Morphodynamics of submarine channel inception revealed by new experimental approach.

Jan de Leeuw,Joris T. Eggenhuisen,Matthieu J. B. Cartigny

doi:10.1038/ncomms10886

Jan de Leeuw, Joris T. Eggenhuisen + Show 1 more

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https://doi.org/10.1038/ncomms10886

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Abstract

Submarine channels are ubiquitous on the seafloor and their inception and evolution is a result of dynamic interaction between turbidity currents and the evolving seafloor. However, the morphodynamic links between channel inception and flow dynamics have not yet been monitored in experiments and only in one instance on the modern seafloor. Previous experimental flows did not show channel inception, because flow conditions were not appropriately scaled to sustain suspended sediment transport. Here we introduce and apply new scaling constraints for similarity between natural and experimental turbidity currents. The scaled currents initiate a leveed channel from an initially featureless slope. Channelization commences with deposition of levees in some slope segments and erosion of a conduit in other segments. Channel relief and flow confinement increase progressively during subsequent flows. This morphodynamic evolution determines the architecture of submarine channel deposits in the stratigraphic record and efficiency of sediment bypass to the basin floor.

Highlights

Submarine channels are ubiquitous on the seafloor and their inception and evolution is a result of dynamic interaction between turbidity currents and the evolving seafloor
Classical turbidity current experiments[23,24,27,28,29,30,31,32,33,34,35] have focused on two non-dimensional scaling characterizations of the fluid flow: the Froude number (Fr), which is the ratio between momentum and gravitational forces of the flow, and the Reynolds number (Re), characterizing the ratio between the momentum and the viscous forces that determine the turbulent state of the flow
As it is not possible to keep both Fr and Re equal to the natural analogues while scaling down flow size, it is common to keep the Fr similar to natural values and to only require a Re above the laminar-turbulent threshold[36,37]. This Froude scaling approach has proven to be valuable in understanding the flow dynamics of turbidity currents but it does not guarantee that flows are able to transport sediment in suspension

Summary

Introduction

Submarine channels are ubiquitous on the seafloor and their inception and evolution is a result of dynamic interaction between turbidity currents and the evolving seafloor. A limited number of experiments successfully produced subaqueous channels using a saline flow over a mobile substrate[20,21,22] These flows could not produce depositional morphologies, as there was no suspended sediment load, which is vital for levee formation[22]. These experiments provide limited insight into contributions of deposition and erosion during channel inception. Rowland et al.[23] reviewed the full range of published numerical and physical experiments that have tried to achieve self-channelization[24,25,26] by sediment-laden flows and concluded that channelization was not achieved in any of the cases

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