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Schmidt-hammer exposure ages from periglacial patterned ground (sorted circles) in Jotunheimen, Norway, and their interpretative problems

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

Schmidt-hammer exposure ages from periglacial patterned ground (sorted circles) in Jotunheimen, Norway, and their interpretative problems Thumbnail


Authors

Stefan Winkler

John Matthews

John A. Matthews

Peter Wilson



Abstract

© 2016 Swedish Society for Anthropology and Geography Periglacial patterned ground (sorted circles and polygons) along an altitudinal profile at Juvflya in central Jotunheimen, southern Norway, is investigated using Schmidt-hammer exposure-age dating (SHD). The patterned ground surfaces exhibit R-value distributions with platycurtic modes, broad plateaus, narrow tails, and a negative skew. Sample sites located between 1500 and 1925 m a.s.l. indicate a distinct altitudinal gradient of increasing mean R-values towards higher altitudes interpreted as a chronological function. An established regional SHD calibration curve for Jotunheimen yielded mean boulder exposure ages in the range 6910 ± 510 to 8240 ± 495 years ago. These SHD ages are indicative of the timing of patterned ground formation, representing minimum ages for active boulder upfreezing and maximum ages for the stabilization of boulders in the encircling gutters. Despite uncertainties associated with the calibration curve and the age distribution of the boulders, the early-Holocene age of the patterned ground surfaces, the apparent cessation of major activity during the Holocene Thermal Maximum (HTM) and continuing lack of late-Holocene activity clarify existing understanding of the process dynamics and palaeoclimatic significance of large-scale sorted patterned ground as an indicator of a permafrost environment. The interpretation of SHD ages from patterned ground surfaces remains challenging, however, owing to their diachronous nature, the potential for a complex history of formation, and the influence of local, non-climatic factors.

Citation

Winkler, S., Matthews, J. A., Mourne, R. W., & Wilson, P. (2016). Schmidt-hammer exposure ages from periglacial patterned ground (sorted circles) in Jotunheimen, Norway, and their interpretative problems. Geografiska Annaler: Series A, Physical Geography, 98(3), 265-285. https://doi.org/10.1111/geoa.12134

Journal Article Type Article
Acceptance Date May 18, 2016
Online Publication Date Jul 20, 2016
Publication Date Sep 1, 2016
Deposit Date Nov 29, 2016
Publicly Available Date Jul 21, 2018
Journal Geografiska Annaler, Series A: Physical Geography
Print ISSN 0435-3676
Electronic ISSN 1468-0459
Publisher Taylor & Francis
Peer Reviewed Peer Reviewed
Volume 98
Issue 3
Pages 265-285
DOI https://doi.org/10.1111/geoa.12134
Keywords sorted circles, periglacial patterned ground, alpine permafrost, Schmidt-hammer exposure-age dating (SHD), mechanical Schmidt hammer, RockSchmidt, alpine permafrost, Holocene climatic variations, Jotunheimen, Jotunheimen, Norway
Public URL https://uwe-repository.worktribe.com/output/908714
Publisher URL http://dx.doi.org/10.1111/geoa.12134
Additional Information Additional Information : This is the peer reviewed version of the following article: Winkler, S., Matthews, J., Mourne, R. and Wilson, P. (2016) Schmidt-hammer exposure ages from periglacial patterned ground (sorted circles) in Jotunheimen, Norway, and their interpretative problems. Geografiska Annaler: Series A, Physical Geography, 98 (3). pp. 265-285, which has been published in final form at http://dx.doi.org/10.1111/geoa.12134. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

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