Speaking from an extreme technical viewpoint this might be true--perhaps 1 atom out of 1,, of a certain isotope has leaked out of nearly all rocks, but such a change would make an immeasurably small change in the result.
In these cases, usually the half-life of interest in radiometric dating is the longest one in the chain, which is the rate-limiting factor in the ultimate transformation of the radioactive nuclide into its stable daughter.
When sediments cover an archaeological site they are exposed to light and the mineral grains are bleached.
Such events can be dated by luminescence methods and the age employed to determine the age of an archaeological site through its related sediments.
Long-term field investigations and laboratory works in the Black Sea — Caspian region and its drainage basin within Eastern Europe provided a factual basis for the work.
At the first stage, we searched for extreme hydro-climatic events through the last 18-20 thousand years, first of all, for most striking ones, such as marine transgressions in the Pontian and Caspian basins; our attention was focussed on possible sources of water for those events, such as overfloods in river valleys and relict permafrost thawing on watersheds.
Retrieved from " https: Evidence for the period of accelerated decay is found in zircon crystals. Different methods of radiometric dating vary in the timescale over which they are accurate and the materials to which elements may exist in different isotopes.