Niels de Winter
Proud to be on this publication in GCA by Barbora Krizova et al. We show #clumped #isotope reordering in #Cretaceous rudist bivalves is location-specific. Understanding burial history is essential for selecting shell material for #paleoclimate #reconstructions. https://www.sciencedirect.com/science/article/pii/S0016703725004193
The #clumped #isotope paleo temperature proxy is one of the most reliable means of temperature reconstruction in #geology. This new study shows that it can be applied equally on various carbonate minerals (calcite, aragonite, dolomite, witherite and siderite).
https://www.sciencedirect.com/science/article/pii/S0016703725003072
Check out our latest #preprint in which we use a combination of #clumped and #oxygen #isotope measurements to reconstruct extreme summer temperatures experienced by #fossil #rudist bivalves from the Late #Cretaceous in Oman. All feedback is welcome!
https://egusphere.copernicus.org/preprints/2025/egusphere-2025-2308/
https://egusphere.copernicus.org/preprints/2025/egusphere-2025-2308/
Living on the edge: Response of rudist bivalves (Hippuritida) to hot and highly seasonal climate in the low-latitude Saiwan site, Oman
Abstract. Earth’s climate history serves as a natural laboratory for testing the effect of warm climates on the biosphere. The Cretaceous period featured a prolonged greenhouse climate characterized by higher-than-modern atmospheric CO2 concentrations and mostly ice-free poles. In such a climate, shallow seas in low latitudes probably became very hot, especially during the summers. At the same time, life seems to have thrived there in reef-like ecosystems built by rudists, an extinct group of bivalve molluscs. To test the seasonal temperature variability in this greenhouse period, and whether temperature extremes exceed the maximum tolerable temperatures of modern marine molluscs, we discuss a detailed sclerochronological (incrementally sampled) dataset of seasonal scale variability in shell chemistry from fossil rudist (Torreites sanchezi and Vaccinites vesiculosus) and oyster (Oscillopha figari) shells from the late Campanian (75-million-year-old) low latitude (3° S paleolatitude) Saiwan site in present-day Oman. We combine trace element data and microscopy to screen fossil shells for diagenesis, before sampling well-preserved sections of a Torreites sanchezi rudist specimen for clumped isotope analysis. Based on this specimen alone, we identify a strong seasonal variability in temperature of 19.2 ± 3.8 °C to 44.2 ± 4.0 °C in the seawater at the Saiwan site. The oxygen isotopic composition of the seawater (δ18Osw) varied from -4.62 ± 0.86 ‰ VSMOW in winter to +0.86 ± 1.6 ‰ VSMOW in summer. We use this information in combination with age modelling to infer temperature seasonality from incrementally sampled oxygen isotope profiles sourced from the literature, sampling multiple shells and species in the assemblage. We find that, on average, the Saiwan seawater experienced strong seasonal fluctuations in monthly temperature (18.7 ± 3.8 to 42.6 ± 4.0 °C seasonal range) and water isotopic composition (-4.33 ± 0.86 to 0.59 ± 1.03 ‰ VSMOW). The latter would strongly bias the interpretation of stable oxygen isotopes in shell carbonate without independent control on either temperature or seawater composition. Combining our seasonal temperature estimates with shell chronologies based on seasonal cyclicity in stable isotope records and daily variability in trace element data, we show that T. sanchezi rudists record temperatures during the hottest periods of the year as well as during the winters, which were characterized by cooler temperatures and enhanced influx of freshwater. Both O. figari and V. vesiculosus plausibly stopped growing during these seasonal extremes. This study aims to demonstrate how high-resolution geochemical records through fossil mollusc shells can shed light on the variability in past warm ecosystems and open the discussion about the limits of life in the shallow marine realm during greenhouse climates. Future work should apply the clumped isotope paleothermometer on incrementally sampled bio-archives to explore the upper-temperature limits experienced by calcifiers in different environments throughout geological history.
A very cool study using #clumped #isotope measurements in #oyster shells from the Early #Cretaceous showing high and variable #seasonality in response to climate changes caused by atmospheric #CO2 shifts. #mollusk shells again demonstrated as useful climate archives!
https://www.science.org/doi/10.1126/sciadv.adr9417
https://www.science.org/doi/10.1126/sciadv.adr9417
Nice study testing models for #solid #state #reordering of #clumped #isotope values in #carbonate.
https://www.sciencedirect.com/science/article/pii/S0016703725001012
https://www.sciencedirect.com/science/article/pii/S0016703725001012
Great paper by Gray and Brandon @G-cubed @Agu on the #clumped #isotope #temperature relationship in gar fish scales. I especially enjoyed reading about the treatment of effective vs mean temperatures and seasonal bias in these calibration studies.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GC011714
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GC011714
Sebastian BreitenbachJust out: our latest work reveals environmental changes in southern Patagonia. A fine multi-proxy study led by @NehmeCarole gives you everything: #stableisotopes #clumped #isotopes #fluidinclusions #XRF and more. Proud to be part of such nice team! 😍 https://www.sciencedirect.com/science/article/pii/S0921818123000231?dgcid=author