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).
Species which make good index fossils are able to tolerate a wide range of ecological conditions, are geographically widespread, common, easy to find, and evolutionarily short-lived (that is, they speciated and then quickly became extinct).