Stratigraphic sequence and age of the Neogene in the Nanjing-Yizheng area：a discussion

Abstract：Since the 1970s， the stratigraphic sequence and age of the Neogene in the Nanjing-Yizheng area have long been controversial because the contact relationships between the Yuhuatai Formation and other sand-gravel beds have not been found. After restudy and division of the Xinyi No.1 hole section at Dayiji， Yizheng Town， the authors find that the superimposition relation of various strata of the Neogene is distinct. Based on this relation and previous work， combined with an analysis of other sections and lithofacies and paleogeography， the authors discuss the stratigraphic sequence and age of the Neogene. The stratigraphic sequence of the Neogene in the area includes the middle Miocene Dongxuanguan Formation (N1d)， late Miocene Liuhe Formation (N1l) and Huanggang Formation (N1h) and Pliocene Yuhuatai Formation (N2y)， as well as an informal lithostratigraphic unit-the Fangshan basalt (fb). The Yuhuatai Formation is another sand-gravel sequence overlying the Liuhe Formation and its age is late Pliocene.