Isotope compositions of dinosaur eggs and associated depositional settings in the Upper Cretaceous Huizhou Formation from the Qiyunshan area, Anhui Province, China: implications for paleoenvironmental reconstruction.

We analysed the stable isotope compositions of dinosaur eggshells and their associated depositional settings of the egg-bearing rocks in the Upper Cretaceous of the Qiyunshan area, Anhui Province, China. Data show that δ13C values for Similifaveoloolithus qiyunshanensis and Umbellaoolithus xiuningensis range between −5.94‰ and −3.55‰; this suggests that C3-type vegetation was consumed by dinosaurs with relatively high atmospheric CO2. δ18O values vary between −8.45‰ and −4.95‰, indicative of high temperature and low humidity within nesting areas. The lithological characteristics of the egg-bearing section evaluated in this study are dominated by red-brown fine sandy siltstone, correlating with pebbly medium-fine grained and medium-fine grained lithic sandstones. Grain size parameters, histograms, and sample probability cumulative curves are also all characterised by fine-grained sediments and suspension populations, likely indicative of floodplain and point bar environments. Therefore, the paleoclimate of the dinosaur nesting habitat was semiarid-to-arid based on food types as well as the colour and high Fe content of sediments. We suggest that this fluvial environment provided the best nesting and egg laying area for drought-adapted dinosaurs in the Upper Cretaceous of the Qiyunshan area and that the excavated nesting could be concluded in view of the periodic flooding events. [ABSTRACT FROM AUTHOR]