The basis for stratigraphy seems quite intuitive today, but its applications were no less than earth-shattering to archaeological theory.For example, JJA Worsaae used this law to prove the Three Age System.Stratigraphy is based on the law of superposition--like a layer cake, the lowest layers must have been formed first.
Cross-dating of sites, comparing geologic strata at one site with another location and extrapolating the relative ages in that manner, is still an important dating strategy used today, primarily when sites are far too old for absolute dates to have much meaning.
The scholar most associated with the rules of stratigraphy (or law of superposition) is probably the geologist Charles Lyell.
Seriation is thought to be the first application of statistics in archaeology. The most famous seriation study was probably Deetz and Dethlefsen's study Death's Head, Cherub, Urn and Willow, on changing styles on gravestones in New England cemeteries.
For more information on stratigraphy and how it is used in archaeology, see the Stratigraphy glossary entry.
Seriation, on the other hand, was a stroke of genius.