A Holocene record of snow-avalanche and flood activity reconstructed from a lacustrine sedimentary sequence in Oldevatnet, western Norway

• Published in: The Holocene
• Main Authors: Vasskog, Kristian, Nesje, Atle, Nagel Støren, Eivind, Waldmann, Nicolas, Chapron, Emmanuel, Ariztegui, Daniel
• Other Authors: Department of Earth Science Bergen (UiB), University of Bergen (UiB), Institut des Sciences de la Terre d'Orléans (ISTO), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Université de Tours (UT)-Centre National de la Recherche Scientifique (CNRS), Institut Forel and Department of Geology and Paleontology, University of Geneva Switzerland
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: density currents; floods; Holocene; palaeoclimate; proglacial lake sediments; snow-avalanches; western Norway; envir; geo; Norway; glacier
• Online Access: https://doi.org/10.1177/0959683610391316; https://hal-insu.archives-ouvertes.fr/insu-00665776

International audience Two lacustrine sediment cores from Oldevatnet in western Norway have been studied in order to produce a record of floods, mass-wasting events and glacier fluctuations during the last 7300 years. River floods, density currents and snow-avalanches have deposited distinct 'event layers' at the lake floor throughout this time interval. In this study, a novel approach has been applied to distinguish event layers from the continuous background sedimentation, using Rb/Sr-ratios from X-Ray Fluorescence data. Grain-size distribution and the sedimentological parameters 'mean' and 'sorting' were used to further infer the depositional processes behind each layer. Our data suggest a record dominated by snow-avalanches, with the largest activity occurring during the 'Little Ice Age' (LIA). This increase in snow-avalanche activity observed during the LIA was probably caused by a combination of generally increasing winter precipitation and the advance of local glaciers towards the steep valley sides. Several fluctuations in snow-avalanche activity are also recognized prior to the LIA. Proxies of glacial activity from the background sediments indicate a similar development as earlier palaeoclimatic reconstructions from the area. It differs from previous reconstructions, however, by suggesting a lower glacial activity in the period from 2200 to 1000 cal. yr BP.