试论浙江白垩系的顶、底界

本文综合应用生物地层学，同位素年代学、磁性地层学方面的资料，论述了浙江白垩系顶、底界的位置。指出浙江白垩系的最高层为发育于桐乡凹陷中的桐乡组．其层位与江苏的泰州组相当；对白垩系底界进行了较详细的讨论，指出建德群古生物组合的总面貌显示早白垩世的色彩。劳村组同位素年龄测定值小于130Ma，属于白恶纪范畴。磁性地层学研究发现M0R负极性超时出现在横山组，层位相当于阿普第阶的底部。因此，古地磁资料也不支持将建德群归入侏罗系。浙江白垩系的底界应划在劳村组的底部。

DISCUSSION ON THE UPPER ANE BASAL LIMITS OF CRETACEOUS IN ZHEJIANG PROVINCE

Based on the data of biostratigraphy, isotopic geochronology, magnetostratigraphy, the author has studied the upper and basal limits of Cretaceous in Zhejiang province and pointed out that the Tongxiang formation deve developed in Tongxiang Sag is the highest horizon of Cretaceous in Zhejiang province, it can be correlated with Taizhor formation in Jiangsu province. The bounbary between Palaeogene and cretaceous should be drawn between Changhe group and Tongxiang formation.The basal limit of Cretaceous in Zhejiang province is discussed by the author in decail. six kinds of fossils as ostracoda, estheria, bivalve, ghasterpod, insects and plant have been found in Laocun formation. The feature of palaeontological assemblage in Laocun formation is inclined to Early cretaceous. The isotopic age of Laocun formation is less than l3OMa, it belongs to Cretaceors. MOR magnetopolarity zone that is near to the base of Aptian stage was found in Hengshou formation, which can indirectly show that the Jiande group is not suitable for Jurassic. The data mentioned above show that the basal limit of Cretaceous in Zhejiang province should be delimited on the basal limit of Laocun formation.