What kind of fossil aging is used when scientists use the law of superposition?

When scientists use the law of superposition to determine the age of a fossil, they go by the principle of 'every undisturbed layer of rock is older than the layer above it. This is not the most precise way of determining age, and in fact this method can only reveal the approximate age, but not the exact one.

When scientists use the law of superposition, the type of fossil aging they use is known as relative aging.

Explanation:

Scientists use different methods of aging to determine the 'age of rock fossils'. One of these techniques is that of relative aging. In this technique, the scientists 'determine the age of the bottom-most rock fossil' first and go by the principle that every new layer of rock superpositioned above the lower rock is comparatively younger than the lower rock.