HR: 09:00h
AN: OS11A-05    [PDF]
TI: Sediment Transport Under Monsoon Conditions on the Fly River Clinoform, Papua New Guinea
AU: * Ogston, A S
EM: ogston@ocean.washington.edu
AF: University of Washington, School of Oceanography Box 357940, Seattle, WA 21015 United States
AU: Crockett, J S
EM: crockett@ocean.washington.edu
AF: University of Washington, School of Oceanography Box 357940, Seattle, WA 21015 United States
AU: Sternberg, R W
EM: rws@ocean.washington.edu
AF: University of Washington, School of Oceanography Box 357940, Seattle, WA 21015 United States
AU: Nittrouer, C A
EM: nittroue@ocean.washington.edu
AF: University of Washington, School of Oceanography Box 357940, Seattle, WA 21015 United States
AB: As part of the NSF Margins Source to Sink program, sediment-transport studies on the Fly River clinoform were performed during the monsoon season to establish the transport mechanics during this quiescent season and to explore the occurrence of high density near-bed suspensions thought to contribute to clinoform formation. Profiles of suspended-sediment concentration and water-column properties were collected in conjunction with seabed coring and geochemical studies on the subaqueous delta and to the northeast of the Fly River mouth. In addition, a time-series bottom-boundary layer tripod was deployed for a 7-day interval in 16-m water depth to document near-bed currents, waves and suspended sediment concentrations. Results show that suspended-sediment concentrations on the delta itself were low and increased to the northeast. In all cases suspended-sediment concentrations and surface bed sediment porosities were greatest in depths of less than 10 meters. Although there was minimal wave activity at the time of sampling, concentrations observed near shore reached 1 g/l. Tidal currents measured at the time-series site exceeded 15 cm/s at the approach to spring tide, suggesting that tidal currents may be the mechanism that suspends these relatively high concentrations in the bottom boundary layer and maintains seabed sediment in an unconsolidated state. The data, combined with seabed observations, suggest that there is temporary storage of sediment in shallow water to the northeast of the Fly River mouth during the monsoon season. Subsequent data collection will determine if trade-wind conditions are sufficiently strong to generate wave-supported fluid mud and downslope gravity flows which are hypothesized to transfer sediment to the foreset of the Fly River clinoform and contribute to the high accumulation rates observed there.
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting