| Xinghua 2ndCore locates at the subsidence center- Gaoyou hollow in the northern Jiangsu basin.The northern Jiangsu basin is the only basin which concurrently crosses flood and field in eastern monsoon area of our country- land part in the South Yellow Sea basin.The whole northern Jiangsu basin subsided from Pliocene,started to accept the deposition and gradually developed to plain.The continual deposit in the basin since Late Cenozoic is the important carrier which is used to study on long time-scale New tectonic movement and the coupling mechanism of global climate change,the formation and development of the East Asia monsoon in Our country.At the same time it has great comparability with Multi-proxy analysis,such as monsoon fringe area,Northwest arid area,Tibetan Plateau area,deep sea drilling,etc,and it can been used to dicuss the New tectonic movement and the regional and global character of climate change.The research material is the deposition in Xinghua 2ndCore.According to the B/M boundary of the drilling deposition lies in about 80.6m,We select 82.18m core at the top of the drilling hole to measure granularity index and analyses the granularity character change of deposition,we determine sedimentary facies of the drilling core by granularity parameter,probability accumulation curve,c-m chart and lithology characterization.The granularity(less than 3.9μm) percentage is carried on the linear interpolation through Age control points which is established by dating data and Paleomagnetism event.Establish the 80.6m age rod of Xinghua 2ndCore by tuning track and the evolution sequence of sediment environment since Middle Pleistocene.Comparing with the ice age and interglacial cycle curve reflected by deep sea oxygen isotope,we preliminary discuss evolution influencing factor of the sediment environment in drilling core.The results of granularity analysis and lithology characterization indicate that the sediment condition has experienced several alternation.The research results are as follows:82.19～80.6m,deposit of lacustrine facies of plain;80.6～78.5m,deposit of lacustrine delta facies;78.5～66.85m,deposit of delta facies;66.85～61.8m,deposit of winding riverway facies; 61.8～57.43m,deposit of lacustrine facies;57.43～52.3m deposit of lacustrine facies;52.3～38.1m, deposit of floodplain facies;38.1～32.1,deposit of flooded plain facies;32.1～26.73m deposit of winding bottomland facies;26.73～19.68,deposit of floodplain-lacustrine facies;19.68～19.53m, deposit of winding bottomland facies;19.53～16.65,deposit of floodplain facies;16.65～11.5m, deposit of floodplain-swamp facies;11.5～9.58m,deposit of floodplain-lacustrine facies;9.58～0.29m,deposit of floodplain-swamp facies.The results of hydrodynamic condition and granularity analysis and other physical index of sediments indicate that the area of Xinghua 2 core exsited 6 prominent fluctuation gyrations since Pleistocene.Every gyration begins with the granularity from thick to thin and the hydrodynamic condition strengthening.When the hydrodynamic condition weakens to a lacustrine environment, the lacustrine will degenerate,and then plants grow,organism cumulate,Iron-manganese nodules and autunite nodules develop vastly.At last,the swamp formed,and the sediment ended.The first gyration:0.799～0.648MaB.P.,plain lacustrine-lacustrine delta-flood plain lacustrine,the second gyration:0.648～0.524MaB.P,winding river deposit-bottomland-floodplain-floodplain lacustrine; the third gyration:0.524.～0.33MaB.P.deposit of lacustrine-floodplain facies;the forth gyration: 0.33～0.129 MaB.P.winding river floodplain--bottomland-floodplain lacustrine enviroment;the fifth gyration:0.129～0.062MaB.P.,fluvial facies- lacustrine- swamp environment;the sixth gyration:0.063MaB.P.～0,floodplain lacustrine- bottomland- swamp enviroment.The granularity characterization by Xinghua core reveals a strong correlation with the deep-sea oxygen isotope record.This indicates that the new basic tectonic movement tends to slow in North Jiangsu Basin.The cyclical change of sedimentary environment is majored by the impact of cyclical fluctuations of climate.As the study area mainly on the plain of shallow lakes and swamp which affected by the rivers,the granularity of sediments records sensitively the change of hydrodynamic condition in the sediment area.It is majored by fine particles and floodplain clay at the upper 82m of the profile.So the vertical changes of the whole profile are quite limited.And the cumulative probability curve shape, cut-off point location,slope and other characteristics are very important index,expecially doing discriminate in the sedimentary environment. |
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