山东沂水地区寒武系张夏组中上部高频旋回层序研究

山东沂水地区寒武系张夏组中上部地层的分布，受控于沂沭断裂（Ｆ４和Ｆ３断裂），分为西区、中区和东区。各区岩性、岩相雷同，只是厚度存在明显差异。地层记录旋回性明显，反映高频旋回特点。根据岩性、沉积相序变化及界面特点，将该套地层划分成１个三级、４个四级、１４～１８个五级和６０～８０余个六级旋回层序。各级别旋回层序均由次一级旋回层序向上变浅、变粗、变厚的进积系列组成。其底部均以相应级别的间断－加深面为界。通过高分辨率层序对比，三级、四级旋回层序具有区域对比意义。因受沂沭断裂的影响，区内地层分布并非原始沉积位置所在，由于地方性因素，造成了五级或六级旋回层序数量上的差异。对于三级旋回层序而言，由早期→晚期，随着沉积环境由陆棚盆地→深潮下带→浅潮下带变化，海水由深→浅；沉积速率由小→大；沉积物质由页岩→瘤状灰岩、泥灰岩→鲕粒灰岩→藻灰岩变化。张夏期各地海平面变化趋势相同，均具有高频率振荡特点，为一个复合海平面变化旋回。

THE STUDY ON THE HIGH FREQUENCY CYCLIC SEQUENCE IN THE MIDDLE UPPER ZHANGXIA FORMATION, CAMBRIAN IN YISHUI AREA,SHANDONG

The distribution of the middle upper Zhangxia Formation, Cambrian in Yishui area, Shandong, is controlled by Yishui rift (including F 4 and F 3 faults). Three regions, i.e., the west, the central and the east, with similar lithologic characteristics and lithofacies, but different thickness are recognized. The stratigraphic records are frequently cyclic. Based on the lithlolgic characteristics, sedimentary facies and sequence boundaries, the stratigraphic unit can be subdivided into one third order cyclic sequence, four fourth order cyclic sequences, fourteen to eighteen fifth order cyclic sequences and sixty to eighty sixth order cyclic sequences. Each order cyclic sequence is composed of progradatinal sequence with increasing grain sizes and thickness upward, with their bases being unconformities. Through high resolution correlation, the third order and the fourth order cyclic sequences here have regional significance. The third order cyclic sequence is composed of a succession from deep water black shale to shallow water limestone. During the Zhangxia period, the sea level in all regions changes similarly resulting from on composite sea level change cycle.