Sequence Stratigraphy And Coal Accumulation Of The Early Cretaceous In Northeastern China

There are abundant coal resources formed in northeastern China during EarlyCretaceous period. Sedimentary facies, sequence stratigraphy and coal accumulation werestudied based on data of cores, outcrop sections and well logs. The coal-bearing series weremainly composed of conglomerate, sandstone, siltstone, mudstone, combustible organic rocksand volcanic rocks, a total of25lithofacies are identified. Then alluvial fan, fluvial, delta andlacustrine depositional systems were recognized and4kinds of typical coal-bearing modelswere establelished. Based on regional unconformity surface, erosional base of incise valleyfill sandstone/conglomerates, vertical facies reversal surface, a total of6sequence boundarieshave been identified, which subdivide the Early Creataceous coal measures into5third-ordersequences. The Jiufotang stage corresponds to Sequence I, the upper and lower Shahai stagecorrespond to Sequence Ⅱ and Sequence Ⅲ, the upper and lower Fuxin stage correspondto Sequence Ⅳ and Sequence V. SequenceⅡand sequence Ⅳare the best coal accumulatingperiod. Based on the comprehensive analysis of single-factor isoline map, paleogeographicmaps of coal-bearing basin in the typical basin and coal-bearing basin in northeastern Chinaare reconstructed. The most favourable depositional paleogeographic units for coalaccumulation are alluvial plain swamp, delta plain swamp, lakeshore plain swamp. Thedistribution features of coal-bearing sequences, coal-bearing properties and coalaccumulating characteristics in the sequence stratigraphic framework were further discussed.The results show that the western zone was the most favourable place for the coalaccumulation. The genesis of the coal seams were deposited at the place whereaccommodation space creation rates balanced with peat/coal accumulation rates was sustained and steady.