The three main parameters that have to be set are the original amount of uranium and lead in the sample, the rate at which uranium and lead enter and leave the sample, and how much the rate of decay changes.
It may sound straight-forward, but there are many variables that have to be considered.
U at the time of sample formation must be known or calculated.
With time, Thorium 230 accumulates in the sample through radiometric decay.
U-Th ages obtained by mass spectrometry in corals from Barbados: sea level during the past 130,000 years.
Calibration of the 14C timescale over the past 30,000 years using mass spectrometric U-Th ages from Barbados corals.