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Quantifying the influence of channel sinuosity on the depositional mechanics of channelized turbidity currents: A laboratory study |
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| Authors: | Kyle M Straub David MohrigJames Buttles Brandon McElroyCarlos Pirmez |
| Institution: | a Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118, USA b Department of Geological Sciences, The University of Texas at Austin, Austin, TX 78712, USA c Shell International Exploration and Production Inc., P.O. Box 481, Houston, TX 77001, USA |
| Abstract: | Here we present results from a suite of laboratory experiments that highlight the influence of channel sinuosity on the depositional mechanics of channelized turbidity currents. We released turbidity currents into three channels in an experimental basin filled with water and monitored current properties and the evolution of topography via sedimentation. The three channels were similar in cross-sectional geometry but varied in sinuosity. Results from these experiments are used to constrain the run-up of channelized turbidity currents on the outer banks of moderate to high curvature channel bends. We find that a current is unlikely to remain contained within a channel when the kinetic energy of a flow exceeds the potential energy associated with an elevation gain equal to the channel relief; setting an effective upper limit for current velocity. Next we show that flow through bends induces a vertical mixing that redistributes suspended sediment back into the interiors of depositional turbidity currents. This mixing counteracts the natural tendency for suspended sediment concentration and grain size to stratify vertically, thereby reducing the rate at which sediment is lost from a current via deposition. Finally, the laboratory experiments suggest that turbidity currents might commonly separate from channel sidewalls along the inner banks of bends. In some cases, sedimentation rates and patterns within the resulting separation zones are sufficient to construct bar forms that are attached to the channel sidewalls and represent an important mechanism of submarine channel filling. These bar forms have inclined strata that might be mistaken for the deposits of point bars and internal levees, even though the formation mechanism and its implications to channel history are different. |
| Keywords: | Turbidity current Sinuous channels Turbidite Submarine channels Run-out |
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