Sedimentary Evolution Characteristics of Fine-Grained Lithofacies under the High-Resolution Isochronous Shelf System: Insights from the Wufeng-Longmaxi Shales in the Sichuan Basin

Abstract The deposition and evolution of fine-grained sediments is a hot topic in sedimentary rock studies important for accurately evaluating shale gas sweet spots. In this paper, the characteristics Wufeng-Longmaxi shales, major targets Chinese exploration, were studied by using core observations, thin section analyses, scanning electron microscopy, geochemical analysis, fossil identification. This work identified six typical lithofacies; among them, organic matter-rich siliceous facies (OMRSSF), high-organic matter argillaceous (HOMSASF), medium-high low calcareous (M-HOMLCSASF) are favorable exploration. high-resolution isochronous unit shelf system was established, differential lithofacies tract discussed. differentiation transgressive controlled scale tectonics under increasingly shallow water conditions. regressive preexisting lithofacies. had more frequent transitions greater than those tract, they exhibited significant spatiotemporal inheritance. Sequential sequences symmetric distinguished continental system. depocenters subsidence centers consistent while tectonically active paleocontinent regression tract. study great significance further exploration marine improvement theory systems.