Radioactive dating methods beyond 60000 years
In this way, calibration tables have been developed that eliminate the discrepancy.Despite its usefulness, radiocarbon dating has a number of limitations.It cannot be applied to inorganic material such as stone tools or ceramic pottery.The technique is based on measuring the ratio of two isotopes of carbon.On April 26, 2007 this facility celebrated 25 years of operation, during which time it had processed over 75,000 radiocarbon measurements on objects ranging from the Dead Sea Scrolls to the Shroud of Turin.Their commercial rate (in 2008) is 5.00 per sample, which somewhat limits its accessibility to chronically under-funded archeological research projects.For example, all carbon atoms have 6 protons, all atoms of nitrogen have 7 protons, and all oxygen atoms have 8 protons.
In Arizona, virtually all dating is performed by the Arizona Accelerator Mass Spectrometry (AMS) Laboratory at the University of Arizona in Tucson.
This dramatically improves accuracy, and reduces the amount of carbon required from about 10 grams to only a few milligrams.
In recent years, dating methods based on cosmogenic isotopes other than carbon (such as beryllium-10 and chlorine-36) have been developed, which allow for the dating of a wider variety of objects over much longer time scales.
(Since humans have only existed in the Americas for approximately 12,000 years, this is not a serious limitation to southwest archaeology.) Radiocarbon dating is also susceptible to contamination.
If the ground in which an object is buried contains particles of coal or other ancient sources of carbon, radiocarbon testing may indicate that the object is far older than it really is.
Note that, contrary to a popular misconception, carbon dating is not used to date rocks at millions of years old.