Methods of dating ancient pottery
In other words, artifacts found in the upper layers of a site will have been deposited more recently than those found in the lower layers.
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.
Stratigraphy is the oldest of the relative dating methods that archaeologists use to date things.
Stratigraphy is based on the law of superposition--like a layer cake, the lowest layers must have been formed first.
Until the 20th century, with its multiple developments, only relative dates could be determined with any confidence.
Absolute dating, the ability to attach a specific chronological date to an object or collection of objects, was a breakthrough for archaeologists.Dendrochronology has been extended in the American southwest to 322 BC, by adding increasingly older archaeological samples to the record.