Reconstruction of Holocene glacier history from distal sources: glaciofluvial stream-bank mires and a glaciolacustrine sediment core near Sota Sæter, Breheimen, southern Norway

• Published in: The Holocene
• Main Authors: Shakesby, Richard A., Smith, Jamie G., Matthews, John A., Winkler, Stefan, Dresser, P. Quentin, Bakke, Jostein, Dahl, Svein-Olaf, Lie, Øyvind, Nesje, Atle
• Format: Article in Journal/Newspaper
• Language: English
• Published: SAGE Publications 2007
• Subjects: glacier
• Online Access: http://dx.doi.org/10.1177/0959683607080514; http://journals.sagepub.com/doi/pdf/10.1177/0959683607080514

This study attempts to reconstruct the Holocene glacier history of Breheimen, southern Norway from four stream-bank mire sites and a downstream lake sediment core near Sota Sæter, based on lithostratigraphy, sediment properties (loss-on-ignition (LOI), magnetic susceptibility (MS), grain size characteristics) and 69 radiocarbon dates. Late-Preboreal deglaciation is indicated by lake-floor accumulation of organic matter (gyttja) largely replacing minerogenic sediment before 9000 cal. BP. A distinct minerogenic layer is thought to represent glacier expansion during the 8.2 ka Finse Event. Following this event until c . 2200 cal. BP, glaciers were mostly smaller than today, indicated by slow accumulation of mainly gyttja with predominantly thin minerogenic layers. A trough in LOI and corresponding small peaks in different silt fractions indicate possible glacial expansion from c. 3500 to 3000 cal. BP. The shorter c. 7500 year stream-bank mire record suggests brief, distinct episodes of Neoglacial glacier activity at c. 5600 and 3650 cal. BP. After c. 2200 cal. BP, up to three possible glacier expansion events are indicated in the lake core compared with up to eight represented in the mire sequences, suggesting greater sensitivity of the latter to small-scale glacier expansion. Marked `suppressed' Neoglacial expansion until after c. 2200 cal. BP contrasts with the more typically reported start at 6000—5300 cal. BP elsewhere in southern Norway. Methodological implications are discussed including: factors responsible for erroneous radiocarbon dates in mire and lake core stratigraphies; high spatial variability in mire stratigraphy; determining the amplitude of glacier contraction episodes; isolating the glacial signal from background `noise'; and further improvement of dating.