Cross-cutting relationships are a principle of geology that states that any geological feature that cuts across another is younger than the feature it cuts. This principle is fundamental in establishing the relative ages of rocks and geological structures, and is widely used in stratigraphy, tectonics, and the interpretation of geological history.
Reference: Ramsay, J. G., & Huber, M. I. (1987). The Techniques of Modern Structural Geology, Volume 2: Folds and Fractures. Academic Press.