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Glacitectonic rafts and their role in the generation of Quaternary subglacial bedforms and deposits

Evans, David J.A.; Phillips, Emrys R.; Atkinson, Nigel

Glacitectonic rafts and their role in the generation of Quaternary subglacial bedforms and deposits Thumbnail


Authors

Emrys R. Phillips

Nigel Atkinson



Abstract

Landforms and sediments on the palaeo–ice stream beds of central Alberta record glacitectonic raft production and subsequent progressive disaggregation and moulding, associated substrate ploughing, and grooving. We identify a subglacial temporal or developmental hierarchy that begins with incipient rafts, including en échelon hill-hole complexes, hill-hole pairs, and strike-slip raft complexes, all of which display patterns typical of transcurrent fault activation and pull apart. Many display jigsaw puzzle–style fragmentation, indicative of substrate displacement along shallow décollement zones and potentially related to patchy ice stream freeze-on. Their gradual fragmentation and smoothing produces ice flow-transverse ridges (ribbed moraine), hill-groove pairs, and paraxial ridge and groove associations. Initiator scarp and megafluting associations are indicative of raft dislodgement and groove ploughing, leading to the formation of murdlins, crag-and-tails, stoss-and-lee type flutings and drumlins, and Type 1 hogsback flutings. Downflow modification of rafts creates linear block trains (rubble stripes), stoss-and-lee type megaflutings, horned crag-and-tails, rubble drumlinoids, and murdlins, diagnostic of an immature palaeo–ice stream footprint. Lateral ice stream margin migration ingests disaggregated thrust masses to form ridged spindles, ladder-type morphologies, and narrow zones of ribbed terrain and Type 2 hogsback flutings, an assemblage diagnostic of ice stream shear margin moraine formation.

Citation

Evans, D. J., Phillips, E. R., & Atkinson, N. (2021). Glacitectonic rafts and their role in the generation of Quaternary subglacial bedforms and deposits. Quaternary Research, 104, 101-135. https://doi.org/10.1017/qua.2021.11

Journal Article Type Article
Acceptance Date Feb 9, 2021
Online Publication Date May 6, 2021
Publication Date 2021-11
Deposit Date May 16, 2021
Publicly Available Date May 17, 2021
Journal Quaternary Research
Print ISSN 0033-5894
Electronic ISSN 1096-0287
Publisher Academic Press
Peer Reviewed Peer Reviewed
Volume 104
Pages 101-135
DOI https://doi.org/10.1017/qua.2021.11
Public URL https://durham-repository.worktribe.com/output/1274952

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Published Journal Article (Advance online version) (6.6 Mb)
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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
Advance online version © University of Washington. Published by Cambridge University Press, 2021. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence
(http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.






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