Study On The Lithofacies Palogeography Of Ordovician In Ordos

The study area is located in the western part of the North China, which is north to the Yinshan Mountain, west to the Helan Mountain, sourth to the Qinling Mountain. The Cambrian of the Ordos is mainly a set of carbonatite deposition. In the area, the horizontal change of thickness change is bigger, the middle,north part is thin,and the sourth,west part is thick.The range of sratigraphic thickness of the whole region is 100-1300m.The study area is wide, the rock stratigraphy have difference in the different region. On the basis of the international stratigraphic Division Scheme of Cambrian, the Ordos region has been divided into Terreneuvian (lost in the area), series 2(stage 3, stage 4), series 3 (stage 5, Drumian, Guzhangian), Furongian (Peibian, stage 9, stage 10). According to the lithology, layer, structure and palaeogeomorphology of the Cambrian in study area, the division and comparison of the stratigraphy has been finished.and established the layer framework of the equitime.According to the multianalysis of the sedimentary facies and depositional system,the typical analysis of the sedimentary facies has been built up through the bore well and outcrop data in different place. It is established the pattern of carbonate platform and barrier coastal deposit and identified the sedimentary facies in this area: tidal flat, restricted platform, open platform, shoal and interbank sea. Based on the sedimentary facies,6 lithofacies and palaeogeography maps have been drown up using stage as the unit, and the evolution of Cambrian in different stages has been researched.