Dating technique

The scholar most associated with the rules of stratigraphy (or law of superposition) is probably the geologist Charles Lyell.

The basis for stratigraphy seems quite intuitive today, but its applications were no less than earth-shattering to archaeological theory.

Absolute dating, the ability to attach a specific chronological date to an object or collection of objects, was a breakthrough for archaeologists.

There are dendrochronological records for Europe and the Aegean, and the International Tree Ring Database has contributions from 21 different countries.

The main drawback to dendrochronology is its reliance on the existence of relatively long-lived vegetation with annual growth rings.

For example, since each Roman emperor had his own face stamped on coins during his realm, and dates for emperor's realms are known from historical records, the date a coin was minted may be discerned by identifying the emperor depicted.

Many of the first efforts of archaeology grew out of historical documents--for example, Schliemann looked for Homer's Troy, and Layard went after the Biblical Ninevah--and within the context of a particular site, an object clearly associated with the site and stamped with a date or other identifying clue was perfectly useful. Outside of the context of a single site or society, a coin's date is useless.

For example, JJA Worsaae used this law to prove the Three Age System.

Seriation, on the other hand, was a stroke of genius.

His research culminated in proving that tree ring width varies with annual rainfall.

Not only that, it varies regionally, such that all trees within a specific species and region will show the same relative growth during wet years and dry years.

Determining calendar rates using dendrochronology is a matter of matching known patterns of light and dark rings to those recorded by Douglass and his successors.

Dendrochronology has been extended in the American southwest to 322 BC, by adding increasingly older archaeological samples to the record.

Clark Wissler, an anthropologist researching Native American groups in the Southwest, recognized the potential for such dating, and brought Douglass subfossil wood from puebloan ruins.

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