【作者】 路波；

【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， 2010， 博士

【摘要】 为了获得西太暖池核心区的上部水体结构变化记录,考察影响海洋生产力变化的因素,评价西太暖池生产力对大气CO₂含量变化的贡献,选择了西太暖池核心区Ontong Java海台西南部WP7站位柱状样沉积物为材料,进行了对浮游有孔虫G. ruber与N. dutertrei壳体δ¹⁸O、δ¹³C,、Mg/Ca分析和沉积物元素地球化学分析。基于有孔虫G. ruber、N. dutertrei壳体δ¹⁸O、δ¹³C和Mg/Ca,得到了WP7站位一致的上部水体结构变化结果,且与赤道太平洋风尘通量和中赤道太平洋ΔpCO₂密切相关。风尘通量增加时,ΔpCO₂升高,WP7站位的上部水体混合程度增强,初级生产力升高;风尘通量减少时,ΔpCO₂降低,WP7站位的上部水体混合程度减弱,初级生产力降低。推测西太暖池核心区的上部水体结构变化是赤道太平洋海区风场变化的结果,并且控制了WP7站位初级生产力的变化。对G. ruber、N. dutertrei壳体δ¹⁸O、δ¹³C和Mg/Ca进行频谱分析,结果发现存在着强烈的半岁差周期,说明西太平洋暖池核心区的古海洋变化受到赤道和低纬太阳辐射控制。对沉积物元素地球化学组成进行了主成分分析,结果显示,WP7沉积物可分为生源组分、碎屑组分和火山物质。火山物质的输入不仅影响了沉积物的组成,也制约了沉积物内许多元素地球化学指标的应用。推测WP7沉积物内的火山物质主要来源于Ontong Java海台西部和西南部岛弧内的火山活动。沉积物中氧化还原敏感元素的变化特征表明,249.5 kyr B.P.（距今）以来,WP7站位的底层水总体为氧化环境或亚氧化环境,但有一定波动;沉积后埋藏阶段,除表层一段沉积物为氧化性环境外,总体为亚氧化环境,当沉积物中有机碳含量高时环境的还原性更明显。WP7站位沉积物中过剩Ba主要来自生物成因,且未受沉积后氧化还原作用影响,反映了生物泵中离开真光层的颗粒有机碳变化。将过剩Ba与反映了离开真光层的颗粒无机碳变化的CaCO₃作比值,可以得到离开真光层的有机碳与无机碳比例,即沉积雨比例。WP7站位的过剩Ba与CaCO₃比值表明,249.5 kyr B.P.以来,西太平洋暖池核心区的沉积雨比例在冰期时低,通过生物泵过程吸收CO₂的能力弱;而在间冰期时沉积雨比例高,吸收CO₂的能力强。更多还原

【Abstract】 Core WP7, which was recovered from the south west Ontong Java Plateau and the heart area of the West Pacific Warm Pool, was chosen to reconstruct the variation of the upper water column structure, to find out the main reason of the productivity changes and its contribution to Atmosphere CO₂ oscillation. Theδ¹⁸O,δ¹³C, and Mg/Ca of the planktonic foraminifer G. ruber and N. dutertrei were analyzed, with sediments’chemistry analysis also performed.Upper water structure variation based on differences between surface dwelling G. ruber and subsurface dwelling N. dutertrei’s Mg/Ca temperature, seawaterδ¹⁸O and shellδ¹³C show great coherence, which also coincide with equatorial pacific eolian flux and central equatorial pacificΔpCO₂ records. High eolian flux, highΔpCO₂, and WP7 strong mixing of the upper water, high primary productivity appeared at the same time; while low eolian flux, lowΔpCO₂, and WP7 weak upper water mixing, low primary productivity emerged coincidently. It is quite possible that the upper water structure variation in West Pacific Warm Pool results from changes of the equatorial Pacific wind field and determines local primary productivity. By spectrum analysis of G. ruber and N. dutertrei’s shell Mg/Ca,δ¹⁸O andδ¹³C, strong half-precessional cycles exist, demonstrating that solar radiation of equatorial and low latitudes determines the local climate and environment changes.With primary components analysis of the sediments’element composition, layers containing significant amount of tephra were recognized, with detritus and biogenic always exist. The appearance of the tephra indicates that the volcanoes in the west and southwest island arcs off Ontong Java Plateau were once quite active. These tephra dilute the biogenic CaCO₃ and constrain the application of some geochemistry proxies. Behaviours of redox sensitive elements showed that the very up top of the sediment is in oxic environment, most sediments appear in suboxic environments, except some layers containing high amounts of organic carbon shows weak anoxic characteristics.The excess Ba was primarily from biogenic and has suffered no redox effects, indicating that it could be used as a proxy of organic carbon leaving from euphotic zone in biological pump process. With CaCO₃ as the inorganic carbon leaving the euphotic zone, the ratio of excess Ba to CaCO₃ could be used as the rain ratio index, which was high during inter-glacials but low in glacials.更多还原