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

How to recognize crescentic bedforms formed by supercritical turbidity currents in the geologic record: insights from active submarine channels
How to recognize crescentic bedforms formed by supercritical turbidity currents in the geologic record: insights from active submarine channels
Submarine channels have been important throughout geologic time for feeding globally significant volumes of sediment from 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.
0091-7613
563-566
Hage, Sophie
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Cartigny, Matthieu J.B.
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Clare, Michael
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Sumner, Esther
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Vendettuoli, Daniela
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Hughes Clarke, John
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Hubbard, Stephen
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Talling, Peter J.
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Lintern, D. Gwynn
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Cooper, Stacey
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Englert, Rebecca
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Vardy, Mark E.
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Hunt, James Edward
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Yokokawa, Miwa
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Parsons, Daniel
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Hizzett, Jamie, Lee
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Azpiroz-Zabala, Maria
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Vellinga, Age, Jan
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Hage, Sophie
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Cartigny, Matthieu J.B.
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Clare, Michael
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Sumner, Esther
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Vendettuoli, Daniela
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Hughes Clarke, John
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Hubbard, Stephen
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Talling, Peter J.
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Lintern, D. Gwynn
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Cooper, Stacey
42917aea-bf71-4e6c-a938-d5c14e5566ea
Englert, Rebecca
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Vardy, Mark E.
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Hunt, James Edward
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Yokokawa, Miwa
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Parsons, Daniel
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Hizzett, Jamie, Lee
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Azpiroz-Zabala, Maria
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Vellinga, Age, Jan
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Hage, Sophie, Cartigny, Matthieu J.B., Clare, Michael, Sumner, Esther, Vendettuoli, Daniela, Hughes Clarke, John, Hubbard, Stephen, Talling, Peter J., Lintern, D. Gwynn, Cooper, Stacey, Englert, Rebecca, Vardy, Mark E., Hunt, James Edward, Yokokawa, Miwa, Parsons, Daniel, Hizzett, Jamie, Lee, Azpiroz-Zabala, Maria and Vellinga, Age, Jan (2018) How to recognize crescentic bedforms formed by supercritical turbidity currents in the geologic record: insights from active submarine channels. Geology, 46 (6), 563-566. (doi:10.1130/G40095.1).

Record type: Article

Abstract

Submarine channels have been important throughout geologic time for feeding globally significant volumes of sediment from 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.

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Accepted/In Press date: 17 April 2018
e-pub ahead of print date: 26 April 2018
Published date: 2018

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Local EPrints ID: 421000
URI: http://eprints.soton.ac.uk/id/eprint/421000
ISSN: 0091-7613
PURE UUID: b0dc8fc7-5796-44e4-b99a-8b33b4f2efb5

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Date deposited: 21 May 2018 16:30
Last modified: 06 Oct 2020 18:14

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