When scientists study ancient seabed cores, they say they can judge the temperature of the water in the past by analyzing the magnesium to calcium ratio in foraminifera shells (both in the form of carbonate, presumably). Supposedly, they added less magnesium when the water was colder.

Why? Is it because the lighter magnesium was more likely to be locked up in ice, like Oxygen-16 vis-a-vis O-18?

Also, why the focus on foraminifera? Why not use diatom shells?

  • 1
    $\begingroup$ Might it have to do with the solubility of magnesium and calcium carbonates with respect to temperature? $\endgroup$ Commented Jun 20, 2019 at 20:19
  • $\begingroup$ Good question.... I will look into it... But still no answers from anybody :( $\endgroup$
    – Kurt Hikes
    Commented Jul 12, 2019 at 3:51


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