Surprisingly, in at least one case the date range given by There may be other examples of systematic variation in isotope decay rates.While the small variations in isotope decay that have been reported may not invalidate all isotopic dating, they raise questions about the assumption of completely uniform decay rates.Carbon-14 dating depends on the amount of atmospheric carbon-14 relative to carbon-12. This ratio would have been different before the Flood. According to these authors, the total mobile (non-carbonate) carbon in the biosphere is about 40,000-45,000 gigatons. The global carbon cycle: a test of our knowledge of Earth as a system. A sample that is sealed from the surrounding environment is more likely to avoid contamination or loss than one in an open environment where materials may be carried into or out of the sample by water or simple diffusion.Violations of this assumption can frequently be identified.It is sometimes thought possible to extend the dating range a few half-lives, so one occasionally sees dates as old as 70,000 years or more.Carbon-14 dating does not produce ages in the millions of years, as do some other types of radioisotope dating.
It is widely used in dating fossils or archaeological samples containing organic material such as wood, charcoal, bone, shells, etc.
Another assumption is that the amounts of carbon-14 present in the geophysical reservoirs must be constant.
The geophysical reservoirs include the atmosphere, the oceans, the biosphere, and the sediments.
If these three conditions are met, the initial concentration of C in the sample can be estimated.
In practice, there are sufficient variations in these conditions that it is necessary to correct a sample’s raw radiocarbon age by comparing it with the standard calibration curve.
A second assumption is that the sample being dated has not experienced any loss or contamination of C over its history.