Holocene gorge excavation linked to boulder fan formation and frost weathering in a norwegian alpine periglaciofluvial system

• Main Authors: McEwen, L., Matthews, J. A., Shakesby, R. A., Berrisford, M. S.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: INSTAAR 2002
• Subjects: Arctic; Norway; Antarctic and Alpine Research
• Online Access: http://eprints.uwe.ac.uk/20348/; http://instaar.colorado.edu/AAAR/about_aaar/index.php

Landform-sediment-process assemblages associated with four gorges and their corresponding downstream boulder fans in the alpine periglaciofluvial system of the Storutla river, Jotunheimen, southern Norway, are described. The potential volume of frost-weathered sediment excavated from the gorges is compared using a sediment-budget approach to calculate the volume of angular sediment within the fans accumulated during the Holocene. Fan volumes represent an estimated 18 to 53% of the total gorge volume. Allowing also for the volume of relatively small caliber material flushed through the system, 24 to 97% of the gorge volume is accounted for by an estimated minimum long-term Holocene rate of gorge excavation of 0.002 to 0.010 m3 m−1 yr−1 (minimum long-term Holocene gorge incision rate of 0.15-0.39 mm yr−1). Most of the remaining gorge volume is attributed to substantial pre-Holocene subglacial gorge incision by meltwater action. These rates of Holocene periglaciofluvial erosion of bedrock appear to exceed those characteristic of temperate fluvial systems unaffected by tectonic uplift. The implied rates of frost weathering (macrogelivation) are less than those under optimum conditions in arctic-alpine environments but support the efficacy of frost weathering in locations susceptible to the annual freeze-thaw cycle.