贵州及邻区中奥陶世十字铺期岩相及古环境重塑

研究区位於上扬子地台康滇古陆的西面。从震旦纪到早奥陶世,研究区逐渐从陆棚发展成一个碳酸盐台地,其西面为滨、浅海,东面为盆地。中奥陶世十字铺期由于受太康运动的影响,其沉积特征和古地理格架明显不同于以前。十字铺期系指Clypt.austrodentatus/Clypt.sinodentatus带的结束到头足类Sinoceras chinense (Foord)的大量出现或Sinoceras chinense (Foord)和牙形刺Hamarodus europaeus同时出现的一段时间。这一时期由于古陆已历经剥蚀,地势平缓,起伏不大,陆源物质供应量逐渐减少,陆表海以内源沉积物为主,广泛发育了碳酸盐岩沉积。黔中地区虽有上升,但仍为平缓的水下隆起,其对台地上南北方向上的岩相变化起到了一定影响。

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.