内蒙古海拉尔盆地大磨拐河组孢粉化石及其时代浅析

海拉尔盆地大磨拐河组所产孢粉化石分属于3个孢粉组合.下部孢粉组合以蕨类植物海金沙科孢子为主,重要分子有Cicatricosisporites australiensis, Cyathidites minor, C. gracilis, C. minutaestriatus, Appendicisporites problematicus, A.jonsonii,Pilosisporites verus, Impardecispora apiverrucata, I. purverulenta, Triporoletes reticulates, Aequitriradites echinatus等;中部孢粉组合则以两气囊花粉如Pinuspollenites, Piceaepollenites, Abietineaepollenites, Abiespollenites等占绝大多数,同时见少量被子植物花粉Asteropollis sp., Tricolpites sp.等;上部孢粉组合中裸子植物花粉略有减少,但仍占重要地位,重要分子有Cicatricosisporites australiensis, C. minutaestriatus,C. gushanensis, Impardecispora purverulenta ,Foraminisporites wonthagiensis, Aequitriradites verrucosus, Triporoletes singularis, T. reticulates, Polyporites? sp.等.上述孢粉组合大体可与松辽盆地登娄库组,黑龙江省东部城子河组、穆棱组,辽西地区沙海组、阜新组等对比,代表了中国北方早白垩世特有的植物群面貌,而其中Asteropollis, Tricolpites和Polyporites等被子植物花粉化石的发现,可能暗示大磨拐河组的时代为早白垩世中、晚期的巴列姆(Barremian)期-阿普第(Aptian)期,其上部可能上延至早阿尔必(Albian)期.

Sporopollen Fossil of the Damoguaihe Formation and Its Age in Hailaer Basin,Inner Mongolia

Abundant sporopollen fossils,belonging to three sporopollen assemblages,have been obtained from the Damoguaihe formation of Hailaer Basin in Inner Mongolia.The fossil assemblage is characterized by Lygodiaceae spores in the lower sporopollen assemblage,with Cicatricosisporites australiensis,Cyathidites.minor,C.gracilis,C.minutaestriatus,Appendicisporites problematicus,A.jonsonii,Pilosisporites verus,Impardecispora apiverrucata,I.purverulenta,Triporoletes reticulates,Aequitriradites echinatus ect..In the middle sporopollen assemblage,Gymnosperm pollen is absolutely dominanted with high percentage of Pinuspollenites,Piceaepollenites,Abietineaepollenites,Abiespollenites,and a little Angiosperm pollen,such as Asteropollis sp.,Tricolpites sp.,is obtained.While Gymnosperm pollen still dominate in the upper sporopollen assemblage,some important genera and species as Cicatricosisporites australiensis,C.minutaestriatus,C.gushanensis,Impardecispora purverulenta,Foraminisporites wonthagiensis,Aequitriradites verrucosus,Triporoletes singularis,T.reticulates,Polyporites? sp.ect.are founded.These sporopollen assemblages may be correlated with Denglouku Formation in Songliao Basin,Chengzihe and Muling Formations in eastern Heilongjiang Province,Shahai and Fuxin Formations in western Liaoning Province.Both represent the distinct flora of early Cretaceous in North China.A little pollen of Asteropollis,Tricolpites,Polyporites occurs in the Damoguaihe Formation,which seems to imply that the age of Damoguaihe Formation is the middle and late of the early Cretaceous,Barremian to Aptian,and the up member of Damoguaihe Formation may be dated up to early Albian.