Index fossils are defined as those fossils that had a wide geographical distribution and they were present for a comparatively shorter period of time. They had great significance in the field of paleontology. It helped in the construction of geological periods that are commonly used today. It basically helped in forming the geological time scale. The age of the rocks in which these fossils were embedded is easily determined by using radioactive dating techniques.
Thus, the index fossils have a shorter time period and wider geographical distribution of fossils.
