Berms on an Intertidal Shoal: Shape and Internal Structure

  1. S.-D. Nio,
  2. R. T. E. Shüttenhelm and
  3. Tj. C. E. Van Weering
  1. J. R. Boersma1 and
  2. J. H. J. Terwindt2

Published Online: 29 JUN 2009

DOI: 10.1002/9781444303759.ch3

Holocene Marine Sedimentation in the North Sea Basin

Holocene Marine Sedimentation in the North Sea Basin

How to Cite

Boersma, J. R. and Terwindt, J. H. J. (1981) Berms on an Intertidal Shoal: Shape and Internal Structure, 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.ch3

Author Information

  1. 1

    Institute of Earth Sciences, Budapestlaan 4, 3508 TA Utrecht, the Netherlands

  2. 2

    Department of Geography, Heidelberglaan 2, 3508 TC Utrecht, 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:

  • Berms on intertidal shoal;
  • deflection of ebb current;
  • local occurrence of slumped bundles;
  • ebb and flood currents making considerable angle (90-180°);
  • Spring- and neap-tide effects well discernible in berms

Summary

On the intertidal part of the Ossenisse shoal, Westerschelde estuary, the Netherlands, elevated ridges or strips (‘berms’) appear which separate areas with different bedform configuration and hydrographic character. The ebb is the dominant tide on one side of the berm; the flood on the other. Ebb and flood currents make an appreciable angle with each other and supply material to the berm which gives rise to its elevated position. The different morphological appearances of berms, varying between a high and sharp negative step and a narrow dome-like elevation, are associated with specific internal structures, in which cross-bedding and cross-lamination participate in a way slightly different from ordinary sandwaves or dunes. Spring- and neap-tides can be distinguished in the typical berm structures by juxta- or superposition of cross-bedded or cross-laminated bundles sets and cosets. Often the cross-bedding rests on sloping faces.

Berms are expected to have a relatively high preservation potential.