SUBDIVISION AND CORRELATION OF THE UPPER BEDS OF THE CRETACEOUS SYSTEM IN ZHEJIANG
CAI Zheng-quan 1) 2) and YU Yun-wen 3) ( 1) Zhejiang Museum of Natural History, Hangzhou, 310012; 2) Laboratory of Palaeobiology and Stratigraphy, the Chinese Academy of Science, Nanjing, 210008; 3) Regional Geological Survey Institute of Zh
The upper beds of the Cretaceous System in Zhejiang were divided into the Yongkang, Tiantai and Qujiang Groups. It has been considered that the Tiantai and Qujiang Groups unconformably overlie the Yongkang Group. Through synthetical analysing to the lithostratigraphic sequences, fossil and isotopic dating in the representative basins, we discover that the lower beds of the three groups (the Guantou, Zhongdai and Tangshang Formations in Tiantai basin) are of Early Cretaceous age, while the upper beds are of Late Cretaceous age. The Tangshang Formation in the Tiantai basin and the Xiaopingtian Formation in the Xianju basin are the synonymous volcanic rocks of late Early Cretaceous age. The Tangshang Formation overlying the Xiaopingtian Formation is the lower part of the Liangtoutang Formation. The age of the dominate fossils from the Yongkang and Qujiang Biotas is respectively late Early Cretaceous and early Late Cretaceous. The fossils of the Yongkang and Qujiang Groups, range in age from late Early Cretaceous to the early Late Cretaceous. The Yongkang, Tiantai and Qujiang Groups are the synchronous heteropic accumulation during the late Early Cretaceous to the Late Cretaceous, and it is impossible for them to over1ap each other.