Research On The Palynoflora From The Paleogene Dongying Formation In Nanpu Sag, Hebei Province

The palynological analysis of 213 samples from 16 wells of the Paleogene Dongying Formation,Nanpu sag was carried out in this dissertation,of which 81 Species of 27 Genera were carefully examined and described.According to sporopollen contents,one assemblage and four sub-assemblages including the two caeval have been proposed which are characterized by the predominance of Ulmipollenites undulosus.The four sub-assemblages from the bottom to the top are: Ulmipollenites undulosus-Quercoidites sub-assemblage(Ed₃);Juglanspollenites-Tiliaepollenites sub-assemblage(Ed₂),Pinaceae-Chenopodipollis sub-assemblage (Ed₂) and Cedripites-Piceapollis sub-assemblage(Ed₁).Since most of the gymnospermous pollens are double-balloon Pinaceae,which are primary Pinuspollenites and Abietinepollenites with abundant Cedripites, Tsugaepollenites and Piceapollis,and since most of angiospermous pollens are Ulmipollenites undulosus with abundant Quercoidites,Juglanspollenites and Betulaceae,the sporopollen assemblage with high Ulmipollenites undulosus content should be assigned to Oligocene in age.As contents of double-balloon Pinaceae pollens of Pinaceae-Chenopodipollis sub-assemblage are outstanding,with only a few of Neogene flourish pollens appeared,such as Chenopodipollis,Graminidites, Artemisiaepollenites,Echitricolporites and Magnatriatites,it is suitable to assign Pinaceae-Chenopodipollis sub-assemblage to Oligocene.Sporopollen assemblages from Dongying Formation in Nanpu sag can be compared with those from other sags in Bohai Bay Basin,Eastern Kunlun Orogenic Belt and Tanggula Mountains.As sporopollens came from plants,paleovegetation features can be outlined based on sporopollen assemblages.Some sporopollens which have obvious ecological characteristics were selected to infer the climate.The result shows that in Oligocene of Nanpu sag the paleovegetation is characterized by the needle-broadleaf mixed forest,which reflects a humid-warm temperate or subtropical climate.The difference between Juglanspollenites-Tiliaepollenites sub-assemblage and Pinaceae-Chenopodipollis sub-assemblage may be caused by the difference of regional sedimentary environments.Sporopollen assemblages indicate a large height and steep terrain slope of Beipu and Laoyemiao oilfields in Nanpu sag.Sporopollen assemblage characters can serve as good index for the regional tectonic features.