Series (stratigraphy)
Series are subdivisions of
geological timescale. A series is therefore a sequence of strata defining a chronostratigraphic unit. Series are subdivisions of systems and are themselves divided into stages
.
Series is a term defining a unit of rock layers formed during a certain interval of time (a chronostratigraphic unit); it is equivalent (but not synonymous) to the term geological epoch (see
epoch criteria
) which defines the interval of time itself, although the two words are sometimes confused in informal literature.
Series in the geological timescale
| 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 |
The geological timescale has all
Mississippian series. In 2008, the International Commission on Stratigraphy had not yet named all four series of the Cambrian. Currently series are limited to the Phanerozoic, but the ICS has stated its intention of subdividing the three systems of the Neoproterozoic (Ediacaran, Cryogenian and Tonian
) into stages too.
Systems and lithostratigraphy
Systems can include many lithostratigraphic units (for example
members
, etc.) of differing rock types that were being laid down in different environments at the same time. In the same way, a lithostratigraphic unit can include a number of systems or parts of them.
See also
References
- ^ Cohen, K.M.; Finney, S.; Gibbard, P.L. (2015), International Chronostratigraphic Chart (PDF), International Commission on Stratigraphy.