Radiometrically dating adjacent rocks


04-Sep-2017 16:21

Carbon-14, the radioactive isotope of carbon used in carbon dating has a half-life of 5730 years, so it decays too fast.It can only be used to date fossils younger than about 75,000 years.Potassium-40 on the other hand has a half like of 1.25 billion years and is common in rocks and minerals.This makes it ideal for dating much older rocks and fossils.The same rock formation also contains a type of trilobite that was known to live 415 to 425 million years ago.

Fossils can't form in the igneous rock that usually does contain the isotopes.Each of them typically exists in igneous rock, or rock made from cooled magma.Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.The most widely known form of radiometric dating is carbon-14 dating.