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Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends. Another term, "zone fossil", is used when the fossil has all the characters stated above except wide geographical distribution; thus, they correlate the surrounding rock to a biozone rather than a specific time period.
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Index fossils (also known as guide fossils, indicator fossils, or dating fossils) are the fossilized remains or traces of particular plants or animals that are characteristic of a particular span of geologic time or environment, and can be used to identify and date the containing rocks. To be practical, index fossils must have a limited ...
Such index fossils must be distinctive, be globally distributed and occupy a short time range to be useful. Misleading results are produced if the index fossils are incorrectly dated. [63] Stratigraphy and biostratigraphy can in general provide only relative dating (A was before B), which is often sufficient for studying evolution.
Due to their widespread abundance, planktonic lifestyle, and well-traced evolutionary trends, graptoloids in particular are useful index fossils for the Ordovician and Silurian periods. [4] The name graptolite comes from the Greek graptos meaning "written", and lithos meaning "rock", as many graptolite fossils resemble hieroglyphs written on ...
Index fossils, also known as guide fossils, indicator fossils or dating fossils, are the fossilized remains or traces of particular plants or animals that are characteristic of a particular span of geologic time or environment, and can be used to identify and date the containing rocks. To be practical, index fossils must have a limited vertical ...
They are valuable as index fossils. The ancient Egyptians used nummulite shells as coins and the pyramids were constructed using limestone that contained nummulites. [ 3 ] [ 6 ] It is not surprising then that the name Nummulites is a diminutive form of the Latin nummulus 'little coin', a reference to their shape.
Trilobites are used as index fossils to subdivide the Cambrian period. Assemblages of trilobites define trilobite zones. [1] The Olenellus-zone has traditionally marked the top of the Lower Cambrian, [2] and is followed by the Eokochaspis zone.