|Subdivision of the Triassic system|
according to the ICS, as of 2018.
The Rhaetian is, in geochronology, the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It ended 201.3 million years ago; it is uncertain when it began but a commonly cited approximation of 208.5 Ma originated in the 2012 ICS timescale. It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age of the Jurassic).
The Rhaetian is named after the Rhaetian Alps, a mountain chain stretching over parts of eastern Switzerland, northern Italy and western Austria. The stage was introduced in scientific literature by Austrian geologist Eduard Suess and German paleontologist Albert Oppel in 1856.
The base of the Rhaetian did not yet have a unanimously agreed upon definition in 2009. In the Tethyan domain, the base of the ammonite biozone of Sagenites reticulatus is used, in the boreal domain (where this species is not found) the base of the biozone of Cochloceras amoenum is used instead. The base is also close to the first appearances of conodont species Misikella spp. and Epigondolella mosheri and radiolarite species Proparvicingula moniliformis.
In the Tethyan domain, the Rhaetian contains two ammonite biozones. The highest ammonite biozone is that of Choristoceras marshi, the lower one that of Rhabdoceras suesii. The end of this period is marked by the Triassic-Jurassic extinction event .
|Ichthyosaurs of the Rhaetian|
|Dinosaurs of the Rhaetian|
|Mammaliaformes of the Rhaetian|
- "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. 2018.
- Brack et al. give 207 to 201 million years ago
- See Gradstein et al. (2004)
- Brack, P.; Rieber, H.; Nicora, A. & Mundil, R.; 2005: The Global boundary Stratotype Section and Point (GSSP) of the Ladinian Stage (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale, Episodes 28(4), pp. 233–244.
- Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.