| 中更新世转型时期南海北部上层水体结构演化特征——ODP1146站浮游有孔虫稳定同位素记录 |
| |
| 引用本文： | 王海粟,党皓文,翦知湣.中更新世转型时期南海北部上层水体结构演化特征——ODP1146站浮游有孔虫稳定同位素记录[J].第四纪研究,2019,39(2):316-327. |
| |
| 作者姓名： | 王海粟 党皓文 翦知湣 |
| |
| 作者单位： | 同济大学海洋地质国家重点实验室,上海,200092;同济大学海洋地质国家重点实验室,上海,200092;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;原)国家海洋局"全球变化与海气相互作用"专项项目(GASI-GEOGE-04 |
| |
| 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δ^18O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δ^18O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δ^18O只在冰期变幅增强,P.obliquiloculata所反映的次表层水体δ^18O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δ^18O的100 ka周期几乎同时显现;但在0.9~0.6 Ma时期P.obliquiloculata的δ^18O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δ^13C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δ^13C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 |
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 Zhi.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[J].Quaternary Sciences,2019,39(2):316-327. |
| |
| Authors: | Wang Haisu Dang Haowen Jian Zhi |
| |
| Institution: | (State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092) |
| |
| 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.obliquiloculataδ^18O 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 ruberδ^18O and benthic foraminiferaδ^18O,we have found that the amplitude of surface waterδ^18O only increased during interglacial,but the subsurface waterδ^18O amplified during both glacial and interglacial.The subsurface waterδ^18O 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 foraminiferaδ^18O while it was weaker in those of G.ruber and benthic foraminifer,and the obliquity and eccentricity cycles are significant in theδ^18O 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,theδ^13C of P.obliquiloculata shows obvious maxima in 0.02 Ma,0.49 Ma and 0.99 Ma,consistent with theδ^13C maximum events observed in other records.The difference between surface and subsurface foraminiferalδ^13C reduced to near 0 during theδ^13C maximum events,probably suggesting weakened productivity in response to theδ^13C maximum events. |
| |
| Keywords: | mid-Pleistocene climate transition thermocline planktonic foraminifera stable isotopes northern South China Sea |
| 本文献已被 维普 万方数据 等数据库收录！ |
|
