Pollen Assemblages and Paleoenvironmental Restoration of the Nen-3 Member of Longhupao Terrace in Songliao Basin

Abstract Taking the D424 well Nen-3 member reservoir in the Da’an structure of the Longhupao terrace in the central depression of the Songliao Basin as the research object, combined with spore pollen and algal fossil research methods, this study deeply explores the longitudinal evolution of spore pollen sequences and geological significance of the Nen San reservoir in the Longhupao terrace. The results indicate that the study interval can be divided into four spore pollen and algal fossil assemblages from bottom to top: Dinogymniopsis-Leiosphaeridia-Pinuspollenites Cicatricosisporites-Pinuspollenites-Bo tryoccocus Dinogymniopsis-Chlamydophorella-Taxodiaceaepollenites Cicatricosisporites-Pinuspollenites-Pediastrum .designated as the Coniacian-Campanian period of the Late Cr etaceous. The ancient vegetation types are mainly coniferous forests, while the ancient temperate type transitions from tropical to northern subtropical to southern subtropical, an d the ancient dry and humid type changes from humid to semi humid. This article focuses on the study of the Nensan Formation, providing a strong basis for the comparison of pollen fossils and stratigraphic division in the later stage.