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Ramparted depressions (doughnut-shaped debris-cored ridges with peat- and/or sediment-filledcentral basins) are commonly perceived to represent the relict collapsed forms of permafrostground-ice mounds (i.e. pingos or lithalsas). In Wales, UK, ramparted depressions of LatePleistocene age have been widely attributed to permafrost-related processes. However, a varietyof alternative glacial origins for these enigmatic landforms are also consistent with the available geologicaland geomorphological evidence, although previous studies have barely considered suchalternative processes of formation. From detailed geophysical, sedimentological and remote-sensingstudies at two field sites, we demonstrate that: (i) thewastage of stagnating glacier ice is a viable alternativeexplanation for the formation of ramparted depressions inWales; (ii) the glacial geomorphologyand geology of these landforms is analogous to supraglacial and subglacial landforms from thelast Laurentide and Fennoscandian ice sheets; (iii) these landforms have significant potential forcharacterising the nature of deglaciation around the margins of the Irish Sea during the last glacialcycle, and may record evidence for the overextension and stagnation of the south-eastern margin ofthe Irish Sea Ice Stream; and (iv) investigations of ramparted depressions within formerly glaciatedterrains must consider both glacial and periglacial mechanisms of formation.
Author(s): Ross N, Brabham PJ, Harris C
Publication type: Article
Publication status: Published
Journal: Annals of Glaciology
Year: 2020
Volume: 60
Issue: 80
Pages: 138-150
Online publication date: 09/01/2020
Acceptance date: 07/11/2019
Date deposited: 09/01/2020
ISSN (print): 0260-3055
ISSN (electronic): 1727-5644
Publisher: Cambridge University Press
URL: https://doi.org/10.1017/aog.2019.40
DOI: 10.1017/aog.2019.40
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