Clumped isotopes in carbonates

The clumped isotope thermometer in carbonates, is based on the measurement of the abundance of ¹³C-¹⁸O bonds in their mineral lattice. Unlike the classic oxygen isotope thermometer this method is independent of the composition of the water from which a mineral is formed. Therefore, it does not require assumptions of the composition of the water, which is commonly the largest source of uncertainty when reconstructing deep-time paleoclimates and diagenetic processes. The clumped isotope thermometer is the only thermodynamically-based thermometer, that can be used for the reconstruction of past climate change in a broad range of environments, ranging from paleosols, to lake sediments, to marine organisms. If original carbonate skeletons have not been altered by diagenesis, clumped isotopes allow the reconstruction of paleotemperatures with an accuracy of ± 2 degrees.
The main limitation for a broader application of this technique is the complex methodology, the long measuring time, and the relatively large amount of sample necessary for an accurate analysis.

In our laboratory we are constantly improving the methodology for the analysis of clumped isotopes in carbonates, in order to simplify the methodology and reduce sample sizes necessary to less than 1 mg of sample for a precise temperature estimate. To further reduce the necessary sample amounts we are using a ThermoFisher 253 Plus Mass spectrometer with 1013 Ohm amplifiers for the rare isotopologuesof mass 47 to 49, and a new Kiel-IV preparation device.

We have also developed a set of carbonate standards that have been distributed to the clumped isotope community to improve interlaboratory data comparability and solve long standing discrepancies in temperature calibrations.

This project is in close collaboration with Thermo Fisher, Bremen