For trace element analyses, single specimens of C. wuellerstorfi have been analyzed using femtosecond laser ablation inductively coupled plasma mass spectrometry (fs-LA-ICP131 MS) at the Geochemistry Laboratory at the Max Planck Institute for Chemistry. Na, Mg, and Sr of 142 specimens of C. wuellerstorfi have been measured at high-resolution on (up to) each of the final five chambers to eliminate possible inaccuracies that are likely to be caused by varying sample size. The fs-LA-ICP-MS analyses were performed on 25-μm diameter spots on each chamber with a pulse repetition rate of 15 Hz at low fluence (0.1-0.3 J/cm2). Calibration was performed with the microanalytical synthetic reference material MACS‐3 for carbonate and NIST612 for silica. Average values of all chambers analyzed in the same specimen were used for further analyses. Since foraminifers from different regions show particular offsets in the Mg/Ca composition of their shell, depending on region specific temperature ranges of ambient seawater, region-specific formulas are used. We have applied the formula Mg/Ca=0.82e^0.19*BWT of Tisserand et al. (2013) from samples collected from similar geographic situations to avoid offsets. The formula has been applied to calculate temperature variability of each analyzed chamber. The average value obtained from chamber-to-chamber temperature variability of each specimen has been applied as average temperature data of the entire test.