Asselian

System/
Period		 Series/
Epoch		 Stage/
Age		 Age (Ma)
Triassic Lower/
Early		 Induan younger
Permian Lopingian Changhsingian 251.902 254.14
Wuchiapingian 254.14 259.1
Guadalupian Capitanian 259.1 265.1
Wordian 265.1 268.8
Roadian 268.8 272.95
Cisuralian Kungurian 272.95 283.5
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, as of 2017.[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 and Bashkortostan.[3]

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.[4] 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

Palaeontology

Amphibians

Amphibians of the Asselian
Taxa Presence Location Description Images
Boskovice Furrow, Czech Republic
Abo Formation, New Mexico and Seymour, Baylor County, Texas

Synapsids

Synapsids of the Asselian
Taxa Presence Location Description Images
Les Télots, Margennem, Autun, France
locality 3, Cutler Formation, San Miguel County, Colorado, USA
Kasimovian-Asselian Ludwikowice Formation, Nowa Ruda, Poland
  1. Haptodus baylei
  2. Haptodus grandis
 H. baylei: Les Télots, Autun, France

H. grandis: Kenilworth, Kenilworth Sandstone Formation, Warwickshire Group, Warwickshire, England

 Haptodus grandis may require its own genus.
Kasimovian-Kungurian

Kenilworth, Kenilworth Sandstone Formation, Warwickshire Group, Warwickshire, England; Autun, France, Cutler Formation, Arizona, Colorado, New Mexico and Utah; Fort riley, Chase Group, Kansas, Green Formation, Dunkard Group, Ohio; Wellington Formation, Oklahoma; Clyde Formation, Texas and Oklahoma; Admiral Formation; Belle-Plains Formation; Wichita Group, all three in Texas,

Königin-Carola-Schacht locality, Dresden , Döhlen Formation, lower Rotliegend Group, Döhlen Basin, Saxony, Germany
Gzhelian-Artinskian New Mexico; Utah-Arizona border region; possibly England The English specimen known as S?. brittanicus ) is now generally classified as Sphenacodontidae incertae sedis separate from the other Sphenacodon species so may need reassigning.

References

  1. ↑ http://www.stratigraphy.org/index.php/ics-chart-timescale
  2. ↑ Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press
  3. ↑ The Nonmarine Permian: Volume 30 of Bulletin of the New Mexico Museum of Natural History and Science, page 48. Editors Spencer G. Lucas, Kate E. Zeigler, 2005
  4. ↑ 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.

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

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