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Keywords:

  • 3D antidunes;
  • fine sand;
  • sedimentary structures;
  • step-pools;
  • flume experiments

Abstract

Antidunes and their sedimentary structures can be useful in reconstructing paleo-hydraulic conditions, especially for large discharge events. However, three-dimensional (3D) antidunes in sand-sized sediments have not yet been studied extensively, as compared to either two-dimensional (2D) antidunes or antidunes in gravel-sized sediments. In this study, we estimated formative conditions of gravel step-pool morphologies and applied them to the formation of 3D antidunes over a sand bed. Formative conditions are expressed in terms of a relationship between the water discharge per unit width and the bed slope. Flume experiments demonstrated that 3D mound-like antidune configurations and their associated internal sedimentary structures could be preserved. Internal sedimentary structures were characterized by shallow lens-like structures whose bases were erosional. Although gently-dipping concave-upward lamination was dominant, convex-upward lamination was occasionally observed. The dimensions of lenticular lamina-sets can be used to estimate antidune geometry. Thus if 3D antidunes can be interpreted in the stratigraphic record, it is possible to estimate the paleo-hydraulic parameters such as water discharge and bed slope more precisely than previously. Copyright © 2010 John Wiley & Sons, Ltd.