Sedimentary and Erosional Processes in a Deepwater Setting: An Ultra-High Resolution Study of Multiple Regions in the Ultra-Deep Water of the Eastern Gulf of Mexico

Deep-marine processes, except for turbid flow, are a grossly understudied area of deep-ocean science. In these settings, gravity induced, as well as current controlled processes affect transport and redistribution of sediments. As industry searches for hydrocarbons in ever deeper marine facies, knowledge about the constructional, as well as the destructional processes and resultant deposits that are active and occur in ultra-deep water settings is needed. A detailed analysis of multibeam bathymetry, side-scan sonar imagery, and chirp (2-10-Hz) subbottom profiles from the Green Canyon area, eastern Gulf of Mexico, was performed in water depths ranging from 4280-7120 feet. Study reveals a region of high relief along diapiric slopes and failure headwalls and near seafloor stratigraphy of sandy and muddy sediments being eroded and re-sedimented by a variety of gravity- and current-driven processes. To date, results show that dynamic behavior of underlying salt causes oversteepening of the Sigsbee Escarpment, promoting gravitational instabilities and pervasive mass-wasting events, with resulting slides, slumps, and debris flows oriented mostly perpendicular to the escarpment. Mass-wasting events follow sedimentary pathways defined by steep conduits within the escarpment; however, flows can be locally diverted by bathymetric irregularities—seafloor expressions of shallow structures. Elongated longitudinal erosional features at the front of the escarpment are formed by deepwater current processes at the continental margin. From an industry perspective, mass-wasting deposits have traditionally been regarded as poor reservoirs and potentially good seals, whereas current-controlled deposits (e.g., contourites) have a higher reservoir potential. Predictive models of these two process and deposit types will be discussed.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California