Petrological Classification of Ancient Deep-Marine Siliceous-Argillaceous-Carbonate Rock Series (SAC)

Ancient deep-marine siliceous-argillaceous-carbonate rock series (SAC) are general name of silicalite, argillite, carbonate rock and their mixed deposit rocks which are all pelagic and hemipelagic sediments. In this paper, it proposes a new mineralogy-based classification scheme of the SAC rock series based on existing classifications. According to quantitative classification standard["pure (>90%)", "dominate(50%-90%)", "rich(50%-25%)", "bearing (< 25%)"] and using triangular midlines of the ternary plot, the SAC rock series are divided into 4 primary classes and 21 classes. By using the new classification, silicalite, carbonate rock and mixed mudstone primary classes are present in the Lower-Middle Cambrian in the Lower Yangtze region and their petrological features are described by optical microscope observation. The SAC rock series of the Lower-Middle Cambrian show the sedimentary evolution trend from siliceous end to carbonate end. The results of classification of three typical SAC rock series indicate that the new classification scheme clearly reflects the mixed sedimentary evolution trend among three terminal minerals. The classification of the SAC rock series may help provide a significant foundation to quantitative description of the ancient pelagic and hemipelagic sedimentation, and also provide an important basis for exploring the evolution of sedimentary environment.