HR: 1330h
AN: OS12A-0187    [PDF]
TI: Sediment Deposition and Accumulation in a Seasonal Repository of the Fly River Shelf Clinoform, Papua New Guinea
AU: * Crockett, J S
EM: crockett@ocean.washington.edu
AF: University of Washington School of Oceanography, Box 357940, Seattle, WA 98195 United States
AU: Nittrouer, C A
EM: nittroue@ocean.washington.edu
AF: University of Washington School of Oceanography, Box 357940, Seattle, WA 98195 United States
AU: Ogston, A S
EM: ogston@ocean.washington.edu
AF: University of Washington School of Oceanography, Box 357940, Seattle, WA 98195 United States
AU: Naar, D F
AF: University of South Florida - Saint Petersburg, 140 7th Ave S, Saint Petersburg, FL 33701
AB: Cores collected from the seabed northeast of the Fly River delta exhibit sedimentary structures and radioisotope profiles that indicate both seasonal deposition and longer-term sediment accumulation. Cores were collected in a grid pattern from an area 45 km $\times$ 30 km northeast of the Fly River mouth in water less than 9 m deep. X-ray photography was used to reveal sedimentary structure, and grain size and $^{210}$Pb activities were measured from selected samples to produce down-core profiles of those parameters. Data indicate that during the relatively quiescent monsoon season, a surficial mud bed of $\sim$30 cm persists on the shelf. Sediment within the mud bed exhibits variable $^{210}$Pb activities and higher porosity than sediment below. $^{210}$Pb activities decay logarithmically below the mud bed indicating sediment accumulation rates of $\sim$1.5 cm/y. Profiles of porosity and $^{210}$Pb activity suggest that wave and tidal currents in the shallow area sampled are sufficient to inhibit consolidation of the surficial mud bed. Sedimentary structures are almost entirely physically stratified probably reflecting physical processes that destabilize the seabed and exclude biological colonization. The area northeast of the Fly River mouth is a vital part of the morphologically diverse sediment dispersal system that feeds the development of the Fly River clinoform. Temporary deposition of relatively unconsolidated sediment creates a repository of sediment hypothesized to be transported (primarily as fluid mud) during energetic trade-wind conditions, which are competent to resuspend sediment in high concentrations. Transport of sediment by wave-supported fluid mud results in the observed high accumulation rates on the foreset of the Fly River clinoform. Sediment accumulation on the shallow topset of the clinoform indicates that sections of the clinoform are aggradational rather than exclusively progradational.
DE: 3022 Marine sediments--processes and transport
DE: 4211 Benthic boundary layers
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting