Radioactive isotope dating calculator
Divisions in the geological time scales still use fossil evidence and mark major changes in the dominance of particular life forms.
For example, the Devonian Period is known as the 'Age of Fishes', as fish began to flourish at this stage.
On the other hand, the concentration of carbon-14 falls off so steeply that the age of relatively young remains can be determined precisely to within a few decades.
For example, the age of the Amitsoq gneisses from western Greenland was determined to be 3.6 ± 0.05 million years ago (MA) using uranium-lead dating and 3.56 ± 0.10 Ma using lead-lead dating, results that are consistent with each other.
He noted that different formations contained different fossils and he could map one formation from another by the differences in the fossils.
As he mapped across southern England, he drew up a stratigraphic succession of rocks although they appeared in different places at different levels.
The basic equation of radiometric dating requires that neither the parent nuclide nor the daughter product can enter or leave the material after its formation.
The possible confounding effects of contamination of parent and daughter isotopes have to be considered, as do the effects of any loss or gain of such isotopes since the sample was created.