摘要:
对成都平原区内5个代表性的第四系剖面上的成都粘土进行了系统的粒度分析。结果表明,成都粘土以粉砂颗粒(5~50μm)为主,平均粒径约为7.1~7.3φ(7.4~6.6μm),缺少粗尾,>63μm颗粒的含量很少,以细颗粒物质为主,呈双峰分布。其粒度分布及粒度参数特征与北方黄土及甘孜黄土非常相似,而与河流相沉积物有很大差异,表明成都粘土属于风成堆积。根据光释光测年(OSL)结果,成都平原区的成都粘土是晚更新世中期至晚期末次冰期堆积物,其物质主体是远源的。
关键词:
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成都粘土
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粒度
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黄土
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末次冰期
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成都平原
Abstract:
The grain size analysis is carried out for the representative samples of the Chengdu clay taken from the Quaternary sections in the Chengdu Plain, Sichuan. The Chengdu clay consists essentially of silty grains of 5 to 50 μm in size, with an average grain diameter of 7.1 to 7.3 φ(i. e., 7.4 to 6.6μm in size) and also a small amount of more than 63μm fraction, and in the diagram, tends to display the bimodal patterns of distribution. The grain size parameters, mean square deviation values and kurtosis values for the Chengdu clay are strikingly similar to those of the northern China loess and Garze loess, but quite different from those of the fluvial deposits. The abovementioned aspects suggest that the Chengdu clay is a kind of aeolian soil. According the results of optically stimulated luminescence(OSL), the Chengdu clay from the Chengdu Plain should be originated from the latest glacial sediments in the middle to late stages of the late Pleistocene. The bulk of the Chengdu clay is distal.
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