HR: 1340h
AN: OS23C-1320    [Abstracts]
TI: Sedimentary Features of the Yangtze Derived Mud Deposits in the Inner Shelf of the East China Sea
AU: * Velozzi, D
EM: davidvelozzi@yahoo.com
AF: North Carolina State University, MEAS Po Box 8208, Raleigh, NC 27695 United States
AU: Liu, P
EM: jpliu@ncsu.edu
AF: North Carolina State University, MEAS Po Box 8208, Raleigh, NC 27695 United States
AU: Li, A
EM: acli@ms.qdio.ac.cn
AF: Inst. of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071 China
AU: DeMaster, D
EM: demaster@ncsu.edu
AF: North Carolina State University, MEAS Po Box 8208, Raleigh, NC 27695 United States
AB: The purpose of the present study is to document the nature of the innermost shelf of the East China Sea, with particular interest in the fate of the Yangtze River sediment, which historically has discharged about 500 million tons of sediment annually. High-resolution Chirp Sonar seismic data together with a number of shallow cores reveal a broad mud wedge up to 100 km wide extending 800 km southward along the inner shelf. The mud wedge is thickest (~ 40 m) near shore between the 20m and 30m isobaths and progressively thins off shore reaching water depths up to 60 meters. Sediment accumulation rates were estimated from the vertical distribution of excess 210Pb in sediment cores collected at 8 stations along the inner shelf. Near the mouth of the Yangtze River sediment accumulation rates have historically been about 1 to 5 cm/y, due to winter resuspension and erosion events. The highest sedimentation rates in the mud wedge (~ .7 - 1.0 cm/yr) were found just south of the Yangtze estuary (30øN). Sedimentation rates generally decrease alongshore toward the south and offshore toward the east (~ .5 -.02 cm/yr). This pattern is consistent with the dispersal of Yangtze River-derived sediments by the Chinese coastal current and tidal systems. Grain size analysis of the surface sediments near the mouth of the Yangtze are dominated by sandy silts and silty/clayey sands. There is a general fining of surface sediments (silty clays) alongshore toward the south. Clay mineral assemblages of the mud wedge are composed primarily of illite (generally more than 60%), and subordinately of chlorite, kaolinite and smectite. Smectite concentrations ($<$5%) are a good indicator that the sediments are derived from the Yangtze River.
DE: 4211 Benthic boundary layers
DE: 4267 Paleoceanography
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 1719 Hydrology
DE: 1724 Ocean sciences
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting