In Situ Mg/Ca Measurements on Foraminifera: Comparison Between Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Wavelength?Dispersive X?Ray Spectroscopy by Electron Probe Microanalyzer

We present a comparison of two different techniques: Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and wavelength-dispersive X-Ray Spectroscopy by electron probe microanalyzer (EPMA) for obtaining Mg/Ca ratios in individual foraminifera shells. The goal is to assess the use EPMA as an alternative technique analyses single foraminiferal calcite Foraminifera obtained from sediments (benthic, Uvigerina spp.) plankton tows (planktonic, Orbulina universa) were analyzed. All specimens prepared epoxy mounts exposed cross-section such that multiple high-resolution could be completed on shells using both techniques. examined our data statistical methods designed assessment measurement In case Uvigerina, mean difference LA-ICP-MS very small (?0.046 mmol mol?1) scale independent. Limits Agreement (LoA, standard deviation bias plus bias) [?0.315, 0.223] mol?1. For samples with lower than 13 mol?1, we found EPMA–LA-ICP-MS ?2.44 mol?1 corresponding LoA [?3.85, ?1.04] higher there appears dependent bias, meaning measured become progressively larger those ratio increases, so metrics are not meaningful. Results indicate it possible collect data, if ?13