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Index fossil identification and geology

A fossil taxon that is useful for correlating and dating the age of rock strata in which it is found. Ideal index fossils are geographically widespread, abundant, easily identified, and restricted to a narrow time range short stratigraphic range . They are fundamental tools in biostratigraphy for establishing relative ages of sedimentary rocks across different geographic areas. Field: stratigraphy. Example: Trilobites are excellent index fossils for the Paleozoic Era—different trilobite species evolved rapidly and had wide geographic distributions, allowing precise correlation of Cambrian through Permian strata worldwide.. Related terms: Biostratigraphy, Zone fossil, Correlation, Relative age.

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.027557+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Index fossil mean in geology?
A fossil taxon that is useful for correlating and dating the age of rock strata in which it is found. Ideal index fossils are geographically widespread, abundant, easily identified, and restricted to a narrow time range short stratigraphic range . They are fundamental tools in biostratigraphy for establishing relative ages of sedimentary rocks across different geographic areas.
What is an example of Index fossil?
Trilobites are excellent index fossils for the Paleozoic Era—different trilobite species evolved rapidly and had wide geographic distributions, allowing precise correlation of Cambrian through Permian strata worldwide.
Which earth-science field uses the term Index fossil?
Index fossil is used in stratigraphy.
Which terms are related to Index fossil?
Related terms in this reference are Biostratigraphy, Zone fossil, Correlation, Relative age.

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