Time range of radiocarbon dating
Radiocarbon dating is essentially a method designed to measure residual radioactivity.
By knowing how much carbon 14 is left in a sample, the age of the organism when it died can be known.
When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.The principal modern standard used by radiocarbon dating labs was the Oxalic Acid I obtained from the National Institute of Standards and Technology in Maryland. Around 95% of the radiocarbon activity of Oxalic Acid I is equal to the measured radiocarbon activity of the absolute radiocarbon standard—a wood in 1890 unaffected by fossil fuel effects.When the stocks of Oxalic Acid I were almost fully consumed, another standard was made from a crop of 1977 French beet molasses.These values have been derived through statistical means.American physical chemist Willard Libby led a team of scientists in the post World War II era to develop a method that measures radiocarbon activity.
Numerous large and small shell middens have been reported throughout the world. 2, but the time range for sediment accumulation overlaps each other.