Sediment gravity-driven vs. bottom-current-controlled processes and interactions : a study of multiple geomorphologic domains in the central Gulf of Mexico and comparison with global systems
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This dissertation advances understanding of active sedimentary processes in deep-water environments and their interaction with topography in the transport and distribution of sediments. Deep-water sedimentation research has benefited from the abundance of areally extensive subsurface data sets across a wide range of deep-water systems that has enabled development of depositional models that predict sediment distribution and architecture in these environments. However, questions remain about the interactions between sediment-gravity-driven and bottom-current-controlled processes in deep-marine settings. I utilize a total of 5738 mi (9235 km) of near-seafloor, high-resolution sonar data from different geomorphologic provinces in the deep-water region of the central Gulf of Mexico (GOM) basin in a study of the role of deep-marine processes in the transport and distribution of sediments in the lower-slope to abyssal-plain transition of a mobile-substrate-dominated terrane. Observations indicate that local structural controls (salt) strongly influence the triggering of sediment-gravity-driven processes and (indirectly) affect bottom-current-controlled processes. The complex oceanographic regime in the GOM and the interaction with highly irregular topography of the basin results in an increased bottom-current activity capable of eroding the lowermost slope and that might increase the likelihood of mass-wasting events. The detailed description of different geomorphologic provinces within the deep-water GOM region also allowed the identification of a series of bed forms, both erosional and depositional, that have not been previously documented in such settings. These bed forms include erosional furrows overlying slump deposits at the base of the continental slope, and sediment waves in salt-withdrawal minibasins. The observations and results from this research provide a more comprehensive understanding of the dynamics of deep-water systems, and emphasize the influence of persistent oceanographic processes that affect the seafloor. Results from this study might also highlight implications for slope instability and geological-hazard assessments. The findings might also be applicable to industry in its development of alternative reservoir depositional models, which might be difficult to explain using conventional models.