安徽巢湖二叠系栖霞组碳酸盐岩斜坡沉积

长期以来,人们均认为下扬子地区广泛发育的栖霞组碳酸盐岩属于浅海碳酸盐岩台地沉积。但以巢湖地区为例研究表明,栖霞组主要为碳酸盐岩斜坡沉积。碳酸盐岩碎屑流沉积物形成了臭灰岩段和顶部灰岩段的层状石灰砾岩,分布于斜坡上部;等深流沉积物形成了上、下硅质层段的砂屑硅质粒泥灰岩,主要分布于斜坡下部。而上、下硅质层段中的钙、硅质页 (泥 )岩属于斜坡远端和盆地沉积;唯有本部灰岩段可能属于浅海碳酸盐岩台地沉积。这一认识不仅突破了传统观念,而且有助于重新认识下扬子板块二叠纪的古地理特征和盆地构造演化。

Sedimentation on a Carbonate Slope of Permian Qixia Formation in Chaohu Region, Anhui

The carbonate rocks of Qixia Formation developed extensively on the Lower Yangtze Region have been considered to be deposits of shallow sea carbonate platform for along time. The study indicates, in the case of Chaohu Region, that deposits of Qixia Formation occur mostly in carbonate slope environment. Bedded limestone conglomerates of Swine Limestone and the top limestone members are products of carbonate debris flows and develop on the upper of the carbonate slope. Calcarenite silicon-wackestone of the upper and lower silicon members deposit from contour currents and occur on the lower of the carbonate slope. Calcium-silicon shale (mudstone) developed on the upper and lower silicon members forms in the end of slope and basin environment. Only the limestone of the middle limestone member may deposit in shallow sea carbonate platform environment. This breaks through the traditional idea and is helpful for understanding paleogeographic features and tectonic evolution of Lower Yangtze Plate in Permian period.