Clumped isotope reordering kinetics in rudist fossils: Impact of burial history and paleoclimatic implications
Krizova, B.; de Winter, N.J.; Ziegler, M.; Riva, A.; Claeys, P.; Goderis, S.; Arbulla, D.; Frijia, G. (2025). Clumped isotope reordering kinetics in rudist fossils: Impact of burial history and paleoclimatic implications. Geochim. Cosmochim. Acta 407: 282-294. https://dx.doi.org/10.1016/j.gca.2025.08.013
In: Geochimica et Cosmochimica Acta. Elsevier: Oxford,New York etc.. ISSN 0016-7037; e-ISSN 1872-9533, more
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| Author keywords |
Clumped isotopes;Rudist bivalves;Adriatic Carbonate Platform;Thermal history;Paleoclimate;Carbonate diagenesis;Solid-state reordering;multicomponent carbonate system;low-mg calcite;temperature evolution;chemical diagenesis;bivalves mollusca;c-13-o-18 bonds;stable-isotopes;thermometry;seawater;stratigraphy |
| Authors | | Top |
- Krizova, B.
- de Winter, N.J., more
- Ziegler, M.
- Riva, A.
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- Claeys, P., more
- Goderis, S., more
- Arbulla, D.
- Frijia, G.
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| Abstract |
The low-Mg calcite shells of bivalves can record paleotemperatures over geological time scales. Stable oxygen isotope thermometry (delta 18O) is a widely used paleotemperature proxy for past oceans. However, it relies on an estimate of the delta 18O of the calcification fluid. Carbonate clumped isotope analysis, a paleothermometer independent of the delta 18O of water, overcomes this issue and is a valuable tool for reconstructing Phanerozoic paleotemperatures. In both oxygen and clumped isotope paleothermometry, preservation of the original isotopic signal is essential for paleoenvironmental reconstructions. Apart from recrystallization, clumped isotope resetting at elevated burial temperatures can affect the clumped isotope composition. In this study, we analyzed Late Cenomanian to Santonian rudist bivalves from two regions with different time-temperature evolution (FriuliVenezia Giulia, in Italy and southern Istria, in Croatia). The reconstructed Delta 47-based temperatures (T(Delta 47)) differ significantly between the two regions, ranging from 34 to 41 degrees C in the Istria region and 73 to 101 degrees C in the FriuliVenezia Giulia region. Thorough screening excluded any significant contribution of diagenetic alteration of the chemical composition and shell texture, pointing towards clumped isotope resetting in the rudist fossils from Friuli-Venezia Giulia. Modeling solid-state reordering effects in the Friuli-Venezia Giulia rudists suggests that the rudist T(Delta 47) should be interpreted cautiously and demonstrates the need for research on fossil-specific reordering kinetics. The available data do not permit a definite conclusion on rudist reordering kinetics. However, the rudist data correspond most closely to the reordering kinetics similar to that of the belemnites, resulting in resetting at low burial temperatures and at a faster rate. These results further demonstrate the variability in clumped isotope reordering kinetics in calcite fossils. Excluding the effect of clumped isotope resetting on the Istrian rudists allowed for delta 18Oseawater reconstruction. The resulting values of -0.1 to 1.4 %o are within the range observed in modern oceans but are high compared with the assumed Late Cretaceous value of -1 %o. These results point out the importance of using delta 18Oseawaterindependent paleothermometers, especially in the shallow marine environment. |
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