Distribution of organic geochemical elements in differentsedimentary microfacies of tidal flats from north branch of the Yangtze River mouth
Li Lin1 Wang Zhanghua2 Wu Xuxu1 Gao Xiaoqin1
1 Department of Geography, East China Normal University, Shanghai 200062; 2 State Key Laboratory for Estuarine and Coastal Research, East China Normal University, Shanghai 200062
Abstract:We examined the spatial distribution of total organic carbon(TOC),total nitrogen(TN),and total sulfur(TS)in the surficial sediments of tidal flats from Beisiyaogang(SY),Beipugang(BBG),and Xinweicun(XW),Chongming island at the north branch of the Yangtze River mouth.Factors controlling distribution of the organic elements were discussed and TOC/TN,TS/TOC ratios and TS-TOC relationship were analyzed to explore their potential for distinguishing different sedimentary microfacies of tidal flats in the study area.The results indicate that the content of TOC and the type of organic matter played a key role in the spatial distribution of TN and TS.In the progradational tidal flat,TOC/TN in upper tidal flat was generally larger than 10,but was smaller than 10 in middle tidal flat.The vegetation zone of the middle tidal flat had the highest average TS/TOC value of 0.063.The TS/TOC value in Spartina alterniflora zone of upper tidal flat and the bare area of middle tidal flat ranked the second(0.055 and 0.054,respectively);while in the Phragmites australis zone of upper tidal flat it showed the lowest value.The slope of TS-TOC linear regression was remarkably low in the Phragmites australis zone of upper tidal flat and gradually increased seaward.In the regradational tidal flat,TOC/TN in the whole intertidal zone exceeded 10,with higher values in mid-low tidal flat than in upper flat.However,TOC/TN was much smaller than 10 in the subtidal zone.TS/TOC increased gradually from land to sea.The slopes of TS-TOC regression lines were maximum in the middle tidal flat and minimum in the upper tidal flat.Moreover,the TS-TOC slope in regradational tidal flat was apparently lower than that in progradational tidal flat.We concluded that TOC/TN,TS/TOC and the liner regression of TS-TOC varied among different sedimentary microfacies of tidal flats in the study area,and therefore these proxies could be applied in the identification of different sedimentary microfacies of tidal flats for the Holocene core sediments.
Li Lin,Wang Zhanghua,Wu Xuxu et al. Distribution of organic geochemical elements in differentsedimentary microfacies of tidal flats from north branch of the Yangtze River mouth[J]. JOPC, 2013, 15(1): 95-104.
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