In some parts of the world, sedimentary layers can be traced for long distances so that the relative positions of the various layers and, hence, their relative ages can be established. Plutonic igneous intrusions are always younger than the rocks that they cut across or intrude. Events that produce a plutonic igneous intrusion - Formation of the rocks that subsequently will be intruded. Intrusion of magma into the pre-existing rocks. Cooling of the magma to form a dike, sill volcanic neck or batholith.
Faults are always younger than the rocks that they cut across or displace.
Faulting of the pre-existing rocks. Uplift or tilting or folding of the sedimentary rocks below the unconformity. Erosion of the tilted or folded sedimentary rocks. Formation of igneous or metamorphic rocks deep within the crust of the earth. Uplift and erosion of a large thickness of the rocks that are overlying the igneous or metamorphic rocks.