【作者】 黄杰；

【导师】 李安春；

【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】 本论文通过对南海北部陆坡ODP1148站和ODP1144站两个钻孔岩芯及KNG7站和KNG5站两个重力活塞短柱状沉积物的陆源矿物组成和堆积速率、粘土矿物组成、结晶学特征、微形貌和化学成分、陆源物质粒度、石英氧同位素和微形貌、AMS14C测年和稀土元素的综合研究,分析了ODP1148站34Ma以来的陆源物质来源的演变及南海的演化历史,利用ODP1144站的1.1Ma以来的沉积矿物学记录探讨了其古环境意义,以KNG5和KNG7孔岩芯记录为依据分析了南海北部陆坡18 ka BP以来的海平面升降、东亚夏季风演化、海流形成历史以及蕴含的古气候信息,重建了东亚夏季风自全新世以来的演化历史,并探讨了其可能的驱动机制。南海海盆的演化可以划分为5个大的阶段:即34～28.5,28.5～23,23～16.5,16.5～5和5Ma至今。高陆源组分含量及堆积速率和高石英氧同位素值显示在渐新世南海扩张初期,ODP1148站以近源沉积为主,沉积物主要来源于礼乐-东北巴拉望地块;30Ma以来随着南海扩张,礼乐-东北巴拉望地块不断向南运动,使得ODP1148站陆源组分含量及堆积速率呈现减小趋势,强烈的构造运动使得物理剥蚀作用增强,从而石英氧同位素值偏低;随着礼乐-东北巴拉望地块的向南运动,印澳板块与欧亚板块碰撞加剧导致青藏高原隆升加剧,中国西高东低的古地理格局逐步形成,石英氧同位素数据显示25.4-23.3Ma是ODP1148站物源转换阶段,华南地块开始成为ODP1148站主要的物源区;之后随着珠江溯源侵蚀的加剧,华南地块古老的沉积岩区逐渐成为ODP1148站的主要源区,石英氧同位素值偏高,南海北部转为以远源沉积为主。冰期时,南海北部大陆架大面积出露,珠江口向陆架区延伸,陆源物质搬运至ODP1144站的距离大为缩短,从而有利于大量陆源物质向研究站位的输运,石英含量、长石含量及平均粒径值均升高,各陆源组分堆积速率也均很高;间冰期时则反之。在0.9和0.47 Ma以后,整个钻孔剖面的石英和长石含量、平均粒径值及各陆源组分堆积速率在冰期呈现高值,间冰期为低值,冰期和间冰期差异明显增强,表明此时季风系统强化引起气候发生明显变化,这种变化可能与青藏高原的阶段性隆起有关。1.1 Ma以来石英含量变化存在明显的92 ka轨道周期以及20 ka的岁差周期。岁差周期的存在也反应了热带低纬过程对气候变化的影响。KNG5孔高岭石主要来自于珠江,蒙脱石主要由吕宋岛提供,伊利石和绿泥石分别由珠江和台湾提供。我们的分析表明KNG5孔17.5 kaBP～12.5 kaBP的沉积物主要来源于珠江,南海的现代环流系统自12.5 kaBP开始形成,西行的广东沿岸流导致向外扩散的珠江物质减少,由于北太平洋深层水(NPDW)的作用,自12.5 kaBP以来台湾成为研究站位沉积物的主要贡献者。KNG5孔末次冰期晚期的粘土矿物、粒度和稀土元素变化主要受控于海平面的变化。全新世早期(11.0 kaBP～8 kaBP)1～2.2μm粒级含量和稀土元素浓度达到极大值可能是强盛的夏季风作用的结果。全新世中晚期(8 kaBP～0 kaBP)1～2.2μm组分含量和稀土元素浓度的减少是8 kaBP以来东亚夏季风减弱的具体体现,其能和北半球其它季风指标能很好地对应起来,展现了全新世以来季风变化的全球性。晚全新世(4-2 kaBP)1～2.2μm组分含量及稀土元素含量的增加可能是对晚全新世ENSO活动增强的响应。更多还原

【Abstract】 Sediments from ODP Site 1148, ODP Site 1144, KNG7 and KNG5 in the northern South China Sea were used to trace sediment sources and reconstruct the sedimentary evolution of the South China Sea since Oligocene, obtain the paleoenvironmental evolution of the South China Sea since 1.1 Ma, ascertain sea level change, the evolution of East Asia Summer Monsoon, current transport and paleoclimatic change of the South China Sea since 18 ka BP based on a multi-proxy approach including a monomineralic quartz isolation procedure, identification of clay minerals by X-ray diffraction, grain-size analysis of isolated terrigenous materials, transmission electron microscope combined with energy dispersive X-ray spectrometer (TEM-EDS), dating of AMS14C, oxygen isotope ratios (δ18O) and scanning electron microscope (SEM) analysis of isolated quartz and rare earth elements analysis. The major conclusions are as follows:It was found that the evolution of South China Sea Basin could be divided into five stages, namely 34～28.5,28.5～23,23～16.5,16.5～5 and 5 Ma to present. The sediment source of ODP Site 1148 was mainly from Palawan during the early expansion period of the South China Sea, with the extensive expansion of the South China Sea since 30 Ma, Palawan block moving southward gradually, making the contents of the terrigenous components and terrigenous mass accumulation rate decreasing. Then, with Palawan block moving southward, the collision of Indian-Australian Plate and Eurasian Plate led to the intensified uplift of Qinghai-Tibet Plateau, and the ancient geography of high in the west and low in the east was gradually formed, and quartz oxygen isotope data showed that the 25.4-23.3 period was a source conversion phase of ODP Site 1148, South China block turning to be the main source of ODP Site 1148. Later, with the intensification of the Pearl River headward erosion, ancient sedimentary rocks of South China block have changed to be the major source of ODP Site 1148.During glaciations, quartz and feldspar contents, terrigenous mass accumulation rate and mean grain size of ODP Site 1144 were much higher, indicating a dry and cold climate, low sea level, and exposed continental shelf. During the interglaciations, quartz and feldspar contents, terrigenous mass accumulation rate and mean grain size of ODP Site 1144 were much lower, implying a warm and humid climate, high sea level and submerged continental shelf. The differences between glaciations and interglaciations significantly increased after 0.9 and 0.47 Ma, which was attributed to the strengthened monsoon system caused by gradual uplift of the Tibetan Plateau. Spectrum analyses of quartz content reveal the presence of Milankovitch cycles, including～92 ka (eccentricity),～20 ka (precession), indicating that the tropical low-latitude processes also have an impact on the climate change.Clay minerals of Core KNG5 mainly consist of illite, chlorite and kaolinite, with associated smectite. Sediment source studies indicate that kaolinite mainly from the Pearl River, smectite mainly from the Luzon River, and illite and chlorite were mainly offered by the Pearl River and Taiwan, respectively. Our results indicate that clay minerals are mainly from the Pearl River during stage 17,500~12,500 cal yr BP, and the South China Sea modern current system began to form since 12,500 cal yr BP, as a result, Taiwan turns to be the major contributor of clay minerals after 12,500 cal yr BP. Grain size, clay minerals and rare earth elements of Core KNG5 in the late glacial were controlled by relative changes of Sea Level. The 1-2.2μm grain-size population and rare earth elements record demonstrates that East Asian Summer Monsoon intensity generally follows changes in insolation and that the response is similar for a large area of China and other northern low-latitude records, implying the globality of the monsoon evolution since Holocene. The anomalous environmental conditions in the northern South China Sea may imply intensified ENSO activity during the late Holocene.更多还原