Problem of carbon dating
Argon/argon dating works using only the ratio of the concentration of the argon isotopes. For the purposes of this debate, "accurate" means that 95% of the dating errors are within 10% of the measured date, within the time span for which the isotope pair is utilized.Since carbon dating depends upon variable cosmic ray intensity, a calibration curve is assumed to be applied to account for that.Every few years, new geologic time scales are published, providing the latest dates for major time lines.Older dates may change by a few million years up and down, but younger dates are stable.For dating back to about 35,000 years, sediment layers are precise. Sediments include different types of pollen depending upon the season.Consequently, individual years can be identified by season, so there is no possibility of layers being confused.other isotope pairs cover intermediate time periods between the spans for carbon 14 and uranium.
A key point is that it is no longer necessary simply to accept one chemical determination of a rock's age.
Age estimates can be cross-tested by using different isotope pairs.
Results from different techniques, often measured in rival labs, continually confirm each other.
For example, the C14 concentration in the atmosphere depends upon cosmic ray intensity.
To take this into account, a calibration curve is developed using other dating methods to establish the C14 levels over time.