Asselian

System/ Period	Series/ Epoch	Stage/ Age	Age (Ma)
Triassic	Lower/ Early	Induan	younger
Permian	Lopingian	Changhsingian	252.2–254.1
		Wuchiapingian	254.1–259.8
	Guadalupian	Capitanian	259.8–265.1
		Wordian	265.1–268.8
		Roadian	268.8–272.3
	Cisuralian	Kungurian	272.3–283.5
		Artinskian	283.5–290.1
		Sakmarian	290.1–295.0
		Asselian	295.0–298.9
Carboniferous	Pennsylvanian	Gzhelian	older
Subdivision of the Permian system according to the ICS (Geologic Time Scale 2013).[1]

In the geologic timescale, the Asselian is the earliest geochronologic age or lowermost chronostratigraphic stage of the Permian. It is a subdivision of the Cisuralian epoch or series. The Asselian lasted between 298.9 and 295 million years ago (Ma). It was preceded by the Gzhelian (the latest or uppermost subdivision in the Carboniferous) and followed by the Sakmarian.^[2]

Stratigraphy

The Asselian stage was introduced into scientific literature in 1954, when the Russian stratigrapher V.E. Ruzhenchev split it from the Artinskian. At that moment the Artinskian still encompassed most of the lower Permian - its current definitions are more restricted. The Asselian is named after the Assel River in the southern Ural Mountains of Kazakhstan.

The base of the Asselian stage is at the same time the base of the Cisuralian series and the Permian system. It is defined as the place in the stratigraphic record where fossils of the conodont Streptognathodus isolatus first appear. The global reference profile for the base (the GSSP or golden spike) is located in the valley of the Aidaralash River, near Aqtöbe in the Ural Mountains of Kazakhstan.^[3] The top of the Asselian stage (the base of the Sakmarian stage) is at the first appearance of conodont species Streptognathodus postfusus.

The Asselian contains five conodont biozones:

• zone of Streptognathodus barskovi
• zone of Streptognathodus postfusus
• zone of Streptognathodus fusus
• zone of Streptognathodus constrictus
• zone of Streptognathodus isolatus

References

Notes

1. "Chronostratigraphic chart 2013". ICS. Retrieved 27 March 2013.
2. See Gradstein et al. (2004) for a detailed geologic timescale
3. The GSSP was first proposed by Davydov et al. (1998)

Literature

• Davydov, V.I.; Glenister, B.F.; Spinosa, C.; Ritter, S.M.; Chernykh, V.V.; Wardlaw, B.R. and Snyder, W.S.; 1998: Proposal of Aidaralash as Global Stratotype Section and Point (GSSP) for base of the Permian System, Episodes 21(1): pp 11–18.
• Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press

External links

• GeoWhen Database - Asselian
• Upper Paleozoic stratigraphic chart at the website of the subcommission for stratigraphic information of the ICS

Coordinates: 50°14′45″N 57°53′29″E / 50.2458°N 57.8914°E

Preceded by Proterozoic Eon	Phanerozoic Eon
	Paleozoic Era						Mesozoic Era			Cenozoic Era
	Cambrian	Ordovician	Silurian	Devonian	Carboniferous	Permian	Triassic	Jurassic	Cretaceous	Paleogene	Neogene	4ry