Characteristics of Foreset and Topset Bedding in Megaripples Related to Hydrodynamic Conditions on an Intertidal Shoal

  1. S.-D. Nio,
  2. R. T. E. Shüttenhelm and
  3. Tj. C. E. Van Weering
  1. L. H. M. Kohsiek and
  2. J. H. J. Terwindt

Published Online: 29 JUN 2009

DOI: 10.1002/9781444303759.ch2

Holocene Marine Sedimentation in the North Sea Basin

Holocene Marine Sedimentation in the North Sea Basin

How to Cite

Kohsiek, L. H. M. and Terwindt, J. H. J. (1981) Characteristics of Foreset and Topset Bedding in Megaripples Related to Hydrodynamic Conditions on an Intertidal Shoal, in Holocene Marine Sedimentation in the North Sea Basin (eds S.-D. Nio, R. T. E. Shüttenhelm and Tj. C. E. Van Weering), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303759.ch2

Author Information

  1. Department of Physical Geography, Heidelberglaan 2, 3508 TC, Utrecht, the Netherlands

  1. Rijkswaterstaat–Deltastienst, van Alkemadelaan 400 The Hague, the Netherlands

Publication History

  1. Published Online: 29 JUN 2009
  2. Published Print: 23 DEC 1981

ISBN Information

Print ISBN: 9780632008582

Online ISBN: 9781444303759

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Keywords:

  • foreset laminae in cross-bedded sets;
  • magnitude of maximum current velocity;
  • cross-bedding in tidal bundles - showing systematic change in foreset angle;
  • foreset and topset bedding;
  • measurements in field - mega ripple dimensions and form, water depth and mean current velocity in vertical profile

Summary

The succession in the shape of the foreset laminae in cross-bedded sets with increasing current velocity so well documented from flume experiments is also observed in tidal deposits. During the full vortex stage of megaripple migration this succession consists ideally of angular, followed by tangential and concave cross-bedding. In the deceleration stage of the megaripple the concave cross-bedding is followed by sigmoidal cross-bedding produced mainly by suspension fall-out under conditions of decreasing flow velocities. Depending on the magnitude of the maximum velocity of the current in a tidal cycle this succession may be more or less complete.

Topsets may be generated during deceleration and full vortex action under conditions of high maximum flow velocities.

Thresholds could be established of the current velocity for the generation of the different types of foresets and topsets.