Magnetic Fabric Characteristics of Sand‐Dune Sediments and Its Paleowind Field in the Middle Reaches of Yangtze River
Magnetic Fabric Characteristics of Sand‐Dune Sediments and Its Paleowind Field in the Middle Reaches of Yangtze River
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DOI：
10.1002/cjg2.1330
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
Yufen Zhang;Chang‐An Li;Liang Chen;Chunguo Kang;Sihui Hu;Junzhou Huo;Lingling Yan;Xuemei Cheng
中科院分区：
文献类型：
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作者：
Yufen Zhang;Chang‐An Li;Liang Chen;Chunguo Kang;Sihui Hu;Junzhou Huo;Lingling Yan;Xuemei Cheng
通过对江西九江新发现的沙丘沉积物磁化率各向异性的测量和磁化率椭球长轴的统计分析，揭示了不同层位磁性组构参数的变化特征，获得了古风向特征及其演化规律。 (1) 整个时期主导方向为NW-SE和NNW-SSE，但不同时期方向和强度存在一定差异；最显着的变化发生在第二砂层；方向由NW-SE向NE-SW发生根本性转变，沉积环境变得相对稳定； (2) 第二、五、六砂层的P、F、L值较大，q值较低，表明其形成时气候最冷，冬季风力最强，风速稳定，对应于该层发育大面积板状斜层理，颗粒较粗，粘土含量较低； （3）晚更新世末期，长江中游风积沙丘的广泛发育，表明该时期气候最干燥、最寒冷，风能最强，与北方的荒漠黄土气候相似； (4)本文表明，AMS长轴半球投影和玫瑰图是分析古风向变化规律的一种简便有效的方法。
Through the measurement of susceptibility anisotropy and statistical analysis of major axis of the susceptibility ellipsoid of the sand-dune sediments newly found in Jiujiang, Jiangxi, the paper illustrates the variational feature of magnetic fabric parameter in different layers and obtains the feature of paleowind direction and its evolutionary rule. (1) The dominant direction was NW-SE and NNW-SSE during the entire period, but with some variations in direction and intensity in different periods; the most significant change happened in the second sand layer; the direction changed radically from NW-SE to NE-SW, and the sedimentary environment became relatively stable; (2) The second, fifth, and sixth sand layers have greater values of P, F, L and lower q values, indicating that the climate was the coldest when they formed, the winter wind power was the strongest with a stable wind velocity, which corresponds to the development of large-scale tabular oblique bedding in these layers, thicker grain sizes and lower clay contents; (3) In the end of the late Pleistocene, the extensive development of aeolian sand-dunes in the middle reaches of Yangtze River indicates that the climate in that period was the driest and the coldest, and the wind energy was the strongest, similar to the desert-loess climate of the North; (4) The paper shows that hemispherical projection and rose diagram of major axis of AMS is an easy and effective method for the analysis of the variation rule of paleowind direction.