The relative age dating principle of 'Cross Cutting Relationships' states that "If a geologic feature is cut by another geologic feature, the feature being cut is older than the feature cutting it." So, if a geologic unit is cut by an igneous dike or a fault, it must be older than the dike or fault. If you cut a sandwich, the layers of the sandwich had to exist for them to be cut. Hence, they are older than the cut.

свернуть