Formative conditions and sedimentary structures of sandy 3D antidunes: an application of the gravel step‐pool model to fine‐grained sand in an experimental flume

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.

Bedforms: views and new perspectives from the third international workshop on Marine and River Dune Dynamics (MARID3)

“…Breakspear, 2008). Although Yokakawa et al (2010) find the deposits are dominated by concave-upwards strata, they argue that shallow lens-like structures, which are interbedded with planar, or slightly wavy, laminae, may be more characteristic of this bedstate and could be vital in palaeohydraulic reconstructions. These experiments reveal the development of 3D antidunes after an initial 2D antidune state.…”

“…As an example of such an approach, Yokakawa et al (2010) present an investigation linking process to product for supercritical flows. In comparison with our knowledge of bedforms generated under subcritical flow conditions, understanding of the form and behavior of supercritical flow bedforms and their deposits is relatively poor, but has been a topic that has attracted renewed attention in the past decade (e.g.…”

“…In comparison with our knowledge of bedforms generated under subcritical flow conditions, understanding of the form and behavior of supercritical flow bedforms and their deposits is relatively poor, but has been a topic that has attracted renewed attention in the past decade (e.g. Yokakawa et al (2010) extend this recent resurgence of interest to consider flow, morphology and stratification associated with 3D antidunes developed in sandy sediments. Yokakawa et al (2010) extend this recent resurgence of interest to consider flow, morphology and stratification associated with 3D antidunes developed in sandy sediments.…”

Interpreting flash flood palaeoflow parameters from antidunes and gravel lenses: An example from Montserrat, West Indies

“…Sedimentary structures resulting from formation, migration and truncation of antidunes have been documented in sand‐bed flumes with and without bed aggradation (e.g. Alexander et al ., ; Yokokawa et al ., ), but there are no published studies in natural settings that compare the formative flow conditions and the resulting sedimentary structures. Alexander et al .…”

“…(), Breakspear (), Yokokawa et al . () and Cartigny et al . () provides a scheme of reference for field interpretation of the sedimentary architecture of antidune deposits (Table ; Fig.…”