Index Fossil

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index fossil

[′in‚deks ‚fäs·əl]
The ancient remains and traces of an organism that lived during a particular geologic time period and that geologically date the containing rocks.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Index Fossil


fossil remains of an organism that are typical of the sedimentary beds of a certain geological age and, therefore, are frequently used in identifying related beds from different regions. All index fossils are important in stratigraphy because they typically are of broad geographic distribution and narrow vertical distribution (because the organisms existed for a short time, they form relatively thin deposits). Their skeletons generally have specific characteristics in construction that make identification easy, even under field conditions.

Modern paleontology is based on the study of a whole set of fossil remains, not individual index fossils, because the use of index fossils as the only criterion in establishing the age of deposits may lead to erroneous conclusions. Nevertheless, index fossils are very useful for preliminary orientation in geological surveying, especially under field conditions.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
But Ashley's tiny index fossil had even more secrets to reveal.
Because these fossils -- known as index fossils -- are widely distributed around the planet but limited in the time span in which they were laid down, their discovery provides an accurate method of dating other fossils around them.