Olenekian

In the geologic timescale, the Olenekian is an age in the Early Triassic epoch or a stage in the Lower Triassic series. It spans the time between 249.7 ± 0.7 Ma and 245 ± 0.7 Ma (million years ago).^[1] The Olenekian follows the Induan and is followed by the Anisian.^[2]

The Olenekian saw the deposition of a large part of the Buntsandstein in Europe. Archosaurs - a group encompassing crocodiles, pterosaurs, dinosaurs, and ultimately birds - are diapsid reptiles that first evolved from Archosauriform ancestors during the Olenekian.

The Olenekian is roughly coeval with the regional Yongningzhenian stage used in China.

Stratigraphic definitions

The Olenekian stage was introduced into scientific literature by Russian stratigraphers in 1956.^[3] The stage is named after Olenëk in Siberia. Before the subdivision in Olenekian and Induan became commongood, both stages formed the Skythian stage, which has since disappeared from the official timescale.

The base of the Olenekian is at the lowest occurrence of the ammonites Hedenstroemia or Meekoceras gracilitatis, and of the conodont Neospathodus waageni. It is defined as ending near the lowest occurrences of genera Japonites, Paradanubites, and Paracrochordiceras; and of the conodont Chiosella timorensis. A GSSP (global reference profile for the base) has in 2009 not yet been established.

The Olenekian is sometimes divided into the Smithian and the Spathian subages or substages.

Palaeontology

• Gnathorhizids

• Archosaurs
• Erythrosuchids
• Proterosuchids
• Crurotarsi
  • Rauisuchia

†Archosauromorphs (non-archosaurian)

†Ichthyosaurs

†Therapsids (non-mammalian)

See also

• Geologic time scale

References

Notes

Literature

• 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.
• Kiparisova, L.D. & Popov, J.N.; 1956: Расчленение нижнего отдела триасовой системы на ярусы (Subdivision of the lower series of the Triassic System into stages), Doklady Akademii Nauk SSSR 109(4), pp 842–845 (Russian).

External links

• GeoWhen Database - Olenekian
• Lower Triassic timescale at the website of the subcommission for stratigraphic information of the ICS
• Lower Triassic timescale at the website of Norges Network of offshore records of geology and stratigraphy.