Hello, my name is David Bajnai (pronounciation: ˈdaːvid ˈbɒjnɒi). I am a lecturer in geochemistry at the University of Göttingen.
My scientific goals are to reconstruct accurate and precise seawater temperatures in geological times to learn about past and future climates. The stable isotope composition of the fossil remains of marine calcifiers, e.g., belemnites and brachiopods, holds information on the surrounding water temperatures. By measuring this, palaeoceanographers can postulate how warm the oceans were millions of years ago. However, vital effects (stable isotope fractionations that happen during mineralisation) and diagenetic alteration of the of the fossils (physical and chemical changes after deposition) bias these temperature estimates. I am using the clumped isotope (∆47 and ∆48) and the triple oxygen isotope (∆17O) proxies to map these effects, correct for them, and thus determine unbiased, accurate temperature reconstructions.
2021-11-16: New article published in ACS Earth and Space Chemistry: Kinetic oxygen isotope fractionation between water and aqueous OH– during hydroxylation of CO2. We observe a 24‰ offset between the experimental and theoretical-equilbrium isotope fractionation values. We argue that this offset derives from kinetic isotope effects related to the preferential reaction of isotopically light OH– during CO2(aq) hydroxylation. Read the article here.
2021-06-04: New article published in Paleoceanography and Paleoclimatology: Warm high-elevation mid-latitudes during the Miocene Climatic Optimum: Paleosol clumped isotope temperatures from the Northern Rocky Mountains, USA. Palaeosol carbonate ∆47 records from Montana and Idaho suggest stable (21±2 °C) continental temperatures over the Miocene Climatic Optimum (ca. 17–15 million years ago). Read the open access article here.
2021-06-02: New article published in Geophysical Research Letters: Devils Hole calcite was precipitated at ±1 °C stable aquifer temperatures during the last half million years. In this study, we investigated the Devils Hole caves that provide a reference oxygen isotope time series for North America. Dual clumped isotope thermometry (∆47 and ∆48) reveals that groundwater temperature did not change significantly in the last half-million years. Variations in the oxygen isotope composition of the deposited carbonates solely reflect variations in the oxygen isotope composition of the groundwater. Read the open access article here.
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