Characteristics sequence-palaeogeography and coal accumulation ofPermo-Carboniferous coal measures in Shanxi Province

In order to investigate the coal accumulation pattern under the time-equivalent stratigraphic framework for the Carboniferous and Permian coal measures in Shanxi Province, this paper analyzed the lithofacies of coal-bearing searies association based on the outcrops and borehole data, and also drawn the contour maps of stratalisopachs, percentages of limestones, sandstone to mudstone thickness ratios,and coal thickness. The study results showed that four depositional systems were identified, including carbonate platform-barrier-lagoon, delta, fluvial, and lacustrine systems, the three third-order sequences were subdivided for Benxi,Taiyuan,and Shanxi Formations, and also the sequence-based Palaeogeography maps were reconstructed with the major Palaeogeographical units including fluvial plain, delta, barrier island, tidal-lagoon, and carbonate shelf. Transgression direction changed from the northeast in Sequence I into the southeast in Sequences II and III.The coals in Sequence I were mainly formed in the tidal-lagoon environment, while the coals in Sequences II and III were formed in the delta plain environment, meanwhile from Sequence I though Sequence III,the coal-accumulating center migrated from north to south,specifically coals were well developed in Sequence II.