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Abstract
High‐precision chmidt‐hammer exposure‐age dating () is applied to ice‐cored moraine‐ridge complexes at three high‐alpine glaciers in otunheimen and reheimen, southern orway. Local calibration curves were established using moraine ridges dating from the last 50 years and bedrock surfaces deglaciated ∼9700 years ago. ages, with 95% statistical confidence intervals, ranged from 3920 ± 790 years to a negative (futuristic) age of –890 ± 580 years at Gråsubreen, 420 ± 700 to 260 ± 710 years at esle‐Juvbreen and 2250 ± 450 to 1605 ± 410 years at stre Tundradalskyrkjabreen. Negatively skewed ‐value distributions were interpreted as the result of weathered boulders from reworked surfaces. This leads to the interpretation of these ages as maximum estimates of moraine‐ridge age. strem's hypothesis (that the proximal ridges are the oldest and survived being overridden many times) is rejected on the basis of our ages. Although ice‐cored moraine ridges resemble the flow structures of rock glaciers, Barsch's hypothesis (that these ice‐cored moraine complexes are rock glaciers) is also rejected. Instead, the ice‐cored moraine‐ridge complexes are considered to be glaciotectonic structures produced by the interaction of polythermal glaciers and alpine permafrost over the late olocene. All the individual ridges were essentially formed during the ‘ittle ce ge’ glacier advance from material deposited earlier by multiple neoglacial events. The considerable size of the moraine complexes is attributed not only to the accumulation of material from these different events over a long period of time but also to their survival in the landscape during phases of glacier retreat when ice cores do not melt and fluvial and other destructive processes remain ineffective in the permafrost environment.
Acknowledgements
The fieldwork was carried out on the Swansea University Jotunheimen Research Expedition 2013, and this paper constitutes Jotunheimen Research Expeditions, Contribution No. 188. We thank Ole Humlum, Andreas Kellerer‐Pirklbauer, Danny McCarroll, Richard Shakesby and an anonymous referee for comments on the manuscript; and Anna Ratcliffe for preparing the diagrams for publication.
Additional information
Notes on contributors
John A. Matthews
John A. Matthews, Department of Geography, College of Science, Swansea University, Singleton Park, Swansea SA2 8PP, UK
Email: [email protected]
Stefan Winkler
Stefan Winkler, Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
Email: [email protected]
Peter Wilson
Peter Wilson, Environmental Sciences Research Institute, School of Environmental Sciences, University of Ulster, Cromore Road, Coleraine, Co. Coleraine, BT52 1SA, Northern Ireland, UK
Email: [email protected]