The Open UniversitySkip to content

Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis

Elderfield, H.; Yu, J.; Anand, P. and Nyland, B. (2006). Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis. Earth and Planetary Science Letters, 250(3-4) pp. 633–649.

DOI (Digital Object Identifier) Link:
Google Scholar: Look up in Google Scholar


Benthic foraminiferal magnesium/calcium ratios were determined on one hundred and forty core-top samples from the Atlantic Ocean, the Norwegian Sea, the Indian Ocean, the Arabian Sea and the Pacific Ocean, mostly at sites with bottom water temperatures below 5 °C. Mg/Ca ratios are consistently lower, by 0.2 mmol/mol, in samples cleaned using oxidative and reductive steps than using oxidative cleaning. Differences between Cibicidoides species have been identified: Mg/Ca of Cibicidoides robertsonianus > Cibicidoides kullenbergi > Cibicidoides wuellerstorfi. Comparison with bottom water temperatures support observations of lowered Mg/Ca of C. wuellerstorfi at temperature below 3 °C compared with values predicted by published calibrations and from other Cibicidoides species. Hydrographic data shows that carbonate ion saturation (Δ[CO32−]) decreases rapidly below this temperature. An empirical sensitivity of Δ[CO32−] on Mg/Ca has been established for C. wuellerstorfi of 0.0086 ± 0.0006 mmol/mol/μmol/kg. A novel application using modern temperatures and Last Glacial Maximum temperatures derived via pore fluid modelling supports a carbonate ion saturation state effect on Mg incorporation. This may significantly affect calculated δ18Oseawater obtained from foraminiferal δ18O and Mg/Ca temperature.

Item Type: Journal Item
ISSN: 0012-821X
Keywords: benthic foraminifera; proxy; magnesium; temperature; carbonate ion
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 9296
Depositing User: Pallavi Anand
Date Deposited: 01 Oct 2007
Last Modified: 07 Dec 2018 09:07
Share this page:


Altmetrics from Altmetric

Citations from Dimensions

Actions (login may be required)

Policies | Disclaimer

© The Open University   contact the OU