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Knickpoints and crescentic bedform interactions in submarine channels

Knickpoints and crescentic bedform interactions in submarine channels
Knickpoints and crescentic bedform interactions in submarine channels

Submarine channels deliver globally important volumes of sediments, nutrients, contaminants and organic carbon into the deep sea. Knickpoints are significant topographic features found within numerous submarine channels, which most likely play an important role in channel evolution and the behaviour of the submarine sediment-laden flows (turbidity currents) that traverse them. Although prior research has linked supercritical turbidity currents to the formation of both knickpoints and smaller crescentic bedforms, the relationship between flows and the dynamics of these seafloor features remains poorly constrained at field-scale. This study investigates the distribution, variation and interaction of knickpoints and crescentic bedforms along the 44 km long submarine channel system in Bute Inlet, British Columbia. Wavelet analyses on a series of repeated bathymetric surveys reveal that the floor of the submarine channel is composed of a series of knickpoints that have superimposed, higher-frequency, crescentic bedforms. Individual knickpoints are separated by hundreds to thousands of metres, with the smaller superimposed crescentic bedforms varying in wavelengths from ca 16 m to ca 128 m through the channel system. Knickpoint migration is driven by the passage of frequent turbidity currents, and acts to redistribute and reorganize the crescentic bedforms. Direct measurements of turbidity currents indicate the seafloor reorganization caused by knickpoint migration can modify the flow field and, in turn, control the location and morphometry of crescentic bedforms. A transect of sediment cores obtained across one of the knickpoints show sand–mud laminations of deposits with higher aggradation rates in regions just downstream of the knickpoint. The interactions between flows, knickpoints and bedforms that are documented here are important because they likely dominate the character of preserved submarine channel-bed deposits.

Crescentic bedforms, knickpoints, sedimentary records, submarine channels, turbidity currents
0037-0746
1358-1377
Chen, Ye
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Parsons, Daniel R.
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Simmons, Stephen M.
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Williams, Rebecca
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Cartigny, Matthieu J. B.
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Hughes Clarke, John E.
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Stacey, Cooper D.
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Hage, Sophie
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Talling, Peter J.
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Azpiroz‐zabala, Maria
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Clare, Michael A.
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Hizzett, Jamie L.
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Heijnen, Maarten S.
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Hunt, James E.
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Lintern, D. Gwyn
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Sumner, Esther J.
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Vellinga, Age J.
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Vendettuoli, Daniela
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Slootman, Arnoud
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Chen, Ye
42b24968-5aaf-4108-ab70-1aebc81d291d
Parsons, Daniel R.
59f2673a-9c73-437a-8865-52d52830a3aa
Simmons, Stephen M.
1aa65c10-98f2-4e55-aa91-9e6edcd9c5ab
Williams, Rebecca
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Cartigny, Matthieu J. B.
bda1b79b-7e11-4790-8238-b86d80a88bb3
Hughes Clarke, John E.
e36310a7-529a-4383-a875-7194eb73bfd6
Stacey, Cooper D.
0365dcd2-137a-48b4-99f0-0ab0422f1641
Hage, Sophie
a914d294-89b9-4686-94f3-e3d7b0c41d76
Talling, Peter J.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf
Azpiroz‐zabala, Maria
d26dcdf2-afdd-4788-a6ca-b70360f238c5
Clare, Michael A.
b26da858-9c08-4784-aaa9-7092efcd94bd
Hizzett, Jamie L.
e653991a-457e-4bd7-b261-f0539d736f34
Heijnen, Maarten S.
69912afb-cc7a-4757-9d25-109117f4114e
Hunt, James E.
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Lintern, D. Gwyn
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Sumner, Esther J.
dbba4b92-89cc-45d9-888e-d0e87e5c10ac
Vellinga, Age J.
9957dfd4-70a8-4327-b66c-af7f718a0e75
Vendettuoli, Daniela
16879a32-0874-4edf-a368-52ec101c8967
Slootman, Arnoud
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Chen, Ye, Parsons, Daniel R., Simmons, Stephen M., Williams, Rebecca, Cartigny, Matthieu J. B., Hughes Clarke, John E., Stacey, Cooper D., Hage, Sophie, Talling, Peter J., Azpiroz‐zabala, Maria, Clare, Michael A., Hizzett, Jamie L., Heijnen, Maarten S., Hunt, James E., Lintern, D. Gwyn, Sumner, Esther J., Vellinga, Age J., Vendettuoli, Daniela and Slootman, Arnoud (2021) Knickpoints and crescentic bedform interactions in submarine channels. Sedimentology, 68 (4), 1358-1377. (doi:10.1111/sed.12886).

Record type: Article

Abstract

Submarine channels deliver globally important volumes of sediments, nutrients, contaminants and organic carbon into the deep sea. Knickpoints are significant topographic features found within numerous submarine channels, which most likely play an important role in channel evolution and the behaviour of the submarine sediment-laden flows (turbidity currents) that traverse them. Although prior research has linked supercritical turbidity currents to the formation of both knickpoints and smaller crescentic bedforms, the relationship between flows and the dynamics of these seafloor features remains poorly constrained at field-scale. This study investigates the distribution, variation and interaction of knickpoints and crescentic bedforms along the 44 km long submarine channel system in Bute Inlet, British Columbia. Wavelet analyses on a series of repeated bathymetric surveys reveal that the floor of the submarine channel is composed of a series of knickpoints that have superimposed, higher-frequency, crescentic bedforms. Individual knickpoints are separated by hundreds to thousands of metres, with the smaller superimposed crescentic bedforms varying in wavelengths from ca 16 m to ca 128 m through the channel system. Knickpoint migration is driven by the passage of frequent turbidity currents, and acts to redistribute and reorganize the crescentic bedforms. Direct measurements of turbidity currents indicate the seafloor reorganization caused by knickpoint migration can modify the flow field and, in turn, control the location and morphometry of crescentic bedforms. A transect of sediment cores obtained across one of the knickpoints show sand–mud laminations of deposits with higher aggradation rates in regions just downstream of the knickpoint. The interactions between flows, knickpoints and bedforms that are documented here are important because they likely dominate the character of preserved submarine channel-bed deposits.

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Knickpoints and crescentic bedform interactions ... - Accepted Manuscript
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Accepted/In Press date: 15 April 2021
e-pub ahead of print date: 27 April 2021
Published date: 1 June 2021
Keywords: Crescentic bedforms, knickpoints, sedimentary records, submarine channels, turbidity currents

Identifiers

Local EPrints ID: 450069
URI: http://eprints.soton.ac.uk/id/eprint/450069
ISSN: 0037-0746
PURE UUID: b78b9efd-fc27-4a3e-886c-8b94c8610106

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Date deposited: 08 Jul 2021 16:30
Last modified: 09 Jul 2021 16:33

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Contributors

Author: Ye Chen
Author: Daniel R. Parsons
Author: Stephen M. Simmons
Author: Rebecca Williams
Author: Matthieu J. B. Cartigny
Author: John E. Hughes Clarke
Author: Cooper D. Stacey
Author: Sophie Hage
Author: Peter J. Talling
Author: Maria Azpiroz‐zabala
Author: Michael A. Clare
Author: Jamie L. Hizzett
Author: Maarten S. Heijnen
Author: James E. Hunt
Author: D. Gwyn Lintern
Author: Age J. Vellinga
Author: Arnoud Slootman

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