https://orcid.org/0000-0002-2610-863X
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ABSTRACT
Eleven snow-avalanche boulder fans were dated from two high-alpine sites in Jotunheimen using Schmidt-hammer exposure-age dating (SHD) and lichenometry. Average exposure ages of the surface boulders ranged from 2285 ± 725 to 7445 ± 1020 years and demonstrate the potential of SHD for dating active landforms and diachronous surfaces. Application of GIS-based morphometric analyses showed that the volume of rock material within 10 of the fans is accounted for by 16–68% of the combined volume of their respective bedrock chutes and transport zones. It is inferred that the fans were deposited entirely within the Holocene, mainly within the early- to mid Holocene, by frequent avalanches carrying very small debris loads. Relatively small transport-zone volumes are consistent with avalanches of low erosivity. Excess chute volumes appear to represent subaerial erosion in the Younger Dryas and possibly earlier. Debris supply to the fans was likely enhanced by early-Holocene paraglacial processes following deglaciation, and by later permafrost degradation associated with the mid-Holocene Thermal Maximum. The latter, together with the youngest SHD age from one of the fans, may presage a similar increase in geomorphic activity in response to current warming trends.
Acknowledgements
Fieldwork was carried out on the Swansea University Jotunheimen Research Expeditions of 2017, 2018 and 2019. We thank Mats and Jonas Hiemstra for assistance in the field, and Ole Jacob and Tove Grindvold for logistical support. Anna C. Ratcliffe prepared most of the figures for publication, and Atle Nesje and Peter Wilson made useful comments on the manuscript. This paper constitutes Jotunheimen Research Expeditions Contribution No. 214 (see http://jotunheimenresearch.wixsite.com/home)
Notes on contributors
Professor John A. Matthews is Emeritus Professor of Physical Geography at Swansea University, Wales, UK. His main research interests are in the physical geography of mountain landscapes, the geoecology of glacier forelands, Holocene environmental change, and associated dating techniques (with particular reference to southern Norway).
Stefan Haselberger is a PhD candidate in physical geography at the University of Vienna, Austria. His primary research focus is on biogeomorphic interactions in glacier forelands, focusing on the quantification of the bi-directional relationship of sediment transport and primary succession.
Professor Jennifer L. Hill is a geographer who researches environmental resource management in extreme environments, focusing on cold mountain environments, tropical forests and hot deserts. She is passionate about teaching, researching and developing curricula in geography and cognate disciplines and she has recently turned her attention to academic development, seated in research-informed practice.
Dr. Geraint Owen is an Honorary Senior Lecturer at Swansea University. His research ranges from Holocene processes to Precambrian palaeoenvironments, with a focus on post-depositional deformation structures developed in sandy deposits.
Professor Stefan Winkler is Professor of Geography at the Julius-Maximilians-University of Wuerzburg, Germany. His main research activities are in Holocene mountain glacier chronologies, glacial and periglacial geomorphology, and related dating techniques, with main focus on Norway and New Zealand.
Dr. John F. Hiemstra is an Associate Professor of Physical Geography at Swansea University. His research interests include the reconstruction of past glacial environments, and the study of more recent glacier and permafrost dynamics in response to changing climate.
Helen Hallang is a PhD candidate in physical geography at Swansea University, Wales, UK. Her research is focused on long-term environmental changes in alpine permafrost regions and their effect on carbon dioxide emissions from permafrost soils.
Disclosure statement
No potential conflict of interest was reported by the author(s).
ORCID
John A. Matthews http://orcid.org/0000-0002-2610-863X
Jennifer L. Hill http://orcid.org/0000-0002-0682-783X
Stefan Winkler https://orcid.org/0000-0002-0650-1207
John F. Hiemstra https://orcid.org/0000-0003-3148-0206
Helen Hallang https://orcid.org/0000-0002-2425-8247