Subrecent sediment dynamics and sediment budget of the braided sandur system at Sandane, Erdalen (Nordfjord, Western Norway)

Abstract

A study was carried out of the subrecent sediment budget of a braided sandur system in a U-shaped valley linked to the Jostedalsbreen ice field in Nordfjord, in Western Norway. Special focus was on (i) the detection of different zones with negative, positive or balanced subrecent (following the Little Ice Age advance) sediment budget within the braided sandur system, (ii) the identification of sediment sources upstream of Sandane and from the slope systems to both sides of the braided sandur system, and (iii) the analysis of the subrecent sediment budget of the entire Sandane system. A combination of methods was applied in the analysis. The upstream part of Sandane was found to be characterised by a negative subrecent sediment balance, with erosion of coarse sediments from the Little Ice Age advance. In comparison, the downstream parts of Sandane have a balanced to slightly positive subrecent sediment budget, with formation of younger flood sediments and more stable channels. Thus, the subrecent sediment budget of Sandane appears to be slightly negative. Present-day coupling of slope and fluvial systems is limited and only a rather small amount of sediments is directly transported from the slopes into the braided sandur. In sum, fluvial sediment transport following the Little Ice Age period appears to be supply-limited.

Keywords:

• landform evolution
• Little Ice Age advance
• subrecent sediment dynamics
• stabilisation
• supply-limited system
• Western Norway

Acknowledgements

Ongoing research in Erdalen is funded by The Research Council of Norway (NFR), the German Exchange Service (DAAD), the Geological Survey of Norway (NGU), and the Norwegian University of Science and Technology (NTNU). Analyses of sediment samples were performed in the Laboratory of the Geological Survey of Norway (NGU) in Trondheim. ¹⁴C analyses were carried out in the Laboratory for Radiocarbon Dating of the Norwegian University of Science and Technology (NTNU) in Trondheim. The support from the following field assistants is greatly acknowledged: Ulrika Åberg, Frida Andersson, Maciej Dominiak, Marion Kandziora, Dagmar Kleemann, Timi Lopez, and Christopher Schmidt. We thank the two reviewers for their helpful critical comments which have improved this paper.