Abstract: The Yintun Formation is distributed in the west of Dadianzi basin in Tieling, Northern Liaoning Province, lying on Changcheng to Jixian systems with angular unconformity. This formation, characterized by developed till conglomerate, corresponds to the product of Nantuo Ice Age. Its lithological assemblage is comparable with that of the Nantuo Formation of Nanhua System in Xiadong area, Western Hubei Province. Therefore, this study assigns the Yingtun Formation to Nanhua Period.