Gzhelian

The Gzhelian (/ˈʒɛli.ən/ ZHELL-ee-ən) is an age in the ICS geologic time scale or a stage in the stratigraphic column. It is the youngest stage of the Pennsylvanian, the youngest subsystem of the Carboniferous. The Gzhelian lasted from 303.7 to 298.9 Ma.^[4] It follows the Kasimovian age/stage and is followed by the Asselian age/stage, the oldest subdivision of the Permian system.

Gzhelian
303.7 ± 0.1 – 298.9 ± 0.15 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type locality for the Gzhelian in Gzhel, Russia
Chronology
−360 — – −355 — – −350 — – −345 — – −340 — – −335 — – −330 — – −325 — – −320 — – −315 — – −310 — – −305 — – −300 — – Paleozoic D Carboniferous P Mississippian Pennsylvanian LD Early Middle Late Early Mid Late CS Famennian Tournaisian Viséan Serpukhovian Bashkirian Moscovian Kasimovian Gzhelian Asselian     ← Carboniferous Rainforest Collapse ← Mazon Creek Fossils ← End of Romer's Gap ← Start of Romer's Gap Subdivision of the Carboniferous according to the ICS, as of 2021.[1] Vertical axis scale: millions of years ago
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Type section	Gzhel horizon, Ghzel, Moscow Oblast, Russia
Lower boundary definition	Not formally defined
Lower boundary definition candidates	FAD of the Conodont Idiognathodus simulator[2]
Lower boundary GSSP candidate section(s)	Southern Ural Mountains[2] Nashui, Luodian County, Guizhou, China
Upper boundary definition	FAD of the Conodont Streptognathodus isolatus within the morphotype Streptognathodus wabaunsensis chronocline
Upper boundary GSSP	Aidaralash, Ural Mountains, Kazakhstan 50.2458°N 57.8914°E / 50.2458; 57.8914
Upper GSSP ratified	1996[3]

The Gzhelian is more or less coeval with the Stephanian Stage of the regional stratigraphy of Europe.

Name and definition

The Gzhelian is named after the Russian village of Gzhel (Russian: Гжель), nearby Ramenskoye, not far from Moscow. The name and type locality were defined by Sergei Nikitin (1851–1909) in 1890.

Photogrammetry model of geology outcrop in Gzhel (2022)

The base of the Gzhelian is at the first appearance of the Fusulinida genera Daixina, Jigulites and Rugosofusulina, or at the first appearance of the conodont Streptognathodus zethus. The top of the stage (the base of the Permian system) is at the first appearance of the conodont Streptognathodus isolatus within the Streptognathus "wabaunsensis" chronocline.^[5] Six metres (20 ft) higher in the reference profile, the Fusulinida species Sphaeroschwagerina vulgaris aktjubensis appears.

Currently, a golden spike for the base of the Gzhelian Stage has not been allocated. A candidate is a section along the Ussolka river (a tributary of the Belaya river) at the edge of the hamlet of Krasnoussolsky, about 120 kilometres (75 mi) southeast of Ufa and 60 kilometres (37 mi) northeast of Sterlitamak (in Bashkortostan).^[6]

Biozones

The Gzhelian Stage is subdivided into five biozones, based on the conodont genus Streptognathodus:

• Streptognathodus wabaunsensis and Streptognathodus bellus Zone
• Streptognathodus simplex Zone
• Streptognathodus virgilicus Zone
• Streptognathodus vitali Zone
• Streptognathodus simulator Zone

References

1. "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
2. "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 23 December 2020.
3. Davydov et al. 1998.
4. Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press
5. Davydov, V.I.; Glenister, B.F.; Spinosa, C.; Ritter, S.M.; Chernykh, V.V.; Wardlaw, B.R.; Snyder, W.S. (1998). "Proposal of Aidaralash as Global Stratotype Section and Point (GSSP) for base of the Permian System" (PDF). Episodes. 21 (1): 11–18. doi:10.18814/epiiugs/1998/v21i1/003. Archived from the original (PDF) on 2007-09-28. Retrieved 2007-09-28.
6. Chernykh, V.V.; Chuvashov, B.I.; Davydov, V.I.; Schmitz, M. & Snyder, W.S.; 2006: Usolka section (southern Urals, Russia): a potential candidate for GSSP to define the base of the Gzhelian Stage in the global chronostratigraphic scale Geologija 49(2): pp 205–217, "Usolka section (southern Urals, Russia): a potential candidate for GSSP to define the base of the Gzhelian Stage in the global chronostratigraphic scale" (PDF). Archived from the original (PDF) on 2007-12-14. Retrieved 2007-12-14.

External links

• Carboniferous timescale at the website of the Norwegian network of offshore records of geology and stratigraphy
• Gzhelian, GeoWhen Database