Sequence Stratigraphy and Coal Accumulation of the Lower Permian in Xinji Mining Area of Huainan Coalfield

Abstract

The coal-bearing formation of Lower Permian in Huainan coalfield is well developed with lagoon-tidal flat deposition and delta system deposition. According to the identification of the sequence boundaries represented by regional unconformity and incised valley filling sandstone base, combined with the characteristics of sedimentary cycles, the high resolution sequence stratigraphy of the Early Permian coal seams (the Shanxi formation and Lower Shihezi formation) have been analyzed. The coal seams are divided into 3 third-order sequences from bottom to top and the sequence stratigraphic framework has been established. The thickness variation of the coal seams shows that the major minable seams were developed in the transgressive systems tract of lagoon-tidal and the delta plain environments, in which the total coal seams are thicker in SQ3 and thinner in sequence SQ2, with the thinnest in SQ1.Within the sequence, the thickest coals were developed in the transgressive systems tract, the thicker coals in the high-stand systems tract and the thinnest coals were preserved in the low-stand systems tract.