Experimental Turbidity Current Transport and Deposition Using Scaled Realistic Bathymetry

Jaco H. Baas¹, William. D. McCaffrey¹, Marco Patacci², and Joanne Wyton^2
1 University of Leeds, Leeds, United Kingdom
² School of Earth & Environment, University of Leeds, Leeds, United Kingdom

There is growing awareness that sediment dispersal patterns in deep-marine sedimentary basins are affected by bottom topography. Turbidity currents can be deflected, reflected and flow over topography, depending on, for example, flow properties, topographic form and angle of approach of the flow. Different parts of a turbidity current may behave in different ways when experiencing topography, leading to complex, yet predictable, depositional and textural patterns. Most laboratory-scale research has been confined to single topographic elements, such as dome-shaped topographic highs and lateral slopes. Yet, sediment gravity flows moving through natural basins will experience many topographic features, each imposing a unique imprint on bed-scale architecture and on flow properties downstream of the feature. Based on present knowledge, it is difficult to make predictions of sediment dispersal patterns in such highly complex natural conditions. It is therefore worthwhile to simulate real-world scenarios by conducting physical experiments of turbidity current flow over scaled bathymetry. Two case studies were investigated, based on bathymetric reconstructions of existing fields in the Gulf of Mexico and the North Sea basin. The first series of experiments involved turbidity currents moving across topography consisting of a channel linked to a minibasin, flanked by topographic highs and comprising a corridor to a downdip minibasin. In the second series, a relay ramp configuration in an extentional tectonic regime was used. The ramps were oriented transverse to main flow direction. Sediment distribution patterns will be discussed in relation to changes in initial velocity of turbidity currents, their grain size and their duration.