南沙群岛海区NS97-13柱样沉积物磁化率各向异性研究  

The anisotropy of magnetic susceptibility of Core NS97-13 sediments from the Nansha Islands sea area in the southern South China Sea

作　　者：汤贤赞[1] 陈木宏[1] 刘建国[1] 张兰兰[1] 陈忠[1] 

机构地区：[1]中国科学院南海海洋研究所边缘海地质重点实验室,广东广州510301

出　　处：《海洋学报》2009年第6期69-76,共8页

基　　金：国家自然科学基金项目(40631007);国家"九七三"项目(2007CB815905);中国科学院知识创新工程重要方向项目(KZCX2-YW-228)

摘　　要：通过南海南沙群岛海区NS97-13柱样磁化率各向异性系统测试、统计计算和测年等分析,给出了沉积物的磁化率椭球几何形态,重建了研究海区的古水流方向、沉积物的沉积形式。研究结果表明:(1)压扁型椭球(E>1)的择优方向位于磁性线理-磁性叶理直线的上方,夹角β的范围为0°<β≤33.14°,拉长型椭球(E<1)的择优方向位于磁性线理-磁性叶理直线的下方,夹角α的范围为33.14°<α<56.86°,指示磁性颗粒沉降时受动力作用的大小及其受力方向不同;(2)由磁化率各向异性参数(磁性线理-各向异性度,磁性叶理-各向异性度)确定的沉积物有改造沉积、再沉积和稳定沉积三种形式,前两种形式掺杂在稳定沉积层中的不同部位,构成部分混合沉积;(3)最大磁化率和中间磁化率的轴向分布表征研究海区距今近62 ka以来古水流方向主要为南北和北东-南西向,总磁化率记录了Heinrich层中的冷事件H1—H6。The anisotropy of magnetic susceptibility（AMS） of Core NS97-13 sediments from the Nansha Islands sea area in the southern South China Sea was analyzed combining with 14C dating,which afforded the magnetic susceptibility ellipsoid of geometry shapes,and paleocurrent directions and depositional forms of sediments were rebuilded in the study area.Results show that（1） the predominant direction of staved ellipsoid（E〉1）is always located above the L-F straight line,whose nip angle（β） is 0°〈β≤33.14°,whilst the predominant direction of elongated ellipsoid（E〈1） is located below the L-F straight line,whose nip angle（α） is 33.14° 〈α〈56.86°.These denote that the direction of hydrodynamic action is different when the magnetic granules deposit in the process of sedimentation.（2） The AMS parameter,（L-P,F-P） are demonstrated that the core sediments experience of reworked,redeposited and undisturbed three forms,and the former two are adulterated in the undisturbed sediment layers,resulting in the intermingled layers.（3） The axial distributions of the maximum susceptibility and the middle susceptibility are mainly NS and NE-SW,explaining that the paleocurrent direction has been mostly NS and NE-SW since about 62 ka BP.The total magnetic susceptibility recorded six cold events,namely,the Heinrich layers（H1-H6）,showing that there are six cold events in the Nansha Islands sea area.

关 键 词：磁化率各向异性 沉积形式 古水流方向 Heinrich层 南沙群岛海区 

分 类 号：P318.4[天文地球—固体地球物理学] P736.21[天文地球—地球物理学]