Carbon cycle used dating artifacts
Until the 20th century, with its multiple developments, only relative dates could be determined with any confidence.
Since the turn of the century, several methods to measure elapsed time have been discovered.
Using local pine trees, Douglass built a 450 year record of the tree ring variability.
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.
The first and simplest method of absolute dating is using objects with dates inscribed on them, such as coins, or objects associated with historical events or documents.
Plotting several curves can allow the archaeologist to develop a relative chronology for an entire site or group of sites.For example, JJA Worsaae used this law to prove the Three Age System.For more information on stratigraphy and how it is used in archaeology, see the Stratigraphy glossary entry.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.Each tree then, contains a record of rainfall for the length of its life, expressed in density, trace element content, stable isotope composition, and intra-annual growth ring width.
It was now possible to assign a calendar date to archaeological sites in the American southwest for over 1000 years.