Subaqueous Liquefied and Fluidized Sediment Flows and their Deposits
- Dorrik A. V. Stow
Published Online: 29 APR 2009
Copyright © 1992 The International Association of Sedimentologists
Deep-Water Turbidite Systems
How to Cite
Lowe, D. R. (1991) Subaqueous Liquefied and Fluidized Sediment Flows and their Deposits, in Deep-Water Turbidite Systems (ed D. A. V. Stow), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304473.ch4
Department of Geology, University of Southampton, UK
- Published Online: 29 APR 2009
- Published Print: 11 NOV 1991
Print ISBN: 9780632032624
Online ISBN: 9781444304473
- liquefied and fluidized systems;
- ‘proximal turbidites’ or ‘fluxoturbidites’;
- sediment gravity flow;
- fluidized sediment flows;
- spontaneous liquefaction;
- one-dimensional two-phase systems;
- non-Newtonian dilatant behaviour of loose sand
A clear distinction must be made between liquefied and fluidized systems. In liquefied beds and flows, the solids settle downward through the fluid, displacing it upward, whereas, in fluidized beds, the fluid moves upward through the solids, which are temporarily suspended without net downward movement. Many recent references to fluidized sediment gravity flows refer, in fact, to flows of liquefied debris.
Most uniformly liquefied beds of well-sorted sand- or gravel-sized sediment will resediment as simple two-layer systems. Liquefied flows can originate either by liquefaction followed by failure, as in many retrogressive flow slides, or by failure followed by liquefaction, as in the case of some slumps. Empirical and theoretical estimates of flow velocity, thickness, and travel distance suggest that natural laminar liquefied flows of fine-grained sand will generally resediment after moving a kilometre or less. Laminar flows of coarse-grained sand will resediment after moving only a few metres. Grain dispersive pressure is thought to be of little significance in the development or maintenance of liquefied flows.
Many surficial submarine sand beds are apparently susceptible to liquefaction, including submarine canyon and continental rise deposits. Within submarine canyons and narrow fjords, steep slopes and channels promote the evolution of liquefied flows from slumps by liquefaction after failure and of high density turbidity currents from liquefied flows by the development of turbulence. Upon moving into the lower parts of submarine canyons or into proximal fan channels, liquefied flows will resediment and high density turbidity currents will tend to decline to flows transitional between liquefied flows and turbidity currents. The liquefied, coarser detritus within such transitional flows will be deposited while finer-grained debris will remain in suspension and continue downslope as dilute turbidity currents. Resedimentation of the liquefied portions of such flows may be responsible for the deposition of the A-subdivision of many turbidites and many thick, structureless ‘proximal turbidites’ or ‘fluxoturbidites’. Similar units can originate by liquefaction of the traction deposits of normal turbidity currents.
Fluidized flows are probably uncommon, thin, and, where formed, originate through fluidization of the fine-grained tops of liquefied graded beds.