USGS

Index Fossils

Keyed to the relative time scale are examples of index fossils, the forms of life which existed during limited periods of geologic time and thus are used as guides to the age of the rocks in which they are preserved.

Diagram showing index fossils

Return to Relative Time Scale



This page is URL: <http://pubs.usgs.gov/gip/geotime/fossils.html>
Last updated July 28, 1997
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