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Controls on upstream-migrating bed forms in sandy submarine channels

Englert, Rebecca G.; Vellinga, Age J.; Cartigny, Matthieu J.B.; Clare, Michael A.; Eggenhuisen, Joris T.; Hubbard, Stephen M.

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Authors

Rebecca G. Englert

Age J. Vellinga

Michael A. Clare

Joris T. Eggenhuisen

Stephen M. Hubbard



Abstract

Submarine channels parallel river channels in their ability to transport sediment. However in contrast to rivers, sediment transport and bed-form development in submarine channels are less well understood. Many steep (>1°), sandy submarine channels are dominated by upstream-migrating bed forms. The flow conditions required to form these upstream-migrating bed forms remain debated because the interactions between turbidity currents and active bed forms are difficult to measure directly. Consequently, we used a depth-resolved numerical model to test the role of flow parameters that are hypothesized to control the formation of upstream-migrating bed forms in submarine channels. While our modeling results confirmed the importance of previously identified flow parameters (e.g., densiometric Froude number), we found that basal sediment concentration in turbidity currents is the strongest predictor of upstream-migrating bed-form formation. Our model shows how locally steep gradients enable high sediment concentrations (average >5 vol%) in the basal parts of flows, which allow the development of cyclic step instabilities and their associated bed forms. This new insight explains the previously puzzling observation that upstream-migrating bed forms are abundant in proximal, steep, sandy reaches of submarine channels, while their occurrence becomes more intermittent downslope.

Journal Article Type Article
Acceptance Date Sep 15, 2023
Online Publication Date Sep 27, 2023
Deposit Date Oct 25, 2023
Publicly Available Date Oct 25, 2023
Journal Geology
Print ISSN 0091-7613
Electronic ISSN 1943-2682
Publisher Geological Society of America
Peer Reviewed Peer Reviewed
DOI https://doi.org/10.1130/g51385.1
Keywords Geology
Public URL https://durham-repository.worktribe.com/output/1816258

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