Cretaceous Palynological Flora In Hailar Basin

Based on the investigation of the Cretaceous stratigraphic sections in Hailar basin and theresearch history of the Cretaceous in this area and nearby, the petrological stratigraphicsequences of Cretaceous in Hailar basin are established following the international stratigraphycriterion. Taxonomic research of the pollen and spores in the Cretaceous is undergonesystematically, totally 105 species of 61 genera (including 3 new species of 1 new genus) aredescribed in the Hailar basin. Moreover, 10 pollen and spores assemblages are recognized bytheir vertical distribution of different palynological taxa in descending order for the Cretaceousof the Hailar basin. Based on the discovery of angiosperm pollen fossil from the YiminFormation, the evolutionary stages of early angiosperm pollen in China are discussed, and twostages are propose d for the evolution of early angiosperm pollen. hat the evolution should bedivided into. In order to study the geological time of the pollen and spores assemblages, thebiostratigraphic significance of 8 genera of pollen and spores are summarized in detail. Thegeological ages of every petrological stratigraphic unites are discussed based on thepalynological data. Finally, the Jurassic-Cretaceous boundary, Lower-Upper Cretaceousboundary and the Cretaceous-Tertiary boundary in Hailar basin are studied also.The sedimentary strata of the Hailar basin can be divided into three groups in ascendingorder. The Hinganling Group: Middle Jurassic-Lower Cretaceous Tamulangou Formation, LowerCretaceous Tunbomiao Formation, Lower Cretaceous Nantun Forma-tion(the Tunbomiao andNantun formations equal to the Shangkuli Formation in the basin margin)and Lower CretaceousYiliekede Formation. The Zhalainor Group: Lower cretaceous Damoguaihe Formation and theLower Cretaceous Yimin Formation. The Bairhu Group: Upper Cretaceous QinyuangangFormation, Pliocene Hucashan Formation and Quanternary.Totally 105 species of 61 genera (including 3 new species of 1 new genus) are describedfrom the Cretaceous of Hailar basin. The new species are Hailarspora spinulosus Wan et Qiaogen. et sp. nov., Hailarspora reticulates Wan et Qiao gen. et sp. nov. and Hairalsporasudeerteensis Wan et Qiao gen. et sp. nov., They were found only in the Tunbomiao Formationof Hailar basin, serving as an indicators of the division and correlation of the formation.There are some special pollen and spores in the Cretaceous of the Hailar basin, such asCicatricosisporites, Paleoconifers (Paleoconiferus, Protoconiferus, Paleopinus, Paleopicea,Pseudopicea, Piceites, Protoabies, Pseudopinus, Protopicea, Pseudopodo-carpus, Walchites,Pseudowalchia, Protopinus, Protocedrus, Pinites, Protopodocarpus, etc.), Pilosisporites,Triporoletes, Aequitriradites, Appendicisporites, Clavatipollenites, Asteropollis, Tricolpites, etc.These fossils are very important for the division and correlation of the Cretaceous, and areusually taken as index fossils in determining the geological age of the strata. The biostratigraphicsignificance of these index fossils is particularly summarized.Of the early angiosperm pollens in Hailar basin, 11 species of 7 genera are found. They areClavatipollenites hughesii, C. minutus, C. sp., Asteropollis asteroides, A.vulgaris, A.sp.,Tricolpopollenites sp., Tricolpites sp., Tricolporoidites sp., Hammenia fredericksburgensis andPolyporites aster. They can be divided into two suites in ascending order, ie. Monocolpate pollensuite and Tricolpate pollen suite. This shows the general characters of the middle and late EarlyCretaceous angiosperm pollen in China.10 pollen and spores assemblages are recognized from the Cretaceous in the Hailar basin.They are: 1) Cyathidites – Biretisporites – Podocarpidites Ass.,distributed in the lower part ofTunbomiao Formation;2) Cicatricosisporites – Osmundacidites – Hailaerisporites Ass.,distributed in the upper part of Tunbomiao Formation;3) Classopollis sp. – Pseudopiceavariabiliformis – Piceaepollenites multigrumus Ass., distributed in the Nantun Formation;4)Deltoidospora hallii – Piceaepollenites exilioides Ass., distributed in the first member ofDamoguaihe Formation;5) Cicatricosisporites australiensis – Laevigatosporites ovatus Ass.,distributed in the second member of Damoguaihe Formation;6) Impardecispora purveruleta –Abietineaepollenites microalatus Ass., distributed in the first member of Yimin Formation;7)Triporoletes reticulatus – Stereisporites antiquasporites – Pinuspollenites minutus Ass.,distributed in the second member of Yimin Formation;8) Appendicisporites sp. –Inaperturopollenites dubius – Asteropollis asteroides Ass., distributed in the lower and middlepart of the third member of Yimin Formation;9) Pilosisporites trichopapillosus –Crybelosporites punctatus – Hammenia fredericksburgensis Ass., distributed in the upper partof the third member of Yimin Formation;10) Schizaeoisporites laevigataeformis –Callistopollenites radiato-striatus Ass., distributed in the Qingyuangang Formation. These 10pollen and spores Assemblages are not only the biostratigraphic criteria for the division andcorrelation of Cretaceous in the wells of Hailar basin, but also the main evidence to ascertain thegeological age of every petrological stratigraphic unite.Of all kinds of fossils, palynological fossil records of the Hailar basin are most abundantand continuous, playing an important role in confirming the geological age of the strata. Theresults of palynological chronology analysis show that the volcano-sedimentary rocks of theBudate Group is about Early Jurassic in age. Pollen and spores assemblage of the TamulanFormation shows the characters of late Middle Jurassic to early Late Jurassic palynologicalassemblages. The geological age of the Tunbomiao Formation and Nantun Formation might beBerriasian–Valanginian. The two pollen and spores assemblages of the Damoguaihe Formationindicate that the formation might be Valanginian-Hauterivian in age or even early Barremian,although there are not any angiosperm pollen in these assemblages. Quite a lot of diversifiedspores of Lygodiaceae and other palynomorphs which are blooming during middle and late EarlyCretaceous were record in the four assemblages of Yimin Formation show that the geologicalage of Yimin Formation might be Barremian–Albian, since there are trusty angiosperm pollenfound. Angiosperm pollen start to play role in the pollen and spores assemblage of theQinyuangang Formation, although the Schizaeoisporites comes its acme. This indicates that theQinyuangang Formation might be Campanian–Early Maastrichtian in age.Palynological stratigraphic research shows that the Jurassic–Cretaceous boundary should belain between the Tamulangou Formation and the Tunbomiao Formation, and there are quite along gap between the two formations;the Lower and Upper Cretaceous boundary might bebetween the Yimin Formation and the Qingyuangang Formation, and also a long gap betweenthe two formations;and the Cretaceous–Tertiary boundary might be between the QingyuangangFormation and the Paleocene.The palynofloristic characters of the Cretaceous of Hailar basin are analyzed for the firsttime. The results show that the early Cretaceous palynoflora of Hailar basin is within the SouthLaurasia Region (Brenner, 1976), or the Second Phytogeographic Realm (Srivastava, 1978), orthe Sibiria Province (Herngreen & Chlonova, 1981), or Disaccia-trileti–CicatricosisporitesRegion (Li Wenben, 1983);the late Cretaceous palynoflora of Hailar basin belongs to theAquilapollenites Province (Srivastava, 1978) or the Northeast Mesophytic Warm Region (ZhangYiyong, 1990).The Cretaceous climate and vegetation are reconstructed quantitatively for the first time inHailar basin. The vegetation of the lower Tunbomiao Formation is conifer forest and brushwoodbelonging wet warm-temperate climates, the upper Tunbomiao Forma-tion's vegetation isgrassland and shrubs of wet south sub-tropical climate. The vegetation of Nantun Formation isconifer forest of damp warm-temperate climates. The vegetation of lower DamoguaiheFormation is conifer mixed forest of wet warm-temperate climate, that of upper DamoguaiheFormation is grassland and sparse forest of wet north sub-tropical climates. The vegetation ofthe first member of Yimin Formation is conifer mixed forest and shrub hassock of wet southsub-tropical climate, that of the second member of the formation is conifer forest and shrubhassock of wet south sub-tropical climate, while that of thee third member of the formation isconifer (mixed) forest and shrubs of wet tropical climate. The vegetation of the QinyuangangFormation is conifer mixed forest and brushwood of sub-arid south sub-tropical climate.Totally 12 figures, 24 tables and 17 plates are included in the present thesis.