Answer:
Correlation
Step-by-step explanation:
Correlation of rock is one of the efficient method, that is generally used by the geologists, by collecting information about any rock type from different geographical location, and thereby helps in the calculation of the age of rocks. This is how they can identify, demarcate and match the rocks found at different places but are of same age.
This method is efficient depending on the presence of index fossils, that are helpful in calculation of absolute age of the rocks, as these fossils are found for a shorter period of time and are found in large geographical extent.