A New Study on the Stratotype and Biostratigraphy of the Yixian Stage in the Yixian—Beipiao Region, Liaoning——Establishment and Study of the Stratotype of the Yixian Stage

Abstract

The stratotype and auxiliary stratotype of the Yixian Stage in the Yixian—Beipiao region are established on the basis of the typical section of the Yixian Formation and the major sections bearing rare fossils. The major fossil-bearing sedimentary layers in the section of the Yixian Stage include the Laogonggou, Yenangou, Zhuanchengzi and Dakangpu beds in the Yixian area and the Lujiatun, Xiatulaigou and Jianshangou beds in the Beipiao area. The three beds of the Beipiao area can be correlated with the first three beds of the Yixian area (in ascending order). It is confirmed that abundant fossil vertebrates, invertebrates and plant assemblages occur just in these strata. Biostratigraphically the beds may be subdivided into the Jeholosaurus—Eosestheria (Diformograpta) ovata— Cypridea rehensis assemblage at the bottom, the assmblages of numerous fossil animal categories and the Brachyphyllum longispicum—Otozamites turkestanica plant assemblage and the Cicatricosisporites—Densoiporites—Jugella sporopollen assemblage in the lower part, and the Jinzhousaurus—Diestheria yixianensis—Karataviella pontoforma assemblage in the upper part. The bottom boundary of the Yixian Stage is represented by Eosestheria and Lycoptera.