A culture-based calibration of benthic foraminiferal paleotemperature proxies: δ18O and Mg/Ca results
- 1GeoBiosphere Science Centre, Dept. of Geology, Quaternary Sciences, Lund University, Sölvegatan 12, 22362 Lund, Sweden
- 2Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- 3Dept. of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Abstract. Benthic foraminifera were cultured for five months at four temperatures (4, 7, 14 and 21 °C) to establish the temperature dependence of foraminiferal calcite δ18O and Mg/Ca. Two Bulimina species (B. aculeata and B. marginata) were most successful in terms of calcification, adding chambers at all four temperatures and reproducing at 7 and 14 °C. Foraminiferal δ18O values displayed ontogenetic variations, with lower values in younger individuals. The δ18O values of adult specimens decreased with increasing temperature in all but the 4 °C treatment, exhibiting a relationship consistent with previous δ18O paleotemperature calibration studies. Foraminiferal Mg/Ca values, determined by laser ablation inductively coupled plasma mass spectrometry, were broadly consistent with previous Mg/Ca calibration studies, but extremely high values in the 4 °C treatment and higher than predicted values at two of the other three temperatures make it challenging to interpret these results.