西菲律宾海盆XT06孔第四纪磁性地层与深海沉积动力过程

菲律宾海是西太平洋典型的风尘汇集区，也是南极底层水影响的远端地区。由于水深较大等原因，这一热点地区沉积物的古环境研究尚未全面展开。本文对菲律宾海中部XT06孔沉积物开展了磁性地层和粒度测试工作，分析了XT06孔沉积记录的年代学特征和沉积过程，初步探讨了区域沉积演化的控制因素与古环境意义。结果表明：（1）通过系统交变退磁实验，XT06孔沉积物可以辨识出6个磁极性区间，分别对应于布容正极性时、加拉米洛亚极性时、奥杜维尔正极性时和松山负极性时。通过与国际标准磁极性序列对比，发现XT06孔的沉积速率由快转慢，指示了在1.0～1.5 Ma曾发生过一次明显的沉积转折，可能代表了区域深海沉积中心的迁移，与东亚-西太平洋构造活动等密切相关。（2）XT06沉积物属于典型的远洋悬浮体，反映了较弱的沉积动力环境。通过多种粒度分析方法的交叉对比和验证，发现XT06孔沉积物包含粗、细两个互为消长的动力学组分，指示了较为稳定的深海沉积环境。通过对比其他古环境指标，我们推测在构造时间尺度上，亚洲内陆干旱化导致的粉尘输入增加可能是控制XT06孔沉积物粒度逐步变细的主要因素；而在更高时间分辨率上XT06孔沉积物粒度粗细变化可能主要受深海环流强度的控制作用，体现了冰期南极深/底层水团影响减弱、而间冰期增强的区域特征。本文结果展现了菲律宾海中部沉积过程的一些关键特征，揭示了菲律宾海沉积记录在深入研究地球系统多圈层耦合过程中的巨大潜力。

Magnetostratigraphy of core XT06 and Quaternary sedimentary dynamics of the deep-sea deposits in the West Philippian Basin

The Philippine Sea,as a key area in the Western Pacific Warm Pool,is a characterized by wind-dust deposition.Sedimentary and paleo-environmental researches are relatively rare in the region due to large water depth and other reasons.In this paper,magnetic stratigraphy and sediment grain size data from the gravity core XT06,which is located in the central Philippine Sea,are used as the raw materials to establish the chronological sequence and to reveal the sedimentary processes.Upon the basis,the controlling factors on regional sediment distribution pattern and paleoenvironmental processes are discussed.The results suggest that:(1)After alternative demagnetization,the core XT06 can be subdivided into 6 magnetic polarity intervals,corresponding to the Brunhes(C1n)chron,the Jaramillo(C1r.1n)subchron,the Olduvia(C2n)chron,and the successive polarity-reversed intervals of the Matuyama chron respectively.After calibrated with the geomagnetic polarity timescale(GPTS),it is found that the sedimentation rate of core XT06 had an obvious change from fast to slow at 1.0~1.5 Ma,indicating a regional deep-water environment transition event,probably controlled by the tectonic activities related to the interaction between the Asian continent and the Pacific plate.(2)The core sediments are dominated by pelagic suspended matters,reflecting a weak sedimentary dynamic environment.Grain-size data further suggest that there occur two,coarse and fine,dynamic components in a compensated relationship,indicating a relatively stable dynamic environment. By comparisons with the proxies of global ice volume, deep-sea ventilation, and Inner Asianaridification, we proposed that regional tectonic activities with enhanced aridification and increased flux of aeolian input are the major factors tocontrol the regional sedimentation on tectonic timescales, and the bottom-water circulation is the dominating factor on glacial-interglacialtimescales. This paper presented some key sedimentary features for the central part of the Philippine Sea which may contribute much to the indepthstudy of the coupling process of some key Earth systems.