It was based for decades in nonscientific methods that used stylistic analysis of imagery to establish one-way evolutionary schemes.
Picture from Glen Canyon National Recreation Area, Utah.
This is the concept of --or the Law of Superposition.
Stratigraphic sequences in the field, however, are sometimes unreliable.
But absolute dating methods are not always useful; the particular circumstances to which they apply do not exist at every site.
Dating methods, such as radiocarbon dating, dendro-chronology or tree-ring dating, and potassium-argon dating, that may furnish an date for an archaeological site, are a contribution of the physical and the natural sciences.