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Experimental determination of carbonate-associated sulfate δ^(34)S in planktonic foraminifera shells

Paris, Guillaume and Fehrenbacher, Jennifer S. and Sessions, Alex L. and Spero, Howard J. and Adkins, Jess F. (2014) Experimental determination of carbonate-associated sulfate δ^(34)S in planktonic foraminifera shells. Geochemistry, Geophysics, Geosystems, 15 (4). pp. 1452-1461. ISSN 1525-2027. doi:10.1002/2014GC005295.

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Understanding the coupling of oxygen, carbon, and sulfur cycles in the past is critical for reconstructing the history of biogeochemical cycles, paleoclimatic variations, and oceanic chemistry. The abundance of sulfur isotopes (δ^(34)S) in sulfate from ancient marine carbonates, or carbonate-associated sulfate (CAS), is commonly used, along with other archives (mainly evaporites and barite), to estimate the δ^(34)S of seawater throughout Earth history. Analyses of CAS from hand-picked foraminifera are potentially valuable because this group of organisms is used in numerous paleoceanographic studies. They could provide coupled, high-resolution records of δ^(13)C, δ^(18)O, and δ^(34)S isotopic changes directly linked to orbitally tuned records of climate change through the Cenozoic. Such measurements have not previously been possible due to limitations of sensitivity in conventional IRMS-based techniques. However, the recent development of CAS analysis by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) now allows us to work on samples containing just a few nmol of sulfur with accuracy for δ^(34)S values approaching 0.1‰ and, consequently, to analyze hand-picked samples of foraminifera shells. Here we report the results of culture experiments with the planktonic species Orbulina universa, that establish a shell:seawater δ^(34)S calibration for future applications to the fossil record. Our new method uses <650 μg of carbonate (∼15 shells) per analysis. The results show that S isotopes are fractionated consistently by −1‰ between seawater and O. universa tests. We also demonstrate that O. universa faithfully records the [SO^(2−)_(4)]/[Ca^(2+)] ratio of the seawater in which it grew.

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URLURL TypeDescription
Paris, Guillaume0000-0001-8368-1224
Sessions, Alex L.0000-0001-6120-2763
Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2014 American Geophysical Union. Received 11 February 2014; Accepted 2 April 2014; Accepted article online 4 April 2014; Published online 29 April 2014. We gratefully acknowledge the field assistance of Kate Holland, Jordan Snyder, and Lael Vetter and the staff of the Wrigley Marine Science Center and Ann Russell for alkalinity and pH measurements. We also thank Greg Baxter for assistance with sample preparation/polishing. NanoSIMS measurements were performed at Caltech with the assistance of Chi Ma. We thank two anonymous reviewers and Robert Leeds for their constructive reviews. This research was supported by National Science Foundation awards ATM-0903099 (JFA) OCE-0550703 (HJS), and OCE-1261519 (JSF) and the Camille and Henry Dreyfus Foundation (GP).
Funding AgencyGrant Number
Camille and Henry Dreyfus FoundationUNSPECIFIED
Subject Keywords:sulfur isotopes; foraminifera; MC-ICP-MS; paleoenvironment
Issue or Number:4
Record Number:CaltechAUTHORS:20140627-090728672
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Official Citation:Paris, G., J. S. Fehrenbacher, A. L. Sessions, H. J. Spero, and J. F. Adkins (2014), Experimental determination of carbonate-associated sulfate δ34S in planktonic foraminifera shells, Geochem. Geophys. Geosyst., 15, 1452–1461, doi:10.1002/2014GC005295.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46546
Deposited By: Jason Perez
Deposited On:27 Jun 2014 18:57
Last Modified:10 Nov 2021 17:27

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