Skip to Main Content
Book Chapter

Factors influencing the deposit geometry of experimental turbidity currents: implications for sand-body architecture in confined basins

By
Omar S. Al Ja’Aidi
Omar S. Al Ja’Aidi
College of Science, Sultan Qaboos University, PO Box 36, Al-Khod, Oman
Search for other works by this author on:
William D. McCaffrey
William D. McCaffrey
School of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK mccaffrey@earth.leeds.ac.uk
Search for other works by this author on:
Benjamin C. Kneller
Benjamin C. Kneller
Institute for Crustal Studies, Girvetz Hall, University of California Santa Barbara, CA 93106, USA
Search for other works by this author on:
Published:
January 01, 2004

Abstract

Two sets of scaled laboratory experiments were performed to examine the effect of flow volume, flow density and grain-size distribution on the transport efficiency of turbidity currents. The experiments employed two sediment analogues (ballotini and silica flour) intended to model medium- to coarse-grained sand and mud respectively. In the first set of experiments each parameter was varied to examine its effect upon deposit geometry. Increases in the initial flow density, volume and proportion of fines had the effect of increasing the amount of sediment that was transferred to the floor of the experimental tank by the turbidity currents. Increase of each of these parameters has a characteristic effect on the three-dimensional geometry of the deposit: the deposits of large-volume flows are elongate, and those of fines-rich flows are broad. Increase of flow density increases the initial potential energy of the flow, thus increasing the runout distance; increase of the initial density beyond a sediment concentration of 13% by mass results, however, in a reverse of the geometrical trend of deposit elongation, possibly because of turbulence suppression at high densities. Increase of flow volume also increases the initial potential energy, and reduces the rate of velocity decrease due to gravitational spreading. Increase in the proportion of fines leads to maintenance of negative buoyancy, as the fine fraction remains suspended until the flow has virtually come to rest; it also decreases the settling velocity of the coarser fraction and thus delays its sedimentation. The second set of experiments was performed to investigate the influence of flow efficiency on the interaction of turbidity currents with topography. A single arcuate obstacle was placed in the path of the flows. In successive experiments flow efficiency was increased by progressively increasing the proportion of fines (silica flour). Both the proportion of sediment reaching the obstructing topography and the proportion of it able to surmount the topography increased as flow efficiency increased. Thus flow efficiency may determine whether or not an enclosed basin hosts deposits whose geometry has been affected by the confinement, and may also determine the relative effectiveness of the topography in confining inbound turbidity currents, and thus trapping their sediment load.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

Geological Society, London, Special Publications

Confined Turbidite Systems

S. A. Lomas
S. A. Lomas
Baker Atlas Geoscience, UK
Search for other works by this author on:
P. Joseph
P. Joseph
Institut Français du Petrole, France
Search for other works by this author on:
Geological Society of London
Volume
222
ISBN electronic:
9781862394704
Publication date:
January 01, 2004

GeoRef

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

View Article Abstract & Purchase Options

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

Subscribe Now