2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 9
Presentation Time: 10:00 AM

Transport and Depositional Features Associated with Submarine Mudflows, Mississippi Delta, Gulf of Mexico

HITCHCOCK, Christopher1, ANGELL, Michael2, GIVLER, Robert1 and HOOPER, Jim3, (1)William Lettis & Associates, Inc, 1777 Botelho Drive, Suite 262, Walnut Creek, CA 94596, (2)Fugro William Lettis & Associates, Inc, Walnut Creek, CA 94596, (3)Fugro-McClelland Marine Geosciences, Inc, 6100 Hillcroft, Houston, TX 77081, hitch@lettis.com

Mudflows along the submerged Mississippi Delta apron in the Gulf of Mexico are part of a complex, dynamic system of sediment transport and deposition on the seafloor bottom. Mudflow transport within the Delta generally occurs within well-defined submarine channels or gullies, supplying a complex zone of overlapping mudlobes. Sediment transport in active gullies and deposition in deeper water are associated with localized damage to pipeline and offshore facilities. Three-dimensional visualization of seafloor geomorphic features and historic seafloor change derived from interpretation of 130 years of bathymetric data allows for the identification of portions of the seafloor that have been relatively stable over time, and thus likely less susceptible to future failure. In addition, locations of active mudflow transport channels and related zones of active mudlobe deposition are associated with distinctive seafloor features and changes in the historic record that can be observed in the available low- and high-resolution bathymetric data sets. Documented changes in bathymetry and geologic features have been incorporated into a GIS-based hazard mapping approach that allows for the severity ranking of mudflow susceptibility. Results indicate that hazard from mudflows on the submerged Mississippi Delta is related to position within the erosion-transport-deposition system. These relationships allow for a first-order assessment of location-specific susceptibility and severity of hazard to seafloor installations due to mudflow activity.