Laboratory Experimentation in Self-Channelization by Turbidity Currents

Fernandes, Anjali M.¹; Mohrig, David ¹; Buttles, Jim ¹; Peyret, Aymeric ¹; Steel, Ron ^1
1 Department of Geological Sciences, University of Texas at Austin, Austin, TX.

Self-channelization by turbidity currents is driven by a set of processes that remain incompletely understood. We show here the results of two experiments focused on resolving the mechanisms controlling development of erosionally based channel forms by turbidity currents. These experiments concentrate on properties of bank cohesion for laboratory-scale channels and on cohesive sediment deposition from laboratory-scale turbidity currents; important steps in the generation of self-channelizing turbidity currents.

A lack of cohesion in the substrate causes too much bank erosion and widening of proximal sections of channels, which consequently reduces the ability of turbidity currents to erode the sediment necessary to propagate channel forms down slope. Too much cohesion, on the other hand, results in minimal bed erosion and almost a complete lack of erosional channelization. The second problem is deposition of cohesive channel levees from experimental turbidity currents. Without this, depositional channel margins do not have sufficient strength to resist over-widening of proximal sections of channels.

The first set of experiments focused on running density currents over cohesive substrates. Evolutions of resulting erosional channel forms are captured by a collection of high resolution bathymetric maps. These maps show unsteadiness in the rate of channel elongation and widening associated with development of local irregular topography at the fronts of channels as well as on their sidewalls. The second set of experiments highlight conditions and processes associated with construction of channel levees and deepening of channels through selective depositional processes. Taken together these laboratory experiments provide insight into a wide range of processes controlling the production of submarine channel stratigraphy that will aid reconstructions of submarine channel development via interpretation of preserved deep-water deposits.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009