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Home , Seriation (archaeology)

Dating Artifacts

No doubt every docent has heard the question, "How old is it?" Stone, metal, and ceramic artifacts are dated using several archeological techniques. The dating methods furnish an absolute or a relative date. Absolute methods include radio-carbon dating, thermoluminescence dating, and . Dates are expressed in specific units: year, century, millennium. Living plants absorb radioactive carbon (C14) from the atmosphere. Animals contain C14 because they eat plants. When a plant or animal dies, the C14 decays at a known rate. Radio-carbon dating will determine how long an organism has been dead. If a plant or animal is buried with something made of stone, metal or ceramic, the can be given the same age as the decaying plant or animal. On a molecular level, ceramics trap nuclear radioactive energy. Heated ceramic samples will release that trapped energy in the form of a light flash called thermoluminescence. Measuring this light intensity can determine the last time the ceramic was heated or fired. Thermoluminescence dating is relatively new and not as accurate as radio-carbon dating, but it could substantiate another dating method. Dendrochronology is the study of tree ring growth. Each tree ring is a layer of cell growth formed in each growing season. Thick or thin ring sizes depend on soil and weather. If you compare soil samples or weather records with a wood sample, you can come up with an accurate historical record for the wood. If that wood is buried with an artifact, then this gives you some for the artifact as well. methods include and seriation. Relative dating assembles artifacts in a linear time sequence: which object came first and which came last. Stratigraphy or the is a layer technique. Older things will be buried beneath newer things. Relative dating this way is not as easy as it sounds if the site has been disturbed by burrowing animals, vegetation, erosion, or tectonics. Seriation is working out a by interpreting cultural changes. Egyptologist Flinders Petrie said that the pot with no handle is older than the pot with a handle because that handle represents progress. The idea behind seriation is that cultures become more sophisticated, and over time artifacts become more complicated. So, a time line can be constructed by observing changes in an accumulation of artifacts. Seriation has an advantage over stratigraphy since seriation does not require a dig site to be discovered intact. All relative dating methods are going to be less effective when a dig site provides few items to analyze. With relative methods, the more artifacts found, the better. If the setting is just right, methods can be used on sites with a single artifact. Artifacts outside of their discovery context, that is, in a store room or in a museum case can be dated, too. Absolute dating methods are useful: thermoluminesence with ceramics and radio-carbon dating with organic material. If stone or metal is attached to something made from plant (cotton, linen) or animal (feather, bone, fur) then carbon dating may help you connect a date to the item. Dating artifacts is where art meets science. It can be great fun, too. I love a good detective story.

Researched by Mark Watkins