Living on the edge: Response of Late Cretaceous rudist bivalves (Hippuritida) to hot and highly seasonal climate in the low-latitude Saiwan site, Oman
de Winter, N.J.; al Fudhaili, N.; Arndt, I.; Claeys, P.; Fraaije, R.; Goderis, S.; Jagt, J.; López Correa, M.; Munnecke, A.; Stolarski, J.; Ziegler, M. (2025). Living on the edge: Response of Late Cretaceous rudist bivalves (Hippuritida) to hot and highly seasonal climate in the low-latitude Saiwan site, Oman. Clim. Past 21(11): 2361-2387. https://dx.doi.org/10.5194/cp-21-2361-2025
In: Climate of the Past. Copernicus: Göttingen. ISSN 1814-9324; e-ISSN 1814-9332, more
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| Author keywords |
Hippuritida; Torreites sanchez; Vaccinites vesiculosus; Oscillopha figari |
| Authors | | Top |
- de Winter, N.J., more
- al Fudhaili, N.
- Arndt, I.
- Claeys, P., more
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- Fraaije, R.
- Goderis, S., more
- Jagt, J.
- López Correa, M.
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- Munnecke, A.
- Stolarski, J.
- Ziegler, M.
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| 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 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. |
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