【作者】 刘海生；

【导师】 余钦范； 程业勋； 李家熙；

【作者基本信息】 中国地质大学（北京） ， 地球探测与信息技术， 2003， 博士

【摘要】 东北印度洋地处喜马拉雅山以南，是青臧高原与喜马拉雅山隆升剥蚀产物的主要沉积区，孟加拉扇是世界著名的深海扇，以沉积厚度巨大、保存有高分辨率的古环境信息而著称，一直是古海洋、古气候研究的热点地区。论文首次尝试利用海洋沉积物热释光（Thermoluminescence，简称TL）技术研究古气候变化。结合已有丰富的岩芯资料和能代表气候变化的氧同位素地层、碳酸岩地层、生物地层、磁化率地层以及粒度、粘土矿物、色谱等资料，详细开展热释光与古气候变化的对比研究。 论文对东北印度洋地区不同地理位置的MD81349、MD77190、MD77181、BAR9427四支岩芯的全岩热释光和MD81349岩芯纯净有孔虫的热释光测量，与已知氧同位素地层资料对比后发现四支岩芯的热释光变化与氧同位素地层揭示的气候变化及可能的隆升事件有良好的对应关系。尤以位于东经90°海岭上的以远洋沉积作用为主的MD81349岩芯最为理想，陆源剥蚀产物在其沉积记录中所占比例较少，有孔虫和超微化石为代表的远洋成因的灰白色生物软泥构成主要的沉积组分。无论全岩还是有孔虫，它们的热释光均与氧同位素δ¹⁸O有极好的对应关系，热释光高值区与氧同位素指示的间冰期（1、3、5、7期）相对应；热释光低值区与氧同位素指示的冰期（2、4、6、8期）相对应。进一步研究发现MD81349岩芯纯净有孔虫壳体（方解石）的热释光与碳酸盐含量不存在显著正相关，说明有孔虫热释光变化与碳酸盐矿物有关，但并不主要受碳酸盐量的控制，反应的是质的差异，相反全岩热释光与CaCO₃含量表现出显著正相关，说明物质成分的差异仍然对热释光有影响。 采用Pearson相关分析法对MD81349岩芯的全岩热释光、有孔虫热释光、δ¹⁸O、CaCO₃含量、Mg／Ca、色谱、有孔虫含量7项指标进行相关分析和显著性检验。结果表明，有孔虫热释光与δ¹⁸O相关性最好，呈显著正相关(R=0.418，r_0.01=0)；TL与Mg／Ca比呈显著负相关(R=-0.365，r_0.01=0)；TL与有孔虫含量（R=-0.222）和碳酸钙含量（R=-0.114）、色谱（R=-0.104）都呈负相关。 MD77190岩芯位于孟加拉下扇的沟道间，岩芯碳酸盐含量在12.25％-56.85％之间，氧同位素可分出1、2、3、4、5期，与全岩热释光1、2、3、4、5期的界线一致，受岩性变化的影响，热释光的效果没有MD81349好，但对一些特殊变化的反应，如3期气候波动强烈、4期向3期缓慢过度、5期高于3期等与氧同位素曲线有很好的可比性。 MD77181岩芯位于孟加拉上扇与中扇的结合部位，受陆源输入物的影响最大，全岩热释光结果与氧同位素对应关系不理想。该岩芯热释光的特点是在9米深左右，距今约0.15Ma左右，热释光值突然增大，而磁化率则突然失去变化，表明沉积环境发生了突变，与青藏高原隆升的共和运动（0.15MaB.P.）在时间上相一致。 BAR9427岩芯位于苏门答腊岛北部，氧同位素只测到1、2、3期，3期尚未测试完全，热释光显示1期最高，2期最低，3期高于2期，与氧同位素的界线基本一致。 有孔虫热释光的微观结构研究表明，在冰川旋回的不同阶段，热释光主要受样品中结晶矿物的结晶程度控制。间冰期有孔虫壳体的热释光曲线类似于人工晶体，发光强度也大于冰期的有孔虫壳体。说明间冰期有孔虫壳体结晶程度好，晶体排列整齐，晶体内影响热释光的杂质和缺陷与冰期不同。无论冰期还是间冰期，热释光只有单一的发光峰，峰值温度在375℃-395℃之间，平均387℃，与陆地沉积型碳酸盐晶体有多个发光峰的热释光特征明显不同。代表了有孔虫（方解人结晶体）特有的标地矿物特征。 为了获得可靠的测量结果和对热释光机理进行解释，还研究了热释光与粒度、岩性的关系，以及与其它元素的相关性。研究表明，热释光随测试物质粒度的减小而降低，说明细粒样品中结晶矿物校少以及在破碎过程中，机械磨擦、碰撞作川使原有的热释光受到损大。岩性变化对热彩光的影响规律是：砂岩比泥岩的热郑光高。 放射性核素的含量与热释光的关系比较复杂。通过新疆、江西相山、渤海等地区不同类型样品的热释光测量结果与U、Ra、Th、K结果做相关分析后发现，热释光指标与＿已述核素之间没有明显的正相关性，相山铀矿石与渤海沉积物的热秆光甚至与U、Ra、Th、Ky显关负相关。 从新疆十使铜矿的多元素与热释光的相关分析和显著性检验结果看出：①热释光与常量元素的相关性不显著，与引；（R。0．426）和 K。O（R＝0．4if）的相关性最好，其次是Na；O，A12O。。②与微量兀素 CSy显公止相关（R—0．56，f005—0刀13），其次是 Hf、Rb；与 CO兀票上显著负相关（R二0．48，r00；一0．037），其次是 Ni、Cr、Ba、Cu。③与 U（R—0．02）、Th（R—0．247）含员z上相关，但相关性不显著。④与稀土元素 EU 的含量是显具负相关（R二0497，r。。。一0刀26），其次是 Gd，其余稀士元素均与热释光是上相关。说明常量元素的氧化物S。、hO、＊。；O、A！。Q可能在矿物中以单晶体的形式存在。微量元素＊。、＊I、＊r、＊。、＊u在浓度达到一定量时对热种光起犯灭作川。稀十元素除EU、口d外，多数有可能成为热释光的释光中心。 论文更多还原

【Abstract】 The Northeastern Indian Ocean lies to the south of Himalayas. It is the main sedimentary areas of the denudation due to the uplift of Qinghai-Tibet Plateau and Himalayas.The Bay of Bengal and its adjacent water hosted a great deal of terrigenous sediments have denuded from the Tibetan plateau and transported by the GangeBrahampoutra fluvial system. The oceanic sediment in Northeastern Indian not only distributes widely but also is of high deposit rate. In addition, these sediments also contain reliable high-resolution paleoenvironmental information both with long-timescale and short-timescale. Therefore, this area is an ideal one for the research on the paleoceanography and paleoclimate.For the last decade Thermoluminescence (TL) has been used for a viable tool for age determination of a variety of rock types and sediments. The TL in oceanic sediments has been used for the first time to study paleoclimatic change successfully. Based on the elaborate research on the stable Oxygen isotope stratigraphy, carbonate stratigraphy, biostratigraphy, magnetic susceptibility, grain size and clay mineral of cores marked MD81349, MD77190, MD77181 and BAR9427 in the Northeastern Indian Ocean, this thesis focus on the application of the TL properties in the above cores to infer the paleoclimatic change, and discuss the response of TL of sedimentary records with climatic cycles during the last 300,000 years. The results improve our understanding of the utility of TL as an indicator of sedimentary environment and provide insight into what types of ocean sediments are amenable for study.The comparison of the 18O with the TL cycles indicates that the TL dose display the expected coupling relation with interglacial and glacial climate cycles. It is noteworthy that TL dose shows an increase associated with the interglacial cycles (Oxygen Isotopic Stage 1,3,5,7) and a decrease associated with the glacial cycles (Oxygen Isotopic Stage 2,4,6,8). The carbonate content is high during the interglacial interval and low during the glacial interval. However the TL dose of pure foraminiferan (Calcite) dose not have direct correlation with the carbonate, which leads to a result that the TL changes in the samples might be induced by the difference of crystallization. Temperature and pressure play key roles for the TL properties of a crystal, even the temperature difference between glacial and interglacial is very small. The TL capacity of crystal of calcite is closely related to the type and quantity of lattice defects existed in the crystal resulting from the physical-chemical conditions which existed at the time of crystallization. The TL study of samples in the Northeastern Indian Ocean show that there is one peak on the TL glow curve between 375 and 395 while terrestrial calcite show peaks between 177 and 456 .This study also reveal that no direct correlation between the TL does and U, Ra, Th, K activity, exist.The trace element analyses show negative correlation between Fe, Cu, Cr, Co, Ni, Eu ,clay and TL. and positive correlation between Cs and TL, but the research on concrete mechanism is needed.更多还原