There is often confusion between chronostratigraphic and geochronological terms. In stratigraphy, scientists describe geological deposits, while geochronological terms related to temporal intervals during which stratigraphic units were formed. The main stratigraphic unit is a stage, which geochronological equivalent is an age. All utints with higher rank have a more conditional status. The largest stratigraphic and geochronological units are eonothems and eons, respectively.
| Comparison of chronostratigraphic and geochronological terms:[1] | ||||
| Chronostratigraphic unit |
Geochronological equivalent | |||
|---|---|---|---|---|
| Eonothem | Eon | |||
| Erathem | Era | |||
| System | Period | |||
| Series | Epoch | |||
| Stage | Age | |||
Thus, since Allosaurus jimmadseni is known by fossils from the Kimmeridgian stage of the Upper Jurassic series of the Jurassic system of the Mesozoic erathem of the Phanerozoic eonothem, it is correct to say that this animal existed during Kimmeridgian age of the Late Jurassic epoch of the Jurassic period of the Mesozoic era of the Phanerozoic eon.
Several units have the additional subdivisions. For example, the Carboniferous system is divided into two subsystems, Mississippian and Pennsylvanian. All Neogene and Quaternary series (from Miocene to Holocene) are divided into two or three subseries (Lower, Middle, Upper), which, sometimes, are equal to a single stage in their volume. The similar situation can be seen in Carboniferous series, all of which (except Upper Pennsylvanian) are equal to a single stage. The Pridoli series of the Silurian system is equal to the stage of the same name.[1] Most stages are divided into substages and/or horizons.
Parallels with historical periodization[]
Geological temporal intervals should not be confused with the periodization adopted in historical science. Geological ages are distinguished by the characteristics of rocks, while the Stone, Copper, Bronze, Iron Ages, the Middle Ages, Age of Discovery, Age of Enlightenment or Digital Age are associated exclusively with the development of human society. The same applies to historical epochs and eras: they associated with the social evolution of Homo sapiens and are not related to geological epochs and eras, although they are all within the Holocene epoch of the Cenozoic era.
References[]
- ↑ 1.0 1.1 "International Chronostratigraphic Chart (September 2023)". International Commission on Stratigraphy. https://stratigraphy.org/ICSchart/ChronostratChart2023-09.pdf. (archived copy)