Provenance of loess deposits in the Eastern Qinling Mountains (central China) and their implications for the paleoenvironment

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• 作者：Hongyan Zhang^a ; Huayu Lu^a ; ^{huayulu@nju.edu.cn} ; Shao-Yong Jiang^b ; Jef Vandenberghe^a ; ^c ; Shejiang Wang^d ; Richard Cosgrove^e
• 关键词：Eastern Qinling Mountains ; Chinese Loess Plateau ; Loess provenance ; East Asian monsoon ; Paleolithic
• 刊名：Quaternary Science Reviews
• 出版年：2012
• 期刊代码：78_02773791
• 类别：ear
• 出版时间：8 June, 2012
• 卷：43
• 期：Complete
• 页码：94-102
• 文件大小：1232 K

摘要

Loess deposits in the Eastern Qinling Mountains (central China) provide a detailed archive for reconstructing the paleoenvironment during early hominin occupation. The study of the loess deposits also provides a unique opportunity to understand Pleistocene atmospheric circulation in this transitional climatic zone. However, the provenance and formation of the loess deposits were not well understood until now. In this paper, we report on new geomorphologic investigations and depositional analyses of the loess deposits. The results suggest that Gobi deserts and drylands in northern and northwestern China were one of the dust sources. These loess deposits show similar geochemical composition as the average upper crust (UCC), and may indicate that they experienced multiple sedimentary processes, with the dust being well mixed before deposition. However, the higher ⁸⁷Sr/⁸⁶Sr ratios (between 0.719650 and 0.721043) and extremely low 蓻_Nd(0) values (between聽鈭?1.98 and聽鈭?8.97), which are different from the typical loess of the Chinese Loess Plateau, demonstrate that proximal clastic sediments that were apparently derived from the weathered Qinling orogen bedrocks, form the other important source for the loess deposits. The chemical Index of Alteration [CIA聽=聽Al₂O₃/(Al₂O₃聽+聽CaO*聽+聽Na₂O聽+聽K₂O)聽脳聽100] and Chemical Proxy of Alteration [CPA聽=聽100聽脳聽Al₂O₃/(Al₂O₃聽+聽Na₂O)], both in molar proportions show that the loess has experienced intense pedogenesis. We conclude that the loess deposit has a mixed provenance. The palaeoclimate in the Eastern Qinling Mountains remained mild in the glacial periods due to the topography and unique geographic locations, providing a suitable place for hominine occupation.