CONCENTRATION-DEPENDENT FLOW STRATIFICATION IN EXPERIMENTAL HIGH-DENSITY TURBIDITY CURRENTS AND THEIR RELEVANCE TO TURBIDITE FACIES MODELS

Basal divisions of turbidite deposits often show characteristics that are interpreted as expression of high-density layers forming at the bases of turbidity currents; however, this link between deposit characteristics and the flow process occurring in these basal high-density layers is still poorly constrained. Here we present the results of a set of experiments were the flow dynamics of high-density layers within turbidity currents were studied, and linked to their depositional behavior. The experiments showed the formation of three types of flow layers depending on the initial sediment concentration and slope. As the sediment concentration increases, the layers show different rheological properties with characteristics expressions in the velocity and turbulence profiles of the flows. Internal flow instabilities, arising from the different density interfaces within the stratified flows, are shown to be increasingly suppressed as sediment concentrations step up over the different flow layers. Suppression of these internal instabilities in the basal layers is shown to have a distinct effect on variations in the aggradation rate, which at lower sediment concentrations can be directly linked to these instabilities. Suppression of these fluctuations in aggradation rate is here used to link the different type of high-density flow stratification to different turbidite facies.