A tectonic escape model for the formation of sedimentary basins in the Yangzhou block of the Lower Yangtze Region, Eastern China

Abstract

This paper presents a tectonic escape model for the formation of sedimentary basins in the Yangzhou Block of the Lower Yangtze Region, Eastern China. Nine sedimentary basins are identified in which the Pukou Formation of the Upper Cretaceous has been deposited. From south to north, the nine sedimentary basins are named: Wangjing, Qianshan, Wuwei, Nanxuan, Changzhou, Jurong, Nanjing, Quanjiao and Subei basins. They form a wedge-shape fragment (the Yangzhou Block) occupying an area of 100,000 km 2 in the Lower Yangtze Region. The two side boundaries of the Yangzhou Block are the strike-slip Tanlu Fault and the strike-slip Quangjiao-Xiangshui Fault on the northwest and the strike-slip Qingyang-Nantong Fault on the southeast. The wide end of the wedge faces the Southern Yellow Sea in the northeast and the narrow end contacts the Dabie Block in the southwest. During the Early Mesozoic, collision between the Yangtze Block and the North China Block resulted in the formation of the Qinling- Dabie Orogenic Belt and caused the Lower Yangtze Region to become a foreland basin with many strike-slip faults. During the Late Mesozoic, wide spread extension in Eastern China and shortening in Qinling/Dabie Shan and in the Huaying Shan region resulted following establishment of an Andean-type arc margin to the east of the Southern Yellow Sea area, when 'Greater Japan' collided with Asia. Consequently, the wedge-shaped Yangzhou Block escaped tectonically toward the northeast and formed distinctive geological features in nine sedimentary basins during Pukou time in the Late Cretaceous. These geological features are reflected in basin spatial distributions, basin geometries, sedimentary facies, sediment thicknesses, sedimentary environments, and the petrology of fanglomerates and sandstones. These basin are part of a large population of arc-crestal rifts formed on top of that Andean arc. The proposed tectonic escape model could be useful in petroleum exploration and mining in the region. © 2002 Elsevier Science Ltd. All rights reserved.