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How to recognize crescentic bedforms formed by supercritical turbidity currents in the geologic record: Insights from active submarine channels

Hage, Sophie; Cartigny, Matthieu J.B.; Clare, Michael A.; Sumner, Esther J.; Vendettuoli, Daniela; Clarke, John E.Hughes; Hubbard, Stephen M.; Talling, Peter J.; Gwyn Lintern, D.; Stacey, Cooper D.; Englert, Rebecca G.; Vardy, Mark E.; Hunt, James E.; Yokokawa, Miwa; Parsons, Daniel R.; Hizzett, Jamie L.; Azpiroz-Zabala, Maria; Vellinga, Age J.

Abstract

© 2018 Geological Society of America. Submarine channels have been important throughout geologic time for feeding globally significant volumes of sediment f rom land to the deep sea. Modern observations show that submarine channels can be sculpted by supercritical turbidity currents (seafloor sediment flows) that can generate upstream-migrating bedforms with a crescentic planform. In order to accurately interpret supercritical flows and depositional environments in the geologic record, it is important to be able to recognize the depositional signature of crescentic bedforms. Field geologists commonly link scour fills containing massive sands to crescentic bedforms, whereas models of turbidity currents produce deposits dominated by back-stepping beds. Here we reconcile this apparent contradiction by presenting the most detailed study yet that combines direct flow observations, time-lapse seabed mapping, and sediment cores, thus providing the link from flow process to depositional product. These data were collected within the proximal part of a submarine channel on the Squamish Delta, Canada. We demonstrate that bedform migration initially produces back-stepping beds of sand. However, these back-stepping beds are partially eroded by further bedform migration during subsequent flows, resulting in scour fills containing massive sand. As a result, our observations better match the depositional architecture of upstream-migrating bedforms produced by fluvial models, despite the fact that they formed beneath turbidity currents.

Journal Article Type Article
Publication Date Jun 1, 2018
Journal Geology
Print ISSN 0091-7613
Electronic ISSN 1943-2682
Publisher Geological Society of America
Peer Reviewed Peer Reviewed
Volume 46
Issue 6
Pages 563-566
DOI https://doi.org/10.1130/G40095.1
Publisher URL https://pubs.geoscienceworld.org/gsa/geology/article/46/6/563/530687/How-to-recognize-crescentic-bedforms-formed-by

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Copyright Statement
© The Authors. Gold open access: This paper is published under the terms of the CC-BY licence.



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