correlation fossils tend to be common.
Correlation is a statistical measurement that indicates that there is evidence that two facts or two variables are related or occur together. In geology, it is possible to make a temporal correlation between the fossils found and the type of rock. This allows to date the age of the rocks.
For example, all rocks, even of different types, that contain the same type of fossil are of the same age, regardless of where they are found. This comparison of fossils and rocks is called Geological Correlation and allows us to determine the relative ages of the rocks.
Thus, correlation fossils tend to be very common.