海拉尔盆地南部早白垩世地层及其孢粉组合

EARLY CRETACEOUS STRATIGRAPHY AND SPOROPOLLEN ASSEMBLAGES IN THE SOUTHERN HAILAER BASIN

本文对内蒙古海拉尔盆地南部探井地层中孢粉化石进行了系统研究 ,自下而上建立了 9个孢粉化石组合。根据孢粉化石组合中 Cicatricosisporites,Pilosisprites,Impardecispora,Aequitriradites等重要分子的地质时限特性 ,认为其时代应属早白垩世。这些孢粉化石资料对建立海拉尔盆地地层层序 。

Abundant sporopollen fossils have been obtained from the dark clastic rocks of the wells of the Beier Depression and Wuerxun Depression, southern Hailaer Basin, Inner Mongolia. Based on the composition and distribution of sporopollen fossils, nine sporopollen assemblages have been established as follows in ascending order: 1. Cycadopites-Abietineaepollenites assembla-ge, from the Longjiang Formation. 2. Cicatricosisporites-Densoisporites-Osmunda-cidites assemblage, the Jiufengshan Formation. 3. Cicatricosisporites-Cyathidites-Appendicispo- rites assemblage, obtained from the Tongbomiao Formation. 4. Piceaepollenites/Pinuspollenites-Abietineaepollenites assemblage, in the first member of the Nantun Formation. 5. Classopollis-Pinuspollenites-Piceaepollenites assemblage, in the second member of the Nantun Formation. 6. Concentrisporites-Perinopollenites-Pinuspollenites assemblage, in the first member of the Damoguaihe Formation. 7. Cyathidites-Concentrisporites-Pinuspollenites assemblage, from the second member of the Damoguaihe Formation. 8. Cicatricosisporites-Cyathidites-Leiotriletes as- semblage, in the first member of the Yimin Formation. 9. Cyathidites-Leiotriletes-Pinuspollenites assemblage, in the second and third member of the Yimin Formation. All of the nine sporopollen assemblages contain pteridophytic spores and gymnospermous pollen grains, few angiospermous pollen grain found. Among the pteridophytic components, most genera of pteridophytic spores bear strong aspect of Early Cretaceous, such as Cicatricosisporites, Pilosisporites, Impardecispora, Hsuispo- rites, Fixisporites, Foraminisporis, Triporoletes, Schizaeoisporites. Only in the second member of the Nantun Formation and Yimin Formation, a few angiospermous pollen grain have been obtained, such as Asteropollis, Clavatipollenites, Tricolpites, Polyporites. It is important in reconstructing the stratigraphic sequence and guiding the exploration of the basin that a lots of sporopollen fossils have been discovered in the Hailaer Basin.