A possible causal relationship between extinction of dinosaurs and K/T iridium enrichment in the Nanxiong Basin, South China: evidence from dinosaur eggshells

Multiple distinct iridium anomalies have been observed in dinosaur eggshells in the K/T boundary sections of the Nanxiong Basin, Guangdong Province, South China. The eggshells collected at and near the fossil–pollen-defined K/T boundary interval show iridium increases of about 19 and 28 times, respectively, above the background level. The enrichment of other trace elements in the eggshells occurs mostly at and near the interval. The distribution of Ir-bearing levels proves the existence of at least six Ir-delivering events from the latest Cretaceous into the earliest Paleocene. The enrichment of Ir and other trace elements in eggshells may have been caused by the assimilation of these elements into the dinosaur body through food, and then into the eggs laid by them.