Interactions between turbidity currents, turbidites and topography generated by a mobile substrate
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Models for development and filling of submarine minibasins remain incomplete for the following reasons: (1) they seldom account for growth of seafloor topography via subsurface salt motion that coincides with turbidite sedimentation; (2) they seldom account for interactions between turbidity currents and seafloor topography that influence subsequent sedimentation patterns; and (3) they seldom consider the degree to which the evolution of seafloor topography associated with any single minibasin is affected by its neighboring minibasins. These points have now been addressed through a novel set of laboratory experiments. In the suites of experiments, turbidity currents consisting of 1.5% sediment by volume were released onto a 1.2 m x 1.2 m x 0.05 m platform filled by a composite layer of PDMS polymer and pliable putty (Silly Putty™). Interactions between pre-existing bed topography and turbidity currents result in differential loading of the substrate and influence depositional patterns. These interactions are achieved through a combination of blocking and focusing of currents by topography and by remobilization and removal of deposits from steeply sloping surfaces. Spatially varying deposit thicknesses generate locations that exceed the threshold load and begin to deform the mobile substrate. Turbidites of insufficient thickness are simply “along for the ride” and do not contribute to substrate deformation. Additionally, the tendency of the far-field surface to uplift or subside is preconditioned by the topography of the initial surface. These findings represent contributions towards the goal of better defining the important transition from turbidite sedimentation on an unconfined slope to deposition in minibasins.