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What controls submarine channel development and the morphology of deltas entering deep-water fjords?

What controls submarine channel development and the morphology of deltas entering deep-water fjords?
What controls submarine channel development and the morphology of deltas entering deep-water fjords?

River deltas and associated turbidity current systems produce some of the largest and most rapid sediment accumulations on our planet. These systems bury globally significant volumes of organic carbon and determine the runout distance of potentially hazardous sediment flows and the shape of their deposits. Here we seek to understand the main factors that determine the morphology of turbidity current systems linked to deltas in fjords, and why some locations have well developed submarine channels while others do not. Deltas and associated turbidity current systems are analysed initially in five fjord systems from British Columbia in Canada, and then more widely. This provides the basis for a general classification of delta and turbidity current system types, where rivers enter relatively deep (>200 m) water. Fjord-delta area is found to be strongly bimodal. Avalanching of coarse-grained bedload delivered by steep mountainous rivers produces small Gilbert-type fan deltas, whose steep gradient (11°–25°) approaches the sediment's angle of repose. Bigger fjord-head deltas are associated with much larger and finer-grained rivers. These deltas have much lower gradients (1.5°–10°) that decrease offshore in a near exponential fashion. The lengths of turbidity current channels are highly variable, even in settings fed by rivers with similar discharges. This may be due to resetting of channel systems by delta-top channel avulsions or major offshore landslides, as well as the amount and rate of sediment supplied to the delta front by rivers.

deltas, fjords, geomorphology, processes, submarine channels, turbidity currents
0197-9337
Gales, Jenny A.
7ac1a1cc-0147-42d1-bb93-729c68983e96
Talling, Peter J.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf
Cartigny, Matthieu J.B.
bda1b79b-7e11-4790-8238-b86d80a88bb3
Hughes Clarke, John
3cbe9c9e-d4cc-4f68-b30e-0e4e6ec99ace
Lintern, Gwyn
b5270537-984f-4ec0-a128-025b36ecb411
Stacey, Cooper
36936140-b618-47d1-9d32-76060722ab05
Clare, Michael A.
b26da858-9c08-4784-aaa9-7092efcd94bd
Gales, Jenny A.
7ac1a1cc-0147-42d1-bb93-729c68983e96
Talling, Peter J.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf
Cartigny, Matthieu J.B.
bda1b79b-7e11-4790-8238-b86d80a88bb3
Hughes Clarke, John
3cbe9c9e-d4cc-4f68-b30e-0e4e6ec99ace
Lintern, Gwyn
b5270537-984f-4ec0-a128-025b36ecb411
Stacey, Cooper
36936140-b618-47d1-9d32-76060722ab05
Clare, Michael A.
b26da858-9c08-4784-aaa9-7092efcd94bd

Gales, Jenny A., Talling, Peter J., Cartigny, Matthieu J.B., Hughes Clarke, John, Lintern, Gwyn, Stacey, Cooper and Clare, Michael A. (2018) What controls submarine channel development and the morphology of deltas entering deep-water fjords? Earth Surface Processes and Landforms. (doi:10.1002/esp.4515).

Record type: Article

Abstract

River deltas and associated turbidity current systems produce some of the largest and most rapid sediment accumulations on our planet. These systems bury globally significant volumes of organic carbon and determine the runout distance of potentially hazardous sediment flows and the shape of their deposits. Here we seek to understand the main factors that determine the morphology of turbidity current systems linked to deltas in fjords, and why some locations have well developed submarine channels while others do not. Deltas and associated turbidity current systems are analysed initially in five fjord systems from British Columbia in Canada, and then more widely. This provides the basis for a general classification of delta and turbidity current system types, where rivers enter relatively deep (>200 m) water. Fjord-delta area is found to be strongly bimodal. Avalanching of coarse-grained bedload delivered by steep mountainous rivers produces small Gilbert-type fan deltas, whose steep gradient (11°–25°) approaches the sediment's angle of repose. Bigger fjord-head deltas are associated with much larger and finer-grained rivers. These deltas have much lower gradients (1.5°–10°) that decrease offshore in a near exponential fashion. The lengths of turbidity current channels are highly variable, even in settings fed by rivers with similar discharges. This may be due to resetting of channel systems by delta-top channel avulsions or major offshore landslides, as well as the amount and rate of sediment supplied to the delta front by rivers.

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More information

Accepted/In Press date: 13 September 2018
e-pub ahead of print date: 19 September 2018
Keywords: deltas, fjords, geomorphology, processes, submarine channels, turbidity currents

Identifiers

Local EPrints ID: 426896
URI: http://eprints.soton.ac.uk/id/eprint/426896
ISSN: 0197-9337
PURE UUID: c60a4ad1-2a8d-4bb0-8941-d6c955414c5f

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Date deposited: 14 Dec 2018 17:30
Last modified: 07 Oct 2020 00:36

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Contributors

Author: Jenny A. Gales
Author: Peter J. Talling
Author: Matthieu J.B. Cartigny
Author: John Hughes Clarke
Author: Gwyn Lintern
Author: Cooper Stacey
Author: Michael A. Clare

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