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Aggradational Cyclic Steps: Sedimentary Structures Found in Flume Experiments

Author(s): M. Yokokawa; K. Okuno; A. Nakamura; T. Muto; Y. Miyata; H. Naruse; G. Parker

Linked Author(s): Gary Parker

Keywords: No Keywords

Abstract: Cyclic steps are spatially periodic bedforms where each wavelength is delineated by an upstream and downstream hydraulic jump. They migrate upstream keeping the same wavelength. Recently cyclic steps have been reported from various environments, such as fluvial and deep-sea settings, and in various bed materials, such as bedrock, non-cohesive sediments, and cohesive sediments. As a corollary of this universal existence of cyclic steps, it is expected that they leave a some kind of signature in the rock record. Sedimentary structures due to cyclic steps, however, have not yet been examined experimentally. Here we provide some first examples of the sedimentary structure emplaced by cyclic steps in a flume. Cyclic steps migrate upstream in association with hydraulic jumps, so resulting in significant erosion. Under equilibrium conditions, the erosional base of each step marches upstream at the equilibrium slope, so that no sedimentary structures are left. In this study, we succeeded in the preservation of sedimentary structures emplaced by bed aggradation, during which time cyclic steps migrated upstream in the same was as prevailed at equilibrium conditions.


Year: 2009

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