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Field observations of turbidity currents remain scarce, and thus there is continued debate about their internal structure and how they modify underlying bedforms. Here, I present the results of a new imaging method that examines multiple surge-like turbidity currents within a delta front channel, as they pass over crescent-shaped bedforms. Seven discrete flows over a 2-h period vary in speed from 0.5 to 3.0 ms−1. Only flows that exhibit a distinct acoustically attenuating layer at the base, appear to cause bedform migration. That layer thickens abruptly downstream of the bottom of the lee slope of the bedform, and the upper surface of the layer fluctuates rapidly at that point. The basal layer is inferred to reflect a strong near-bed gradient in density and the thickening is interpreted as a hydraulic jump. These results represent field-scale flow observations in support of a cyclic step origin of crescent-shaped bedforms.
Center for Coastal and Ocean Mapping
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Hughes Clarke, J. E. 2016, First wide-angle view of channelized turbidity currents links migrating cyclic steps to flow characteristics. Nature Communication, 7:11896 doi: 10.1038/ncomms11896.
This is an article published by Springer Nature in Earth and Planetary Science Letters in 2015, available online: https://dx.doi.org/10.1038/ncomms11896