晚第四纪劳伦泰德冰盖扩张及其气候响应：加拿大海盆冰筏碎屑记录

Canada Basin in Arctic ocean is the mainly sedimentary aera of ice-rafted debris transported from Laurentide ice sheet (LIS). However, the basin also received IRD transported from the Eurasian continental shelves (EACS). Therefore, distinguishing LIS-source from EACS-source is the key to study the expansion history of Laurentide ice sheet. In this project, we take two sediment cores in the Canada Basin as objects. Data for mineralogy, petrologic and isotopic geochemistry can be used as indicating the material sources for IRD with the grain size of ＞63μm and quantitatively calculating the respective contributions of different sources. The age scales for these two cores were constructed by the following three different means, i.e., AMS14C dating, paleomagnetic method, and sediment color reflectance.On the basis of above studies, variations in LIS-source IRD contributions with time can be used to infer individual ice sheet growth, variability and decline of LIS. This study attempts to reveals the relationship between glacial/interglacial regimes, abrupt climate change events and evolutionary history of LIS through comprehensive studies.

北冰洋加拿大海盆是源自劳伦泰德冰盖的冰筏碎屑（Ice-rafted Debris, IRD）的主要沉积区，同时也有源自欧亚陆架的IRD混入，如何识别IRD的来源是研究劳伦泰德冰盖扩张历史的关键。本项目以加拿大海盆两个岩心为研究对象，通过沉积物中＞63μm的IRD的矿物学、岩石学特征、非碳酸盐岩IRD的元素地球化学、Sr-Nd同位素组成等查明IRD的物质来源并定量估计各个物源端元的贡献量，并基于AMS14C测年、古地磁及沉积物颜色反射率等建立年代地层框架，探讨源自劳伦泰德冰盖的IRD贡献比例随时间的变化特点，重建晚第四纪以来劳伦泰德冰盖的扩张历史。尝试开展综合对比研究，探索冰盖扩张历史与冰期-间冰期气候旋回和气候突变事件的关系。

BN05钻孔的年代框架是基于AMS 14C测年，古地磁，粉白层以及富Mn褐色层等特征层位并与前人的研究进行对比建立的，共识别出MIS1-15期，其中MIS2发生沉积间断。粘土和全岩矿物组成结合粒度、Ca和Mn的含量以及有孔虫数量对北冰洋西部沉积环境及物质来源的研究提供重要信息。高含量的粗碎屑颗粒含量可以作为冰期冰盖崩塌的一个指示，可以根据其矿物组成识别这些崩塌事件中沉积物的物质来源。比较显著的，白云石的峰值可以指示劳伦泰德冰盖的卸载，主要发生在MIS 3, MIS 5 中段和MIS7, MIS 8和 MIS 10。东西伯利亚冰盖的扩张则以在粗碎屑含量高的层位中，蒙皂石、绿泥石和高岭石同时出现峰值为特征，主要发生在MIS 4, MIS 6和 MIS 12。劳伦泰德冰盖和东西伯利亚冰盖对沉积物输入的不同受海平面变化时的冰盖规模、输送机制（冰筏搬运、悬浮搬运、浊流等）以及洋流结构影响。沉积物输入模式的长期变化，比较明显的是在MIS 7/8 (ca. 0.25 Ma)，推测在北冰洋西部有全面的冰盖扩张，尤其是在北美。