董楠^1,3,,
朱立平^1,2,3,,,
陈浩¹,
鞠建廷¹,
彭萍¹,
王君波^1,2,3,
许腾^1,3
1. 中国科学院青藏高原研究所青藏高原地表过程与环境变化实验室, 北京 100101
2. 中国科学院青藏高原地球科学卓越创新中心, 北京 100101
3. 中国科学院大学, 北京 100049

基金项目: 第二次青藏高原综合科学考察研究项目（批准号：2019QZKK0202）、国家自然科学基金重点项目（批准号：41831177）和中国科学院（A类）战略性科技先导专项项目"泛第三环极境变化与绿色丝绸之路建设"（批准号：XDA20020100）共同资助


详细信息

作者简介: 董楠, 女, 25岁, 硕士研究生, 湖泊沉积与环境变化研究, E-mail: dongnan@itpcas.ac.cn

通讯作者: 朱立平, E-mail: lpzhu@itpcas.ac.cn

中图分类号: P426.6;P941.78

收稿日期:2020-11-28
修回日期:2021-01-16
刊出日期:2021-03-30

Climate changes of past 13000 years based on Ostracod in Chibuzhang Co, Tibetan Plateau

DONG Nan^1,3,,
ZHU Liping^1,2,3,,,
CHEN Hao¹,
JU Jianting¹,
PENG Ping¹,
WANG Junbo^1,2,3,
XU Teng^1,3
1. Key Laboratory of Tibetan Plateau Environment Changes and Land Surface Process, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101
2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101
3. University of Chinese Academy of Sciences, Beijing 100049


More Information

Corresponding author: ZHU Liping,E-mail:lpzhu@itpcas.ac.cn

MSC: P426.6;P941.78

--> Received Date: 28 November 2020
Revised Date: 16 January 2021
Publish Date: 30 March 2021


摘要
摘要:了解印度季风和西风对该区环境的影响程度及变化历史对认识青藏高原与全球变化的关系具有重要意义。本研究以青藏高原中部赤布张错湖泊5.48 m沉积岩芯中的介形虫为研究对象，利用介形虫属种和丰度变化以及介壳δ¹⁸O、δ¹³C、Mg/Ca和Sr/Ca等环境代用指标，重建晚冰期末期以来的湖泊环境与气候变化历史。研究表明，赤布张错近13 cal.ka B.P.的环境与气候变化历史分为3个阶段：阶段Ⅰ为13.0~9.2 cal.ka B.P.，白玻璃介出现较多，介壳δ¹⁸O、δ¹³C为高值，具有气候相对温暖、湖泊由降水补给为主转为融水为主的变化特征，其中，12.3~11.1 cal.ka B.P.低水位指示的寒冷干旱反映了本区对Younger Dryas事件的响应；阶段Ⅱ为9.2~4.4 cal.ka B.P.，湖泊由以降水补给为主的相对温暖的浅水状态，转向以冰川融水补给为主的温凉状态，水深逐渐加大，该阶段的4个亚阶段分别为9.2~7.7 cal.ka B.P.、7.7~6.8 cal.ka B.P.、6.8~5.4 cal.ka B.P.和5.4~4.4 cal.ka B.P.，分别具有浅水下的温暖湿润、温凉湿润、温凉干旱和深水下温凉湿润特征；阶段Ⅲ为4.4 cal.ka B.P.~现在，介壳Mg/Ca指示湖区环境出现相对剧烈的波动，总体上为高湖面状态，呈现温暖-寒冷-温暖的变化特征。与青藏高原的其他湖泊环境变化记录相比，赤布张错环境记录反映了西风季风过渡区在晚冰期末期到全新世早期受到季风加强的影响，气候转暖；全新世早期到中期受西风影响更为明显；全新世晚期湖泊水量增加与季风加强下的降水和冰川融水增加均有密切关系。
关键词: 青藏高原/
赤布张错/
介形虫/
同位素和微量元素/
湖泊沉积物/
西风季风过渡区

Abstract:We selected a sediment core of a proglacial lake(Chibuzhang Co) to elucidate the relationships between glacial melt water and lake changes during past 13 ka B.P. period under the interaction between the Westerlies and the Indian monsoon. The Lake Chibuzhang Co(33.31°~33.67°N, 90.01°~90.43°E; 4941 m a.s.l.) is located in the transition zone between the Westerlies and the Indian monsoon domains of the central Tibetan Plateau. According to the field investigation in 2016, the maximum water depth of Chibuzhang Co is 116.3 m, its surface area is 575.4 km², pH is 9.13, surface temperature is 5℃, conductivity is 7954.6 μS/cm, and dissolved oxygen is 6.26 mg/L. The annual average air temperature is approximately -4.0℃, and the annual precipitation is about 500 mm. The lake is mainly supplied by glacial melt water from the glaciers in the eastern part of the basin, and may be connected to its neighbor lake(Duoersuodong Co) through a narrow channel under the high lake level periods.
The sediment core with a length of 5.48 m, named CBZLC16-1, was retrieved by a PISTON corer in the water depth of 60 m in the center of Chibuzhang Co in 2016. Sedimentological chronology based on AMS ¹⁴C and ²¹⁰Pb dating showed that the bottom age was about 12.7 cal.ka B.P. In this study, samples of 5 cm intervals were used to analyze Ostracod assemblage and shell δ¹⁸O, δ¹³C, Mg/Ca and Sr/Ca from core CBZLC16-1. Results showed that two Ostracod species, Leucocythere dorsotuberosa and Candona candida, in the samples, and L. dorsotuberosa dominate throughout the core. The total abundance is 0~4valves/g between 13.0 cal.ka B.P. and 9.2 cal.ka B.P., then increases to the highest level between 9.2 cal.ka B.P. and 4.4 cal.ka B.P., reaching about 550 valves/g. From 4.4 cal.ka B.P. to present, the abundance fluctuates at low level. Shell δ¹⁸O ranges from -5.95‰~0.08‰, with an average value of -3.94‰; shell δ¹³C ranges from -0.29‰~1.92‰, with an average value of 0.71‰; shell Mg/Ca ranges from 0.001~0.174, with an average value of 0.042; and shell Sr/Ca ranges from 0.011~0.025, with an average value of 0.019.
The environmental changes of past 13 cal.ka B.P., based on our results, is divided into three stages: Stage Ⅰ: 13.0~9.2 cal.ka B.P., presence of C.candida and high value of shell δ¹⁸O and δ¹³C indicated that the lake area was relatively warm and the main lake water supplies changed from precipitation to glacial-melt water. In between, an interval of 12.3~11.1 cal.ka B.P. characterized by cold and dry status was the response of Younger Dryas Event in this area. Stage Ⅱ: 9.2~4.4 cal.ka B.P., the lake changed from a warm and shallow water status mainly supplied by precipitation to a cool and deep water status mainly supplied glacial melt water. It can be further divided into four sub-stages: Ⅱ-1, 9.2~7.7 cal.ka B.P., shallow lake with warm and wet climate; Ⅱ-2, 7.7~6.8 cal.ka B.P., low lake level with cool and wet climate; Ⅱ-3, 6.8~5.4 cal.ka B.P., still shallow lake with cool and dry climate; and Ⅱ-4, 5.4~4.4 cal.ka B.P., cool and wet climate under deep lake condition. Stage Ⅲ: 4.4 cal.ka B.P.~present, the lake level was high, while relatively drastic fluctuations of lake environment was indicated from Ostracod Mg/Ca in Chibuzhang Co, showing a trend from warm to cold and to warm climate. Compared with other lake records in different areas of TP, the environmental records of Chibuzhang Co reflected that the climate was warm and the monsoon was enhanced in the transition zone between the Westerlies and the Indian monsoon from Late Glacial to Early Holocene. From Early Holocene to Middle Holocene, the Westerlies was obviously dominant in this transition zone, while in the Late Holocene the increased lake water level of Chibuzhang Co and other lakes were closely related to the increase in precipitation and glacial-melt water under the enhancing of the Indian monsoon.
Key words:Tibetan Plateau/
Chibuzhang Co/
Ostracod/
isotope and trace element/
lake sediment/
transition zone between the Westerlies and Indian monsoon



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