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Relict blockstreams at Insteheia, Valldalen-Tafjorden, southern Norway: Their nature and Schmidt-hammer exposure age

Wilson, Peter; Matthews, John; Matthews, John A.; Mourne, Richard; Mourne, Richard W.

Authors

Peter Wilson

John Matthews

John A. Matthews



Abstract

Two small blockstreams, the first such landforms to be recorded in the mountains of Scandinavia, are described from Insteheia, a col at 910 m asl on the watershed between Valldalen and Tafjorden (Møre og Romsdal), southern Norway. Both blockstreams display morphological and sedimentological characteristics indicative of boulder accumulations that have moved downslope by means of solifluction most probably under a permafrost climatic regime. These comprise boulder preferred orientation and dip patterns; inverse grading comprising surface boulders overlying successively finer, well-sorted cobble, pebble and finegrained (sand/silt dominated) sediment layers; imbrication, with the packing of small boulders behind larger boulders; and proximity to boulder-strewn hillslopes whose constituent boulders (organised into lobes and terraces) feed downslope into the blockstreams. Schmidt-hammer exposure-ages of 7.24 to 11.17 ka indicate that the blockstreams were last active during the Younger Dryas Stadial – Holocene transition (~9.5-11.2 ka). It is inferred that blockstream development began at ~18 ka, following the Last Glacial Maximum, and lasted for ~8 ka, and that since the blockstreams became inactive fine grained material has been progressively lost as a result of snowmelt runoff. The small areal extent and relatively recent age of the blockstreams contrast with larger-scale forms of considerably greater age in the Southern Hemisphere.

Citation

Wilson, P., Matthews, J., & Mourne, R. (2017). Relict blockstreams at Insteheia, Valldalen-Tafjorden, southern Norway: Their nature and Schmidt-hammer exposure age. Permafrost and Periglacial Processes, 28(1), 286-297. https://doi.org/10.1002/ppp.1915

Journal Article Type Article
Acceptance Date Jun 30, 2016
Online Publication Date Sep 19, 2016
Publication Date Feb 24, 2017
Publicly Available Date Nov 30, -0001
Journal Permafrost and Periglacial Processes
Print ISSN 1045-6740
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 28
Issue 1
Pages 286-297
DOI https://doi.org/10.1002/ppp.1915
Keywords blockstreams, Schmidt-hammer exposure-age dating, Younger Dryas, Norway
Public URL https://uwe-repository.worktribe.com/output/898151
Publisher URL http://dx.doi.org/10.1002/ppp.1915
Additional Information Additional Information : This is the peer reviewed version of the following article: Wilson, P., Matthews, J. and Mourne, R. (2016) Relict blockstreams at Insteheia, Valldalen-Tafjorden, southern Norway: Their nature and Schmidt-hammer exposure age. Permafrost and Periglacial Processes, which has been published in final form at http://dx.doi.org/10.1002/ppp.1915. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.