High‐Resolution Mg/Ca Measurements of Foraminifer Shells Using Femtosecond LA‐ICP‐MS for Paleoclimate Proxy Development.

Jochum, K. P. , Jentzen, A., Schiebel, R. , Stoll, B., Weis, U. , Leitner, J. , Repschläger, J., Nürnberg, Dirk and Haug, G. H. (2019) High‐Resolution Mg/Ca Measurements of Foraminifer Shells Using Femtosecond LA‐ICP‐MS for Paleoclimate Proxy Development. Open Access Geochemistry, Geophysics, Geosystems, 20 (4). pp. 2053-2063. DOI 10.1029/2018GC008091.

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Abstract

Determination of Mg/Ca in foraminifer shells as a proxy of seawater temperature is of particular interest in paleoclimate reconstruction. Here we show that femtosecond–200 nm–laser ablation–inductively coupled plasma–mass spectrometry is a suitable technique to precisely and accurately determine Mg/Ca in the micrometer-sized calcareous chambers of foraminifers. At low fluence (0.3–0.6 J/cm 2 ) the double-charged 44 Ca ++ and the single-charged 25 Mg + ions are measured nearly simultaneously. Integrated single-shot measurements using a pulse repetition rate of 1 Hz enable precise analyses at a depth resolution of about 50–100 nm/pulse corresponding to an ablated material of 0.3–0.6 ng calcite/pulse for a spot size of 55 μm. High-resolution analyses can be performed until a depth of 10–20 μm and thus particularly suitable for thin-shelled foraminifers. Reproducibility (relative standard deviation) is about 5% as approved by homogeneous reference materials. Calibration is performed with the microanalytical synthetic reference material MACS-3. Magnesium and Ca data of different carbonate and silicate reference materials agree within uncertainties with reference values. The procedure has been successfully applied for detailed analyses of single chambers and shell-depth profiles of live individuals and empty planktic and benthic foraminifer tests from different ocean basins.

Document Type: Article
Keywords: High‐Resolution Femtosecond LA‐ICP‐MS, Foraminiferal Mg/Ca, Paleoclimate Proxy
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2018GC008091
ISSN: 1525-2027
Expeditions/Models/Experiments:
Date Deposited: 20 May 2019 09:35
Last Modified: 02 Oct 2019 23:38
URI: http://oceanrep.geomar.de/id/eprint/46749

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