Late Cenozoic history of deep water circulation in the western North Pacific: Evidence from Nd isotopes of ferromanganese crusts  

作　　者：HU Rong CHEN TianYu LING HongFei 

机构地区：[1]State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210093,China

出　　处：《Chinese Science Bulletin》2012年第31期4077-4086,共10页

基　　金：supported by the Chinese Association for Research of Oceanic Mineral Resources (DY-115-01-2-2)

摘　　要：尽管有它在调整全球气候的重要性，在西方的诺思太平洋的过去深的海洋发行量仍然是糟糕理解。铁锰合金外壳的 Nd 同位素被证明了是一个好代理监视 paleoceanic 发行量变化。在这研究，迟了的新生代 Nd 同位素的记录从在玛丽安娜弧附近，但是在不同的水深度定位的二个铁锰合金外壳被恢复(MKD13：1530 m， MDD53：2700 m ) ，并且他们为在这个区域的 paleocirculation 变化的含意被探索。从对早晚中新世， MDD53 的 Nd 同位素的作文留下了马厩，和他们被最不放射产生的签名(到 5.0 的 Nd 4.0 ) 也在中新世的诺思太平洋与类似的水深度的外壳相比描绘。后来，它的 Nd 价值的突然的增加发生在上新世。相反， MKD13 的 Nd 同位素与时间变得更放射产生在中新世并且此后是几乎不变的。更浅的外壳 MKD13 的 Nd 的不断的增加作为反映印度尼西亚的航道的进步闭合在被解释中新世，当从南部的太平洋采购的深西方的边界水流可能在一样期间统治了更深的外壳 MDD53 的 Nd 同位素时，预定间隔。在上新世的 MKD13 的 Nd 同位素的变化的缺乏显示在在印第安人之间的更浅的水和最后的限制里的 Nd 来源没有变化，太平洋从那以后可能仅仅发生了。因此，到在上新世的 MDD53 的更放射产生的 Nd 同位素的观察大移动不应该在垂直输入从变化被结果从对更深的水更浅。相反，沿着学习的水深度范围(2700 m ) 的深南部的部件电流的减少的通风可能在上新世继续了。Despite its importance in regulating the global climate, the past deep ocean circulation in the western North Pacific has still been poorly understood. Nd isotopes of ferromanganese crusts have been proven to be a good proxy to monitor paleoceanic circulation changes. In this study, late Cenozoic Nd isotopic records are recovered from two ferromanganese crusts located near Mariana arc but at different water depths （MKD13：1530 m, MDD53：2700 m）, and their implications for paleocirculation change in this area are explored. From the early to late Miocene, Nd isotopic compositions of MDD53 remained stable, and they were also character- ized by the least radiogenic signatures （εNd --4.0 to --5.0） compared to crusts of similar water depths in the Miocene North Pacific. Afterward, an abrupt increase in its εNd value occurred in the Pliocene. In contrast, Nd isotopes of MKDI3 became more radio- genic with time in the Miocene and were almost invariable thereafter. The continual increase in CNd of shallower crust MKD13 is interpreted as reflecting progressive closure of Indonesian Seaway in the Miocene, while the deep western boundary current sourced from the Southern Pacific may have dominated Nd isotopes of deeper crust MDD53 during the same time interval. The lack of Nd isotopic variation of MKD13 in the Pliocene indicates that there were no changes in Nd sources in shallower waters and the final restriction between the Indian and Pacific may have only occurred since then. Therefore the observed large shift to more radiogenic Nd isotopes of MDD53 in the Pliocene should not be resulted from changes in vertical input from shallower to deeper water. Instead, a decreased ventilation of deep southern component current along the studied water depth range （~2700 m） may have continued in the Pliocene.

关 键 词：ND同位素 西北太平洋 铁锰结壳 晚新生代 循环水 早中新世 证据 历史 

分 类 号：P736[天文地球—海洋地质]