Tectonic Setting and Eastward Migration of Mesozoic-Cenozoic Sedimentary Basins, Eastern China: ABSTRACT

Abstract

Basins of eastern China are characterized by thin crust and alternately arranged NE or NNE-trending regions of subsidence and uplift. During the Indosinian (Late Triassic), the western part of eastern China was depressed relative to eastern areas. Upper Triassic and Jurassic formations comprise the major basin fill of the Sichuan and Eerduos basins, while only minor Upper Triassic-Jurassic rifts and related basins are superimposed on earlier swells in eastern regions. In the Early Cretaceous, the depocenters of the Sichuan and Eerduos (Ordos) basins shifted westward or southward, and soon afterward were uplifted as a whole. In contrast, the most extensive and intensive subsidence in the Songliao basin occurred during the Quantou-Nenjiang stage (middle Cretaceous). To the outh, the Huabei basin had a multi-cyclic, rifted history, but the most intensive subsidence occurred during the Eocene-Oligocene. Still farther east, the present-day marginal seas formed mainly during the Late Cretaceous-early Neogene. Thus, the history of these basins clearly shows the eastwardly migratory nature of the timing of basin formation in eastern China. The development of these basins was influenced not only by subduction of the Pacific plate in the formation of initial stage shearo-compressional swells and depressions, but also by the motion of Tethys-Indian plate northeastward. The latter movements resulted in an eastward component which led to the progressive elevation of the west. Back-arc spreading also played an important role in this process. Basins of eastern China can be classified into two groups, one formed in compressive or shearo-compressive settings, the other in tensile or shearo-tensile settings. Basins of the former type formed as structural depressions or flexures due to lithosphere deformation. These display foreland fold-thrust belts on their western borders. The tensile group of basins includes: (1) complex rift-depression types (monocyclic or polycyclic); (2) simple rift valleys or minor block-fault depressions; (3) coastal delta-shelf basins on the rifted continental margin; and (4) back-arc spreading basins. End_of_Article - Last_Page 597------------