A fossil can be used in finding the absolute age of rocks when it existed for a long period of time and in a wide area. To determine the age of rocks, scientists use a method called radiometric dating, which relies on the radioactive decay of isotopes within minerals in the rocks. By analyzing the ratio of parent isotopes to daughter isotopes, scientists can calculate the age of the rock. Fossils can help in this process by providing a relative age constraint. If a fossil is found in multiple locations over a wide area and can be correlated with a particular rock layer, then the age of that fossil can be used as an indicator of the age of the corresponding rock layer. The more widespread the fossil is and the longer its existence, the more reliable it becomes in determining the absolute age of rocks.
