Our dataset shows Si isotopic, geochemical andmineralogical trendswith depth and as a function of pedogenic time, providing an orthogonal dataset which sheds light on the origin and evolution of pedogenic clayminerals in the clay fraction. The depletion in light 28Si in pedogenic clay minerals in topsoil increases over time (from +1.01 to +2.04‰) and a part of light 28Si released accounts for the relative enrichment in light 28Si in pedogenic clayminerals in subsoil (−0.91‰).