The Mississippi River is experiencing a historic flood of major geological significance. The flooding provides an excellent chance to document sedimentation associated with the event and contrast it with storm deposition data from hurricanes Ivan, Katrina, and Rita. It is possible that the massive sediment load carried through Southwest Pass will lead to gravity flows on the delta front that could be documented with repeat coring. This research will determine the stratigraphic signature of the flood on the Mississippi subaqueous delta and will compare the sedimentological, radiochemical, and geochemical signature of the recent flood deposits on the shelf with previously studied hurricane deposits as well as examine strata of the delta front for evidence of flood-induced sediment-gravity flows. The proposed research provides a rare opportunity to study the critical processes of sediment and solute supply to the coastal ocean for a major river system. Broader impacts of the work include the training of up to six students in seagoing science and understanding the importance of major flooding events and sediment transport in the replenishment and erosion of the Mississippi Gulf Coast coastline.
The Mississippi River experienced a flood of historic proportions in 2011. This was a geologically significant flood, and we determined its grain size, erodibility, stratigraphic and geochemical signature in the northern Gulf of Mexico. This opportunity provided an excellent chance to document sedimentation associated with this event and contrast it with previous storm depositions. In addition, the study fills a gap in previous studies in the Mississippi dispersal system, by providing a link between these short-term disturbances and investigation of decadal and millennial strata development. By studying the mechanisms of transport and short-term deposition on the shelf associated with river floods and oceanographic forcings, we hope to further advance our understanding of the sediment dispersal of deltaic system. Results show that most sediment samples’ mean grain sizes are between 6 and 7 phi except samples next two sandy shoals south of Atchafalaya Bay. Most samples are fine-skewed and the standard deviations are around 1.5-2.5 phi, with various bimodal distributions. Highly erodible sediments are located close to the Mississippi Delta and the shallow waters southwest of the Atchafalaya Bay, indicating newly-deposited flood materials are more mobile than old seabed sediment on the shelf. Clearly the proximity to the source play a role in controlling the sediment mobility. The sediment sample collected inside the Mississippi Canyon has the lowest erodibility. We have also developed connections with scientists from TAMU, VIMS, NRL, and LUMCON in the process of this experiment, and will continue to foster these ties for stronger scientific cooperation. Our study is closely linked to other studies, such as hypoxia, geochemical cycling, benthic ecosystems, and resource management .
