RECONSTRUCTION OF THE SHIZIPUIAN(MIDDLE ORDOVICIAN)SEDIMENTARY FACIES AND PALAEOENVIRONMENTS IN GUIZHOU AND ITS ADJACENT AREAS

The carbonate rocks are best developed in the Shizipuian (Middle Ordovician)strata in Guizhou and its adjacent areas. The clastic rocks occur locally in the western part of the study area, while the endogenic deposits occupy the vast area of the epeiric sea. The central Guizhou region was getting into an uplifted area during the middle stage of the Caledonian orogeny. The regular carbonate microfacies belts from south to north are superposed on the pre-existing NNE—SSW-trending facies belts in northern Guizhou, southern Sichuan and northeastern Yunnan. This is characteristic of the Shizipuian sedimentary facies distribution. The biologic assemblages have revealed both the vertical evolution of the carbonate microfacies of different ages and horizontal palaeogeographic framework consisting of ancient land, lagoon, littoral and shallow sea, carbonate platform, platform-margin beach and ramp, continental shelf and slope. The present paper deals with the Shizipuian sedimentary facies and palaeoenvironments in terms of the data about nearly fifty sections in combination with modern sedimentological theorics and methods.