Sedimentary facies and element variation of Upper Permian strata in Qujiang-Renhua area,Guangdong, China

The Upper Permian strata of the Qujiang-Renhua area, Guangdong Province, is a coal-bearing sequence. Sedimentary facies analyses and correlation of element-content variation in sedimentary rocks reveal the following regularities: (1) The evolution of continental facies → transition facies → marine facies is reflected by a tendency for K, Ga and Ti to decrease and for Mg, Ca and Sr to increase. (2) K, Ga and Ti show a tendency to decrease, but Ca, Mg, V and Sr tend to increase in the order of lacustrine facies → littoral facies → gulf and lagoonal facies. (3) Lacustrine facies → lagoonal facies → gulf facies is paralleled by a decrease in K, Cu, Pb, V and Ba, as well as by an increase in Ca, Mg and Mn in siderite nodules. Discussions are also made in the present paper of the differences between drill core samples and surface samples, between pyrite, siderite and calc-siliceous nodules, and between light and heavy minerals separated from sandstone in respect to their components.