Chapter 29, Problem 15TE

Which isotopes are most appropriate for dating rocks from early Precambrian time? How about the late Pleistocene epoch?

To determine

The isotopes that is most suitable for dating rocks from early Precambrian time and late Pleistocene epoch.

Answer to Problem 15TE

Uranium-$238$ and carbon-$14$ isotopes are most appropriate for dating rocks from early Precambrian time and late Pleistocene epoch respectively.

Explanation of Solution

The method used to determine the age of rocks is called radiometric dating. In this method, the ratio between radioactive isotopes and corresponding decay products is measured to determine the age. The half-life of the isotopes used for dating should have a half-life equal to or greater than the age of rocks.

The Pre Cambrian period ranges from $4.5$ billion years ago to $543$ million years ago. So, the age of rocks also comes in the same time range. The half-life value of Uranium-238 is $4.5$ billion years. Therefore, Uranium-$238$ isotope is most suitable for dating rocks from the Pre Cambrian period.

The Pleistocene epoch ranges from $2.6$ million years ago to $1200$ years ago. So, the late Pleistocene epoch is around $1200$ years ago. The half-life period of carbon-$14$ is $5760$ years. Since the late Pleistocene epoch comes in the range of half-life of carbon-$14$, it is the most suitable isotope for dating of rocks fom the epoch.

onclusion:

Therefore, uranium-$238$ and carbon-$14$ isotopes are most appropriate for dating rocks from early Precambrian time and late Pleistocene epoch respectively.