Sedimentary Features of the Yangtze Derived Mud Deposits on the Inner Shelf of the East China Sea

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dc.contributor.advisor Dr. J. Paul Liu, Committee Chair en_US Velozzi, David Micheal en_US 2010-04-02T18:16:19Z 2010-04-02T18:16:19Z 2005-07-20 en_US
dc.identifier.other etd-04132005-164824 en_US
dc.description.abstract The purpose of this study is to document the nature of sedimentation on the inner shelf of the East China Sea (ECS), with particular interest in the fate of the Yangtze River sediment. The Yangtze River has discharged about 500 million tons of sediment annually. High-resolution Chirp Sonar seismic data and shallow cores reveal a broad mud wedge up to 100 km wide extending 800 km southward along the Zhejiang-Fujian coasts. The mud wedge is thickest (~ 40 m) between the 20 m and 30 m isobaths and progressively thins offshore reaching water depths up to 60 and 70 meters. The mud wedge has a clinoform morphology with gently dipping topset, steeply dipping foreset, and gently dipping bottomset beds. 14C age dates indicate the clinoform began to form around 7000 yrs BP after sea-level reached the middle Holocene Highstand stage and decelerated to its present position. 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-1, due to winter resuspension and erosion events. The highest apparent accumulation rates in the mud wedge (2.1 cm yr-1) were found just south of the Yangtze estuary (30.5&deg;N). Apparent accumulation rates generally decrease alongshore toward the south and offshore toward the east (~ 1.6 - .33 cm yr-1). This pattern is consistent with the dispersal of Yangtze River-derived sediments by the Chinese coastal current and tidal systems. A calculated sediment budget using Pb-210 apparent accumulation rates (100-yr time scale) indicates that 35% of the sediment annually accumulating in the inner shelf mud deposit can be accounted for in the sediments north of 30&deg;N. This portion of the inner shelf mud deposit accounts for 55 % of the annual sediment discharge from the Yangtze River. Surface sediments of the inner shelf mud wedge are composed of clayey-silts and silty-clays. Coarser grained sandy-silts and silty-sands identified from cores on the thin bottomset deposits are a mixture of the fine Yangtze River sediment and coarse relict sands. Clay mineral assemblages of the mud wedge are composed primarily of illite (generally more than 70 %), and subordinately of chlorite, kaolinite and smectite. Smectite concentrations (< 5 %) are a good indicator that the sediments are derived from the Yangtze River. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject yangtze River en_US
dc.subject delta en_US
dc.subject sea level en_US
dc.subject Pb-210 en_US
dc.subject clay mineral analysis en_US
dc.subject seismic stratigraphy en_US
dc.title Sedimentary Features of the Yangtze Derived Mud Deposits on the Inner Shelf of the East China Sea en_US MS en_US thesis en_US Marine, Earth and Atmospheric Sciences en_US

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