Radiometric dating isotopes
One good example is granite, which normally has some potassium feldspar (Figure 8.15).Feldspar does not have any argon in it when it forms.The red-blue bars represent 40K and the green-yellow bars represent 40Ar.[SE] In order to use the K-Ar dating technique, we need to have an igneous or metamorphic rock that includes a potassium-bearing mineral.Radiometric dating of rocks and minerals using naturally occurring, long-lived radioactive isotopes is troublesome for young-earth creationists because the techniques have provided overwhelming evidence of the antiquity of the earth and life.
When radiometric techniques are applied to metamorphic rocks, the results normally tell us the date of metamorphism, not the date when the parent rock formed.
It has a half-life of 1.3 billion years, meaning that over a period of 1.3 Ga one-half of the Figure 8.14 The decay of 40K over time.
Each half-life is 1.3 billion years, so after 3.9 billion years (three half-lives) 12.5% of the original 40K will remain.
C) can be applied to many geological materials, including sediments and sedimentary rocks, but the materials in question must be younger than 60 ka.
Fragments of wood incorporated into young sediments are good candidates for carbon dating, and this technique has been used widely in studies involving late Pleistocene glaciers and glacial sediments.