HR: 0800h
AN: OS51B-1300    [Abstracts]
TI: Sedimentological Records of Organic Matter Accumulation in the Inshore Region of the Fly River Clinoform (Papua New Guinea)
AU: * Gisewhite, 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: Clinton, 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: McKay, M
AF: University of South Carolina, Dept. of Geological Sciences, Columbia, SC 29208 United States
AU: Crockett, J
AF: University of Washington, School of Oceanography, Seattle, WA 98195 United States
AU: Nittrouer, C
AF: University of Washington, School of Oceanography, Seattle, WA 98195 United States
AB: Thirteen kasten cores collected from the northeast and southwest regions of the clinoform topset off the Fly River Delta and from the Umuda Channel were selected for elemental (organic carbon, nitrogen), mineral surface area (SA), stable isotope (d13C and d15N) and biomarker (lignin phenols) analyses. The depth of the cores ranged from 30 to over 250 cm and represent variable periods of depositional history. The average organic carbon content (OC) of sediments ranged from 0.6 to 2 wt. percent, depending on the site location. The highest OC levels were observed in the northeast region off the Fly River Delta, while the lowest levels were found in cores located in the southern offshore region. Average molar organic carbon:nitrogen ratios ranged from 10 to 18, with the lowest C/N ratios found in the sites located to the south of the delta. Average d13C and nitrogen d15N signatures ranged from -26 to -25 per mil and from 1.4 to 2.5 per mil, respectively. Average OC/SA ratios for the sediments in these cores ranged from 0.4 to 1.7 mg C/m2, with the lowest values measured in samples from the Umuda Channel and the most distal site in the northeast region of the topset. Overall, these compositions indicate organic matter accumulation in all these sites is dominated by the burial of terrigenous derived soil organic matter. Down core peaks in C/N and OC/SA ratios indicate the presence of discrete layers enriched in vascular plant detritus. Low OC/SA ratios indicative of extensive decay were only measured in selected sites and in specific horizons. In contrast, most samples were characterized by "normal" organic carbon loadings that are consistent with the active burial and effective preservation of terrigenous organic matter in this region of the Fly River Delta and clinoform. There is little evidence for the preservation of marine-derived organic matter in these deposits. These data will be further interpreted in the context of additional sedimentological data (X-rays, grain size, radioisotope activities).
DE: 4805 Biogeochemical cycles (1615)
DE: 4850 Organic marine chemistry
DE: 4863 Sedimentation
DE: 4558 Sediment transport
DE: 4564 Tsunamis and storm surges
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting