Evidence for Lateral and Longitudinal Compensational Stacking in Sub-Basins Based on Numerical Models of Turbidity Currents on Complex Margin Topographies
Luthi, Stefan M.; Wang, Xiaoxi
Geotechnology, Delft University of Technology, Delft, Netherlands.
Complex seafloor topography, such as sub-basins formed on converging margins plays a significant role in controlling turbidity current behavior and sediment dispersal pattern. One method to investigate the interaction of sediment gravity currents and topography is process-based numerical simulation. Potential topographical templates can be generated from laboratory analogue experiments or directly obtained from 3D bathymetric data.
In this study we adopt the above two sets of topographical seafloor data, experimental topographies and high-resolution surfaces from areas of the present-day seabed, where there is evidence of sub-basin formation. These inputs not only provide both experimental and 'real-world' templates to investigate the extent these topographies affect flow character, routing and the resulting deposit geometry, but also offer a perspective on the validation of the experimental method by comparison among a variety of results.
To simulate natural subaqueous density flows, a range of parameter combinations (flow volume, height, input velocity, frequency) has been chosen within the appropriate ranges expected to occur in nature. The flows show complex behaviour that includes extensive entrainment of ambient fluid, flow splitting and run-up on topographic bends. A significant result we found is that the resulting deposits in sub-basins not only show lateral compensational stacking, but also in the direction of the flow. This longitudinal compensational stacking occurs as deposition on the counterslopes shifts the topographic lows upstream, which in turn moves the depocenters upstream. Continued infill there moves subsequently the depocenters again downstream. These cycles are repeated until the topographic depression is no longer an active sediment trap and bypass occurs. The implications on reservoir architecture and development are discussed.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012