The effects of confining minibasin topography on turbidity current dynamics and deposit architecture
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This dissertation advances our understanding of how turbidity currents interact with three-dimensional (3-D) minibasin topography and the resulting deposits that form. Conceptual Gulf of Mexico-centric models of minibasin fill development have become the foundation for exploring and identifying strategic deep-water hydrocarbon reserves on continental slopes around the world. Despite the abundance of subsurface data, significant questions remain about the 3-D physical processes through which minibasins fill and the relationship between these processes and the topography of the basin. To overcome this problem, I utilize techniques in physical laboratory modeling to query established models of the role that turbidity currents play in minibasin fill development, and observe the relationships between fill from the Lobster minibasin located in a proximal continental slope position in the Gulf of Mexico and from the Safi Haute Mer (SHM) minibasin located in the distal continental slope of offshore western Morocco. First, existing published literature are reviewed and assessed for the known state of minibasin development and fill processes, and the strengths and weaknesses of our current knowledge base. Second, results are presented from two series of experiments that document the interaction between steady, depletive turbidity currents and 3-D minibasin topography. Experimental results suggest that turbidity currents produce deposits that are more likely to drape pre-flow topography than pond within it. Turbidity current velocity data show a strong 3-D physical component in minibasin fill sedimentation that also influences extra-basinal sedimentation patterns. Details of these results provide insight into processes that have not been previously considered in published conceptual models of minibasin fill. Third, a comparison of the two subsurface datasets show that the types and abundance of architectural elements vary depending on the location of the minibasin on the continental slope (i.e. proximal vs. distal), and suggests key differences in the processes responsible for their infilling. Finally, a comparison of experimental results to preserved deposit architectures in the Lobster and SHM datasets suggest a more complex relationship of process-driven sedimentation than that derived primarily from suspension fallout. This improved understanding of minibasin fill is applicable to industry for increasing confidence in subsurface interpretations and reducing risk while exploring for quality reservoirs in deepwater regions.