Evolving sources of eolian detritus on the Chinese Loess Plateau since early Miocene: Tectonic and climatic controls
Evolving sources of eolian detritus on the Chinese Loess Plateau since early Miocene: Tectonic and climatic controls
复制标题
早中新世以来中国黄土高原风成碎屑来源的演变：构造和气候控制
DOI：
10.1016/j.epsl.2013.03.044
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发表时间：
2013-06-01
影响因子：
5.3
通讯作者：
Li, Gaojun
中科院分区：
文献类型：
--
作者：
Chen, Zhong;Li, Gaojun
中国黄土高原厚厚的风尘沉积为探索气候和构造振荡响应过去地表过程的变化提供了难得的机会。本文报道了长达22 Ma的风成源的Nd、Sr同位素记录。早中新世至约7 Ma，风成沉积物的epsilon(ND)值减小，而Sr-86/Sr-87比值增大，表明祁连山相对戈壁阿尔泰山的物质贡献在增加。22-7 Ma期间的震源位移反映了祁连山对地表隆升的侵蚀响应。结果表明，在7~12 Ma之间，风成沉积物的Nd锶同位素组成相对恒定，表明祁连山与戈壁-阿尔泰山之间存在恒定的物源贡献。这两个山脉在此期间的同步隆升可能解释了源区贡献率恒定的原因。自1.2 Ma以来，Ndsr同位素记录表明，祁连山的相对碎屑输入迅速下降。由于在这么短的时间内不会发生大范围的地形变化，1.2 Ma以来的物源转移可能是由于祁连山和戈壁阿尔泰山在中更新世过渡后对全面冰川气候发展的不同侵蚀响应。这项工作表明，尘埃记录的组合Ndsr同位素特征对于监测百万年时间尺度上过去的地表过程是有价值的。(C)2013爱思唯尔B.V.保留所有权利。
The thick deposits of eolian dust on the Chinese Loess Plateau provide a rare opportunity to explore the past changes of surface processes in response to climatic and tectonic oscillations. Here we report a 22 Ma-long Nd and Sr isotopic records of the eolian sources. Decreasing epsilon(Nd) values and increasing Sr-86/Sr-87 ratios of the eolian deposits has been observed from early Miocene to about 7 Ma, which indicates growing material contribution from Qilian Mountains relative to the Gobi Altay Mountains. The source shift during 22-7 Ma is interpreted to reflect the erosional response of the Qilian Mountains to its surface uplift. Between 7 Ma and 12 Ma, the results show relative constant Nd and Sr isotopic compositions of the eolian deposits, and thus suggest a constant source contribution between Qilian Mountains and Gobi Altay Mountains. Synchronized uplift of the two mountain ranges during this period may explain the constant ratio of source contribution. Since 1.2 Ma, Nd and Sr isotopic records indicate that the relative debris input from Qilian Mountains drops rapidly. As large-scale topographic changes would not be expected in such a short time period, the source shift since 1.2 Ma might be by the differing erosional responses in Qilian Mountains and Gobi Altay Mountains to the development of full glacial climate after the middle Pleistocene transition. This work shows that combined Nd and Sr isotopic signatures of the dust records are valuable proxies to monitoring past surface processes on the million years time scale. (C) 2013 Elsevier B.V. All rights reserved.