【作者】 孙晗杰；

【导师】 李铁刚； 于心科；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质学， 2011， 博士

【摘要】 本论文基于IMAGES XIV MD155-Marco Polo 2航次MD06-3050岩芯(15°57.0943′N, 124°46.7747′E,水深2967 m)的浮游有孔虫氧碳同位素,沉积物中碳酸盐含量,钙质超微化石特征种属相对丰度等古环境替代指标,讨论了西菲律宾海2.36 Ma以来的古海洋学变化特征。MD06-3050岩芯浮游有孔虫G.ruber的氧同位素记录与LR04标准氧同位素曲线进行对比,建立了西菲律宾海2.36 Ma以来的年代模式。几个钙质超微化石及有孔虫地层学事件验证了氧同位素年代的可靠性。应用MD06-3050岩芯和MD06-3047岩芯进行第四纪钙质超微化石地层学研究,识别了7个钙质超微化石地层学事件,分别是Discoaster Brouweri的末现, Calcidiscus macintyrei的末现, Large Gephyrocapsa的初现, Large Gephyrocapsa的末现, Pseudoemiliania lacunosa的末现, Gephyrocapsa Caribbeanica的快速增长,以及Emiliania huxleyi的初现。结果表明钙质超微化石地层学在西菲律宾海区的应用具有可靠性,为西太海区第四纪氧同位素地层学提供了可靠的年代控制点。在MD06-3050岩芯中发现了澳亚散落区微玻陨石的分布。通过氧同位素地层学校正,得到了天外物体撞击事件发生时间大约在794±2 ka,与其它海区该微玻陨石发生时间具有一致性。浮游有孔虫表层种G.ruber和次表层种P.obliquiloculata的氧同位素差值显示了2.36Ma以来西菲律宾海温跃层具有长期的变动特征。而颗石藻下透光带种属Florisphaera profunda则用来指示1040 ka以来该海区营养跃层的冰期/间冰期变化特征,且在中布容事件前后呈现相反的变动趋势。温跃层/营养跃层变动的最大特征是MIS13之后,两者呈现不同步。对浮游有孔虫G.ruber和P.obliquiloculata的氧碳同位素进行滤波分析,其结果显示了中更新过渡时期(MPT)的周期转型特征。根据有孔虫氧碳同位素记录及碳酸盐百分含量等指标,认为MPT大约开始于1.0 Ma。各替代性指标在MPT的记录说明了该时期气候系统发生深刻变化,且该研究进一步表明MPT为一个过渡性的气候时期,而非快速变化的气候事件。另外,δ13C和碳酸盐含量的变化在MPT时期领先于上部水体结构变动。沉积物中碳酸盐百分含量在冰期高,而在间冰期低。应用浮游有孔虫碳同位素差值作为古生产力替代指标,表明冰期时生产力高而间冰期生产力低。有孔虫碎壳率和大于63μm粗组分指示溶解作用在冰期弱而在间冰期强。因此,认为该海区的碳酸盐变化呈现太平洋型旋回,主要受到溶解作用和生产力的共同控制。有孔虫次表层水种P.obliquiloculata碳同位素重值现象叠加于冰期-间冰期旋回之上,显示了第四纪以来的长周期性。对比MD06-3050岩芯与其它海区岩芯的δ13C记录,识别了六次重大的全球范围内δ13C重值事件。值得注意的是,这六次δ13C重值事件恰好同碳酸盐含量快速降低以及强烈的溶解条件相对应,推断全球碳库相对应发生了重大改变,且碳库变动可能与全球气候变化有关。更多还原

【Abstract】 This thesis discusses paleoceanography of the Western Philippine Sea over the last 2.36 million years on the basis of stable oxygen and carbon isotopes on planktonic foraminifers (δ13O andδ13C), bulk carbonate content and calcareous nannofossil assemblages from IMAGES XIV MD155-Marco Polo 2 cruise.Based on theδ18O of the planktonic foraminifer G.ruber, a 2.36 Ma timescale for the West Phillipine Sea was established through visual alignment to LR04. The age of several calcareous nannofossil bioevents and one foraminiferal bioevent agreed with the age model.Two sediment cores MD06-3050 (15°57.0943′N, 124°46.7747′E, 2967 m) and MD06-3047 (17°00.44′N, 124°47.93′E) recovered in the Benham Rise, east off Luzon Island in the Western Philippine Sea, were analyzed to study the Quaternary calcareous nannofossil records based on oxygen isotope stratigrapy. 7 calcareous nannofossil bioevents were identified over the past 2.36 Ma: LAD of Discoaster Brouweri, LAD of Calcidiscus macintyrei, FAD of Large Gephyrocapsa, LAD of Large Gephyrocapsa, LAD of Pseudoemiliania lacunosa, abrupt increase in the abundance of Gephyrocapsa Caribbeanica, and FAD of Emiliania huxleyi. The results suggested that calcareous nannofossil stratigraphy was reliable in the Western Philippine Sea, hence provided the proper age control points in building Quaternary oxygen isotope stratigraphy in the Western Pacific. In addition to, we observed that Australasian microtektites were distributed in the core MD06-3050, with maximum abundance in the layer 1364-1366 cm. Calibrated with the oxygen isotope stratigraphy, the average age for layer of 1360-1366 cm was 794±2 ka, which was deemed to microtektites occurred time. It was concurrent with Australiasian microtektites events dated in other regions.Oxygen isotopic differences between G. ruber and P. obliquiloculata demonstrate the upper ocean thermocline variations of the Western Philippine Sea during the Pleistocene. And the relative abundance of lower-photic layer coccolith species, Florisphaera profunda, were be used to construct the nutricline changes since 1040 ka.The variations ofΔδ18O indicated that thermocline changed in long term cycles over the past 2.36Ma. Nutricline showed two evolution patterns before and after MBE. The notable feature in the upper water structure was not changed in phase since MIS13. The filter analysis of both oxygen and carbon isotope in shells of planktonic foraminifera demonstrates the existence of the mid-Pleistocene transition (MPT). The event appears to start at about 1.0 Ma suggested by theδ18OG.ruber,δ18OP.o,δ13CG.ruber,δ13CP.o, bulk carbonate content, indicating its impacts on these climatic variables as a system. Accordingly, the transition of the dominant climatic cycles at ~1Ma can be interpreted as a stepwise but not an abrupt process. Futhermore, changes ofδ13C, CaCO3% lead the shift of upper water structure during the MPT.Carbonate content in bulk show high values during glacial period and low values in the interglacial. Carbon isotope differences between G. ruber and P. obliquiloculata demonstrate was used as paleoproductivity (PP) proxies in the study area, which suggested that the productivity was high in glacial and low in interglacial. Both the planktonic foraminifera fragments ratio and >63μm coarse fraction indicated the dissolution was more intense during interglacial periods than in glacial interval. So, we considered that the preservation of carbonate as Pacific Pattern, which was controled by dissolution and PP.δ13CP.O peaks in different periods suggest that shift is independent from G-IG clycle, so show the long term cycles since the Pliocene. Comparison of the foraminiferalδ13C of core MD06-3050 with other cores records in different basins, we recognized sixδ13Cmax events in the study core. It’s worthy noting that theδ13Cmax event coincided with the abrupt decreasing carbonate content and the intensely dissolution condition, so we infered that global carbon reservoir was changed obviously and linked to large climate changes.更多还原