杨一博^1,2,,
方小敏^1,2,3,
AlbertGaly⁴,
杨戎生^2,3,4
1. 中国科学院青藏高原地球科学卓越创新中心, 北京 100101
2. 中国科学院青藏高原研究所, 大陆碰撞 与高原隆升重点实验室, 北京 100101
3. 中国科学院大学, 北京 100049
4. Centre de Recherches Pétrographiques et Géochimiques(CRPG), CNRS-Université de Lorraine, Nancy 54501, France

基金项目: 国家自然科学基金项目（批准号：41402156和41620104002）和中国科学院国际合作局对外合作重点项目（批准号：131C11KYSB20160072）共同资助


详细信息

作者简介: 杨一博, 男, 32岁, 副研究员, 第四纪地质学专业, E-mail:yangyibo@itpcas.ac.cn

中图分类号: P594;P532;P534.63

收稿日期:2017-09-22
修回日期:2017-11-13
刊出日期:2018-01-30

Quaternary climate change and catchment weathering in the western Qaidam Basin

Yang Yibo^1,2,,
Fang Xiaomin^1,2,3,
Albert Galy⁴,
Yang Rongsheng^2,3,4
1. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101
2. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101
3. University of Chinese Academy of Sciences, Beijing 100049
4. Centre de Recherches Pétrographiques et Géochimiques(CRPG), CNRS-Université de Lorraine, Nancy 54501, France


MSC: P594;P532;P534.63

--> Received Date: 22 September 2017
Revised Date: 13 November 2017
Publish Date: 30 January 2018


摘要
摘要:长期以来关于构造隆升、气候变化和大陆化学风化的相互关系存在诸多争议。在气候和构造相互作用典型区域建立高精度大陆化学风化序列是解决上述科学问题的有效途径之一。位于青藏高原东北缘长期封闭的柴达木盆地，其独特的位置和连续的沉积使其成为研究构造隆升、气候变化和大陆化学风化的理想场所。本文以柴达木盆地西部千米深钻SG-1钻孔高质量的连续细粒湖相岩芯为研究对象，使用盐类矿物的硫酸根和钾离子含量、碳酸盐锰含量和硅酸盐化学蚀变指数（CIA）和Nd同位素分析，重建该区第四纪以来湖泊流域气候变化过程和硅酸盐化学风化及可能的物源变化。结果表明柴达木盆地西部第四纪以来流域物源相对稳定，流域整体呈现出气候干旱化、流域硅酸盐风化强度减弱、湖水盐度增加和湖面降低的长期一致性演化过程；上述演化进程在2.2 Ma到2.0 Ma期间短暂加强，在约1.2 Ma和约0.6~0.5 Ma出现逐步加强趋势。过去60万年，柴达木盆地西部在冰期存在的相对高湖面时期与黄土高原粒度指标反映的冬季风减弱阶段可以很好对比。北大西洋海表温度反映的高纬过程是长时间尺度（>10⁵年）驱动柴达木盆地西部气候变化和流域硅酸盐风化强度变化的主要因素；西伯利亚高压系统和西风系统的"跷跷板关系"可能是冰期-间冰期或者更短尺度影响柴达木盆地西部气候变化的主要因素。
关键词: 青藏高原/
湖泊沉积/
化学风化/
蒸发盐/
碳酸盐

Abstract:The Qaidam Basin on the northeastern part of the Tibetan Plateau provides a good opportunity for investigating the relationships between tectonic uplift, climate change and continental chemical weathering, due to the unique location and continuous deposits. A Sino-German research team has carried out a joint scientific drilling program in the depocenter of the Chahansilatu subbasin (38°24'35.3″N, 92°30'32.6″E) in the western Qaidam Basin. The deep drilling core (SG-1) (938.5 m in depth)is characterized by high-quality continuous fine-grained lacustrine sediments with an average recovery of ca. 95%. Combined with previously reported acetic acid-dissolved manganese (Mn)records this study uses the new 722 evaporite sulfate and potassium ions data, and 239 chemical alternation index (CIA)and 20 Nd isotopes data in acid-residues of the SG-1 core sediments, to reconstruct the regional catchment climate change, silicate chemical weathering, and to explore further their influence factors during the Quaternary period.
ε_Nd values in acid-residues vary between -9 and -10.5, show a stable secular trend, suggesting a nearly stable provenance in the paleo-lake catchment. The CIA values in acid-residues range from 54 to 72 with a mean of 65, indicating a moderate-weak catchment silicate weathering intensity. The CIA record exhibits a long-term decrease trend with a short low stage between 2.2~2.0 Ma, and two accelerating shifts at ca. 1.2 Ma and 0.6~0.5 Ma. The CIA variation is quite similar with those of sulfate ion and acetic acid-Mn as well as the reconstructed lake level change, collectively suggesting a coupled long-term evolution between the catchment and lake. The catchment-lake system displays long-term catchment climatic aridification, weakened silicate weathering, lake salinity increase and lake level decline, with a short enhancement period between 2. 2~2. 0 Ma and two obvious stepwise enhancement stages starting at ca. 1. 2 Ma and ca. 0. 6~0. 5 Ma, respectively. On a longer timescale (>10⁵ years), the reconstructed climate change and silicate weathering intensity in the western Qaidam Basin can correlate well with North Atlantic Ocean sea surface temperature, suggesting that global cooling, especially cooling in high latitudes of the Northern Hemisphere, through regulating moisture in the Westerlies, exerts a dominate control on the paleolake evolution in the western Qaidam Basin. On a glacial-interglacial timescale, the region's climate also correlates closely with East Asian Winter Monsoon activity as recorded by the grain size variations in loess-paleosol sequences on the Chinese Loess Plateau. In particular, during glacial periods, some relatively warm/humid stages accompanied by high paleo-lake levels in the western Qaidam Basin are generally conformable with relatively weak East Asian Winter Monsoon, but exhibit less relations with marine benthic oxygen isotopes, North Atlantic Ocean sea surface temperature and East Asian Summer Monsoon. These observations collectively provide evidence that climate change in the western Qaidam Basin is, and was, not only controlled by the Westerlies, but also strongly influenced by the Siberian High, at least during glacial periods. The potential driving mechanisms may be a direct injection of cold air masses linked with an enhanced Siberian High into the basin through low altitude mountain passes (ca. 3000 m)particularly during glacials/stadials, or an indirect influence of the Siberian High on the moisture content of the Westerlies, and/or the position of the Westerly jet stream. The spatio-temporal impact of the Siberian High now needs to be assessed further across the northern Tibetan Plateau.
Key words:Tibetan Plateau/
lacustrine sediments/
chemical weathering/
evaporite/
carbonate



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