AGE OF RED CLAY AT CHAONA SECTION NEAR EASTERN LIUPAN MOUNTAIN AND ITS TECTONIC SIGNIFICANCE
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摘要: 黄土高原地区黄土之下的红粘土的年代和形成可为六盘山隆起、鄂尔多斯夷平面解 体以及青藏高原隆升等构造事件提供重要证据。六盘山东麓厚达303m的朝那黄土-红粘土剖面的磁性年代地层学表明：朝那红粘土开始堆积于8．1MaB．P．，是目前黄土高原上发现的最老的红粘土。8.1MaB.P．前后一次强烈构造运动使得鄂尔多斯夷平面解体，相对下沉地区接受红粘土沉积，六盘山地区开始隆起，这可能与青藏高原强烈的构造抬升事件有关。Abstract: The red clay underlying the Chinese Loess Plateau was thought to be an eolian deposition continuous to loess and thus was linked to the history of monsoon and drying Asia in relation to tLhe Tibet uplift. The lower boundary of red bed has been regarded as a signal to indicate the Tibetan uplift or the initiation of the polar ice sheet. Thus, the age and origin of red clay hold the key to unravel uplift of Liupan Mountain and disintegration of Ordos plantation surface. Here we report a 303m complete loess-red clay sequence, which contains 175m of Quatemary loess-paleosols and 128m of red clay, from Chaona at the eastem foot of Liupan Mountain bordered by Liupan Mountain thrust connected physically to north boundary thrusts of the Tibet Plateau. Detailed paleomagnetism shows that the age of Chaona red clay reaches8.1Ma B.P., at least 0.5 Ma older than previously reported oldest ages of the red clay sections in the Loess Plateau. It provides so far an oldest constraint to the Ordos planation surface below red clay.
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Key words:
- red clay /
- magnetostratigraphy /
- tectonic movement
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