Intensified aridity of the Asian interior recorded by the magnetism of red clay in Altun Shan, NE Tibetan Plateau
Intensified aridity of the Asian interior recorded by the magnetism of red clay in Altun Shan, NE Tibetan Plateau
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青藏高原东北部阿尔金山红粘土磁性记录的亚洲内陆干旱加剧
DOI：
10.1016/j.palaeo.2014.06.017
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发表时间：
2014-10-01
影响因子：
3
通讯作者：
Guo, Lei
中科院分区：
文献类型：
--
作者：
Li, Jianxing;Yue, Leping;Guo, Lei
中国黄土高原著名的黄土和红粘土序列的高分辨率研究已经追踪了季风占主导地位的地区的干旱历史。然而，中国西部的干旱化过程以及与季风体制的差异尚不清楚，因为在这些地区没有发现连续的风成序列。在这里，我们描述和解释了88.4米厚的新近纪风成序列包含40个视觉定义，棕红色粘土和灰色钙质结核层在西藏高原东北部的索霍尔盆地东部。磁性地层学研究表明，该层序的沉积时代为13 ~ 2.6Ma。根据磁化率（MS）的不同，可将层序划分为气候条件不同的两个部分：下部（13- 11.5Ma），气候变化较大，MS值较高（平均15 x 10（-8）m（3）kg（-1）），主要为磁铁矿;上部（103-2.6 Ma）反映了较干燥的气候，具有较低的稳定的MS值（平均9.5 x 10（-8）m（3）kg（-1）），主要来自赤铁矿。我们的研究结果表明，亚洲内陆干旱的加剧开始于11.5 Ma和10.3 Ma之间，当MS显着下降，由于青藏高原向外生长在12 Ma左右，以及持续的全球冷却和在新生代的新特提斯洋的海退。(c)2014爱思唯尔有限公司版权所有。
The aridity history of monsoon-dominated areas has previously been traced by high-resolution studies of the well-known loess and red clay sequences on the Chinese Loess Plateau. However, the aridity process further west in China and the differences from the monsoon regime are unclear because no continuous aeolian sequences have been found in those areas. Here we describe and interpret an 88.4-m-thick Neogene aeolian sequence containing 40 visually-defined, brownish-red clay and gray caliche nodule layers in the eastern Xorhol Basin, northeast of the Tibetan Plateau. Magnetostratigraphic results show that the sequence was deposited between similar to 13 and 2.6 Ma. The sequence can be divided into two parts with different climate conditions according to magnetic susceptibility (MS): the lower part (13-11.5 Ma) indicates a more changeable climate with higher MS values (average 15 x 10(-8) m(3) kg(-1)) dominated by magnetite; the upper part (103-2.6 Ma) reflects a drier climate with lower, stable MS values (average 9.5 x 10(-8) m(3) kg(-1)) mainly arising from hematite. Our results indicate that the intensified aridity of the Asian interior started between 11.5 Ma and 10.3 Ma, when MS decreased significantly due to outward growth of the Tibetan Plateau at around 12 Ma, together with ongoing global cooling and regression of the Neotethys Ocean during the Cenozoic. (c) 2014 Elsevier B.V. All rights reserved.