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Geology & Earth Sciences vocabulary · Geologic Time & Fossils

Index fossil

Meaning in geology & earth sciences, with examples

nounCommon term

In geology & earth sciences, index fossil means: A fossil of a species that lived for only a short time but was widespread and easy to identify, so it is used to date rock layers and match them between areas.

In Turkish: kılavuz fosil, rehber fosil

How it is used

Used in biostratigraphy and correlation. Ammonites, trilobites and foraminifera are classic index fossils. In Turkey, nummulites are well-known index fossils of Eocene limestones. Also called a guide fossil or zone fossil.

Example sentences

  1. This ammonite is an index fossil for the Early Jurassic.

  2. Index fossils allowed us to correlate the two sections across the valley.

Common collocations

  • use index fossils
  • a good index fossil
  • biostratigraphy
  • fossil zone
  • fossilThe remains or traces of a plant or animal that lived long ago, preserved in rock, such as shells, bones, leaf impressions or footprints.
  • geologic time scaleThe system that divides the Earth's roughly 4.6-billion-year history into named units such as eons, eras, periods and epochs, based on rocks and fossils.
  • stratumA single layer of sedimentary rock or sediment with similar features throughout, separated from the layers above and below it. The plural is strata.
  • radiometric datingA method of finding the age of rocks and minerals by measuring how much of a radioactive element has decayed into its products, using the known rate of decay.

More terms: Geologic Time & Fossils

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