What materials can be dated with radiocarbon dating dating of fossil
AMS technology has allowed us to date very small samples (such as seeds) that were previously undatable.
Since there are practical limits to the age range of the method, most samples must be younger than 50,000 years and older than 100 years.
This discovery meant that there are three naturally occurring isotopes of carbon: Whereas carbon-12 and carbon-13 are stable isotopes, carbon-14 is unstable or radioactive.
Carbon-14 is produced in the upper atmosphere when cosmic rays bombard nitrogen atoms.
However, when the organism dies, the amount of c14 declines such that the longer the time since death the lower the levels of c14 in organic tissue.
Many laboratories now use liquid scintillation counters with the samples being converted to benzene.
All of these counter types measure the C-14 content by monitering the rate of decay per unit time.
The diminishing levels via decay means that the effective limit for using c14 to estimate time is about 50,000 years. Subsequent work has shown that the half-life of radiocarbon is actually 5730 ± 40 years, a difference of 3% compared to the Libby half-life.
However, to avoid confusion all radiocarbon laboratories continue to use the half-life calculated by Libby, sometimes rounding it to 5570 years.