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通过对玉溪遗址地层AMS14C测年、粒度、重砂矿物组分与形态、锆石微形态、磁化率、Rb/Sr和Hg等地球化学指标研究发现,7.6kaBP以来,水位在吴淞高程147.024m(a.s.l.)以上的古洪水至少在玉溪遗址T0403探方新石器时代地层中留下了16次沉积记录,判定依据主要是:(1)玉溪遗址古洪水层与该处现代洪水层以及中坝遗址现代洪水层沉积物在粒度概率累积曲线上具有相似的三段式河流相沉积特征;(2)古洪水层与现代洪水层沉积物在重砂矿物组分及形态特征上具有相似性;(3)洪水层磁化率值均很低(分布于40.44～70.10SI之间),而文化层较高(范围在59.59～188.68SI之间);(4)洪水层Hg的含量较低(在290.71～742.51ng/g)之间,文化层偏高,在344.16～10518.17ng/g之间;(5)洪水层的Rb/Sr值高于文化层,第4,5,6,7和8这5个文化层的Rb/Sr值亦较高表明遭受过洪水浸淹的影响.该遗址具有较多洪水层的原因,与其位于一级支流入长江干流交汇处一级阶地处的地貌部位有关.由于下游中坝遗址古洪水沉积亦有与此类似的特征,表明从以上几方面判定遗址古洪水层的存在与否是确实的.
Based on the dating of AMS14C dating, grain size, mineral composition and morphology of heavy sands, zircon micromorphology, magnetic susceptibility, Rb / Sr and Hg geochemical indicators, it is found that the water level at the Wusong elevation of 147.024m Asl), the ancient floods left at least 16 sedimentary records in the Neolithic strata of T0403 in Yuxi Site. The main evidences are as follows: (1) The ancient flood layers in Yuxi site and the modern flood layer in the site and the modern The flood sediment has a similar three-phase river facies sedimentary feature on the cumulative probability curve of grain size; (2) the similarity between the ancient flood and the modern flood sediment in the composition and morphological characteristics of the heavy sand; (3) The values of magnetic susceptibility of the flood layer are very low (distributed between 40.44 and 70.10 SI), while the cultural layer is higher (ranging from 59.59 to 188.68 SI). (4) The content of Hg in the flood layer is relatively low (at 290.71 to 742.51 ng / g), and the cultural layer is high, ranging from 344.16 to 10518.17 ng / g. (5) The Rb / Sr value of the flood layer is higher than that of the cultural layer. The higher Rb / Sr values in the cultural layer indicate that they have been affected by flood flooding, the reason that the site has more flood layers, Branches and flows into the Yangtze River Interchange first terrace is located in the relevant parts of the landscape due to flooding downstream dam ruins of ancient sedimentary features are also similar to this, judging from the above aspects show the presence of ruins of the ancient flood layer is true or not.