华北地台中、上寒武统露头层序地层学研究的新认识

在生物地层对比基础之上通过对河北顺平清醒剖面、山东张夏和河北赵各庄标准剖面以及北京西山剖面的层序地层研究,将华北地台张夏阶和上寒武统自下而上划分并命名了5个总体向上变浅、以间断加深面为界的层序:张夏层序、崮山层序、崮长层序、长山层序和风山层序,并将上寒武统的4个层序与美国的相应层序进行了对比;阐述了层序地层单位与原来的生物地层、岩石地层和年代地层单位之间的关系,并用层序界面对原有岩石地层和年代地层单位的界线进行了优化;同时探讨了在克拉通陆表海背景下层序地层的发育特征以及相应的地质填图方法。

New results from the study on the outcrop sequence stratigraphy of Middle and Upper Cambrian,North China

Correlation of the Middle and Late Cambrion cyclic carbonates of the widely sepa- rated Zhangxia,Qingxing,Xishan and Zhaogezhuan setions has defined five major third-or- der depositional sequences.Biostratigraphic correlation was used to establish equivalence' of stratigraphic sequences between sections.Even though the sections are composed of differ- ent types of component lithofacies and meter-scale cycles that reflect the varied environmen- tal settings of the localities,the overall shallowing-upward character of sequences is evident. The sequences,in ascending order are:1.Zhangxia Sequence,2,Gushan Sequence,3. Guchang Sequence,4.Changshan Sequence and 5.Fengshan Sequence,of which the upper four sequences of Late Cambrian age were correlated with those defined by Osleger and Read (1993)in the United States.The significance of sequence stratigraphy in subdivision,cor- relation and mapping of the Middle and Upper Cambrian carbonates in North China,and in comparison with the traditional bio-,litho-and chronostratigraphic approaches is elucidated. The optimization of the existing bio-and regional chronostratigraphic boundaries with se- quence boundaries is discussed.