The kinetic oxygen cycle in chemical sediments

Temperature is probably the most fundamental parameter is Earth sciences, but vigorously debated for most of Earth’s history.

Temperature derived from carbonate 18O/16O isotope ratios (δ18Oc) can be biased by i) kinetic effects, ii) alteration, or iii) late precipitation of secondary carbonates. KinO shows that each of these mechanisms is expected to follow a different trajectory in δ18Oc vs. δ17Oc space.

Within this triple oxygen isotope space, different precipitation mechanisms and different types of kinetic effects fall on characteristic slopes, allowing to correct for these effects, which allows attaining absolute paleo-temperatures.Oxygen isotopes are classically analysed in materials presumed to form in near-equilibrium with the water mainly aiming to attain paleo-temperatures.

KinO follows a completely different paradigm by specifically focussing on materials with large kinetic isotope effects. This allows quantitative estimates for fundamental parameters other than temperature such as paleo-pH. Sulfate δ18OSO4 is in notorious disequilibrium with water. While sulfite (SO32-) equilibrates with water, the final oxidation step to sulfate (SO42-) induces a kinetic effect.

KinO shows how the respective kinetic effects can be identified and corrected for, providing insight into the formation mechanisms, the respective physicochemical conditions (e.g. pH) and formation temperatures.

This approach can provide an alteration resistant paleo-thermometer for the Archean.The methodological development proposed in KinO will be employed to understand marine C and O isotope excursions in the geological record including the Paleocene-Eocene-Thermal-Maximum (PETM) and the Neoproterozoic Shurham anomaly.

The later represents the largest negative carbon excursion on Earth and precedes the Cambrian explosion of life.

The PETM represents the most recent equivalent of a CO2 and CH4 induced climatic excursion associated with the sixth largest mass extinction.