Eolian Deposits in the Middle Reaches of the Yangtze River During Late Interstadial of the Last Glacial (4022KaBP) and Its Environmental Significance
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摘要: 定山砂山剖面的下层灰黄色土-淤泥沉积，为末次冰期间冰阶（40～22kaBP）区域降尘堆积。灰黄色土层与淤泥为同源异相沉积，粒度组合基本相同，无特征性差异。频数曲线都以双峰为特征，第一峰为主峰，众值8～32 μm；第二为次峰，众值250～500μm。9.75±0.25Φ~4.25±0.25Φ(1 ~62.5μm)在垂向上具有相似的线形变化，组成第一峰态，各粒级垂向上的含量变化是区域冬季风强弱变化的敏感指标；2.25±0.25Φ ~-0.75±0.25Φ (180~2000 μm)具有相似的线形，组成第二峰态，各粒级剖面含量变化则揭示了冬半年环境干湿状况与局地尘暴事件。在对应区域降尘堆积较弱的两个时段，存在局地尘暴的增强事件，指示局地冬半年环境干燥。
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关键词:
- 长江中游 /
- 末次冰期间冰阶 /
- 灰黄色土—淤泥沉积层 /
- 区域降尘 /
- 局地尘暴事件
Abstract: The bottom yellowgrey soilsilt deposits layer at Dingshan sand dune profile originated from the regional dustfall accumulation in the late interstadial of the Last Glacial( 4022 ka BP). Thus the yellowgrey soilsilt had the same origin but had different facis deposits, grain combination are the same and have not characteristic differences; All curves of frequency have character of two apices, the first apex is main and cell value is 832 μm, the second apex is subordinate and cell value is 250500 μm. Cell value of 9.75±0.25Φ~4.25±0.25Φ(1~62.5 μm) have the similar linear change at vertical and compose the first kurtosis, the content changes at different grain vertical is sensitive index on strong and weak changes of winter monsoon; 2.25±0.25Φ~-0.75±0.25Φ (180~2000 μm) have the similar linear change and compose the second kurtosis, the content changes at different grain profiles indicate dry and wet situation at the circumstance of the winter climate and regional dust storm events. At the weak stage of regional dustfall accumulation it had strongly regional dust storm events, indicating that it was dry at local places in the winter. -
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