Research Themes

Paleoclimate Proxy Developement

One of my primary research focuses is to develop novel paleoclimate proxies, such as carbonate dual clumped isotopes and triple oxygen isotopes. In addition to exploring the potential of these new methods to progress paleoclimate research, I am also interested in inter-laboratory standardization.

  • Bajnai, D., Guo, W., Spötl, C., Coplen, T.B., Methner, K., Löffler, N., Krsnik, E., Gischler, E., Hansen, M., Henkel, D., Price, G.D., Raddatz, J., Scholz, D. & Fiebig, J. (2020) Dual clumped isotope thermometry resolves kinetic biases in carbonate formation temperatures. Nature Communications, 11, 4005. https://doi.org/10.1038/s41467-020-17501-0
  • Bajnai, D., Klipsch, S., Davies, A. J., Raddatz, J., Gischler, E., Rüggeberg, A., Pack, A. & Herwartz, D. (2024). Correcting for vital effects in coral carbonate using triple oxygen isotopes. Geochemical Perspectives Letters, 31, 38–43. https://doi.org/10.7185/geochemlet.2430

Paleoclimate Reconstruction

I apply both novel and classical isotope proxies to investigate Earth’s past climate. My work spans from the Precambrian through the Mesozoic to the Cenozoic and focuses on both marine and terrestrial archives.

  • Price, G.D., Bajnai, D. & Fiebig, J., 2020. Carbonate clumped isotope evidence for latitudinal seawater temperature gradients and the oxygen isotope composition of Early Cretaceous seas. Palaeogeography, Palaeoclimatology, Palaeoecology, 552, 109777. https://doi.org/10.1016/j.palaeo.2020.109777
  • Page, M., Licht, A., Dupont-Nivet, G., Meijer, N., Barbolini, N., Hoorn, C., Schauer, A., Huntington, K., Bajnai, D., Fiebig, J., Mulch, A. & Guo, Z. (2019) Synchronous cooling and decline in monsoonal rainfall in northeastern Tibet during the fall into the Oligocene icehouse. Geology, 47, (3), 203-206. https://doi.org/10.1130/g45480.1

Biomineralization

Looking at biological isotope fractionation signatures, I am investigating how brachiopods and corals build their carbonate hard parts.

  • Bajnai, D., Fiebig, J., Tomašových, A., Milner Garcia, S., Rollion-Bard, C., Raddatz, J., Löffler, N., Primo-Ramos, C. & Brand, U. (2018) Assessing kinetic fractionation in brachiopod calcite using clumped isotopes. Scientific Reports, 8, (1), 1-12. https://doi.org/10.1038/s41598-017-17353-7
  • Davies, A. J., Brand, U., Tagliavento, M., Bitner, M. A., Bajnai, D., Staudigel, P., Bernecker, M., and Fiebig, J. (2023). Isotopic disequilibrium in brachiopods disentangled with dual clumped isotope thermometry. Geochimica et Cosmochimica Acta, S0016703723003952. https://doi.org/10.1016/j.gca.2023.08.005

Cyclostratigraphy

Timing carbon cycle perturbations using cyclostratigraphy.

  • Bajnai, D., Pálfy, J., Martinez, M., Price, G.D., Nyerges, A. & Főzy, I. (2017) Multi-proxy record of orbital-scale changes in climate and sedimentation during the Weissert Event in the Valanginian Bersek Marl Formation (Gerecse Mts., Hungary). Cretaceous Research, 75, 45-60. https://doi.org/10.1016/j.cretres.2017.02.021
  • Müller, T., Price, G.D., Bajnai, D., Nyerges, A., Kesjár, D., Raucsik, B., Varga, A., Judik, K., Fekete, J., May, Z. & Pálfy, J. (2016) New multiproxy record of the Jenkyns Event (also known as the Toarcian Oceanic Anoxic Event) from the Mecsek Mountains (Hungary): Differences, duration and drivers. Sedimentology, 64, (1), 66-86. https://doi.org/10.1111/sed.12332
  • Vallner, Z., Müller, T., Bajnai, D., Szives, O., Csicsek, L. Á., Héja, G., Heszler, B., Zajzon, N., & Pálfy, J. (2026). Integrated astrochronology, isotope and biostratigraphy of the Albian-Cenomanian transition and expression of the OAE 1d in an expanded record of a rapidly subsiding Tethyan synorogenic basin (Core Jásd-42, Transdanubian Range, Hungary). Cretaceous Research, 181, 106311. https://doi.org/10.1016/j.cretres.2025.106311

Analytical Chemistry

I study isotope fractionation kinetics in aqueous systems, focusing on reactions that are involved in carbonate formation. I also love tinkering in the lab, improving the methods we use for geochemical analyses.

  • Bajnai, D., Cao, X., Klipsch, S., Pack, A., & Herwartz, D. (2024). Triple oxygen isotope systematics of CO2 hydroxylation. Chemical Geology, 654, 122059. https://doi.org/10.1016/j.chemgeo.2024.122059
  • Bajnai, D., Pack, A., Arduin Rode, F., Seefeld, M., Surma, J., Di Rocco, T., 2023. A dual inlet system for laser spectroscopy of triple oxygen isotopes in carbonate-derived and air CO2. Geochemistry, Geophysics, Geosyststems, 24, e2023GC010976. https://doi.org/10.1029/2023GC010976

Atmospheric Chemistry

As a new avenue of research, I am analyzing triple oxygen isotopes in atmospheric CO2. These measurements have the potential to reveal changes in global primary productivity and to quantify the contributions from different natural and anthropogenic CO2 sources.

  • Bajnai, D., & Hare, V. J. (2025). Sensitivity of tunable infrared laser spectroscopic measurements of ∆’17O in CO2 to analytical conditions. Atmospheric Measurement Techniques, 18, 7405–7419. https://doi.org/10.5194/amt-18-7405-2025
  • Bajnai, D., Pack, A., Arduin Rode, F., Seefeld, M., Surma, J., & Di Rocco, T. (2023). A dual inlet system for laser spectroscopy of triple oxygen isotopes in carbonate-derived and air CO2. Geochemistry, Geophysics, Geosystems, 24, e2023GC010976. https://doi.org/10.1029/2023GC010976