混合沉积特征精细刻画:以江苏徐州寒武系馒头组为例OA北大核心CSTPCD

The Cambrian Mantou Formation in the Xuzhou area of Jiangsu Province is characterized by mixed siliciclastic-carbonate sedimentation.In this study,a set of typical mixed siliciclastic-carbonate sequences from the Mantou Formation were systematically analyzed for their petrological characteristics based on section and microscopic features.By analyzing the mixed sedimentation characteristics in various sedimentary environments,a mixed siliciclastic-carbonate sedimentation model was established in the epi-continental sea environment.The different types of mixing,mixing processes,and controlling factors of various mixed siliciclastic-carbonate rocks were investigated.Research has shown that there are mainly 11 types of mixed sedimentary combination types in the sequence,including sandy-bearing oolitic limestone,sandy limestone with intraclast,fine-grained limy sandstone,and limy-bearing siltstone.The overall se-quence is a result of frequent fluctuations in secondary sea-level variation,accompanied by multiple peri-ods of storm activity,within the context of epicontinental transgression.It mainly evolves from an inshore mixed carbonate-siliciclastic tidal flat to a mixed restricted platform.The sedimentation in the study area consists of facies mixing and punctuated mixing,with localized occurrences of in situ mixing and source mixing.Climate,terrestrial input,sea level changes,and carbonate yield rate serve as the primary fac-tors influencing facies mixing,with additional influences from biological activities and hydrodynamic con-ditions.The multi-stage storm activity can dominate the formation of punctuated mixing,and promote the development of facies mixing and source mixing to some extent.Under the superimposed influence of vari-ous factors,the study area is characterized by the development of a combination of multiple mixing types.Clarifying the distribution of various mixing types and mixing process can provide reference for the restora-tion of the Cambrian paleoenvironment and sedimentary evolution of the North China Plate.It also offers typical examples for the study of mixed sedimentation in the'deep time'epeiric platform.