Study Of Sequence Stratigeaphy And Coal Accumulation Regularities In Coal Bearing Formation Of Eastern Ningxia Coalfield

With the rapid development of economy of Ningxia， ningdong coalfield is particularattention as an important energy chemical base in Ningxia Hui autonomous region， in recentyears. But now the research of ningdong coalfield is mostly confined to a strata group or aformation of small groups, and with the focus has gradually shifted to the development of coalresources in Ningxia ningdong coalfield, ningdong coalfield the urgent need to undertake acomprehensive study on the occurrence law of coal resources.This article using the theory of high resolution sequence stratigraphy of the system,combining with the theory of geodynamic and coal geology, establish the high resolutionsequence stratigraphy of coal-bearing series in ningdong coalfield. Studies have shown that,major coal accumulation period is divided into the late Carboniferous, the early Permian andthe middle Jurassic period in this coalfield, Through the study of sedimentary environment,Ningdong coalfield is mainly with shallow lake delta system which can be segmented out thedelta plains facies, delta front facies and delta front shallow lake delta facies; the system ofrivers can be divided into, alluvial channel facies, flood basin facies and floodplain marshefacies,etc. Jurassic Yanan formation as the major coal-accumulation period is to identify the3three-stage sequence, the sequence "ternary structure" development is complete, total9sequence groups are identified, and can be further divided into9grade sequence in detail.Coal seams are mainly located in the TSS and HSS sequence groups in central, districtdevelopment situation is not entirely the same. Further with the three level layer sequence asdrawing unit, using the single factors statistics method of the parameter of Lithofaciespalaeogeography which under domain system, draw out the contours about thickness of strata,thickness of sandstone, thickness of mudstone, ratio of sand-mud and thickness of coal onHongdunzi mining area and Lijiaxiaozhuang mining area. This provides theoretical basis for analysis of coal-accumulating regulation though ancient geographic features analysis, andreflects on deposition environment of changes process.Studies show that the distribution characteristics of coal seam’s thickness has a goodconsistency with sediment sag,ancient geographical environment and sedimentary faciesdistribution which have happened at the same time; Its part of the sag, that is the most part ofthe development of delta, is also the most development of coal seam area. In the deltaenvironment, which is in the upper and lower parts of the transition zone of the Delta plain,is the center of the coal-rich area. The total variation of coal-bearing, has different levels inTaiyuan group, Shanxi group and Yanan group.