HR: 11:50h
AN: OS22A-07    [Abstracts]
TI: Processes and Patterns of Fluvial Sediment Transport and Accumulation on Continental Shelves
AU: * Nittrouer, C A
EM: nittroue@ocean.washington.edu
AF: School of Oceanography, University of Washington, Seattle, WA 98195, United States
AU: Figueideo, A G
EM: alberto@igeo.uff.br
AF: Department of Geology, LAGEMAR Universidade Federal Fluminense, Niteroi, RJ , Brazil
AU: Ogston, A S
EM: ogston@ocean.washington.edu
AF: School of Oceanography, University of Washington, Seattle, WA 98195, United States
AB: Wet-tropical settings produce much weathering and sediment supply to the coastal ocean. The processes that control the fate of the sediment have some distinctions from those operating in other latitudinal settings. For example, river hydrographs are sufficiently constant that sediment is delivered throughout the year, as opposed to temperate latitudes where there is a dramatic seasonal variability. In tropical locations, fluctuations in trade-wind conditions (speed, direction) dominate the physical forcing that drives sediment transport. Sedimentation active on the Amazon shelf and in the Gulf of Papua (Papua New Guinea) can be contrasted with that active in temperate settings off North American (Eel, Columbia), European (Po, Rhone) and Asian (Yangtze, Huanghe) rivers. Among the differences are the mechanisms that lead to high-concentration gravity flows (fluid muds). Because much sediment is transported across shelf by these mechanisms, they have a dominant control on the fate of particles and the patterns of sediment accumulation (e.g., clinoform deposits). The continuous discharge of sediment in wet-tropical settings allows tidal currents to intensely rework the seabed. Coupled with other processes (e.g., estuarine trapping, intensified trade-winds) this leads to very turbid boundary layers (>10 g/l) and extensive physical mixing of surficial seabed sediments. Interdisciplinary impacts are to remineralize geochemical components and to inhibit benthic habitation. In contrast, temperate settings have some of the same processes operating, but in a different fashion. In particular, episodic river discharge and/or storm activity can create different results (e.g., wave-generated fluid muds) and sedimentary products (e.g., flood and storm deposits). Integrated over time scales of centuries, evidence for operational processes in tropical and temperate coastal settings are preserved in high-resolution stratigraphic records. Among the fluctuations recorded are impacts of El Nino and longer-term climatic variability, as well as human perturbations. Together, tropical and temperate records provide a diverse and comprehensive history of terrestrial and marine processes, which will become important for demonstrating the impact global change has on Earth surface processes.
DE: 3002 Continental shelf and slope processes (4219)
DE: 3022 Marine sediments: processes and transport
DE: 4217 Coastal processes
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly