Question

You have found a fossil of a soft-bodied animal. You suspect it is from the late Proterozoic (about 600 million years old). Which isotope would be the best choice to approximate the actual age of the fossil?

A. phosphorus-32
B. carbon-12
C. potassium-40
D. carbon-14

Answer 1

The correct answer is option d. Potassium-40 is the best isotopic choice for dating a fossil that is around 600 million years old because it has a longer half-life suitable for dating ancient materials, compared to the much shorter half-life of Carbon-14.

Step-by-step explanation:

To approximate the actual age of a soft-bodied animal fossil suspected to be from the late Proterozoic (about 600 million years old), potassium-40 would be the best isotopic choice. Carbon-14 dating is effective only for materials that are up to about 50,000 years old, because its half-life is 5,730 years.

For older fossils like the one in question, isotopes with longer half-lives are required. Potassium-40 has a much longer half-life of 1.25 billion years, making it suitable for dating ancient fossils.