王海粟,
党皓文,
翦知湣^,
同济大学海洋地质国家重点实验室, 上海 200092

基金项目: 国家自然科学基金项目(项目号：41630965和41606049)和(原)国家海洋局“全球变化与海气相互作用”专项项目(批准号：GASI-GEOGE-04)共同资助


详细信息

作者简介: 王海粟, 女, 24岁, 硕士研究生, 海洋地质专业, E-mail:hiso@tongji.edu.cn

通讯作者: 翦知湣, E-mail:jian@tongji.edu.cn

中图分类号: P722.7;P736.2;P534.63⁺1

收稿日期:2018-11-20
修回日期:2019-01-15
刊出日期:2019-03-30

Variations in the upper water structure of northern South China Sea during the mid-Pleistocene Climate Transition Period: Planktonic foraminifera oxygen isotope records of ODP site 1146

Wang Haisu,
Dang Haowen,
Jian Zhimin^,
State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092



More Information

Corresponding author: Jian Zhimin,E-mail:jian@tongji.edu.cn

MSC: P722.7;P736.2;P534.63⁺1

--> Received Date: 20 November 2018
Revised Date: 15 January 2019
Publish Date: 30 March 2019


摘要
摘要:文章以南海北部ODP1146站沉积物岩芯为研究材料, 利用浮游有孔虫次表层水种Pulleniatina obliquiloculata壳体的氧、碳稳定同位素, 结合该站位浮游及底栖有孔虫氧碳同位素数据, 分析中更新世以来南海北部上层水体结构的演化。1.2 Ma以来ODP1146站P.obliquiloculata壳体δ¹⁸O的变化可分3个阶段：1)1.2~0.9 Ma, 冰期-间冰期变化幅度较小、主导周期为41 ka斜率周期；2)0.9~0.6 Ma, 冰期旋回变化幅度逐渐增强、100 ka偏心率周期开始强化；3)0.6 Ma以来, 冰期旋回呈现稳定且幅度较大的100 ka周期变化。0.9 Ma以来南海北部上层海水δ¹⁸O的冰期旋回变幅增强, 可能反映东亚冬季风在0.9 Ma之后显著强化。其中, 表层水体δ¹⁸O只在冰期变幅增强, P.obliquiloculata所反映的次表层水体δ¹⁸O的变化幅度在冰期和间冰期都显著增强。约0.9 Ma浮游和底栖有孔虫δ¹⁸O的100 ka周期几乎同时显现；但在0.9~0.6 Ma时期P.obliquiloculata的δ¹⁸O偏心率周期更为显著、斜率周期的强度也更高。因此, 冰期旋回周期转型及幅度变化两方面的证据共同反映温跃层结构演化在南海北部中更新世转型(MPT)气候转变过程中的特殊性。1.2 Ma以来ODP1146站P.obliquiloculata的δ¹³C在0.02 Ma、0.49 Ma和0.99 Ma左右呈明显的碳重值, 同时表层种-次表层种之间的δ¹³C差值减小到近于0, 可以解读为碳重值事件期间南海北部生产力相对减弱。
关键词: 中更新世气候转型/
温跃层/
浮游有孔虫/
同位素/
南海北部

Abstract:The mid-Pleistocene Transition (MPT), during 1.2~0.7 million years ago (Ma), marks a critical time when the Glacial-cycles changed from a 41-ka-cycle dominated low-amplitude mode to a 100-ka-cycle dominated high-amplitude mode.Climate changes during MPT are believed to be associated with processes including glacial intensification, carbon-cycle reorganization, ocean-circulation variation, as well as tropical sea-air feedbacks.However, studies about the changes in the behavior and mechanisms of tropical ocean thermocline are relatively short.To reconstruct and explore the mid-to Late-Pleistocene changes in the upper-water structure of northern South China Sea (SCS), here we analyzed the oxygen and carbon isotopes of Pulleniatina obliquiloculata, a sub-surface dwelling planktonic foraminifer, from the sediment records of site 1146 (19.46°N, 116.27°E; 2092 m depth)recovered during the Ocean Drilling Program (ODP)Leg 184.In this work, a total of 223 samples of sediments between 9.80~140.17 m, deposited during about 4~1200 ka from ODP Site 1146 were analyzed.The overall trend of P.obliquiloculata δ¹⁸O of ODP1146 shows step-wise variations: (1)1.2~0.9 Ma, the amplitude of glacial-interglacial was relatively small (ca.0.75 ‰)with a dominant cycle of 41 ka; (2)0.9~0.6 Ma, the amplitude gradually increased with strengthening 100 ka eccentricity cycle; (3)0.6~0 Ma, the glacial cycle further increased to an amplitude of ca.1.25 ‰ with a dominant 100 ka periodicity.Compared with Globigerinoides ruber δ¹⁸O and benthic foraminifera δ¹⁸O, we have found that the amplitude of surface water δ¹⁸O only increased during interglacial, but the subsurface water δ¹⁸O amplified during both glacial and interglacial.The subsurface water δ¹⁸O increased from approximately -0.79‰ to -1.04‰ in the interglacial and -0.06 ‰ to 0.2 ‰ in the glacial during MPT.These phenomena may be associated with the strengthening of the East Asian winter monsoon since 0.9 Ma.The eccentricity cycle started to show at the same time of ca.0.6 Ma in all planktonic and benthic foraminifera δ¹⁸O while it was weaker in those of G.ruber and benthic foraminifer, and the obliquity and eccentricity cycles are significant in the δ¹⁸O of P.obliquiloculata during 0.9~0.6 Ma.Both evidences of periodicity transition and amplitude intensification of glacial cycles indicates the special role played by changes in the thermocline structure during the Mid-Pleistocene climate transition in the northern SCS.In addition, the δ¹³C of P.obliquiloculata shows obvious maxima in 0.02 Ma, 0.49 Ma and 0.99 Ma, consistent with the δ¹³C maximum events observed in other records.The difference between surface and subsurface foraminiferal δ¹³C reduced to near 0 during the δ¹³C maximum events, probably suggesting weakened productivity in response to the δ¹³C maximum events.
Key words:mid-Pleistocene climate transition/
thermocline/
planktonic foraminifera/
stable isotopes/
northern South China Sea



PDF全文下载地址:

http://www.dsjyj.com.cn/data/article/export-pdf?id=dsjyj_11596