Ubiquitous clay refers to the widespread presence of clay minerals in various geological environments, including soils, sedimentary rocks, and hydrothermal deposits. These clays are significant in sedimentology, soil science, and economic geology for their role in soil formation, sedimentary processes, and the development of clay-rich mineral deposits.
Reference: Moore, D. M., & Reynolds, R. C. (1997). “X-ray Diffraction and the Identification and Analysis of Clay Minerals.” Oxford University Press.