Abstract
Multiple knickpoints have been observed in recent years on the lakefloor of Wabush Lake, Labrador, Canada. Two or more sequential high-resolution geophysical surveys have revealed that these knickpoints tend to migrate updip, i.e. upstream relative to the turbidity currents that overflow them. In order to understand the different processes accountable for the migration of these knickpoints, laboratory studies have been performed to reproduce the sedimentological setting and hydrodynamics of Wabush Lake. Knickpoints are topographic depressions, characterized by a steep slope and a flatter profile downslope and upslope. In the present case they are initiated by morphodynamic interaction between an erodible bed and an overriding turbidity current. A set of 22 experiments have been performed in a facility able to run continuous turbidity currents. Knickpoints created in laboratory are up to 1 cm deep and migrate upstream at variable speed. Experimentation results show that migration of the knickpoints is controlled by two factors: erosion by the turbidity current and a landsliding process in the knickpoint head scarp. Knickpoint migration has also been observed when no turbidity current was present. These results show that this phenomenon is governed by not only hydraulics, as previously described in the literature, but must also be studied from a geotechnical point of view.
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Acknowledgments
The authors are grateful to A. Waratuke, E. Eke and E. Viparelli for their help with the experiments. We thank the Fonds de recherche sur la nature et la technologie du Québec (FQRNT) for a student grant to Dominique Turmel. We also thank Rio Tinto and the National Science and Engineering Research Council of Canada for their financial support. The authors would also like to acknowledge both reviewers, Hajime Naruse and Norihiro Izumi, for their constructive remarks.
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Turmel, D., Locat, J., Parker, G. (2012). Upstream Migration of Knickpoints: Geotechnical Considerations. In: Yamada, Y., et al. Submarine Mass Movements and Their Consequences. Advances in Natural and Technological Hazards Research, vol 31. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-2162-3_11
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DOI: https://doi.org/10.1007/978-94-007-2162-3_11
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