Preliminary Study on Late Quaternary Paleosols and Paleoenvironments of the Yangtze Delta
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摘要: 长江三角洲地区第一硬粘土层中有植物根、植屑、裂隙、粘粘胶膜、土壤结构体、结核等古土壤特征，系古土壤。粒度、化学分析及磁组构分析揭示它为多期成土作用形成的复合古土壤层。根据硬粘土层与南京下蜀土、黄土高原黄土一古土壤系列及上海亚近代潮坪沉积的磁性参数对比，推断该古土壤的母质系河流冲积物。硬粘土层中裂隙的广泛发育及充填，软锰矿的分布表明当时地下水位波动较大，干湿季节分明，古季风的影响较强。Abstract: The first stiff clays at the Yangtze Delta are considered to be paleosols by their characteristics, such as plant debris and roots, clay-filled cracks, cutans, peds, and nodules, etc. It is learned from the clay contents, chemical and magnetic fabrics analyses that the stiff clays are complex polygenetic paleosols. The parent material of the paleosols are inferred to be alluvium based on the comparisons of their magnetic parameters with those of Xiashu Loess, Loess-Paleosol Series of Central China and tidal flat sediments of Shanghai.It is learned from the concentration of MnO2. nH2O that the depth of groundwater was about three meters, which was due to the higher elevation of this area during the period of glacial low stand of sea level.The well -developed and clay - filled cracks, along with the fluctuations of groundwater, indicate that the dry and wet seasons were distinctive and the effects of monsoon were stronger than nowadays.Paleosols are thicker than modern soils, and are thinner in the east than in the west of this area, which relates to the different time spans of pedogenesis caused by transgression and regression.
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Key words:
- Paleosol /
- Yangtze Delta /
- Late Quaternary /
- Paleoenvironment
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