苏、浙、皖地区沉积-大地构造演化

中国南部近东西延伸的扬子板块形成于距今800Ma 前。自震旦纪开始,在其东缘苏、浙、皖地区形成了两个呈北东东向展布的并在其东端相联的裂陷槽。其沉积厚度达万米。沉积演化晚期形成了复理石与磨拉石。复理石堆积于晚奥陶世,此时裂陷槽为两个向东开口的海湾,碎屑物来自盆地南北两侧的扬子古陆。磨拉石堆积的时代从晚奥陶世末到中泥盆世,碎屑物

THE SEDIMENTOLOGIC AND TECTONIC EVOLUTION IN THE ZHEJIANG-ANHUl-JIANGSU REGION

The Yangtze Plate, extending from east to west in eastern China, was formed about 800 Ma ago. Since the Sinian the Yangtze Plate entered a stage of intraplate development.After investigations in the eastern part of the Yangtze Plate, the authors concluded that there are two Sinianearly Palaeozoic aulacogens in western Zhejiang and southern Anhui. The aulacogens initiated at the beginning of the Sinian (as evidenced by the existence of alkalic volcanic rocks at the bottom of the basin) and closed in the Late Devonian (as evidenced by the development of the molasse formation). The sedimentary environments have gone through a process from continental facies to marine facies and again to continental facies. The sedimentary sequence in the basins amounts to 10000 meters in thickness. Two important formations——the flysch formation and the molasse formation——at both ends of the sequencewere investigated.The flysch was deposited in the Late Ordovician, when the two aulacogens were gulfs that opened to the east. The clastic materials were derived from the Yangtze Plate on both northern and southern sides of the basins and were transported mainly along the basin axis in a northeast direction.The molasse was deposited from the terminal Late Ordovician to Middle Devonian. The elastics came from an uplifted orogenic belt in the east and were transported towards the northwest-west.The facts mentioned above show that from the end of the Late Ordovician to the Early Silurian a drastic change of the basin form and the tectonic framework took place in the Jiangsu-Zhejiang-Anhui region.