南京—巢县一带震旦纪灯影期碳酸盐台地沉积特征

<正>1975年,南京大学地质系师生在江苏旬容仑山原“仑山组”下部发现一套藻白云岩,命名为灯影组。在该组顶界往上约40余米处的泥云岩中采获Redlichia sp.,确定有下寒

The depositional characteristics of the carbonate platform of the Dengying age of Late Sinian, Nanjing-Chaoxian region

The study of the carbonate rocks of Tongying Formation (Upper Sinian) in Jiangsu and Anhui provinces suggests that in early Tongying age there was a shallow-water carbonate platform in Nanjing-Chaoxian region. On the margins of the Nanjing-Chaoxian Platform, laminated-type and non-laminateo type cryptalgal carbonate rocks (laminated cryptalgal dolos-tone, ' spongy' cryptalgal dolostone, cryptalgal f ragmental dolosparite, and so on) are very well developed, in which the traces of filament and coccoid blue-green alga may be frequently found. The carbonate rocks by fine-grained and evaporated features, such as dolomicrite with pseudomorphes after gypsum, dolomicrite or dolomicrosparite with sand-sized intraclasts, on-eomierite and so forth, are developed on the centre of the platform. They are considered as algal bank facies and lagoon facies respectively. Between the Nanjing-Chaoxian Platform and the Huaiyang Land there probably was a gulf (Zhuxian Gulf), and the South Anhui Basin was in the southeast of the platform.The Nanjing-Chaoxian Platform extended in the direction of northeast-southwest. It is believed that this paleogeography mode was controlled by paleotectonies at that time, which had not only effected the distribution of sedimentary facies in Tongying age, but also led to the complexly alternated belts of the sedimentary and biological facies in the studied region in Cambrian, especially Lower Cambrian.