Morphodynamics of supercritical high-density turbidity currents

Abstract

Seafloor and outcrop observations combined with numerical and physical experiments show that turbidity currents are likely 1) to be in a supercritical flow state and 2) to carry high sediment concentrations (being of high-density). The thesis starts with an experimental study of bedforms characteristic of supercritical flows. In different experiments the influence of high sediment concentrations and hydraulic jumps on the behaviour of turbidity currents and their deposits is explored. Natural sediment waves on the modern seafloor and fossil examples are compared with bedforms produced by numerically modelled supercritical turbidity currents. Results are synthesized and a conceptual model for supercritical high-density turbidity currents is constructed. This model was tested on turbidity current deposits in the Miocene Tabernas Basin in SE Spain. These deposits show many of the characteristics found in the numerical and physical experiments, such as a variety of near-horizontal to low-angle wavy deposits on a decametre scale, consisting of interstratified structureless beds and more crudely stratified deposits. The proximal to distal variation can now be explained in terms of decreasing sediment concentrations and variations in Froude number