Asselian

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 293.52 million years ago (Ma). It was preceded by the Gzhelian (the latest or uppermost subdivision in the Carboniferous) and followed by the Sakmarian.

Asselian
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definitionFAD of the Conodont Streptognathodus isolatus within the morphotype Streptognathodus wabaunsensis chronocline
Lower boundary GSSPAidaralash, Ural Mountains, Kazakhstan
50.2458°N 57.8914°E / 50.2458; 57.8914
Lower GSSP ratified1996[2]
Upper boundary definitionFAD of the Conodont Mesogondolella monstra
Upper boundary GSSPUsolka section, Southern Urals, Russia.
53.9247°N 56.7287°E / 53.9247; 56.7287
Upper GSSP ratified2018[3]

Stratigraphy

The Asselian Stage was introduced into scientific literature in 1954, when the Russian stratigrapher V.E. Ruzhenchev split it off from the Artinskian. At the time, 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.[4]

The base of the Asselian Stage is equivalent to the base of the Cisuralian Series and the Permian System. It is defined as the point 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.[5] Other reference species which approximate the base of the Asselian include Streptognathodus invaginatus and Str. nodulinearis (conodonts) and Sphaeroschwagerina vulgaris and Sph. fusiformis (fusilinids).[5]

The top of the Asselian stage (the base of the Sakmarian stage) is at the first appearance of conodont species Mesogondolella monstra.

Asselian biostratigraphy is mostly defined by the evolution of Streptognathodus. There is some debate over the exact sequence of species; one option, according to Henderson (2018),[6] lists the following biozones, from youngest to oldest:

  • zone of Streptognathodus postfusus / Streptognathodus barskovi
  • zone of Streptognathodus fusus
  • zone of Streptognathodus constrictus
  • zone of Streptognathodus sigmoidalis
  • zone of Streptognathodus cristellaris
  • zone of Streptognathodus glenisteri
  • zone of Streptognathodus isolatus

Regional equivalents

In North America, the regional equivalent of the Asselian is the Nealian stage. The Nealian (lower Wolfcampian) is named after the Neal Ranch Formation in the Glass Mountains of west Texas.[7][8] In South China, the Asselian is equivalent to at least the lower part of the regional Zisongian stage of the Chuanshanian Series.[9][10] Both the Nealian and Zisongian are defined by fusilinid assemblages, so their precise correlation to the conodont-based global timescale is uncertain.

The Asselian occupies a portion of major terrestrial sediment units in Europe, namely the Autunian series of France and the lower Rotliegend of Germany.[11][12][13]

Notable formations

References
  1. "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
  2. Davydov, Vladimir; Glenister, Brian; Spinosa, Claude; Ritter, Scott; Chernykh, V.; Wardlaw, B.; Snyder, W. (March 1998). "Proposal of Aidaralash as Global Stratotype Section and Point (GSSP) for base of the Permian System" (PDF). Episodes. 21: 11–18. doi:10.18814/epiiugs/1998/v21i1/003. Retrieved 7 December 2020.
  3. Shen, Shuzhong (August 2018). "Notes from the SPS Chair" (PDF). Permophile: 4. ISSN 1684-5927. Retrieved 12 December 2020.
  4. 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
  5. 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.
  6. Henderson, Charles M. (2018). "Permian conodont biostratigraphy". Geological Society, London, Special Publications. 450 (1): 119–142. Bibcode:2018GSLSP.450..119H. doi:10.1144/SP450.9. ISSN 0305-8719. S2CID 132523775.
  7. Ross, Charles A.; Ross, June R.P. (1987). "Biostratigraphic zonation of late Paleozoic depositional sequences". Cushman Foundation for Foraminiferal Research, Spec. Publication. 24.
  8. Ross, June R.P.; Ross, Charles A. (1997). "Nealian and Lenoxian (Wolfcampian, Lower Permian) Depositional Sequences, Fusulinid Facies and Biostratigraphy, Glass Mountains, Texas". Cushman Foundation for Foraminiferal Research, Special Publication. 36: 125–128.
  9. Yugan, Jin; Qinghau, Shang; Xiangdong, Wang; Yue, Wang; Jinzhang, Sheng (1999). "Chronostratigraphic Subdivision and Correlation of the Permian in China". Acta Geologica Sinica - English Edition. 73 (2): 127–138. doi:10.1111/j.1755-6724.1999.tb00820.x. S2CID 130794861.
  10. Shen, Shuzhong; Zhang, Hua; Zhang, Yichun; Yuan, Dongxun; Chen, Bo; He, Weihong; Mu, Lin; Lin, Wei; Wang, Wenqian; Chen, Jun; Wu, Qiong; Cao, Changqun; Wang, Yue; Wang, Xiangdong (2019). "Permian integrative stratigraphy and timescale of China". Science China Earth Sciences. 62 (1): 154–188. Bibcode:2019ScChD..62..154S. doi:10.1007/s11430-017-9228-4. ISSN 1674-7313. S2CID 134488821.
  11. Pellenard, Pierre; Gand, Georges; Schmitz, Mark; Galtier, Jean; Broutin, Jean; Stéyer, Jean-Sébastien (2017). "High-precision U-Pb zircon ages for explosive volcanism calibrating the NW European continental Autunian stratotype". Gondwana Research. 51: 118–136. Bibcode:2017GondR..51..118P. doi:10.1016/j.gr.2017.07.014.
  12. Schneider, Joerg W.; Lucas, Spencer G.; Scholze, Frank; Voigt, Sebastian; Marchetti, Lorenzo; Klein, Hendrik; Opluštil, Stanislav; Werneburg, Ralf; Golubev, Valeriy K.; Barrick, James E.; Nemyrovska, Tamara; Ronchi, Ausonio; Day, Michael O.; Silantiev, Vladimir V.; Rößler, Ronny (2020). "Late Paleozoic–early Mesozoic continental biostratigraphy — Links to the Standard Global Chronostratigraphic Scale". Palaeoworld. 29 (2): 186–238. doi:10.1016/j.palwor.2019.09.001. S2CID 210316208.
  13. Schneider, Joerg W.; Scholze, Frank; Ross, Andrew J.; Blake, Bascombe M.; Lucas, Spencer G. (2022). "Improved blattoid insect and conchostracan zonation for the Late Carboniferous, Pennsylvanian, of Euramerica". Geological Society, London, Special Publications. 512 (1): 865–891. Bibcode:2022GSLSP.512..865S. doi:10.1144/SP512-2021-93. ISSN 0305-8719. S2CID 238645303.
  14. Schneider, Jörg W.; Lucas, Spencer G.; Barrick, James E. (2013). "The Early Permian age of the Dunkard Group, Appalachian basin, U.S.A., based on spiloblattinid insect biostratigraphy". International Journal of Coal Geology. 119: 88–92. Bibcode:2013IJCG..119...88S. doi:10.1016/j.coal.2013.07.019. ISSN 0166-5162.

50.2458°N 57.8914°E / 50.2458; 57.8914

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