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).
guide fossil, index fossil - a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found microfossil - a fossil that must be studied microscopically