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The authors studied the depositional environments, sequence stratigraphy, paleogeography and coal accumulation of the Carboniferous-Permian paralic coal measures based on data from outcrop and borehole sections. The sequence boundaries were represented by regional disconformity, transgression direction switching surface, the base of incised valley fill sandstone, facies-reversal surface and associated paleosols. According to these sequence boundaries, the coal measures were subdivided into 7 third-order sequences and related systems tracts. For the paleogeography analysis, the contours of a variety of lithofacies parameters were drawn, including strata thickness, thickness ratio of sandstone and mudstone, limestone contents, and coal thickness. Based on these contours, the lithofacies paleogeography maps of each third-order sequence were reconstructed. The comparison of the contours of coal thickness with the distribution of facies units of the lithofacies paleogeography was made, and it revealed that the favorable coal-accumulating environments were deltas, fluvial plain and lagoon-tidal flat. Coal accumulation was strong in SQ2 (middle and upper Taiyuan Formation) and SQ3 (Shanxi Formation) with the coal accumulating centers were distributed in the Zhungeer, Datong, Shuozhou, Wuhai, Fengfeng areas, and the Beijing-Tainjin-Tangshan area. Coal accumulation in SQ4 (Xiashihezi Formation) and SQ5 (first member of the Shangshihezi Formation) was weak and the coal-accumulating centers were distributed in the southern part of the North China Basin, including Huainan and Huaibei coal fields. [ABSTRACT FROM AUTHOR]

In order to reveal sequence boundary formation mechanism of large scale craton epicontinental basin and coal accumulation characteristics under paleogeographic setting of isochronous sequence stratigraphic framework, sequence stratigraphic framework and coal accumulation were analyzed for the Permo-Carboniferous of Benxi-Shanxi Formation in the eastern Ordos Basin. A total of four types of sequence boundary are identified, which are regional unconformity surface, transgressive direction turnaround surface (BTR) resulted from settlement difference of basin basement, and normal regressive erosion surface (NSS) , exposed surface (NES) , corresponding conformity surface (NCC) , and river erosion surface(FEU) resulted from compulsory regression, exposed surface (FES), corresponding conformity surface (FCC). Coal-bearing strata is divided into three third-order sequences and six fourth-order sequences. Authores find that cyclical changes of base level controls the occurrence of coal accumulation, coal-base depositional environment and basin basement subsidence rate during coal accumulation period controls seam thickness and continuity. Paleogeographic comprehensive coal accumulation model within isochronous stratigraphic framework is proposed. The results show that widely distributed thick coal seams form around II-type sequence interface and the largest regression surface (initial flooding surface) of I-type sequence; under the lagoon-tidal flat context, coal-center is located in the tidal flat depositional environment, whose remaining accommodation space is small; under the lagoon-delta-tidal flat context, coal-center is located in the tidal flat depositional environment, whose remaining accommodation space is moderate and basement subsidence rate is large; under the shallow river delta context, coal-center is located in the restricted sea and lakes and bays of the delta plain depositional environment, whose remaining accommodation space is large and basement subsidence rate is large. [ABSTRACT FROM AUTHOR]