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New perspectives on the English Channel megaflood hypothesis: High-resolution multibeam and seabed camera imaging of submarine landforms in the Northern Palaeovalley

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Title: New perspectives on the English Channel megaflood hypothesis: High-resolution multibeam and seabed camera imaging of submarine landforms in the Northern Palaeovalley
Authors: Arosio, R
Collier, JS
Hawes, J
Gupta, S
Sperry, J
Item Type: Journal Article
Abstract: A network of large, bedrock-incised valleys is preserved on the seabed of the English Channel. Based on analysis of a 30 × 30 m bathymetric grid, the morphology of the valleys was interpreted to be a consequence of erosion by catastrophic flood processes from overspill of a large proglacial lake in the Southern North Sea. The significance of the “megaflood features” has since been recognized by the UK Government with the designation of their protected status in one of three Marine Protected Areas (MPAs) within the palaeovalley in the central English Channel. Here, we analyse recent multibeam bathymetry data (2 × 2 m DEM) from these MPAs, together with backscatter and high-definition seabed camera imagery. The new data allow us to ground truth and refine the earlier interpretation and recognize previously undiscovered finer features. Streamlined valley margins, streamlined islands and metres-deep scours eroded into the valley floor are described at higher detail, while new subtle features on the valley floor such as kilometre-long, sub-parallel inner channels and streamlined bedrock ridges are identified for the first time. These features are consistent with a high energy erosion origin. We also identify isolated large boulders (>1 m length) on flat seabed on the flanks of the palaeovalley, which are consistent with deposition from megaflood processes, although wave action during transgression/regression cannot be ruled out. Our new results enable more robust morphological evidence to support the influence of catastrophic flooding on bedrock valley incision in the English Channel.
Issue Date: 1-Jun-2021
Date of Acceptance: 5-Mar-2021
URI: http://hdl.handle.net/10044/1/88086
DOI: 10.1016/j.geomorph.2021.107692
ISSN: 0169-555X
Publisher: Elsevier BV
Start Page: 1
End Page: 15
Journal / Book Title: Geomorphology
Volume: 382
Copyright Statement: © 2021 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor/Funder: Marine Environment Protection Fund
Funder's Grant Number: 29964
Keywords: Geography
0403 Geology
0406 Physical Geography and Environmental Geoscience
Publication Status: Published
Article Number: 107692
Online Publication Date: 2021-03-09
Appears in Collections:Earth Science and Engineering
Faculty of Engineering



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