Paleogeographic evolution and coal accumulation under sequence stratigraphic framework of a barrier coast

Abstract：Sequence stratigraphic framework and coal accumulation in a barrier coast system were analyzed for the Permo-Carboniferous of Benxi-Taiyuan Formation in SW Shandong Province of China.A total of 5 types of key interface,i.e.regional unconformity,shifting surface of transgression,bottom of paleosol,flooding surfaces and surface of regional forced regression were recognized.Consquently,the studied coal measures were delineated into 17 parasequences（2 types of parasequences）,and 2 third-order sequences.The sequence stratigraphic results suggest that coal accumulation is largely controlled by the high-frequent base level（relative sealevel） fluctuations,and the coals deposited are generally thin with multistoried pattern.The coal accumulation is mainly focused on the transitional zones between barrier island and tidal-flat,then decreases towards lagoon.It is suggested that the peat deposition is dominantly controlled by the residual accommodation and the rate of the accommodation increase（rate of the base level rise）.The accommodation change was analyzed considering various aspects such as absolute sea-level change,basin subsidence and diagenesis of underlying sequences.The coal accumulation model for the barrier coast under sequence stratigraphic framework was also proposed based on the residual accommodation changes.