华北地台东部寒武系层序地层年代格架

北地台寒武系属稳定的克拉通盆地陆表海沉积。其沉积层序表现为复合层序，主要受全球海平面变化和沉积物补给因素的控制。自下而上可划分为１７个正层序，归并为６个正层序组和２个中层序。大部分正层序的边界与生物地层单位一致，与岩石地层单位略有出入。每个正层序的平均时间延续约为３Ｍａ，含两个三叶虫化石带。根据层序地层的研究，可以建立华北寒武系层序地层年代格架，并提出各统和阶的界线参考年龄。

CAMBRIAN SEQUENCE CHRONOSTRATIGRAPHIC FRAME WORK OF THE NORTH CHINA PLATFORM

The Cambrian in the North China platform consists chiefly of shallow water deposits and shows the sedimentary character of an epicontinental sea on a stable craton.Controlled mainly by global sea level changes and sedimentary influx,the depositional sequences in the Cambrian of the North China platform all exhibit as composite sequences,with very well developed parasequences and meter scale cycles.From the bottom upwards,17 orthosequences (3rd order) have been recognized in the Cambrian,which can be grouped into 6 orthosequence sets and further as 2 mesosequences (2nd order).According to the present day study,most of the recognized orthosequences are coincident with the biostratigraphic units,but slightly different from the lithostratigraphic units.Each of the orthosequences has an average duration of 3 Ma and contains two trilobite zones.Based on the study of sequence stratigraphy and the biostratigraphy,a sequence chronostratigraphic framework has been proposed for the Cambrian of the North China platform,and reference ages have been suggested for all the stages and series boundaries in the Cambrian of China.