冀东南堡凹陷古近系东营组孢粉组合及其地层意义

Sporopollen Assemblages and Stratigraphical Significance of Paleogene Dongying Formation in Nanpu Sag,Eastern Hebei Province

冀东探区南堡凹陷北13井、北26井、北28井、高6井、高7井、高10井、高20井、高27井和高39井124个样品的孢粉资料显示南堡凹陷东营组为波形榆粉高含量孢粉组合。其裸子植物的松科花粉含量高,被子植物的榆粉属、栎粉属、胡桃粉属和桦科植物花粉丰富。该孢粉组合在东营组三段上亚段为波形榆粉(Ulmipollenites undulosus)-栎粉属(Quercoidites)亚组合;东营组二段为胡桃粉属(Juglanspollenites)-椴粉属(Tiliaepollenites)亚组合/松科(Pinaceae)-藜粉属(Chenopodipollis)亚组合,并详细分析东营组二段两个不同孢粉亚组合的形成原因;东营组一段为雪松粉属(Cedripi-tes)-云杉粉属(Piceapollis)亚组合。通过南堡凹陷与渤海湾盆地其他凹陷孢粉组合的对比,结果显示南堡凹陷与渤海湾盆地其他凹陷孢粉组合特征总体一致,然而又具有自己的特点。根据孢粉组合中主要裸子植物和被子植物花粉的分布时限以及少量新近系繁盛分子的出现,判断南堡凹陷东营组的时代为渐新世。

The palynological analysis of 124 samples in this paper was carried out from B13,B26,B28,G6,G7,G10,G20,G27 and G39 wells of Dongying Formation,Nanpu sag,eastern Hebei Province.According to the sporopollen contents,one assemblage has been proposed which was characterized by the predominance of Ulmipollenites undulosus,with high content of Pinaceae among gymnospermous pollens and abundant Ulmipollenites,Quercoidites,Juglanspollenites and Betulaceae among angiospermous pollens.Four including the two caeval sub-assemblages can be recognized as Ed3,Ed2 and Ed1,namely,Ulmipollenites undulosus-Quercoidites sub-assemblage,Juglanspollenites-Tiliaepollenites sub-assemblage/Pinaceae-Chenopodipollis sub-assemblage and Cedripites-Piceapollis sub-assemblage.Moreover,the detailed interpretation has been given on difference of the two coeval Ed2 sub-assemblages.Sporopollen assemblages from Dong-ying Formation in Nanpu sag were compared carefully with those from other sags in Bohai Bay Basin and the results show that Nanpu sag sporopollen assemblages possess similar features with others,but with some small differences.The studied assemblage with high content Ulmipollenites undulosus may be assigned to Oligocene in age based on distribution of major Gymnospermous pollens,Angiospermous pollens and the first occurrence of a few Neogene pollens.