华北地台中寒武统张夏组上部高频层序研究

根据华北地台东部寒武系露头层序地层研究，将张夏组划分为两个正层序，其中上部正层序（５３０－５２５ＭａＢ．Ｐ．，三叶虫带Ａｍｐｈｏｔｏｎ－Ｔａｉｔｚｕｉａ带至Ｄａｍｅｓｅｌａ带）由４个亚层序和１７－２３个小层序组成，其中正层序和亚层序具有高分辨率区域地层对比意义。每一级层序均表现为向上变浅和变粗进积型序列，底部常以间断－加深面或洪泛面为界。该时期的海平面变化具有高频振荡特点，构成一个三级复合海平面变化旋回。由不同级别层序所反映的海平面变化旋回可以分别与天文周期的奥特周期（２—５Ｍａ）、米兰科维奇长周期（０．１—０．４Ｍａ）和米兰科维奇短周期（０．０２—０．０４Ｍａ）相对比。据层序地层和相序及相模式的研究，识别出６种类型的小层序，陆棚盆地至上缓坡显示出由Ａ—Ｆ类型的规律性变化。

High frequency Sequence stratigraphy of the Upper Changhia Formation in the North China Platform

On the basis of the study on outcrop sequence stratigraphy,one 3rd order orthosequence,four 4th order subsequences,and some 5th order microsequences are recognized in the upper Changhia Formation belonging to Middle Cambrian Changhia Stage in Yishui of Shandong,in Western Hills of Beijing and in Fuchou of Liaoning in the North China Platform.By the correlation of the trilobite zones,the 3rd order orthosequence ranges approximately from 530Ma to 525Ma B.P.,and includes Amphoton Taitzuia Zone and Damesella Zone.The time span of every subsequences and microsequences are about 0.7Ma and 0.12Ma respectively. Every order sequences are represented by progradational sequences consisting of an upward thickening,shallowing and coarsening carbonates and shales, and bounded by puncturated deeping boundary or flooding surface. In the period,sea level change was characterized by the high frequency oscillation and a composite sea level change controlled by the astronomic cycle was formed.The ortho ,sub and micro sequences are thought to be related to Oort Cycle(sun approaching to asteroids,2—5Ma),longer Milankovitch Cycle(0.1-0.4Ma) and shorter Milankovitch Cycle(0.02—0.04Ma) respectively.All subsequences have significance of regional stratigraphic correlation.Based on sequence stratigraphy,facies succession and model,six kinds of microsequences are recognized,and the changes from type A to type F with environment facies from shelf basin to upper ramp are shown.