HR: 15:25h
AN: OS33D-08    [Abstracts]
TI: The Effect of Hurricane Lili on the Distribution of Organic Matter in the Inner Louisiana Shelf (Gulf of Mexico, USA)
AU: * Clinton, R
AF: University of South Carolina, Dept. of Geological Sciences, Columbia, SC 29208 United States
AU: Goni, M A
EM: goni@geol.sc.edu
AF: University of South Carolina, Dept. of Geological Sciences, Columbia, SC 29208 United States
AU: Gisewhite, R
AF: University of South Carolina, Dept. of Geological Sciences, Columbia, SC 29208 United States
AU: Monacci, N
AF: University of South Carolina, Dept. of Geological Sciences, Columbia, SC 29208 United States
AU: Gordon, E
AF: University of South Carolina, Dept. of Geological Sciences, Columbia, SC 29208 United States
AU: Allison, M
AF: Tulane University, Dept. of Earth & Environmental Sciences, New Orleans, LA 70118 United States
AU: Kineke, G
AF: Boston College, Dept. of Geology & Geophysics, Chesnut Hill, MA 02467 United States
AB: Suspended particles and surface sediments were collected from the inner shelf of the Louisiana central coast following the passage of Hurricane Lili. The elemental and stable isotopic data of these samples were compared to those determined prior to the hurricane. A week after the storm passage, turbidity levels and total suspended sediment concentrations were not that different from pre-storm values, suggesting most of the suspended sediments must have settled soon after the storm passage. Particulate organic carbon (POC) concentrations ranged from 0.1 mg/L to over 2.0 mg/L, with the highest concentrations measured near the seabed and in the inshore portions of the study area. In these locations, suspended particles displayed high POC/Chlorophyll ratios (POC/Chl of 400 to 4,000) and relatively elevated POC/particulate nitrogen ratios (POC/PN of 10 to 14) that indicated their source was locally resuspended seabed sediments. Relatively low POC/Chl (~200) and POC:PN (~7) ratios consistent with significant contributions from phytoplankton were measured only in the surface waters of the most offshore locations. Post hurricane sediment deposition resulted in a storm layer that ranged from 0.5 to 19 cm in thickness. The storm layer was generally composed of silty clays with a coarser, somewhat sandy 1-2 cm basal layer. These storm deposits were characterized by relatively high SA and OC contents. Similarities in the characteristics of the organic matter before and after reinforce the hypothesis that the source of the storm deposits was the finer fraction of locally resuspended seabed sediments, with little evidence for allochthonous land-derived inputs.
DE: 4850 Organic marine chemistry
DE: 4863 Sedimentation
DE: 4558 Sediment transport
DE: 4564 Tsunamis and storm surges
DE: 1055 Organic geochemistry
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting