Abstract: The basement of the Ordos Basin is mainly formed in the ArchaenPaleoproterozoic Era when strong regional metamorphism eventually developed its exceptionally complex petrographic composition. Metamorphism generally reached the (high) amphibolite-granulite-facies highly metamorphosed regional metamorphic rocks which consist largely of schist, gneiss, granulite, quartzite, marble and ranitic gneiss. The basement structure shows obvious partitioning features and can be divided into the north, northwest and central-south regions. The overall regional strike is northeast to the main. From an evolutionary perspective, the basement of the Ordos Basin is one of the Archean microcontinent blocks that formed the North China Craton, where its integration with North China likely occurred in the late Paleoproterozoic Era. The early sedimentary cover mainly experienced four stages of evolution: inland depression of the Changcheng Period, edge sedimentation of the Jixian Period, integral uplift of the QingbaikouNanhua Period, and edge depression of the Sinian Period. The sedimentary environment is mostly marine facies exhibiting continental characteristics in localized areas in the later period. The characteristics of sediment are significantly different for different periods, primarily due to both tectonic and climate constraints. The early sedimentary cover is obviously influenced by basement and tectonic structures, with earlier period experiencing greater influence. The special location of the basement may be the main reason that the most active depression area is at the southwest edge of the basin.

Key words: Ordos Basin, structure of basement, sedimentary cover, Meso-Neoproterozoic, Changcheng System, Jixian System