Paleogeography Reconstruction of the Early- Middle Jurassic Large Ordos Basin and Development and Evolution of Continental Downwarping

Key words: 
• Large Ordos basin /
• sedimentation uniformity /
• paleogeography reconstruction /
• tectonic setting of basin

Abstract: Based on the genetic relation between sedimentary architecture, paleo- drainage systems and faciesdistribution, and the comparative sedimentology analysis, the paper discussed the uniformity existing inthe primary sediment fillings in the Lower- Middle Jurassic developed of the present Ordos basin and inNingwu and Datong to the east of the basin.The uniformity confirmed that the strata were deposited inthe same Large Ordos basin.The Early- Middle Jurassic paleogeography reconstruction,in terms of fourdeposition stages, revealed the tectonic stages of downwarping- uplifting- redow nwarping and the mi-gration of dynamic setting during the formation and evolution of the basin.The study on the tectonic set-ting for continental downwarping could determine the transformation of Indosinian- Yanshanian tecton-ics and the time of tectonic transformation in North China on a smaller scale.