Problems with radiometric dating methods
Measuring the ratio of C14 to C12 and C13 therefore dates the organic matter for periods back to about eight half-lives of the isotope, 45,000 years.After a long enough time the minority isotope is in an amount too small to be measured.
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.
Sediment columns giving an unbroken history for more than 25,000 years have been identified in about 30 locations around the world.
Coral growth patterns are also seasonal and provide a long independent date history. The dates obtained by different radiometric isotope pairs cross-check each other.
Anyone questioning the accuracy of radiometric methods is obliged to explain why the cross-checks to sediments, coral growth, tree rings, and other isotope pairs all have the same errors.