摘要
在燕辽区,狭义的大北沟组产Nestoria-Keratestheria群,Eopa- racypris-Luanpingella-Darwinula组合等化石,白旗组的Rb-Sr等时 线年龄为145.2Ma,以及完整的层序关系均证明狼鳍鱼岩层覆于上侏 罗统之上。热河动物群包括原始Trigonioidids群,Eosestheria群, Lycoptera群…以自身的演化规律阐明其属于白垩系的类群。Eosesthe- ria与Yanjiestheria,Lycoptera和Kuntulunia分别与Eosestheria和 Yanjiestheria等共生关系,以及阜新组及相当地层产早期被子植物和孢 粉化石,都印证狼鳍鱼岩层归属于白垩系。鸡西群中Aucellina的确认和依Trigonioidids和Cvprididae等化石,同西欧及日本相当岩层的对比,得到相应海相层的验证。浙江和松辽的磁性地层资料,初步确定了我国白垩系下部混合极性带和中部正极性带间M_0位于建德群黄尖组上段和登楼库组顶段,以及热河群和建德群放射性同位素年龄数据表明狼鳍鱼岩层的近似地质年龄为135—122Ma。这些都证明狼鳍鱼岩层应划归白垩系。
The Lycoptera-bearing bed lies over the upper part of the Upper Jurassic, which has been verified by the fossil evidence such as the Nestoria-Keratestheria fauna and the Ostracod Eoparacypris-Luanpingella-Darwinula assemblage from the Debei gou Formation (in a narrow sense) and by the age 145.2 Ma as determined with the Rb-Sr isochron method of the Beiqi Formation, and the complete stratigraphical sequence in the Yanliao region. The Jehol fauna includes primitive Trigonioidids, Eosestheria and Lycoptera etc. and their own laws of evolution expound that they belong to the Cretaceous faunas. The association of Eosestheria wit . Yan jiestheria and of Lycoptera and Kuntulunia with Eosestheria and Yanjiestheria, and the occurrence of early angiosperms and spore-pollen in the Fuxin Formation and its equivalents also demonstrate that the Lycopten-bearing bed should be assigned to the Cretaceous.The confirmation of the existence of Aucellina in the Jixi Group and the correlation of Trigonioidids and Cyprididae with those in the equivalent strata of Japan and W. Europe have also verified the existence of the corresponding Cretaceous marine strata. The palaeomagnetic stratigraphical data from Zhejiang and the Song-liao area have ascertained that in China the Cretaceous Mo between the lower mixed polarity zone and the middle normal polarity zone is located in the upper member of the Huangjian Formation of the Jiande Group and the top member of the Deng-louku Formation. Moreover, the isotopic age data obtained from the Jehol and Jiande Groups show that the approximate geological age of the Lycoptera bed is 135-122 Ma. All this has proved that the Lycoptera bed should be attributed to the Cretaceous.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1994年第1期86-100,共15页
Acta Geologica Sinica
关键词
白垩纪
地层
狼鳍鱼
岩层
时代归属
Cretaceous, Juro-Cretaceous boundary, Lycoptera-bearing bed, Jehol fauna
