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Density- and viscosity-stratified gravity currents: Insight from laboratory experiments and implications for submarine flow deposits

Density- and viscosity-stratified gravity currents: Insight from laboratory experiments and implications for submarine flow deposits
Density- and viscosity-stratified gravity currents: Insight from laboratory experiments and implications for submarine flow deposits
Vertical stratification of particle concentration is a common if not ubiquitous feature of submarine particulate gravity flows. To investigate the control of stratification on current behaviour, analogue stratified flows were studied using laboratory experiments. Stratified density currents were generated by releasing two-layer glycerol solutions into a tank of water. Flows were sustained for periods of tens of seconds and their velocity and concentration measured. In a set of experiments the strength of the initial density and viscosity stratification was increased by progressively varying the lower-layer concentration, CL. Two types of current were observed indicating two regimes of behaviour. Currents with a faster-moving high-concentration basal region that outran the upper layer were produced if CL < 75%. Above this critical value of CL, currents were formed with a relatively slow, high-concentration base that lagged behind the flow front. The observed transition in behaviour is interpreted to indicate a change from inertia- to viscosity-dominated flow with increasing concentration. The reduction in lower-layer velocity at high concentrations is explained by enhanced drag at low Reynolds numbers. Results show that vertical stratification produces longitudinal stratification in the currents. Furthermore, different vertical and temporal velocity and concentration profiles characterise the observed flow types. Implications for the deposit character of particle-laden currents are discussed and illustrated using examples from ancient turbidite systems.
Sediment gravity flows, Turbidity currents, Subaqueous debris flows, Flow stratification, Analogue experiments
0037-0738
5-29
Amy, L.A.
ef602b7f-ef4e-4cba-96e7-e34096eb3066
Peakall, J.
2351dbf6-2c4f-4250-bacf-fe1b69870f26
Talling, P.T.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf
Amy, L.A.
ef602b7f-ef4e-4cba-96e7-e34096eb3066
Peakall, J.
2351dbf6-2c4f-4250-bacf-fe1b69870f26
Talling, P.T.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf

Amy, L.A., Peakall, J. and Talling, P.T. (2005) Density- and viscosity-stratified gravity currents: Insight from laboratory experiments and implications for submarine flow deposits. Sedimentary Geology, 179 (1-2), 5-29. (doi:10.1016/j.sedgeo.2005.04.009).

Record type: Article

Abstract

Vertical stratification of particle concentration is a common if not ubiquitous feature of submarine particulate gravity flows. To investigate the control of stratification on current behaviour, analogue stratified flows were studied using laboratory experiments. Stratified density currents were generated by releasing two-layer glycerol solutions into a tank of water. Flows were sustained for periods of tens of seconds and their velocity and concentration measured. In a set of experiments the strength of the initial density and viscosity stratification was increased by progressively varying the lower-layer concentration, CL. Two types of current were observed indicating two regimes of behaviour. Currents with a faster-moving high-concentration basal region that outran the upper layer were produced if CL < 75%. Above this critical value of CL, currents were formed with a relatively slow, high-concentration base that lagged behind the flow front. The observed transition in behaviour is interpreted to indicate a change from inertia- to viscosity-dominated flow with increasing concentration. The reduction in lower-layer velocity at high concentrations is explained by enhanced drag at low Reynolds numbers. Results show that vertical stratification produces longitudinal stratification in the currents. Furthermore, different vertical and temporal velocity and concentration profiles characterise the observed flow types. Implications for the deposit character of particle-laden currents are discussed and illustrated using examples from ancient turbidite systems.

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More information

Published date: 2005
Keywords: Sediment gravity flows, Turbidity currents, Subaqueous debris flows, Flow stratification, Analogue experiments

Identifiers

Local EPrints ID: 54754
URI: http://eprints.soton.ac.uk/id/eprint/54754
ISSN: 0037-0738
PURE UUID: 17a9bbb8-7200-413c-89a3-d813deda9510

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Date deposited: 18 Jul 2008
Last modified: 13 Mar 2019 20:38

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Contributors

Author: L.A. Amy
Author: J. Peakall
Author: P.T. Talling

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