晚新生代北太平洋西部深水洋流演化:来自铁锰结壳Nd同位素的证据

被引:6
作者
胡镕
陈天宇
凌洪飞
机构
[1] 内生金属成矿机制研究国家重点实验室,南京大学地球科学与工程学院
关键词
北太平洋; 铁锰结壳; 印尼海道; Nd同位素; 晚新生代;
D O I
暂无
中图分类号
P736 [海洋地质学];
学科分类号
070704 ; 0709 ;
摘要
尽管深水环流在调节全球气候方面起了重要作用,但对于北太平洋西部的深水循环在过去的变化目前仍知之甚少.铁锰结壳的Nd同位素已经被证明是一个很好的记录古海洋环流变化的指标.通过研究位于马里亚纳岛弧附近不同水深的两块结壳(MKD13,1530m;MDD53,2700m)的Nd同位素组成演化,并结合对已发表资料的综合分析,获得了对该区中新世以来古洋流演化的初步认识:在中新世,结壳MDD53的Nd同位素组成保持稳定(εNd:ε4.0~ε5.0),且比北太平洋同时期类似水深的结壳贫放射成因Nd,反映了该时间段北太平洋西部深水主要受控于来自南太平洋的贫放射成因Nd的深部西边界流;而浅水结壳MKD13的εNd值在中新世持续升高,是由于印尼海道陆续关闭,贫放射成因Nd的印度洋水体通过该海道流入太平洋浅部的水量陆续减少所致.在上新世,结壳MKD13的εNd值保持不变,说明该时间段岛弧来源Nd的量没有发生变化,并且在早上新世时印尼海道对印度洋-太平洋间浅层海水的流通已经关闭;所以结壳MDD53的εNd值迅速升高,不是由于水体从浅层到深层的垂直输入的变化造成的,而是由于贫放射成因Nd的南大洋深水流入研究区深度范围(~2700m)的流通量从早上新世开始减弱的结果.
引用
收藏
页码:2757 / 2766
页数:10
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