Stage (stratigraphy)

Units in geochronology and stratigraphy^[1]
Segments of rock (strata) in chronostratigraphy	Time spans in geochronology	Notes to geochronological units
Eonothem	Eon	4 total, half a billion years or more
Erathem	Era	10 defined, several hundred million years
System	Period	22 defined, tens to ~one hundred million years
Series	Epoch	34 defined, tens of millions of years
Stage	Age	99 defined, millions of years
Chronozone	Chron	subdivision of an age, not used by the ICS timescale

In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.

Rock series are divided into stages, just as geological epochs are divided into ages. Stages are divided into smaller stratigraphic units called chronozones or substages, and added together into superstages.^[2]

The term faunal stage is sometimes used, referring to the fact that the same fauna (animals) are found throughout the layer (by definition).

^ Cohen, K.M.; Finney, S.; Gibbard, P.L. (2015), International Chronostratigraphic Chart (PDF), International Commission on Stratigraphy.
^ "International Stratigraphic Guide". Archived from the original on 2009-08-17.

[1] Cohen, K.M.; Finney, S.; Gibbard, P.L. (2015), International Chronostratigraphic Chart (PDF), International Commission on Stratigraphy.

[2] "International Stratigraphic Guide". Archived from the original on 2009-08-17.

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