晚始新世以来北极重大冰增事件及其演进过程—基于北欧海西部海域的沉积物地球化学记录

本次申请以北欧海西部海域ODP151航次913站和我国北极科考IS-04站样品为研究对象。以63μm、250μm为阈值筛分沉积物。淋滤63-250μm子样，纯化陆源碎屑；测定其元素、Pb-Re-Os同位素组成；分析>250μm子样的矿物组合及矿物元素组成，结合前期工作获得的63-250μm子样Sr-Nd同位素组成，建立冰筏碎屑物源指标体系，明确晚始新世以来北极重大冰增事件及其演进过程。分析渐新统-中新统典型层位全样的元素及Re-Os同位素组成，建立深海通风性指标，厘清研究区北部底层水环境氧化-还原性质变化，确定弗拉姆海峡贯通事件与贯通过程。综合对比海峡贯通前后北极冰盖演进模式，讨论海峡贯通与北极冰增事件的内在联系，加深对北极冰增-冰减旋回内在调控机制的认识。

In this proposal, the western Nordic Sea is used as the study area, and the cores sampled at the 913 site of ODP151 Expedition and IS-04 site of Arctic Scientific Research in China are taken as the object. The grain-size thresholds, 63μm and 250μm, can be used to divide sediments into three subsamples. The 63-250μm subsample was leached to purify terrigenous debris. The elements and Pb-Re-Os isotopic composition will be determined for the purified subsample. Otherwise, the mineral assemblage and element composition of the >250μm subsample were analyzed by a petrographic microscope and electronic probe. These data above are combined with Sr-Nd isotopic ratios of the purified subsample to build an indicator system for the ice-rafted debris. The signal, intensity and provenance of the ice-rafted debris in the 63-250μm subsample are clarified due to the indicator system. After that, the occurrence and evolution of major ice-growth events in the Arctic will be understood since late Eocene. On the other hand, the elements and Re-Os isotopic compositions of bulk sediments from Oligocene and Miocene intervals are determined. Based on these data, the deep-sea ventilation index system which could be used to check oxidation-reduction property of bottom water, also be established. The change of oxidation-reduction property of bottom waters in the western Nordic Sea is clarified, and the opening of the Fram Strait is determined. The evolution models of the Arctic ice before and after the opening of the Strait are used to discuss the influence of the opening event on the evolution of the ice-growths. It is helpful to deepen the understanding of the driving mechanism behind the Arctic ice cycle.