热带西太平洋边缘晚第四纪以来的古环境研究

IOCAS-IR > 海洋环流与波动重点实验室

	热带西太平洋边缘晚第四纪以来的古环境研究
其他题名	Paleoenvironment evolution in the margin region of tropical western Pacific during the late Quaternary
	赵京涛
学位类型	博士
	2007-06-08
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	黑潮源区西太平洋暖池碳酸盐旋回钙质超微化石氧碳同位素 Enso 上层海水结构古生产力太阳活动东亚夏季风
摘要	利用取自热带太平洋边缘的5个柱状岩芯Ph05-5、WP3、MD2908、Z14-6和WP7，通过对其微体古生物和生物地球化学成分的分析，结合浮游有孔虫氧、碳同位素数据、AMS14C测年结果和已有的研究资料，分别研究了热带西太平洋边缘晚第四纪以来的钙质超微化石群落特征、碳酸盐旋回、超微化石氧碳同位素特征、古生产力和上层海水结构演化以及高分辨率东亚夏季风指标，并探讨了碳酸盐旋回、古生产力和上层海水结构演化、全新世东亚夏季风强弱变化的控制机制，以及钙质超微化石下透光带属种Florisphaera profunda的相对百分含量变化在热带太平洋边缘的古环境指示意义及不同环境条件下的控制机制。西菲律宾海Ph05-5岩芯和台湾东南部WP3岩芯中CaCO3和钙质超微化石碳酸盐溶解指数、初级生产力指标的变化显示约190 kyr BP以来CaCO3含量整体上都表现为冰期高、间冰期低的“太平洋型”旋回特征，但菲律宾以东海区在末次冰期（MIS 4~2期）内部又显示出间冰段含量高、冰段含量低的“大西洋型”旋回特征。碳酸盐旋回的主要控制因素在菲律宾以东海区是碳酸盐溶解作用，而台湾东南海区则是初级生产力变化引起的钙质生物输入量的波动。西菲律宾海Ph05-5岩芯中190 kyr BP以来的钙质超微化石δ18O值在末次间冰期（MIS 5e）和全新世明显低于末次冰期（MIS 5d~2）和倒数第二次冰期（MIS 6）。超微化石δ18O值与浮游和底栖有孔虫δ18O值都呈明显的正相关关系，但是超微化石的δ18O平均值重于表层浮游有孔虫Globigeriniodes rubber，轻于中层Neogloboquadrina dutertrei。超微化石δ13C值变化与其绝对丰度变化表明西菲律宾海区大约在MIS 6和MIS 5e期，表层海水初级生产力相当稳定且显著低于其它各时期；约从MIS 5d期开始表层初级生产力显著上升，并一直持续到末次冰期；在MIS1、2期，表层初级生产力有所下降，但仍高于MIS 6和MIS 5e期。 Ph05-5岩芯中钙质超微化石下透光带属种F. profunda相对百分含量和浮游有孔虫转换函数的温跃层深度变化表明西太平洋暖池北缘约190 kyr BP 以来，营养跃层和温跃层冰期（MIS 6期和5d~2期）浅，间冰期（MIS5e）和全新世深，MIS5e期是最近两个冰期旋回中营养跃层和温跃层深度最深的时期。F. profunda百分含量初级生产力转换方程计算结果和与钙质超微化石绝对丰度的变化显示冰期初级生产力高，间冰期和全新世初级生产力低， MIS5e期初级生产力最低。此外，Δδ13C C. wullerstorf-coccolith和Δδ13C C. wullerstorf-N. dutertrei差值的变化也说明190 kyr BP以来冰期表层输出生产力高于间冰期，其中最为突出的特征也是MIS5e期为生产力输出的最低值期。上层海水结构和生产力的上述变化特征与现代La Niňa事件爆发时的海洋环境相当类似，该海区MIS5e期可能是La Niňa事件频繁爆发的一段时期，可以与现代La Niňa现象类比。同时，根据Wyrtki提出的信风张弛理论推测MIS5e期，由于La Niňa事件的频繁爆发黑潮主流应该是增强的。热带西太平洋暖池核心区WP7岩芯中250 kyr BP以来的初级生产力在间冰期明显低于冰期，间冰期生产力相对稳定，冰期(MIS6，4和2)生产力升降幅度较大；冰期向间冰期过渡的冰消期内生产力的降低是相对缓慢的，而间冰期向冰期过渡时生产力的增加是迅速的。初级生产力指标的交叉频谱分析显示出偏心率、斜率、岁差（半岁差）、30kyr和50kyr周期。说明暖池区晚第四纪以来古生产力变动除了受全球冰量变动控制以外，低纬区的岁差驱动也是主要控制因子。约250 kyr BP以来古生产力的变化与Vostok冰心的CO2记录在30kyr周期上高度相关，低CO2值与高生产力相对应，印证了大洋初级生产力在全球碳循环中扮演了重要的“吸收者”的角色，30kyr周期是赤道太平洋地区生物生产力ENSO式变化特征的体现，这也证明了低纬地区生物泵在控制大气CO2浓度方面的重要作用。另外，在岁差周期段，底栖有孔虫U+B含量和N. dutertrei δ13C代表的生产力变动领先于有孔虫δ18O代表的冰体积变化约2.6~7kyr（0.5kyr,2.6 kyr,4.2 kyr, 7kyr），表明在千年时间尺度上日射是该区生产力变化的直接驱动力，两极冰体积变化（δ18O）没有明显的影响低纬气候波动。对热带西太平洋边缘海区WP7、Ph05-5、WP3和Z14-6四个岩芯中晚第四纪以来超微化石下透光带属种F. profunda相对百分含量变化进行横向对比研究表明，F. profunda百分含量分布并非简单受水深控制，而是由海水上层复杂的生态因素所决定；F. profunda相对百分含量变化曲线与浮游有孔虫N. dutertrei氧同位素曲线呈不同程度的相关性，N. dutertrei 氧同位素越轻，对应的F. profunda相对百分含量越高；冲绳海槽中部的Z14-6岩芯中F. profunda相对含量变化的主控因子是黑潮流的强弱变化；WP7和Ph05-5两个岩芯中F. profunda相对含量变化与低纬地区暖池变化特征密切相关。 6800 yr BP以来台湾东北部MD2908岩芯中F. profunda相对百分含量变化与太阳黑子数量呈明显的反相关关系，而且3700 yrBP以来更为明显。由于F. profunda相对百分含量变化与该地区东亚夏季风引起的降雨量密切相关，所以推测6800 yr BP以来东亚夏季风受太阳活动影响，其中的纽带是IZCT的纬向位置变动。
其他摘要	Cores Ph05-5, WP3, MD2908, Z14-6 and WP7, retrieved from the tropical Western Pacific margin region, respectively, are used to reconstruct CaCO3 cycle, oxygen and carbon stable isotopic character of calcareous nannofossils, paleoproductivity and upper water structure changes of the tropical Western Pacific margin region during the late Quaternary (~250-0 kyr BP)based on a multi-proxy approach including micropaleontological and geochemical proxies, combined with detailed AMS14C dates, stable isotope and other data acquired by previous studies. Two deep sea cores Ph05-5 and WP3 retrieved from the western Philippine Sea and Southeast of Taiwan respectively were selected to carry out the CaCO3 and calcareous nannofossil faunas study during the last 190 kyr BP. The carbonate contents showed higher values in the glacial periods and lower during the interglacial and Holocene periods, which characteristics was similar to the tendency of “Pacific Type” carbonate cycle. However, there were high carbonate contents in the warm period and low values during the cold interval, which displayed the same tendency with the “Atlantic Type” carbonate cycle during the last glacial period (MIS4-2) in the east of Phillipines. The variations of primary productivity and carbonate dissolution index indicated that the carbonate dissolution was a major factor controlling the carbonate content in the east of Philippines, and the variations in carbonate contents were mainly affected by the productivity of calcareous organism in the Southeast of Taiwan. The “Atlantic Type” carbonate cycle in the east of Phillipines during the last glacial period (MIS4-2) was an effect of the process of dissolution combined with the change of primary productivity. The δ18O and δ13C values of calcareous nannofossils have been analyzed for the core Ph05-5. The δ18O values of calcareous nannofossils were obviously lower in Holocene and the last interglaciation than those in the last and the penultimate glaciation. The nannofossil δ18O values during the last 190 kyr BP were positively correlated with those of planktonic and benthic foraminifera from the same core. But the average δ18O value of nannofossils was higher than that of planktonic foraminifera Globigeriniodes ruber and was lower than that planktonic foraminifera Neogloboquadrina dutertrei, all which were much lower than that of benthic foraminifera Cibicides wullerstorfi. The similar trends for δ13C records and absolute abundance of calcareous nannofossils in core Ph05-5 corporately reflected the primary productivity variations in the western Philippine Sea. The primary productivity kept a stable but relatively low station at MIS 6 and MIS 5d. There was an abrupt rise at the beginning of MIS 5d for the primary productivity which retains high until the end of MIS 3. The prinary productivity showed a slight decline during MIS 2 and MIS 1, but still higher than that of MIS 6 and MIS 5. The deep sea core Ph05-5 was selected to carry out calcareous nannofossil and foraminifera study. Based on nannofossil and foraminifera indexes, the variations of upper water structure and paleoproductivity were reconstructed and its control factors and paleoceangraphy implications were discussed in this region during the last 190 kyr BP. The down core changes of Florisphaera profunda percentage content and DOT (depth of thermocline) estimated using planktonic foraminifera transfer function inferred that the nutricline and thermocline were shallower in glacial periods (MIS 6 and 5d~2) and deeper in interglacial periods (MIS 5e and Holocene), and the nutricline and thermocline shown the deepest depth in the MIS 5e during the last two glacial cycles. On a glacial-interglacial time scale, the primary productivity variations calculated from F. profunda conversion equation showed that the primary productivity was higher in glacial periods and lower in interglacial periods. Similarly, the lowest primary productivity appeared at MIS5e, which could be confirmed by the variations of absolute abundance of calcareous nannofossils. The δ13C difference between benthic foraminifera Cibicides wullerstorfi and calcareous nannofissils (Δδ13CC. wullerstorf-coccolith), and the δ13C difference between benthic foraminifera C. wullerstorfi and planktonic foraminifera Neogloboquadrina dutertrei (Δδ13CC. wullerstorf-N. dutertrei) both clearly showed that the lower export productivity in interglacial periods and the higher in glacial periods. Also, the export productivity is remarkable low during MIS 5e. The paleoproductivity and upper water structure characters during MIS 5e in core Ph05-5 were consistent with modern La Niňa activity. So, during MIS 5e La Niňa might happen with a high frequency in the northern margin region of WPWP. Furthermore, we presume that the main current of Kuroshio should be intensified during MIS5e based on the trade wind fluctuation theory (Wyrtki, 1975). The productivity indexes based on calcareous nannofossils transfer function and benthic foraminifer’s accumulation rate calculation function showed that the productivity was higher in glacial periods than interglacial periods in the WPWP during MIS 7 which was confirmed by the abundance and accumulation rate of benthic foraminifera, and the productivity was relatively stable during interglacial periods (MIS7, 5, 3 and the Holocene) than during glacial periods (MIS 6, 4 and 2). The decreases of productivity from glacial to interglacial were relatively slower than the increases from interglacial to glacial. Cross-spectral analyses of the two productivity proxies (U+B and N. dutertrei δ13C) showed obvious 100kyr, 41kyr and 23 (19) kyr periods, which indicated that the ice volume changes and the precession drive of the low latitude were both the controlling factors of productivity of WPWP. The paleoproductivity variations reflected by U+B and N. dutertrei δ13C were highly negatively correlated with CO2 concentration recorded in Vostok ice core on 30 kyr period bond during the last 250 kyr BP, which indicated that the primary productivity was the important “absorber” in global carbon cycle, and the 30 kyr period was the exhibition of the ENSO-like oscillation of marine productivity in the Equator Pacific. And, the productivity indexes of U+B and N. dutertrei δ13C led the ice volume variations about 2.6-7kyr (0.5kyr,2.6 kyr,4.2 kyr, 7kyr) on precession bond, which suggested that the sun irradiation was the directed deriver of productivity changes in low latitude region on millennial time scales. Cross-spectral analyses between productivity proxies (U+B and δ13C) and planktonic foraminifera 18O indicated highly significant coherence (all>90%) at 51ka period, and we had a hypothesis that the 51ka period was synthesized by 41 and 23ka period (1/23-1/41=1/52), which should attribute to a shift of energy from the 23 period to 51ka modulated by the 41ka period. Based on cross contrasting analysis of relative abundance of F. profunda in core WP7, Ph05-5, WP3 and Z14-6, we had made such conclusion: 1 the relative abundance of F. profunda was controlled by variations of upper water structure; 2 there was similarity between the relative abundance of F. profunda variation and foraminifer’s δ18O curve, and higher abundance corresponding to lighterδ18O; 3 the relative abundance variations of F. profunda in the middle of Okinawa Trough were still mainly controlled by the oscillation of Kuroshio Current based on contrast with core RN89-PC3, RN87-PC4 and KT84-14P1 in Ryukyu Island Arc; 4 the F. profunda relative abundance in core WP7 and Ph05-5 was correlated with WPWP variation. The relative abundance of F. profunda of core MD2908 was negatively correlated with the number of sun macula in northeast of Taiwan during the last 6800 yr BP which was obviously during the last 3700 yr BP. We hypothesized that EASM was mainly controlled by sun activity across the latitude variation of ITCZ based on the correlation between the relative abundance of F. profunda and the number of sun macula.
页数	168
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/375
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	赵京涛. 热带西太平洋边缘晚第四纪以来的古环境研究[D]. 海洋研究所. 中国科学院海洋研究所,2007.

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