The Coal-accumulating Environment And Characteristics Of Sedimentary Evolution In The Middle Permian Shanxi Formation, Werstern Henan Province

Based on the sedimentological theory, compiled map method of lithofacies paleogeography, the field measurements and lithological description of the outcrops, and combing with the relevant geologic informations including the outcrop, drilling cores and logging data, the integrated stratigraphic column, sedimentary facies column, the stratigraphic isopach map, sand-mud ratio contour map and lithofacies palaeogeography map of the Shanxi Formation have been drawn out in this work, meanwhile, the sedimentary characteristics and depositional successions of the various sedimentary facies, coal-accumulating environment and the characteristics of sedimentary evolution have been analyzed in the study area.On this basis, this paper made great progress in the following aspects:First, seven kinds of maps have been compiled in this work, including six pieces of integrated stratigraphic column, seven pieces of sedimentary facies column, the stratigraphic isopach map, sand-mud ratio contour map, tectonic palaeogeography map, lithofacies palaeogeography map and coal accumulating environment model of the Middle Permian Shanxi Formation, western Henan province.Second, on the basis of comprehensive analysis, five types of sedimentary facies, 7 sub-facies, six micro-facies, and 14 kinds of sedimentary successions in the Shanxi Formation of western Henan have been divided.Third, the coal accumulating environment and depositional sequence features in Shanxi Formation of western Henan are analyzed, and two kinds of coal accumulating environment models in the Shanxi Formation of western Henan, that is, deltaic interdistributary peat bog and tidal flat coal accumulating environments, in which latter contains low-level peat flat and high-level freshwater peat bog, are suggested. The distribution features of different coal accumulating environments in this region are also discussed.In the end, the evolution of depositional environment during the depositional period of the Shanxi Formation are Summarized, it can be divided into three large deposit phases, including the lower cycle of the coal II unit, the middle cycle of the coal II unit and the upper cycle of the coal II unit, and experienced a development of sedimentary environments from the bay and lagoon to tidal flat, and then to Lower delta plain and Upper delta plain.