Both Fossil Assemblage and Radioactive Dating method
Explanation:
Geological time scale is defined as the sequential arrangement of all the major and minor events that have taken place in the geological past since the time of formation of earth about 4.6 billion years back.
This geological time scale is divided, based on the following two segments that together has great importance, and they are as follows-
Fossil assemblage- The earth was comprised of various types of simple and complex living organisms, that existed in the past. The remnants of some of these organisms were preserved in the rocks that were deposited a long time back. From studying these fossils assemblages, a large amount of information has been obtained that helped in the division of the geological time scale.
Radioactive dating- It is a technique by which the age of a rock, the fossil can be obtained by using the radiometric dating method. This helped in the systematic arrangement of the events which were grouped into major and minor events. The major boundaries were separated from one another by the great mass extinction event that has taken place several times in the past.
Thus, both the fossil assemblage and radioactive dating method, together are the important factors based on which the geological time scale was divided.
