Mudstone is a fine-grained sedimentary rock composed primarily of clay and silt-sized particles. It is often formed in low-energy environments such as deep marine basins, lakes, and floodplains. Mudstone is significant in understanding depositional environments, the preservation of fossils, and the geochemical cycles of elements.
Reference: Potter, P. E., Maynard, J. B., & Depetris, P. J. (2005). “Mud and Mudstones: Introduction and Overview.” Springer.