Mesozoic Tectonics and Sedimentation of the Giant Polyphase Nonmarine Intraplate Ordos Basin, Western North China Block

The Mesozoic Ordos Basin is a large intracontinental basin that is characterized by a thick, undeformed stratigraphic succession over a wide region that is bounded by deformed polyphase orogenic belts on all margins. Structural and stratigraphic studies document a diverse history of Late Palaeozoic through Cretaceous shortening, extension and strike-slip on the northern and western basin margins, and a longer-lived contractile setting in the southern part of the basin. In response to these structural episodes, associated basins formed within, or adjacent to, the marginal mountain belts and were filled by a variety of nonmarine depositional processes. Synchronously, subsidence across the whole of the Ordos block resulted in a large, integrated basin, also filled by nonmarine systems, that spanned across distinct structural domains. These stratigraphic and structural characteristics are interpreted to suggest that mechanical contrasts between the basin interior and the marginal mountain belts fundamentally control the timing, distribution and styles of deformation and basin formation on the margins of the Ordos block. This mechanical contrast between the Ordos Basin and its margins encouraged the repeated, polyphase deformation on its margins, whereas the vast area of the Ordos block continued to subside uniformly. These characteristics are typical of many large basin systems found on relatively recently assembled continents, like southern Eurasia. Examples that may be similar in many respects to the Ordos Basin include other collisional successor basins of China, such as the Tarim, Junggar and Sichuan basins.