Sol definition, the syllable used for the fifth tone of a diatonic scale. See more.
Examples of index fossils. Index fossils (also known as guide fossils, indicator fossils or zone fossils) are fossils used to define and identify geologic periods (or faunal stages).
Index fossils help geologists to age rocks in which they form. When layers of rock have index fossils of two different eras, the index fossils are also useful in dating layers between which they form. Many index fossils are types of marine life.