Radon is not used for geological or paleontological dating.
The most important, stable and common isotope of radon is 222Rn.
Mean concentration of radon in air: 150 atoms/cm3 Radon in the earth crust: 4.10-16 mg/kg Radon in the sea water: 6.10-19 mg/L
222Rn is the most stable isotope with a half life of 3,823 days. Other important isotopes: 219Rn with a half life of 3,965 seconds and 220Rn with a half life of 55,6 seconds. Radon has 34 radioactive...
Both are based on radioactive decay.