Microfossil Indictor To Coastal Sedimentary Process During Storm

In this paper,the study of modern typhoon storm deposition in the Guangdong semi-enclosed lagoon(Hailing Island)and bay(Wangcun port)environment in the southern China is carried out.The microfossils of column samples and grain size with 210Pb dataes are analyzed,the historical storm events are studied,which reveal the relationship between storm deposition and Kuroshio current,and provide scientific basis for its application in the study of ancient storms.The mainly research conclusions are summarized as follows:(1)According to the 210Pb data in Hailing Island lagoon and Wangcun Port,the 210Pb activity of HLD1 A and WCG4 column in the 0-33cm and 0-30cm appear the strong mixing phenomenon,much thicker than before typhoon of the bioturbation layer thickness,indicating that the depth of this typhoon incident in the station to reach about 33cm and 30cm.(2)Based on the analysis of the grain size characteristics before and after the typhoon in the Hailing Island and Wangcun Port,it is found that the grain size frequency curve of the sediments after typhoon is dominated by bimodal or multi-peak,and some of the horizons have obvious mutations.The difference between upper and lower layers is significant,indicating that the deposition is affected by the storm event.(3)Through the comprehensive analysis of sediment grain size parameters,chemical and micro-paleontological characteristics,identify four storm deposition events in the lagoon and gulf environment.The average value of ?13Cis-21 and-22%in the lagoon and the bay,respectively,and the TOC/TN ratio is higher than other Low,indicating that the storm sedimentary layer is mainly marine organic matter;in the storm layer,diatoms such as N.granulata,A.nodulifera and N.cocconeiformis are high content,salt water species accounted for more than 50%,the average of broken rate is higher than 30%;foraminifera have a large number of shells living in shallow or deep seas outside the lagoon and the bay,such as A.beccarii vars.,A.compressiuscula,F.simplex and P.cribroepandus,The shells are mainly buried in different places,mainly by the storm handling effect.(4)The storm deposition thickness of Hailing Island is 7-3 5cm and the average thickness is 25cm.The Wangcun Port environment is 18-30cm,the average thickness of 23 cm.The different thickness is mainly determined by the hydrodynamic strength and the size of the bioturbation.We also study the storm deposition pattern in different environments,lagoon environment due to a large number of shell enrichment and coarse particulate matter in the storm layer,which formate biological debris storm deposition phase,and the gulf environment,large number of diatoms and foraminifera,which is mainly affected a strong hydroelectric power during the typhoon,and carried a large number of offshore material deposited here,forming a silty storm sedimentary facies.The above two kinds of storm deposition patterns are an important means to identify the ancient storm deposition.(5)According to the Kuroshio diatom indicator species A.nodulifera and foraminifera species live in the Kuroshio warm area such as C.pseudungerianuns,F.simplex and P.cribroepandus,which are mainly affected by storm,the super typhoon has increased the black tidal flow and range of activities,making the impact of warmer wider.The study shows that the Kuroshio current flows through the action of water vapor and high temperature to increase the development of typhoon convection and promote the typhoon,while the strong typhoon brings the material of the warm zone to the nearshore sediments.At the same time,the commonly used indicators such as Micro-paleontological methods and grain size parameters,and these methods are equally applicable to the ancient Kuroshio study.