Mg/Ca paleothermometry in high salinity environments
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 wh...
| Published in: | Earth and Planetary Science Letters |
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| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Elsevier
2009
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| Subjects: | |
| Online Access: | http://eprints.esc.cam.ac.uk/1100/ http://eprints.esc.cam.ac.uk/1100/1/Hoogakker_Eldefield_Hayward_ESPL_284_3-4_2009.pdf http://www.sciencedirect.com/science/article/B6V61-4WMD2MN-3/2/ef54f7fef730deae02d04cc30f27c6f7 https://doi.org/10.1016/j.epsl.2009.05.027 |
| Summary: | 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. |
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