Study On The Geochemical Character Of Carbon And Nitrogen And The Environments Indications Of North Sand Ridge Of Radial Tidal Sand Ridge System In Jiangsu Offshore,South Yellow Sea

The radial sand ridges with its unique features,sand body bulky,complex dynamic conditions has been a hot research in coastal continental shelf.Through the analysis of the sedimentary of Y5 core where is at Gaoni of radial tidal sand ridge system,the geochemical characteristics of carbon and nitrogen,and a comprehensive comparison of the 07SR03 data at Dabeicao and Dongsha shoal area among radial tidal sand ridge system in the South Yellow Sea.The results show that:?1?The deposition of comprehensive Y5 core phase,grain size,TOC,TN and C/N,organic carbon isotope,TIC,from top to bottom will be divided into four sections:?0-11.41m?B?11.41-18.25m?,C(18.25-23.81m and D?23.81-54.01m?.?2?Y5 core ?¹³C between-25.225‰?-20.2339‰,the average value is-22.646‰The content of TOC ranged from 0.003‰?0.924%,the average is 0.16%,the content of TN was between 0.001%?0.053%and the average is 0.016%,each district has its own characteristics of its contents.The content of organic matter in sediments of the land and sea interaction is mainly affected by the material sources,the degree of degradation and retention of environmental impact,the modern sedimentary organic matterinput Gaoni area mainly from marine plankton,algae,and the unstable sedimentary environment significantly affected by the dynamic effect among this area.Applies to thousand years scale,Gaoni area affected by climate changes,oftransgression and regression of the sea,since the late Pleistocene,the organic matter was controlled mainly by marine algae,lake algae,terrestrial C4.?3?TIC content ranged from 0.014%to 1.336%.The average value is 0.509%.The TIC of Y5 and 07SR03 core are at the lowest value around the last glacial maximum.Mainly due to the sea water receded at glacial maximum,the southern Yellow Sea area become a vast land plain,the CaCO3 of Y5 and 07SR03 core were dilutede by the silicate terrigenous matter,so the TIC of this area was showed low-value.?4??¹³C of Y5 core C section between-24.562‰ to-21.855‰,the mean value is-23.334‰,average of 07SR03 core period section's ?¹³C-22.846‰ per thousand.The 8¹³C content of Y5 core is lower than it of 07SR03 core during the last glacial maximum at the north of the southern Yellow Sea.Because after the sea water receded,Y5 was at lake sedimentary environment showing fine particle size and high value of TOC,TN content,C/N ratio and lower ?¹³C content than 07SR03 core,the source of organic matter may mainly comes from the algae in the lake.Compared to the Y5 core,07SR03 was close to be the fluvial facies,showing the rough grain size,lower value of TOC,TN than Y5 core,and higher ?¹³C content than that of Y5.Because the source of the organic matter come from terrestrial plants containing C4.?5?Comparison of Y5,07SR03,11DT02 and Pudong airport drilling four cores,and distribution of ?¹³C,and C/N,together with facies associations of Y5 and 07SR03 core,led to identify depositional settings related to tidal flat,terrestrial?characterized by the stiff mud deposit?,tidal flat and tidal sand ridge facies from the bottom towards the top parts within the core.