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The Curious Bag
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Index fossils are fossilized remains of animals or plants which represent a specific time period in the history of Earth. Paleontologists use index fossils to help date unidentified fossils.
History
French naturalist Alcide d'Orbigny (1802-1857) first proposed the idea of correlating sediment layers containing fossils with a specific time period.
Significance
Index fossils are used by paleontologists to date newly discovered fossils. By correlating the sediment layer in which the fossil was discovered to fossils previously discovered in a similar sediment layer, paleontologists can determine the age of the fossil.
Types
Some important index fossils include the brachiopods, trilobites, ammonites and graptolites. Nanofossils are microscopic fossils, and can be used as index fossils in sea sediments.
Features
For a fossil to be considered an index fossil, it must be a common species with a large geographic distribution, and restricted to a specific time range.
Benefits
Index fossils help establish the geologic time record. They serve as benchmarks on the time scale.
Source:
University of Hawaii: Index Fossils
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