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

Breitenbach, Sebastian F. M. and Mleneck-Vautravers, Maryline J. and Grauel, Anna-Lena and Lo, Li and Bernasconi, Stefano M. and Müller, Inigo A. and Rolfe, James and Gázquez, Fernando and 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 DOI https://doi.org/10.1016/j.gca.2018.03.010

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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 core top 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 foraminifer 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:	2018AREP; IA74
Subjects:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions:	01 - Climate Change and Earth-Ocean Atmosphere Systems 08 - Green Open Access
Journal or Publication Title:	Geochimica Et Cosmochimica Acta
Volume:	236
Page Range:	pp. 283-296
Identification Number:	https://doi.org/10.1016/j.gca.2018.03.010
Depositing User:	Sarah Humbert
Date Deposited:	28 Mar 2018 15:48
Last Modified:	10 Mar 2021 23:22
URI:	http://eprints.esc.cam.ac.uk/id/eprint/4243

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