Stratigraphy and sporopollen assemblages of well Bei 32 from the Nantun Formation in the Hailar Basin, Inner Mongilia

Form bottom to top, the Nantun Formation may be divided into two sporopollen assemblages. The Piceaepollenites sp.-Pinuspollenites sp.-Abietineaepollenites sp. is distributed in the first member of the Nantun Formation, whereas Concentrisporites sp.-Piceaepollenites sp.-Pinuspollenites sp. assemblage lies in the second member of Nantun Formation. Among the pteridophytic components, most genera of pteridophytic spores bear strong aspects of Early Cretaceous, such as Cicatricosisporites, Densoisporites, Triporoletes, and Pilosisporites. The Nantun Formation is thus considered to be Aptian-Albian in age, and it is important in reconstructing the stratigraphic sequence and guiding the exploration of the Hailar Basin where a lots of sporopollen fossils have been discovered.