Discovery of Balmeisporites in the Upper Cretaceous of Nehe area, Heilongjiang Province: Paleoenvironmental implications

The well HND-1 is located near Keshan Farm in Nehe City, northern Songliao Basin. The sporopollen analysis of mudstone from the 69.12-228.70 m interval indicates that the Cretaceous spore-pollen assemblages in this area are dominated by fern spores(56.5%), followed by gymnosperm pollen(43.5%). The most abundant genus identified is Balmeisporites, which is represented by four species. All of these species lack equatorial projections, showing the morphological characteristic consistent with a Late Cretaceous age. The spore-bearing horizon correlates with the Upper Cretaceous Mingshui Formation. The discovery of Balmeisporites not only enriches the fossil assemblage in the area, but also provides key evidence for the paleoenvironmental reconstruction of Mingshui Formation. Integrating the paleoenvironmental indicators from this genus and its associated sporopollen assemblage, it is inferred that Nehe region during the Late Cretaceous experienced a humid, subtropical climate with abundant water resources.