Carbonate 'clumped isotope' thermometry: A status report

Carbonate ‘clumped isotope’ thermometry can determine the growth temperatures of carbonate minerals based on their abundances of ^(13)C-^(18)O bonds, as reflected by the ‘Δ_(47)’ value of CO_2 extracted by phosphoric acid digestion. This method is precise (as good as ±1 °C), thermodynamically based, and independent of the δ^(18)O of water from which carbonate grew. However, there are many unresolved questions about the general usefulness of this new and unusual proxy. We review recent developments in its calibration and understanding