Aspects of Sediment Movement on Steep Delta Slopes

  1. Albina Colella2 and
  2. David B. Prior3
  1. W. Nemec

Published Online: 2 APR 2009

DOI: 10.1002/9781444303858.ch3

Coarse-Grained Deltas

Coarse-Grained Deltas

How to Cite

Nemec, W. (1990) Aspects of Sediment Movement on Steep Delta Slopes, in Coarse-Grained Deltas (eds A. Colella and D. B. Prior), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303858.ch3

Editor Information

  1. 2

    Universita della Calabria, Italy

  2. 3

    Atlantic Geoscience Center, Nova Scotia, Canada

Author Information

  1. Geological Institute (A), University of Bergen, 5007 Bergen, Norway

Publication History

  1. Published Online: 2 APR 2009
  2. Published Print: 19 OCT 1990

ISBN Information

Print ISBN: 9780632028948

Online ISBN: 9781444303858

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Keywords:

  • aspects of sediment movement;
  • turbidity current;
  • Gilbert-type deltas;
  • slope regime;
  • avalanching;
  • sediment dynamics;
  • rheological behaviour

Summary

Depositional characteristics of coarse-grained, sandy and gravelly steep-face deltas are summarized, and the gravity-driven sedimentation processes operative on the subaqueous slopes of such deltas are reviewed. The review further focuses on the mechanics of these processes, by integrating knowledge from modern and ancient delta slopes and relevant laboratory studies. Mechanical aspects of cohesion-less sediment mobility and downslope momentum flux are discussed, and distinction is made between frictional debris flows and debris falls. Mechanisms for the transfer of coarsest debris to the delta toe zone are suggested, and various depositional aspects of debris falls and debris flows are explored. The origins and behaviour of turbidity currents on delta slopes are discussed, and possible consequences of density current's ‘slumping’ stage are indicated (origin of chutes). Supercritical regime and hydraulic jumps in sediment gravity flows are then considered, with emphasis on their depositional effects; possible origins of ‘backsets’ are suggested. Depositional characteristics of sediment slides are reviewed, with emphasis on the internal shear-strain pattern in slides or flow slides and the origin of another kind of ‘backsets’. It is indicated how several important rheological inferences can be made on the basis of the shear-strain signature in a slide or flow-slide deposit. Some other general sedimentological aspects of delta-foreset deposits are discussed; the need for further detailed research and an integrated analytical approach is emphasized, and specific suggestions are given for the future research.