Science News
Oxygen isotope changes in foram tests
PUBLICATION — Cisneros-Lazaro, D., Adams, A., Stolarski, J., Bernard, S., Daval, D., Baronnet, A., Grauby, O., Baumgartner, L.P., Vennemann, T., Moore, J., Baumgartner, C. Omos, C. M., Meibom, A. 2024. Fossil biocalcite remains open to isotopic exchange with seawater for tens of millions of years. Scientific Reports 14:24933, doi: 10.1038/s41598-024-75588-7
Figure: Tests of modern and fossil (Miocene) foraminifera Ammonia sp. and images of their ¹⁸O-enrichment in experimental conditions.
Fossilized marine calcifiers provide key data for reconstructing ancient seawater temperatures, but diagenesis can bias their isotope and trace-element records. Experiments with modern and 14 Myr-old foraminifera (Ammonia sp.) in ¹⁸O-rich seawater showed slower oxygen isotope exchange in fossils in comparison to modern samples, likely due to organic loss reducing porewater penetration. Despite burial for millions of years, fossil biocalcites remain metastable and more prone to isotope exchange than abiotic calcites.