| The eastern coastal area of China serves as an important base for the economicdevelopment of China,and quite a large of the area are plains with altitudes less than fivemeters，such as Jiangsu and Shanghai,etc.Thus,it is an important work to carry out thegeological investigation for the coastal areas.We can reveal the history of the sea-landinteraction environmental vicissitude,predict regional environment and provide a solidevidence for the global climate changes. At the same time,the research has very importantpractical significance to the local economic development and human life.Taking the Dongtai ZKJ34hole as the research object,the thesis studied338meter-longborehole through using element geochemistry and micropaleontological research methods,combining with the regional landscape,core features and historical literature,and othercomprehensive contrast drills in this area.Through analyzing and researching,someconclusions were obtained as following:First,according to the features of regional data and drilling core,such as sedimentcolor,grain size,lithology,thickness,structure,the contact relation between the structure and thedegree of consolidation,etc,the Quaternary stratigraphy can be divided into four sedimentarygroups: Early Pleistocene: Haimen group (Qp1h),the start-stop depth between195.1and281.8meters;Pleistocene:Qidong (Qp2qd), the start-stop depth from132meters to195.1meters;Late Pleistocene: Kunshan group (Qp3k),with start and end depth between115meters and132meters;Late Pleistocene:Gehu group(Qp3g),depth from43to115meters;Holocene: Rudonggroup (Qhr),depth from0.4to43meters.Second,through the major elements of sediments ratio in Dongtai ZKJ34hole, restoredthe Quaternary climate changes of the drilled sediments.The entired deposit period is dividedinto three main climatic fluctuations.Third,through researching on the Dongtai ZKJ34hole sediment micropaleontologycharacteristics,the river-sea interaction sea continental sedimentary environment anddeposition of element distribution are revealed, the causes and paleo-environment evolutionhistory are discussed. The analysis of the drilling sediment micropaleontology shows thatthe whole drilling sediment has always given priority to the glass of benthic species,with thenearshore type taking the dominant position. It’s also reflects that the place of transgressionsare less than100meters.Fourth,according to the drilling sediment lithologic characteristics,major elements,combined with geochemical changes and the formation distribution of micropaleontology, three transgression events are revealed in this drilling hole:Transgression Ⅲ(It is equivalent to Taihu transgression): Its start-stop depth in ZKJ34drilling is93-115meters,with the inferred time between the late Late Pleistocene and earlyMid-Pleistocene,belonging to the last interglacial period,corresponding to the deep seaoxygen isotope stages of MIS5. Microfossils can not be seen in the sedimentary with220meters of depth.However,there is a significant change of chemical element.Thus,the existenceof transgression needs to be further studied. Transgression Ⅱ(It is equivalent to Gehutransgression) is divided into two periods: transgressionⅡ1: Late Pleistocene,the start andend depth is from43to59.4meters,as the end of the last glacial interglacial stage. It’sequivalent to deep-sea oxygen isotope MIS3stage of3a，time is about45-25kaB.P.TransgressionⅡ2:the start-stop depth is72-80meters, roughly equivalent to a time before theend of the last glacial interglacial epoch, corresponding to the deep sea oxygen isotopeMIS3stage of3c.TransgressionⅠ(It is equivalent to Zhenjiang transgression.)is in the Mid-Holocene, including Boreal period,Atlantic period and Sub-boreal period.Based on the results obtained, Quaternary stratigraphy is divided. We have restored theQuaternary climate changes of the drilled sediments combined with geochemical changes andthe formation distribution of micropaleontology. It’s made a very important reference valueon the study of the ancient climate in eastern China. |
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