Element and isotope compositions of newly discovered dinosaur eggs and geochemical environmental instructions from the early Late Cretaceous of Xiuning Basin, China

New umbellaoolithid and faveoloolithid eggs were discovered from the early Late Cretaceous deposit in the Xiuning Basin, Anhui Province, China, and the samples were examined for elemental and isotopic compositions to reconstruct the geochemical environment. The results show that the trace elements consist of Sr, Mn, Ti, Ba, As, La, Cr, Ni, Pb, Cu, Zn, Co and Ir. The abnormal Sr and Mn were deposited in the eggshell mainly through material exchange of dinosaurs, and the high Ir concentration of surrounding rocks in the Xiuning Basin is conformed to the early Late Cretaceous Ir anomaly. The δ13C compositions of eggshells suggest that the palaeovegetations are supposed to be −20.191‰ and −21.156‰ showing C3 plant and high CO2 concentration, as well as low mean annual precipitation. The δ18O compositions of eggshells indicate that the drinking water was mainly composed of meteoric water and plant leaf water, and the mean palaeotemperature was approximately 19°C. Based on the geochemical compositions of eggshells, the Ni content, the Sr/Ba ratio and the palaeoclimate index of surrounding rocks, the palaeoenvironment in the Xiuning Basin were dominated by alluvial fans and river systems with semi-arid climate in the early Late Cretaceous.