The law of superposition is a major principle of stratigraphy stating that within a sequence of layers of sedimentary rock, the oldest layer is at the base and that the layers are progressively younger with ascending order in the sequence. In another word, the principle states that in an undisturbed sequence of deposits, the older deposits are more deeply buried and younger deposits are more shallowly buried, younger towards the top. The Principle of Association corresponds to the correlation involving a high degree of consciousness and modifiability as well as the occurrence of two or phenotypic characteristics together, that is, things found in the same sediment are of the same age.