Coupled Mg/Ca and clumped isotope analyses of foraminifera provide consistent water temperatures

Breitenbach, Sebastian, Mleneck-Vautravers, Maryline J., Grauel, Anna-Lena, Lo, Li, Bernasconi, Stefano M., Müller, Inigo A., Rolfe, James, Gázquez, Fernando, Greaves, Mervyn and Hodell, David A. (2018) Coupled Mg/Ca and clumped isotope analyses of foraminifera provide consistent water temperatures. Geochimica et Cosmochimica Acta, 236. pp. 283-296. ISSN 0016-7037

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Official URL: https://doi.org/10.1016/j.gca.2018.03.010

Abstract

The reliable determination of past seawater temperature is fundamental to paleoclimate studies. We test the robustness of two paleotemperature proxies by combining Mg/Ca and clumped isotopes (Δ47) on the same specimens of core top planktonic foraminifera. The strength of this approach is that Mg/Ca and Δ47 are measured on the same specimens of foraminifera, thereby providing two independent estimates of temperature. This replication constitutes a rigorous test of individual methods with the advantage that the same approach can be applied to fossil specimens. Aliquots for Mg/Ca and clumped analyses are treated in the same manner following a modified cleaning procedure of foraminifera for trace element and isotopic analyses. We analysed eight species of planktonic foraminifera from coretop samples over a wide range of temperatures from 2 to 29°C. We provide a new clumped isotope temperature calibrations using subaqueous cave carbonates, which is consistent with recent studies. Tandem Mg/Ca–Δ47 results follow an exponential curve as predicted by temperature calibration equations. Observed deviations from the predicted Mg/Ca-Δ47 relationship are attributed to the effects of Fe-Mn oxide coatings, contamination, or dissolution of foraminiferal tests. This coupled approach provides a high degree of confidence in temperature estimates when Mg/Ca and Δ47 yield concordant results, and can be used to infer the past δ18O of seawater (δ18Osw) for paleoclimate studies.

Item Type: Article
Uncontrolled Keywords: Clumped isotopes, Mg/Ca analysis, Planktonic foraminifera, Paleoceanography, Paleoclimatology
Subjects: F600 Geology
F700 Ocean Sciences
F800 Physical and Terrestrial Geographical and Environmental Sciences
F900 Others in Physical Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Rachel Branson
Date Deposited: 20 Feb 2020 14:19
Last Modified: 20 Feb 2020 14:30
URI: http://nrl.northumbria.ac.uk/id/eprint/42160

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