Advanced Lithofacies Analysis by Using X-Ray Computed Tomography

Lithofacies, defined as distinctive assemblages of sedimentary characteristics, necessitate a comprehensive understanding of their past depositional environments to facilitate paleoenvironmental reconstructions, resource explorations, and effective hazard assessments. To unravel the complexities of texture variety and other sedimentary features, along with physicochemical properties, conventional methods such as core description, grain size analysis, and well logging have been widely utilized. However, these approaches have limitations due to observer-dependence, time-consuming processes, discrete sampling, and the restriction to subsurface observations, which may impede the accurate distinction of lithofacies. X-ray Computed Tomography (X-ray CT), a rapid, non-destructive, and high-resolution technique, offers an unbiased and continuous approach. It provides three-dimensional visualization of samples and allows for qualitatively and quantitatively statistical analysis in stratigraphy, addressing the limitations of conventional methods. In this study, X-ray CT was employed to examine five sediment cores containing diverse sedimentary features and distinctive materials near Dapeng Bay in southwestern Taiwan. The research aimed to evaluate the feasibility of X-ray CT in characterizing different lithofacies within this region through a structured three-step workflow, involving systematic X-ray CT scanning, extraction of CT-derived intensity and statistical data, and analogy of lithofacies of cores with modern samples of known depositional conditions. The comparative analysis of CT-derived parameters within the cores was used to distinguish the features of different lithofacies. Furthermore, organic and biological substances such as charcoals and shells were observed and defined by given radio-density, characterizing other unique lithofacies with their presence combination. The classified lithofacies in CT-derived parameters may also correspond to specific depositional processes or events. By demonstrating how the application of X-ray CT quantitatively aids in characterizing and distinguishing various lithofacies, this research may ultimately contribute to providing an analogical foundation for subsequent lithofacies analysis within comparable sedimentary settings and extended time spans in future research.