Pedostratigraphy and paleomagnetism of a∼7.0 Ma eolian loess-red clay sequence at Lingtai, Loess Plateau, north-central China and the implications for paleomonsoon evolution
Pedostratigraphy and paleomagnetism of a∼7.0 Ma eolian loess-red clay sequence at Lingtai, Loess Plateau, north-central China and the implications for paleomonsoon evolution
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DOI：
10.1016/s0031-0182(99)00034-6
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发表时间：
1999-08-15
影响因子：
3
通讯作者：
Liu, TS
中科院分区：
文献类型：
--
作者：
Ding, ZL;Xiong, SF;Liu, TS
位于黄土高原中部的灵台地区，最近发现了一个厚达305 m的黄土-红粘土序列。由完整的更新世黄土-土壤序列组成，厚度约175 m，第三纪红粘土沉积130 m。灵台红粘土层是黄土高原目前已知最厚的红粘土层。野外观测表明，灵台红粘土含有110多个成土B层和水平碳酸盐结核层的耦合体，可视为一个巨厚的复合体。680个样品的古地磁研究表明，灵台黄土-红粘土序列的基底年龄约为7.05Ma。粒度分析表明，红粘土具有与黄土相同的沉积学特征，表明第三纪红粘土的风成成因和黄土高原7.05Ma以来的持续大气降尘作用。更新世黄土中的古土壤和红粘土中的B层的成土特征表明，晚中新世东亚夏季风可能已略强于全新世。这意味着在7.5Ma BP左右，青藏高原可能已经抬升到维持东亚夏季风系统的临界高度。黄土-红粘土序列的观测也表明，东亚夏季风强度的长期变化是非线性的，因为最新的中新世。(C)1999 Elsevier Science B. V.保留所有权利。
A 305-m-thick loess-red clay sequence was discovered recently at Lingtai, which is located in the middle part of the Chinese Loess Plateau. It consists of a complete Pleistocene loess-soil sequence with a thickness of about 175 m and 130 m of Tertiary red clay deposits. The red clay sequence at Lingtai is the thickest one presently known in the Loess Plateau. Field observations show that the Lingtai red clay contains over 110 couplers of pedogenic B horizons and horizontal carbonate nodule horizons, and that it can be regarded as an extremely thick soil complex. Paleomagnetic studies of 680 samples suggest that the basal age of the Lingtai loess-red clay sequence is about 7.05 Ma. Grain size analysis of samples taken at 3.3 cm intervals indicates that the red clay has the same sedimentological characteristics as those observed in the loess, thus suggesting a wind-blown origin of the Tertiary red clay and continuous atmospheric dust deposition in the Loess Plateau during the last 7.05 Ma. The pedogenic characteristics of the paleosols within the Pleistocene loess and the B horizons in the red clay suggest that the East-Asia summer monsoon in the latest Miocene may have already been slightly stronger than that during the Holocene. This implies that at about 7.5 Ma BP, the Tibetan Plateau could have been uplifted to a critical height in maintaining the East-Asia summer monsoon system. Observations of the loess-red clay sequence also suggest that the long-term changes in the East-Asia summer monsoon strength have been nonlinear since the latest Miocene. (C) 1999 Elsevier Science B.V. All rights reserved.