Bedforms Generated by Turbidity Currents in Continental Margins

Abstract

Abstract : Our long-term scientific goal is to develop sound theoretical models for submarine sediment movement that can be used to predict the initiation, spatial development, and time duration of mud flows and turbidity currents. Of particular interest are the characteristics of the sedimentary deposits that these flows generate, in particular their capability to develop bed forms and gullies by means of sediment erosion and deposition in continental margins. This past year we have concentrated on testing the hypothesis that turbidity currents are capable of forming gullies along sloping beds. In particular, our main objective has been to elucidate the role played by flow instabilities at the front of very wide turbidity flows on the formation of submarine channels. A second objective has been to explore, with the help of laboratory experiments, the ability of turbidity currents to generate ripples, dunes and antidunes, along their path. Our approach has consisted of theoretical work, laboratory experiments, and numerical modeling. The theoretical work has concentrated on a perturbation analysis of the equations of motion for turbidity currents carrying a conservative component such as clay, with the goal of assessing the conditions for which bed instabilities will grow and bedforms will develop. Laboratory experiments have been directed to study the formation of bedforms by three-dimensional turbidity currents emanating from a line source at the head of a model slope. Numerical experiments have been conducted as well, to determine the influence of bottom slope and initial sediment concentration on the genesis of gullies at field scale.