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Sediment volume and grain-size partitioning between submarine channel-levee systems and lobes: An experimental study

Sediment volume and grain-size partitioning between submarine channel-levee systems and lobes: An experimental study
Sediment volume and grain-size partitioning between submarine channel-levee systems and lobes: An experimental study

The width and depth of submarine channels change progressively as the channels evolve. This is inferred to act as an important control on the rate of sediment loss due overbank and in-channel deposition. Understanding the downstream extraction of sediment from turbidity currents is important for the prediction of grain-size trends and volume distribution in the stratigraphy. However, the partitioning of sediment by individual turbidity currents as a function of channel dimensions has not been investigated previously. We present a series of physical experiments studying the link between channel dimensions and the resulting partitioning of sediment volume and grain size between sub-environments. The experimental set-up consists of a slope (118) with a straight pre-formed channel and a horizontal basin floor. An identical flow was released repeatedly into channels with different dimensions, resulting in various styles of overspill, erosion, and deposition under varying degrees of channel confinement. The fraction of sediment that was bypassed through the channel to the basin floor varied between 67% and 89%, depending on the amount of levee and in-channel deposition. The volume of levee deposition correlates well with channel depth. A large channel depth relative to flow thickness limits the amount of overspill. The amount of in-channel deposition correlates well with channel width/depth (W/D) ratio, where low-W/D-ratio channels have less deposition. We compare the experiments to natural system to show that the same patterns of volume and grain-size partitioning are present at different scales. The experiments provide snapshots of different phases of evolution of natural submarine channels. Natural submarine channels in an early evolution phase are inferred to be shallow and the experiments demonstrate that this results in significant sediment loss to levee deposition along the channel. The process of levee deposition preferentially extracts the fine-grained sediment fraction, which overspills from the channel. Therefore, we predict that the initial sediment pulse that reaches the basin floor is coarse grained and volumetrically small. As the channel matures and deepens, it will bypass more sediment with a mix of grain sizes to the basin floor.

1527-1404
777-794
De Leeuw, Jan
a7857f44-b451-44d3-a368-813f9ea38f92
Eggenhuisen, Joris T.
157ad755-8819-48cb-8694-6bbffa20b727
Spychala, Yvonne T.
fe297e0f-4abd-457e-85c1-90875e9ec27f
Heijnen, Maarten S.
65fbb0a5-0ee5-4a76-a436-c11f4e2023ae
Pohl, Florian
7aebe37d-d7a0-4a95-8090-1806aa7e13b6
Cartigny, Matthieu J.B.
bda1b79b-7e11-4790-8238-b86d80a88bb3
De Leeuw, Jan
a7857f44-b451-44d3-a368-813f9ea38f92
Eggenhuisen, Joris T.
157ad755-8819-48cb-8694-6bbffa20b727
Spychala, Yvonne T.
fe297e0f-4abd-457e-85c1-90875e9ec27f
Heijnen, Maarten S.
65fbb0a5-0ee5-4a76-a436-c11f4e2023ae
Pohl, Florian
7aebe37d-d7a0-4a95-8090-1806aa7e13b6
Cartigny, Matthieu J.B.
bda1b79b-7e11-4790-8238-b86d80a88bb3

De Leeuw, Jan, Eggenhuisen, Joris T., Spychala, Yvonne T., Heijnen, Maarten S., Pohl, Florian and Cartigny, Matthieu J.B. (2018) Sediment volume and grain-size partitioning between submarine channel-levee systems and lobes: An experimental study. Journal of Sedimentary Research, 88 (7), 777-794. (doi:10.2110/jsr.2018.46).

Record type: Article

Abstract

The width and depth of submarine channels change progressively as the channels evolve. This is inferred to act as an important control on the rate of sediment loss due overbank and in-channel deposition. Understanding the downstream extraction of sediment from turbidity currents is important for the prediction of grain-size trends and volume distribution in the stratigraphy. However, the partitioning of sediment by individual turbidity currents as a function of channel dimensions has not been investigated previously. We present a series of physical experiments studying the link between channel dimensions and the resulting partitioning of sediment volume and grain size between sub-environments. The experimental set-up consists of a slope (118) with a straight pre-formed channel and a horizontal basin floor. An identical flow was released repeatedly into channels with different dimensions, resulting in various styles of overspill, erosion, and deposition under varying degrees of channel confinement. The fraction of sediment that was bypassed through the channel to the basin floor varied between 67% and 89%, depending on the amount of levee and in-channel deposition. The volume of levee deposition correlates well with channel depth. A large channel depth relative to flow thickness limits the amount of overspill. The amount of in-channel deposition correlates well with channel width/depth (W/D) ratio, where low-W/D-ratio channels have less deposition. We compare the experiments to natural system to show that the same patterns of volume and grain-size partitioning are present at different scales. The experiments provide snapshots of different phases of evolution of natural submarine channels. Natural submarine channels in an early evolution phase are inferred to be shallow and the experiments demonstrate that this results in significant sediment loss to levee deposition along the channel. The process of levee deposition preferentially extracts the fine-grained sediment fraction, which overspills from the channel. Therefore, we predict that the initial sediment pulse that reaches the basin floor is coarse grained and volumetrically small. As the channel matures and deepens, it will bypass more sediment with a mix of grain sizes to the basin floor.

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More information

Accepted/In Press date: 26 April 2018
e-pub ahead of print date: 24 July 2018
Published date: July 2018

Identifiers

Local EPrints ID: 425593
URI: http://eprints.soton.ac.uk/id/eprint/425593
ISSN: 1527-1404
PURE UUID: d33343b0-d243-4580-9e26-effc10c8a679

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Date deposited: 25 Oct 2018 16:30
Last modified: 26 Apr 2022 19:54

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Contributors

Author: Jan De Leeuw
Author: Joris T. Eggenhuisen
Author: Yvonne T. Spychala
Author: Maarten S. Heijnen
Author: Florian Pohl
Author: Matthieu J.B. Cartigny

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