中文摘要：

基于西北冰洋楚科奇海台ARC3-P31岩心（水深435m）中介形虫化石群的研究,复原了50ka以来的古水团变迁史。该岩心中介形虫化石较丰富,主要由Krithe、Polycope和Cytheropteron 3个属构成,另有Rabilimis mirabilis、Microcythere medistriatum、Cluthia australis、Pedicythere neofluitans、Pseudocythere caudata等几个种零星分布于不同层位。与MIS3-MIS2相比较,MIS1以来该岩心中的底栖有孔虫和介形虫丰度明显增加,指示了底栖生物生产力有了大幅度的提升,响应于气候的变暖。以末次冰消期为界,介形虫化石群属种构成发生了显著翻转：在末次冰消期之前以Cytheropteron-Polycope组合为主,这两个属占总个体数的81%;而从末次冰消期至全新世,Polycope百分含量快速减少,被更替为Cytheropteron-Krithe组合,该组合的两个属占总个体数的79%。根据现代介形虫属种在北冰洋的分布规律可以推测,冰期里Polycope属成为绝对优势分子,是由于北冰洋中层水的顶部变浅,占据了原本属于大西洋水的空间;而全新世以来Krithe属含量增高是由于海平面上升导致水深增加。以上结果说明,在楚科奇海台一带温暖的大西洋水在末次冰期很可能是完全缺失的,到全新世才进入该海域。

英文摘要：

The history of Arctic water masses over the past 50 ka was reconstructed by fossil ostracods from the sediment core ARC3-P31（59cm long under 435 mof water depth）taken from the Chukchi Plateau,Western Arctic Ocean.The ostracod assemblages of the core are predominated by the species of the three genera Krithe,Polycope and Cytheropteron,with Rabilimis mirabilis,Microcythere medistriatum,Cluthia australis,Pedicythere neofluitans and Pseudocythere caudate sporadically occurring.There is a distinct faunal turnover before and after the Last Deglaciation（LD）;before the LD the ostracods are dominated by Cytheropteron-Polycope assemblages（the two genera account for 81% of the total ostracod individuals）;while after the LD Polycope decreased sharply and followed by apronounced increasing in Krithe,and Cytheropteron-Krithe combination became a feature of the assemblages（the two genera make up about 79% individually）.The blooming of Krithe after the LD can be ascribed to increasing water depth of Chukchi Plateau in Holocene.The predominance of Polycope before the LD,on the other hand,is most likely due to the emergence of Arctic Intermediate Water（AIW）to shallower depths and hence the absence of warm Atlantic Water（AW）in the Last Glacial.Our results imply apossibly complete absence of AW on Chukchi Plateau during the Last Glacial and the spreading of AW into this area since Holocene.