Regimes of bedforms created by down-slope density currents

Bedforms in rivers have been extensively studied for decades. Turbidite outcrops also display bedforms emplaced subaqueously by turbidity currents. Recent breakthroughs in the attainable resolution of deep underwater bathymetric/seismic mapping have revealed that bedforms in submarine environments may be as widespread and diverse as those associated with fluvial flows. Turbidity currents that emplace subaqueous bedforms run down submarine canyons, traverse and overflow leveed channels on submarine fans, or manifest themselves as sheet turbidity currents along continental margins. Submarine bedforms present features that appear to be analogous to their fluvial counterparts. Submarine bedforms have traditionally been interpreted with the use of tools, and in particular phase diagrams, that were developed solely for fluvial bedforms. The use of such tools is motivated by the fact that simultaneous observation of the bedforms as they evolve in the field and the turbidity currents that create them remains at the edge of present capabilities. We fill this gap in part with a technique that has been successfully implemented for fluvial bedforms, i.e. experimentation. We present observations of bedforms emplaced by saline and turbidity currents in laboratory flumes. The experimental flows span a wide range of densimetric Froude numbers, including both subcritical and supercritical regimes, and produced various bedform types including subcritical and supercritical-regime ripples/dunes, upstream-migrating and downstream-migrating antidunes, and cyclic steps. We have gathered a comprehensive set of fluvial and submarine field bedforms worldwide from multiple environments including submarine canyons, levees, slopes, and fans; some of which include associated flow observations. The data are summarized in a set of bedform dimensions and regime diagrams, which are applicable to saline and/or turbidity currents, and generally to any down-slope moving bottom flow. The regimes for submarine bedforms show both similarities and differences with fluvial regimes. Our diagrams and guidelines constitute a new tool for the interpretation of field-scale bedforms generated by turbidity currents.