Time-Transgressive Nature of the Magnetic Susceptibility Record across the Chinese Loess Plateau at the Pleistocene/Holocene Transition.
Time-Transgressive Nature of the Magnetic Susceptibility Record across the Chinese Loess Plateau at the Pleistocene/Holocene Transition.
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更新世/全新世过渡时期中国黄土高原磁化率记录的时间海侵性质
DOI：
10.1371/journal.pone.0133541
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Wen W
中科院分区：
文献类型：
--
作者：
Dong Y;Wu N;Li F;Huang L;Wen W
根据磁化率（MS）确定的黄土地层界线与海洋同位素阶（MIS）2/1界线是同步的，并且在黄土高原不同剖面上大致是时间同步的。然而，尽管这一假设已被用作中国黄土沉积物的代理年龄模型的基础，但很少用绝对定年方法对其进行检验。在这项研究中，我们应用了一个单等分再生剂量（SAR）协议的45-63 μm的石英粒度的部分，以获得发光年龄的末次冰期和全新世的3个黄土剖面上的一个样带从东南到西北横跨CLP。基于来自三个部分的33个紧密间隔的光学受激发光（OSL）样品，在每个部分使用多项式曲线拟合建立OSL年表。根据光释光年代学，更新世/全新世界线（MS值的快速变化）在耀县剖面、泾川剖面和环县剖面的年代分别为10.5ka、8.5ka和7.5ka。这些结果显然与MIS 2/1界线年龄12.05 ka不一致，因此我们得出结论，更新世/全新世过渡的自动相关，从MS记录推断，与MIS 2/1界线是不正确的。结果清楚地表明，沿沿着东南-西北样带MS的显着变化是时间海侵的不同地点之间，与显着的古土壤发展的时间由MS记录所指示的西北比东南延迟3-4 ka。我们的研究结果表明，这种异步古土壤的发展在末次冰消期是由夏季风的延迟到达西北CLP相比，东南部。
The loess stratigraphic boundary at the Pleistocene/Holocene transition defined by the magnetic susceptibility (MS) has previously been assumed to be synchronous with the Marine Isotope Stage (MIS) 2/1 boundary, and approximately time-synchronous at different sections across the Chinese Loess Plateau (CLP). However, although this assumption has been used as a basis for proxy-age model of Chinese loess deposits, it has rarely been tested by using absolute dating methods. In this study, we applied a single-aliquot regenerative-dose (SAR) protocol to the 45–63 μm quartz grain-size fraction to derive luminescence ages for the last glacial and Holocene sections of three loess sections on a transect from southeast to northwest across the CLP. Based on the 33 closely spaced optically stimulated luminescence (OSL) samples from the three sections, OSL chronologies were established using a polynomial curve fit at each section. Based on the OSL chronology, the timing of the Pleistocene/Holocene boundary, as defined by rapid changes in MS values, is dated at ~10.5 ka, 8.5 ka and 7.5 ka in the Yaoxian section, Jingchuan and Huanxian sections respectively. These results are clearly inconsistent with the MIS 2/1 boundary age of 12.05 ka, and therefore we conclude that the automatic correlation of the Pleistocene/Holocene transition, as inferred from the MS record, with the MIS 2/1 boundary is incorrect. The results clearly demonstrate that the marked changes in MS along the southeast to northwest transect are time-transgressive among the different sites, with the timing of significant paleosol development as indicated by the MS record being delayed by 3–4 ka in the northwest compared to the southeast. Our results suggest that this asynchronous paleosol development during the last deglacial was caused by the delayed arrival of the summer monsoon in the northwest CLP compared to the southeast.