层序格架内障壁海岸沉积体系古地理背景下聚煤作用

为了系统揭示层序格架内古地理背景下障壁海岸沉积体系的聚煤特征，运用层序地层学和古地理恢复有关理论、方法以鲁西南地区石炭系-二叠系本溪组-太原组为例进行了障壁海岸沉积体系层序地层学和聚煤作用的研究。识别区域不整合面、海侵方向转换面、古土壤层底界面、海泛面、区域性强制海退面5种关键层序界面类型，将研究煤系划分为17个准层序（2种准层序类型）、2个三级层序；等时层序格架内障壁海岸沉积体系聚煤作用受基准面（相对海平面）高频波动影响，煤层发育层数多、单层厚度小；平面上聚煤作用以障壁岛-潮坪过渡带为中心，向两侧潮坪和澙湖煤层厚度、煤层层数减小。指出聚煤期剩余可容空间大小及新增可容空间产生速率（基准面上升速率）是控制泥炭沉积的关键因素；从绝对海平面变化、盆地基底沉降、下伏地层成岩作用等方面分析了平面上可容空间变化规律，提出了基于层序格架内古地理背景下剩余可容空间变化规律的障壁海岸沉积体系聚煤模式。

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

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.