### Abstract

- Top of page
- Abstract
- 1. Introduction
- 2. Material and Methods
- 3. Results
- 4. Discussion
- 5. Conclusions and Paleoceanographic Implications
- Acknowledgments
- References
- Supporting Information

[1] A laser ablation system connected to an inductively coupled plasma mass spectrometer was used to determine Mg/Ca ratios of the benthic foraminifera *Oridorsalis umbonatus.* A set of modern core top samples collected along a depth transect on the continental slope off Namibia (320–2300 m water depth; 2.9° to 10.4°C) was used to calibrate the Mg/Ca ratio against bottom water temperature. The resulting Mg/Ca–bottom water temperature relationship of *O. umbonatus* is described by the exponential equation Mg/Ca = 1.528*e^{0.09*BWT}. The temperature sensitivity of this equation is similar to previously published calibrations based on *Cibicidoides* species, suggesting that the Mg/Ca ratio of *O. umbonatus* is a valuable proxy for thermocline and deep water temperature.