Mg/Ca paleothermometry in high salinity environments

Babette A. A. Hoogakker*, Gary P. Klinkhammer, Harry Elderfield, Eelco J. Rohling, Chris Hayward

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

57 Citations (Scopus)


Planktonic foraminiferal Mg/Ca ratios have become a fundamental temperature proxy in past climate reconstructions. However, in the highly evaporative seas of the tropics and subtropics, anomalously high planktonic foraminiferal Mg/Ca ratios arise, possibly linked to high salinities. The extent to which salinity affects Mg uptake into foraminiferal calcite remains disputed. Some studies suggest only minor salinity effects, whereas others suggest a dominant role. Here, we present new data from the highly saline (> 40) Red Sea, which separate pure foraminiferal calcite from other phases. The results show that high Mg/Ca ratios (7 to 13 mmol/mol), found by conventional analysis of planktonic foraminifera from a Red Sea sediment core, are not caused by increased Mg uptake into foraminiferal calcite in a high salinity setting (e.g. beyond those predicted by culturing studies), but instead result from secondary high Mg-calcite overgrowths. The overgrowths likely formed near the sediment-seawater interface, from CaCO3 supersaturated interstitial seawater.

Original languageEnglish
Pages (from-to)583-589
Number of pages7
JournalEarth and Planetary Science Letters
Issue number3-4
Publication statusPublished - 15 Jul 2009


  • CaCO3 supersaturation
  • conventional ICP-AES
  • electron microprobe analysis
  • flow-through time resolved analysis
  • Globigerinoides ruber
  • high Mg-calcite overgrowths
  • Mg/Ca paleothermometry
  • Red Sea
  • salinity
  • scanning electron microscopy

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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