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The middle Ordovician of Pingliang area on the west margin of North-China platform is represented by a succession of deep-water sediments in which contourites are well-developed. Contour current deposits are well-developed. The contourites can be classified into:calcarenitic contourite, calcisiltitic contourite and calcilutitic contourite. Three typical contourite successions are recognized: complete contourite succession, incomplete contourite succession and contourite successions consisting only of calcarenitic contourites. According to the palaeocorrent and the palaeogeographic format analyse,carbonate contourite drift in the study area is unfolded crossing northwest-southeast, forwarding from southeast to northwest along the slope, and compared with other contourite drifts, it has some characteristics of coarser-grained sediment, thicker individual layers, and highly developed calcarenitic contourites and so on.

The major rock types of Ordovician Majiagou Formation Ma541 Submember in western Jingbian Tableland include muddy dolomite, gypsum-bearing dolomite, gypsum dolomite, limy dolomite, and muddy powder crystal dolomite. This paper is based on the theory of sedimentary petrology and with the methodology of comprehensive mapping by using single factors to analyze multiple factors.Using stratum thickness, the content of gypsum and penecontemporaneous dolomite as single factors, we studied the lithofacies palaeogeography in Ma541 Submember.The results show that Ma541 is generally a set of sedimentation from supratidal limited evaporation environment and in the period of sea level decline with shallow water. The sedimentary microfacies are mainly composed of gypsum-bearing dolomitic flat and gypsum dolomitic flat ,dolomitic gypsum flat comes second. We combined the areas regional geological background with lithofacies palaeogeography to construct the limited evaporation tidal flat sedimentation maps of Ma541 Submember. Meanwhile,the control of reservoirs was studied. We thought that gypsum-bearing dolomitic flats and dolomitic flats provide a foundation for the development of large-area reservoirs.

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The tight sand in the layer 7 of YanChang Formation, Ordos Basin major develops braided river delta and gravity flow deposits. In this paper, based on previous studies on lake pelvic shape, provenance and hydrodynamic, the sand body in the research area has been systematically studied through core observation, logging data, and sedimentary theory. Various genetic types of sedimentary sand body are developed in this area, mainly as delta deposition, sandy debris flow deposits, turbidites (classic turbidites). We can identify 6 kinds of sand vertical combination type, they are the superimposed sand body (A-type), thick and uniform thickness sand body (B type), thin and uniform thickness sand body (C-type), up thinning sand body (D-type), thickening up sand body (E-type) , thick and thin interbed sand body (F-type). The 6 types mainly controlled by sedimentary facies. The A-type sand body mainly developed in the delta depositional environment, the B type sand body is visible both in the delta and slope belt, while the D-type, E-type, F-type sand body are mainly developed in the deep lake. The distribution of sand body in the plane is zonal pattern.