西太平洋E20岩芯末次冰期以来的沉积特征与环境意义

硅藻席沉积在热带西太平洋陆续被发现，其形成年代和机制对于热带西太平洋碳循环研究具有重要意义。本文对采自西马里亚纳弧，含近2.5 m厚硅藻席沉积的E20岩芯进行了高分辨率的XRF元素扫描、颜色扫描以及AMS14C测年分析。结果表明，E20可分为3个沉积单元，从下至上具有深海黏土—硅质软泥—硅质黏土的沉积序列,Ti、Fe、Cu、Br等元素呈三段式变化，Ca与Si元素呈反向变化。综合AMS14C测年结果推测，E20反映了西太平洋低纬度海区末次冰期以来显著的环境变化，10.9～28.6 ka B.P.为硅藻席勃发期，而末次冰期时风尘输入量的增加可能是勃发的主要原因。硅藻席沉积的保存与其周围的围陷地形有很大关系。

Sedimentary characteristics and environmental significance since the last glaciation recorded in core E20 in the western Pacific Ocean

Diatom mat deposits have been discovered in the tropical western Pacific successively, and its formation time and mechanism are of great significance for the study of carbon cycle in the tropical western Pacific. In this study, high-resolution XRF element scanning, color scanning and AMS14C dating analysis were performed on sediment of core E20, which contains nearly 2.5 meters of diatom mat deposit in the west Mariana Arc. The results showed that the core E20 could be divided into three sedimentary units, those were clay, siliceous ooze, siliceous clay from bottom to top, and elements Ti, Fe, Cu, Br, etc. showed three-stage change, Ca and Si showed reverse change. Based on 14C-AMS ages, E20 reflected the significant environmental changes in the western Pacific since the last glaciation, the bloom time of diatom mats was from 10.9 ka B.P. to 28.6 ka B.P., and the increase of dust input during the last glaciation should be the main reason for the diatom bloom in the oligotrophic tropical western Pacific. Local low-lying topography was conducive to the preservation of diatom mats.