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Crevasse-squeeze ridge corridors: diagnostic features of late stage palaeo-ice stream activity

Evans, D.J.A.; Storrar, R.D.; Rea, B.R.

Crevasse-squeeze ridge corridors: diagnostic features of late stage palaeo-ice stream activity Thumbnail


Authors

R.D. Storrar

B.R. Rea



Abstract

A 200-km-long and 10-km-wide linear assemblage of till-filled geometrical ridges on the bed of the Maskwa palaeo-ice stream of the late Wisconsinan southwest Laurentide Ice Sheet are interpreted as crevasse-squeeze ridges (CSR) developed during internal flow unit reorganization, immediately prior to ice stream shutdown. Ridge orientations are predominantly orientated WNW–ESE, with a subordinate WSW–ENE alignment, both indicative of ice fracture development transverse to former ice stream flow, as indicated by NNE–SSW aligned MSGL. Subglacial till injection into basal and/or full depth, mode I and II crevasses occurred at the approximate centreline of the ice stream, in response to extension and fracturing. Landform preservation indicates that this took place during the final stages of ice streaming, immediately prior to ice stream shutdown. This linear zone of ice fracturing therefore likely represents the narrowing of the fast-flowing trunk, similar to the plug flow identified in some surging valley glaciers. Lateral drag between the final active flow unit and the slower moving ice on either side is likely recorded by the up-ice bending of the CSR limbs. The resulting CSR corridor, here related to an individual ice stream flow unit, constitutes a previously unreported style of crevasse infilling and contrasts with two existing CSR patterns: (1) wide arcuate zones of CSRs related to widespread fracturing within glacier surge lobes; and (2) narrow concentric arcs of CSRs and recessional push moraines related to submarginal till deformation at active temperate glacier lobes.

Citation

Evans, D., Storrar, R., & Rea, B. (2016). Crevasse-squeeze ridge corridors: diagnostic features of late stage palaeo-ice stream activity. Geomorphology, 258, 40-50. https://doi.org/10.1016/j.geomorph.2016.01.017

Journal Article Type Article
Acceptance Date Jan 28, 2016
Online Publication Date Jan 29, 2016
Publication Date Apr 1, 2016
Deposit Date Feb 8, 2016
Publicly Available Date Jan 29, 2017
Journal Geomorphology
Print ISSN 0169-555X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 258
Pages 40-50
DOI https://doi.org/10.1016/j.geomorph.2016.01.017
Keywords Crevasse-squeeze ridge, Palaeo-ice stream, Full depth crevassing, Laurentide Ice Sheet.

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