皖南震旦系冰期地层沉积特征

SEDIMENTARY STRUCTURES OF SINIAN GLACIATION IN SOUTHERN ANHUI,EASTERN CHINA

通过野外观察，发现了以下沉积构造：下冰厂涯埠组的落石构造和与下伏休宁组的连续沉积关系；间冰期洋安组有水平层理和韵律性水平层理；上冰期雷公坞组有顶、底部的重力流沉积构造，外来岩块，变形层纹，砾石团和撕裂片等。根据这些资料，认为本区下涯埠组的沉积环境可能是三角洲前，洋安组为潮下浅海，上冰雷公坞组则为陆坡或外陆架。

It is well known that the Sinian glaciation in Southern Anhui is glaciomarine. This paper shows that a more profound unnderstanding of the environments during the glaciation has been achieved after lots of important data were recognized in the field.The sighficant sedimentary structures are as follows: the continuous sedimentation from pre-glacial unit and dropstone from the lower glacial unit Xiayafu Fm.; horizontal stratification and occasionally rhythmic in the interglacial unit Yang'an Fm. and gravity flow structures, allochthonous blocks, deformed stratification and pebble aggregation, as well as argillaceous rip-up in the upper glacial unit leigongwu Fm. These structures suggest that during the early gladal epoch the studied area had probably changed from delta front environment to subtidal shallow sea in the interglacial epoch, and finally became oilier shelf or slope environments in the time of the late glaical epoch.