A1 Refereed original research article in a scientific journal
Diversity of murtoos and murtoo-related subglacial landforms in the Finnish area of the Fennoscandian Ice Sheet
Authors: Ojala Antti EK, Mäkinen Joni, Ahokangas Elina, Kajuutti Kari, Valkama Markus, Tuunainen Aleksi, Palmu Jukka-Pekka
Publisher: WILEY
Publication year: 2021
Journal: Boreas
Journal name in source: BOREAS
Journal acronym: BOREAS
Number of pages: 21
ISSN: 0300-9483
eISSN: 1502-3885
DOI: https://doi.org/10.1111/bor.12526
Web address : https://onlinelibrary.wiley.com/doi/10.1111/bor.12526
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/59924746
Murtoos are recently discovered triangular-shaped subglacial landforms that form under warm-based ice and in association with significant subglacial meltwater flow. They appear in distinct fields and commonly occur in the area that was covered by the Fennoscandian Ice Sheet during glacial periods. Murtoos potentially represent a transition form from non-channelized to channelized subglacial drainage networks. In the present study, we analyse and classify murtoos and murtoo-related landforms in the Finnish area of the Fennoscandian Ice Sheet based on their characteristics and appearance in LiDAR-based digital elevations models. Combined with morphometric analyses, the observations suggest that five types of murtoos and murtoo-related landforms are common and widespread in Finland: (i) triangle-type murtoos (TTMs), (ii) chevron-type murtoos (CTMs), (iii) lobate-type murtoos (LTMs), (iv) murtoo-related ridges and escarpments (MREs), and (v) other murtoo-related polymorphous landforms (PMRs) that look like small mounds and ridges. The morphometric characteristics of the different types are described here in detail, and it is shown that they are spatially and geomorphologically related. In addition, we provide examples of murtoos other than the TTMs to demonstrate that different murtoo types and murtoo-related landforms are composed of similar sediments and architectural characteristics. The diversity of murtoo landforms and the transition between distinct murtoo types indicate rapid and complicated variations in the configuration of subglacial hydrology at different spatial and temporal scales. This study emphasizes the essential role of subglacial meltwater in the shaping of glacial landscapes and the redistribution of large volumes of sediments during the deglaciation of the Fennoscandian Ice Sheet.
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