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Morphodynamics and depositional signature of low-aggradation cyclic steps: New insights from a depth-resolved numerical model

Vellinga, Age J.; Cartigny, Matthieu J.B.; Eggenhuisen, Joris T.; Hansen, Ernst W.M.

Morphodynamics and depositional signature of low-aggradation cyclic steps: New insights from a depth-resolved numerical model Thumbnail


Authors

Age J. Vellinga

Joris T. Eggenhuisen

Ernst W.M. Hansen



Abstract

Bedforms related to Froude-supercritical flow, such as cyclic steps, are increasingly frequently observed in contemporary fluvial and marine sedimentary systems. However, the number of observations of sedimentary structures formed by supercritical-flow bedforms remains limited. The low number of observations might be caused by poor constraints on criteria to recognize these associated deposits. This study provides a detailed quantification on the mechanics of a fluvial cyclic step system, and their depositional signature. A computational fluid-dynamics model is employed to acquire a depth-resolved image of a cyclic step system. New insights into the mechanics of cyclic steps shows that: (i) the hydraulic jump is, in itself, erosional; (ii) there are periods over which the flow is supercritical throughout and there is no hydraulic jump, which plays a significant role in the morphodynamic behaviour of cyclic steps; and (iii) that the depositional signature of cyclic steps varies with rate of aggradation. Previous work has shown that strongly aggradational cyclic steps, where most of the deposited sediment is not reworked, create packages of backsets, bound upstream and downstream by erosive surfaces. Here, the modelling work is focussed on less aggradational conditions and more transportational systems. The depositional signature in such systems is dominated by an amalgamation of concave-up erosional surfaces and low-angle foresets and backsets creating lenticular bodies. The difference between highly aggradational cyclic steps and low-aggradation steps can be visible in outcrop both by the amount of erosional surfaces, as well as the ratio of foreset to backset, with backsets being indicative of more aggradation.

Citation

Vellinga, A. J., Cartigny, M. J., Eggenhuisen, J. T., & Hansen, E. W. (2018). Morphodynamics and depositional signature of low-aggradation cyclic steps: New insights from a depth-resolved numerical model. Sedimentology, 65(2), 540-560. https://doi.org/10.1111/sed.12391

Journal Article Type Article
Acceptance Date May 19, 2017
Online Publication Date Aug 10, 2017
Publication Date Feb 1, 2018
Deposit Date Sep 18, 2017
Publicly Available Date Mar 28, 2024
Journal Sedimentology
Electronic ISSN 1365-3091
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 65
Issue 2
Pages 540-560
DOI https://doi.org/10.1111/sed.12391

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
Advance online version © 2017 The Authors. Sedimentology published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologists This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.






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