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).
fossils are preserved animals or plants. but index fossils are fossils have wide distribution,many of them,evolves rapidly, and very easy to recognize. Ammonites are index fossils. The fossils were made only in a certain short time period.