Late-Cretaceous Spores And Pollen Assemblages And Palaeoclimte Record In Eastern Of Songliao Basin

The Songliao Basin is a large continental sedimentary basin of Cretaceous in China. The largest lake transgression event of evolution history of the basin has occured during Qingshankou and Nenjiang Stage. Spores and pollen, ostracods and other fossils are abundant. Five sections are analysed in eastern Songliao Basin, which are Niaohe section, Hongshishan section, Hadashan section and Lijiatuozi section of Qingshankou Formation, and Shenjiatun section of Nenjiang Formation. Spores and pollen samples are collected and identified from these sections. By lithology and biotic characters, these sections have been correlated, the palaeoclimate records have been analyzed.The analysis of the spores and pollen fossils has almost covered the whole Qingshankou Formation. The fossils come from Niaohe section and Hongshishan section in Binxian area, Hadashan section in Songyuan area and Lijiatuozi section in Non'an area. The Pinuspollenites-Cyathidites assemblage has been recognized from Niaohe section which is assigned to Member 1 of Qingshankou Formation. The author has identified two fossil assemblages from Lijiatuozi section (in ascending order): the Cedripites-Cyathidites-Classopollis assemblage and the Classopollis- Schizaeoisporites-Callistopollenites assemblage which are assigned to Member 1 to 2 of Qingshankou Formation. The Classopollis - Schizaeoisporites - Cyathidites assemblage has been identified from Hadashan section which is assigned to Member 2 to 3 of Qingshankou Formation.Integrated four sections, in the deposition period of upper part of Member 1 of Qingshankou Formation, the climate state was warm and humid. Up to the deposition period of lower part of Member 2 of Qingshankou Formation, the climate began to drier and heater. Up to the deposition period of Member 3 of Qingshankou Formation, the climate codition changed further hot and dry.The lithology of the Shenjiatun section which is situated in the Nong'an area is dominated by mudstone, and referred to the Member 3 to 4 of Nenjiang Formation. Based on analysis of the spores and pollen fossils of Shenjiatun section, the following three fossil assemblages may be recongnized (in ascending order): the Aquilapollenites-Dictyotriletes-Rugubivessiculites assemblage, the Schizaeoisporites- Classopollis - Beaupreaidites assemblage and the Rugubivessiculites - Schizaeoisporites-Quercoidites assemblage.Based on lithostratigraphic and biostratigraphic features, the assemblages of Shenjiatun section have been correlated to the Campanian Stage, and the paleoeclogy, paleoenvironment, and paleoclimate of this section have been discussed. The quantitative analysis of spores and pollen fossils, such as vegetation type, climate type, and humidity type, diversity and dominance, infers a subhumid, mid-subtropical paleoclimate, with small climatic fluctuation.