The University of Southampton
University of Southampton Institutional Repository

Sedimentary processes in the Selvage sediment-wave field, NE Atlantic: new insights into the formation of sediment waves by turbidity currents

Sedimentary processes in the Selvage sediment-wave field, NE Atlantic: new insights into the formation of sediment waves by turbidity currents
Sedimentary processes in the Selvage sediment-wave field, NE Atlantic: new insights into the formation of sediment waves by turbidity currents
An integrated geophysical and sedimentological investigation of the Selvage sediment-wave field has revealed that the sediment waves are formed beneath unconfined turbidity currents. The sediment waves occur on the lower continental rise and display wavelengths of up to 1 km and wave heights of up to 6 m. Wave sediments consist of interbedded turbidites and pelagic/hemipelagic marls and oozes. Nannofossil-based dating of the sediments indicates a bulk sedimentation rate of 2·4 cm 1000 years-1, and the waves are migrating upslope at a rate of 0·28 m 1000 years-1. Sediment provenance studies reveal that the turbidity currents maintaining the waves are largely sourced from volcanic islands to the south. Investigation of existing models for sediment-wave formation leads to the conclusion that the Selvage sediment waves form as giant antidunes. Simple numerical modelling reveals that turbidity currents crossing the wave field have internal Froude numbers of 0·5-1·9, which is very close to the antidune existence limits. Depositional flow velocities range from <6 to 125 cm-1. There is a rapid increase in wavelength and flow thickness in the upper 10 km of the wave field, which is unexpected, as the slope angle remains relatively constant. This anomaly is possibly linked to a topographic obstacle just upslope of the sediment waves. Flows passing over the obstacle may undergo a hydraulic jump at its boundary, leading to an increase in flow thickness. In the lower 15 km of the wave field, flow thickness decreases downslope by 60%, which is comparable with results obtained for other unconfined turbidity currents undergoing flow expansion
SEDIMENTARY TRANSPORT, TURBIDITY CURRENTS, GEOLOGY
0037-0746
1181-1197
Wynn, R.B.
72ccd765-9240-45f8-9951-4552b497475a
Weaver, P.P.E.
1ab10035-6132-46aa-8a5c-6fb23a1b8ab4
Ercilla, G.
fb4377fa-5b09-4b81-93bb-c393f902f814
Stow, D.A.V.
434350cd-0ae5-4bb3-b71f-e1da90587f74
Masson, D.G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Wynn, R.B.
72ccd765-9240-45f8-9951-4552b497475a
Weaver, P.P.E.
1ab10035-6132-46aa-8a5c-6fb23a1b8ab4
Ercilla, G.
fb4377fa-5b09-4b81-93bb-c393f902f814
Stow, D.A.V.
434350cd-0ae5-4bb3-b71f-e1da90587f74
Masson, D.G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45

Wynn, R.B., Weaver, P.P.E., Ercilla, G., Stow, D.A.V. and Masson, D.G. (2000) Sedimentary processes in the Selvage sediment-wave field, NE Atlantic: new insights into the formation of sediment waves by turbidity currents. Sedimentology, 47 (6), 1181-1197.

Record type: Article

Abstract

An integrated geophysical and sedimentological investigation of the Selvage sediment-wave field has revealed that the sediment waves are formed beneath unconfined turbidity currents. The sediment waves occur on the lower continental rise and display wavelengths of up to 1 km and wave heights of up to 6 m. Wave sediments consist of interbedded turbidites and pelagic/hemipelagic marls and oozes. Nannofossil-based dating of the sediments indicates a bulk sedimentation rate of 2·4 cm 1000 years-1, and the waves are migrating upslope at a rate of 0·28 m 1000 years-1. Sediment provenance studies reveal that the turbidity currents maintaining the waves are largely sourced from volcanic islands to the south. Investigation of existing models for sediment-wave formation leads to the conclusion that the Selvage sediment waves form as giant antidunes. Simple numerical modelling reveals that turbidity currents crossing the wave field have internal Froude numbers of 0·5-1·9, which is very close to the antidune existence limits. Depositional flow velocities range from <6 to 125 cm-1. There is a rapid increase in wavelength and flow thickness in the upper 10 km of the wave field, which is unexpected, as the slope angle remains relatively constant. This anomaly is possibly linked to a topographic obstacle just upslope of the sediment waves. Flows passing over the obstacle may undergo a hydraulic jump at its boundary, leading to an increase in flow thickness. In the lower 15 km of the wave field, flow thickness decreases downslope by 60%, which is comparable with results obtained for other unconfined turbidity currents undergoing flow expansion

Full text not available from this repository.

More information

Published date: 2000
Keywords: SEDIMENTARY TRANSPORT, TURBIDITY CURRENTS, GEOLOGY

Identifiers

Local EPrints ID: 7993
URI: https://eprints.soton.ac.uk/id/eprint/7993
ISSN: 0037-0746
PURE UUID: d4c8f58f-6c8c-480e-b643-0fd4a7e27e21

Catalogue record

Date deposited: 24 Aug 2004
Last modified: 17 Jul 2017 17:13

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×