Neodymium associated with foraminiferal carbonate as a recorder of seawater isotopic signatures

Tachikawa, Kazuyo and Piotrowski, Alexander M. and Bayon, Germain (2014) Neodymium associated with foraminiferal carbonate as a recorder of seawater isotopic signatures. Quaternary Science Reviews, 88. pp. 1-13. ISSN 0277-3791 DOI 10.1016/j.quascirev.2013.12.027

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Abstract

Neodymium isotopic ratios in marine environments have been used as a tracer of water masses and exchange processes between dissolved and particulate phases. The interest in this tracer has been growing with improvement of our knowledge on its chemical behaviour in the modern ocean and the identification of sedimentary phases that preserve past seawater ?Nd values. In the last few decades the Nd isotopic composition measured on Fe–Mn crusts, sediment leachates, bulk carbonate fraction, corals and fish teeth have been increasingly interpreted in the context of understanding the role of the ocean in paleoclimate changes. In particular, calcareous foraminiferal tests (shells) have acquired increasing attention as an archive of seawater Nd isotopic signatures, because it allows continuous high-resolution records to be measured and directly compared to other proxies including stable isotopes and trace metals. The main challenge of interpreting the Nd isotopic composition of foraminifera is determining the origin of the Nd preserved within them. In this review, we present an overview of methodological progress including that of bulk foraminifera and microanalyses within foraminiferal tests, as well as geochemical meaning of extracted Nd concentrations and isotopic compositions. The growing body of evidence suggests that Nd isotopic signatures of sedimentary planktonic foraminifera correspond to bottom water values rather than surface water ones. The Nd-rich phases associated with sedimentary foraminifera are adhesive nano-scale particles of Mn and Fe oxides and hydroxides, and Mn-rich carbonates formed within layers of foraminiferal calcite. Mechanical cleaning to remove clay minerals is likely to be sufficient in most cases to reconstruct past bottom water circulations. Unresolved issues include the potential influence of pore water Nd on ?Nd values extracted from sedimentary foraminiferal tests under different sedimentalogical and oceanographic conditions.

Item Type: Article
Uncontrolled Keywords: 2013AREP; IA67;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Quaternary Science Reviews
Volume: 88
Page Range: pp. 1-13
Identification Number: 10.1016/j.quascirev.2013.12.027
Depositing User: Sarah Humbert
Date Deposited: 14 Feb 2014 19:09
Last Modified: 18 Feb 2014 17:33
URI: http://eprints.esc.cam.ac.uk/id/eprint/2971

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