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

• Published in: Chinese science bulletin Vol. 57; no. 31; pp. 4077 - 4086
• Main Authors: Hu, Rong, Chen, TianYu, Ling, HongFei
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer-Verlag 01.11.2012; SP Science China Press
• Subjects: Chemistry/Food Science; Earth Sciences; Engineering; Humanities and Social Sciences; isotopes; Life Sciences; Marine; multidisciplinary; Nd同位素; Physics; Science; Science (multidisciplinary); surface water level; water flow; 历史; 循环水; 早中新世; 晚新生代; 西北太平洋; 证据; 铁锰结壳; ASW, Equatorial Atlantic, Deep Western Boundary Current; IN, North Pacific; ISEW, Pacific, Mariana Arc; late Cenozoic; Indonesian Seaway; ferromanganese crust; Nd isotopes; North Pacific
• ISSN: 1001-6538; 1861-9541
• DOI: 10.1007/s11434-012-5322-9

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.