz and Akçar, Naki

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0037-0738

Publisher:

Elsevier

Language:

English

Submitter:

Fritz Schlunegger

Date Deposited:

17 Jan 2018 15:17

Last Modified:

25 Sep 2018 01:30

Publisher DOI:

10.1016/j.sedgeo.2017.12.013

BORIS DOI:

10.7892/boris.108228

URI:

https://boris.unibe.ch/id/eprint/108228

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