Abstract:

Using the latest 2D framework section of the Ordos Basin， along with high-precision 3D seismic data and drilling data， we systematically reinvestigate the Wushenqi and Central paleo-uplifts within the basin. Accordingly， the Cambrian-Ordovician sedimentary structural framework of the basin is reestablished and the evolutionary history of these two paleo-uplifts is clarified. The results indicate that during the Ordovician， the Wushenqi paleo-uplift exhibited a structural framework characterized by high in the north and low in the south. The Wushenqi and Central paleo-uplifts produced significant controlling effects on the deposition of the Cambrian and Ordovician strata， respectively. The 3D seismic data reveal that during （or even before） the Huaiyuan movement， the Wushenqi paleo-uplift underwent greater exposure and denudation compared to the Central paleo-uplift， though remaining higher in altitude during the pre-Ordovician. The Wushenqi paleo-uplift was active during the Precambrian， followed by gradual diminishment until the Ordovician when it became largely inactive. In contrast， the Central paleo-uplift got uplifted and came into being in L shape connecting the Yimeng paleo-uplift in the north and the Qingyang paleo-uplift in the south before the deposition of the Ordovician Majiagou Formation， prior to which the Qingyang and Yimeng paleo-uplifts， located in the southwestern and northern parts of the Ordos Basin， respectively， were independently active. The Wushenqi and Central paleo-uplifts jointly govern the distribution of sedimentary facies zones， resulting in the favorable reservoir-caprock assemblages in the eastern and central Ordos Basin. Promising targets for hydrocarbon exploration in the Ordos Basin include the Pre-Ordovician gas play s in weathering crust， lithologic gas plays in the central part， and fault-fractured gas plays in the eastern part.

Key words: tectonic evolution, Ordovician, Cambrian, Central paleo-uplift, Qingyang paleo-uplift, Wushenqi paleo-uplift, Ordos Basin