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Frequency and timing of landslide-triggered turbidity currents within the Agadir Basin, offshore NW Africa: Are there associations with climate change, sea level change and slope sedimentation rates?

Frequency and timing of landslide-triggered turbidity currents within the Agadir Basin, offshore NW Africa: Are there associations with climate change, sea level change and slope sedimentation rates?
Frequency and timing of landslide-triggered turbidity currents within the Agadir Basin, offshore NW Africa: Are there associations with climate change, sea level change and slope sedimentation rates?
Older sequence stratigraphic models suggested that submarine landslide and turbidite activities are greatest during sea-level lowstands. However, growing evidence indicates that many turbidite systems are also active during sea-level transgressions and highstands. The Moroccan Turbidite System comprises three depocentres, of which Agadir Basin is closest to the Moroccan slope and Canary archipelago. The very large volumes of sediment transported by individual sediment flows in this system suggest that they are triggered by landslides. Extensive core coverage and dating control for the Agadir Basin deposits have provided an excellent opportunity to derive accurate records of turbidite (and associated landslide) frequency for the last 600 ka. Previous studies in the more distal Madeira Abyssal Plain depocentre have indicated that large volume (> 50 km3) turbidites occurred at oxygen isotope stage (OIS) boundaries. This study of Agadir Basin confirms that two major turbidites (beds A5 and A12) occurred during glacial–interglacial transitions associated with OIS4 and OIS6. However, this association is based on just two examples, and two other large-volume turbidites (beds A7 and A11), did not occur at a stage boundary. The main conclusion of this study is that 90% of turbidites and landslides occurred during rising and high sea level, which represents 40% of the total time during the last 600 ka. Only 10% of the turbidites and landslides occurred during glacials (40% of the time), with a paucity of turbidites and landslides at peak glacial lowstands. A comparison to sediment accumulation rates in the source area of the turbidite suggests that landslides did not occur preferentially during periods of more rapid sedimentation rate, although sedimentation rates in this area only varied from 4 to 6 g cm? 2 ka? 1.
Submarine landslides, Turbidites, Quaternary stratigraphy, Geohazards, Marine, Sedimentology, Moroccan Turbidite System
0025-3227
274-291
Hunt, James E.
eb7fbfb5-b1c9-4436-b7f6-18c8d13b7a0b
Wynn, Russell B.
72ccd765-9240-45f8-9951-4552b497475a
Talling, Peter J.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf
Masson, Douglas G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Hunt, James E.
eb7fbfb5-b1c9-4436-b7f6-18c8d13b7a0b
Wynn, Russell B.
72ccd765-9240-45f8-9951-4552b497475a
Talling, Peter J.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf
Masson, Douglas G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45

Hunt, James E., Wynn, Russell B., Talling, Peter J. and Masson, Douglas G. (2013) Frequency and timing of landslide-triggered turbidity currents within the Agadir Basin, offshore NW Africa: Are there associations with climate change, sea level change and slope sedimentation rates? Marine Geology, 346, 274-291. (doi:10.1016/j.margeo.2013.09.004).

Record type: Article

Abstract

Older sequence stratigraphic models suggested that submarine landslide and turbidite activities are greatest during sea-level lowstands. However, growing evidence indicates that many turbidite systems are also active during sea-level transgressions and highstands. The Moroccan Turbidite System comprises three depocentres, of which Agadir Basin is closest to the Moroccan slope and Canary archipelago. The very large volumes of sediment transported by individual sediment flows in this system suggest that they are triggered by landslides. Extensive core coverage and dating control for the Agadir Basin deposits have provided an excellent opportunity to derive accurate records of turbidite (and associated landslide) frequency for the last 600 ka. Previous studies in the more distal Madeira Abyssal Plain depocentre have indicated that large volume (> 50 km3) turbidites occurred at oxygen isotope stage (OIS) boundaries. This study of Agadir Basin confirms that two major turbidites (beds A5 and A12) occurred during glacial–interglacial transitions associated with OIS4 and OIS6. However, this association is based on just two examples, and two other large-volume turbidites (beds A7 and A11), did not occur at a stage boundary. The main conclusion of this study is that 90% of turbidites and landslides occurred during rising and high sea level, which represents 40% of the total time during the last 600 ka. Only 10% of the turbidites and landslides occurred during glacials (40% of the time), with a paucity of turbidites and landslides at peak glacial lowstands. A comparison to sediment accumulation rates in the source area of the turbidite suggests that landslides did not occur preferentially during periods of more rapid sedimentation rate, although sedimentation rates in this area only varied from 4 to 6 g cm? 2 ka? 1.

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More information

Published date: 1 December 2013
Keywords: Submarine landslides, Turbidites, Quaternary stratigraphy, Geohazards, Marine, Sedimentology, Moroccan Turbidite System
Organisations: Marine Geoscience

Identifiers

Local EPrints ID: 360793
URI: http://eprints.soton.ac.uk/id/eprint/360793
ISSN: 0025-3227
PURE UUID: cee993d4-c0fd-4081-837e-fb300261a251

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Date deposited: 23 Dec 2013 10:09
Last modified: 14 Mar 2024 15:42

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Contributors

Author: James E. Hunt
Author: Russell B. Wynn
Author: Peter J. Talling
Author: Douglas G. Masson

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