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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Mineral magnetic variation of the Jingbian loess/paleosol sequence in the northern Loess Plateau of China: Implications for Quaternary development of Asian aridification and cooling
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Mineral magnetic variation of the Jingbian loess/paleosol sequence in the northern Loess Plateau of China: Implications for Quaternary development of Asian aridification and cooling

机译：黄土高原北部靖边黄土/古土壤序列的矿物磁变化：对亚洲干旱化和冷却第四纪发展的启示

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A high-resolution mineral magnetic investigation has been carried out on the Jingbian loess/paleosol sequence at the northern extremity of the Chinese Loess Plateau. Results show that the magnetic assemblage is dominated by large pseudo-single domain and multidomain-like magnetite with associated maghemite and hematite. Variations in the ratios of SIRM100mT/SIRM, SIRM100mT/SIRM30mT and SIRM100mT/SIRM60mT (SIRM is the saturation isothermal remanent magnetization; SIRMnmT represents the residual SIRM after an n mT alternating field demagnetization) have been used to document regional paleoclimate change in the Asian interior by correlating the mineral magnetic record with the composite delta(18)O record in deep-sea sediments. The long-term up-section decreasing trend in those ratios in both loess and paleosol units has been attributed to a long-term decrease in the relative contributions of eolian hematite during glacial extrema and of pedogenic hematite during interglacial extrema, respectively, which reveals a long-term decreasing trend in chemical weathering intensity in both glacial-stage source region (the Gobi and deserts in northwestern China) and interglacial-stage depositional area (the Loess Plateau region). We further relate this long-timescale variation to long-term increasing aridification and cooling, during both glacial extrema in the dust source region and interglacial extrema in the depositional area, over the Quaternary period. Changes in those ratios are most likely due to Quaternary aridification and cooling driven by ongoing global cooling, expansion of the Arctic ice-sheet, and progressive uplift of the Himalayan-Tibetan complex during this period. (c) 2005 Elsevier B.V. All rights reserved.
机译：在中国黄土高原北端的靖边黄土/古土壤序列上进行了高分辨率矿物磁研究。结果表明，磁性组合主要由大的伪单畴和多畴状磁铁矿以及伴有磁赤铁矿和赤铁矿组成。 SIRM100mT / SIRM，SIRM100mT / SIRM30mT和SIRM100mT / SIRM60mT之比的变化（SIRM是饱和等温剩余磁化强度; SIRMnmT代表n mT交变磁场消磁后的残留SIRM）已用于记录亚洲内部区域的古气候变化通过将矿物磁记录与深海沉积物中的复合δ（18）O记录相关联。黄土和古土壤单位中这些比例的长期向上下降趋势分别归因于冰川极端期风积赤铁矿和冰川间极端期成岩赤铁矿的相对贡献的长期减少，这表明冰川期源区（中国西北部的戈壁和沙漠）和冰川间期沉积区（黄土高原地区）化学风化强度的长期下降趋势。在第四纪时期，我们进一步将这种长期尺度变化与粉尘源区的冰川极端和沉积区的冰川间极端期间的长期增加的干旱化和降温联系起来。这些比率的变化很可能是由于全球持续冷却，北极冰盖的扩张以及在此期间喜马拉雅－西藏综合体的逐步抬升所驱动的第四纪干旱化和冷却。 （c）2005 Elsevier B.V.保留所有权利。

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