CLUMPED ISOTOPE ANALYSES OF OYSTERS FROM THE MAASTRICHTIAN TYPE SECTION IN SOUTHEAST NETHERLANDS

Understanding the role of climate in past mass extinction events provides important context regarding the impacts of anthropogenic climate change on the modern biosphere. At the end of the Maastrichtian Age (~66 Ma), the Cretaceous-Paleogene (K-Pg) mass extinction wiped out ~70% of species, a rate comparable to projections of extinction resulting from modern global warming. Evidence shows that global warming driven by increasing atmospheric CO₂ at the onset of the most intense phase of Deccan volcanic eruptions (~66.2 Ma) may have destabilized ecosystems and set the stage for amplified extinction when the Chicxulub asteroid hit the Earth. Here we apply clumped isotope paleothermometry to Maastrichtian-age fossil shells from the ENCI Quarry in the Southeast Netherlands (the type section of the Maastrichtian Stage) to reconstruct changing temperatures preceding the K-Pg extinction at a new site. The average temperature in this region during the 1.4 Myr period leading up to the extinction event was 21 °C. The clumped isotope method additionally allows for independent reconstruction of the oxygen isotopic composition of seawater, which is related to regional changes in the hydrological conditions, sea level fluctuations, and/or variations in connectivity or isolation of this basin. During the same time period, the δ¹⁸O of the water in the basin averaged 0.1‰, a value resembling that of modern seawater and indicating a marine environment. Better understanding of climate change in this region will help inform study of extinction patterns and the environmental factors that influence such catastrophic events.