The Gzhelian ( ) is an

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone has been alive or something has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

in the ICS

geologic time scale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochro ...

or a

stage Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...

in the

stratigraphic column A stratigraphic column is a representation used in geology and its subfield of stratigraphy to describe the vertical location of rock units in a particular area. A typical stratigraphic column shows a sequence of sedimentary rocks, with the oldest ...

. It is the youngest stage of the

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, on the International Commission on Stratigraphy, ICS geologic timesc ...

, the youngest

subsystem A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and is exp ...

of the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

. The Gzhelian lasted from to Ma. It follows the

Kasimovian The Kasimovian is a geochronologic age or chronostratigraphic stage in the ICS geologic timescale. It is the third stage in the Pennsylvanian (late Carboniferous), lasting from to Ma.; 2004: ''A Geologic Time Scale 2004'', Cambridge Unive ...

age/stage and is followed by the

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 and million years ago (Ma ...

age/stage, the oldest subdivision of the

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

system. 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

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

n village of

Gzhel Gzhel (Russian: Гжель, IPA: �ʐelʲ is a Russian style of blue and white pottery, blue and white ceramics which takes its name from the Gzhel (selo), Moscow Oblast, village of Gzhel and surrounding area, where it has been produced sinc ...

(), nearby Ramenskoye, not far from

Moscow Moscow is the Capital city, capital and List of cities and towns in Russia by population, largest city of Russia, standing on the Moskva (river), Moskva River in Central Russia. It has a population estimated at over 13 million residents with ...

. The name and type locality were defined by Sergei Nikitin (1851–1909) in 1890. The base of the Gzhelian is at the first appearance of the

Fusulinida The Fusulinida is an extinct order within the Foraminifera in which the tests are traditionally considered to have been composed of microgranular calcite. Like all forams, they were single-celled organisms. In advanced forms the test wall was ...

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

'' Daixina'', '' Jigulites'' and '' Rugosofusulina'', or at the first appearance of the

conodont Conodonts, are an extinct group of marine jawless vertebrates belonging to the class Conodonta (from Ancient Greek κῶνος (''kōnos''), meaning " cone", and ὀδούς (''odoús''), meaning "tooth"). They are primarily known from their hard ...

''Streptognathodus zethus''. The top of the stage (the base of the Permian system) is at the first appearance of the conodont ''

Streptognathodus ''Streptognathodus'' is an extinct genus of conodonts from the Late Carboniferous to Early Permian. Use in stratigraphy Late Carboniferous The top of the Kasimovian stage is close to the first appearance of ''Streptognathodus zethus''. The ...

isolatus'' within the ''Streptognathus "wabaunsensis"'' chronocline. higher in the reference profile, the Fusulinida species '' Sphaeroschwagerina vulgaris aktjubensis'' appears. Currently, a

golden spike The golden spike (also known as the last spike) is the ceremonial 17.6-Carat (purity), karat gold final Rail spike, spike driven by Leland Stanford to join the rails of the first transcontinental railroad across the United States connecting t ...

for the base of the Gzhelian Stage has not been allocated. A candidate is a section along the Ussolka river (a

tributary A tributary, or an ''affluent'', is a stream or river that flows into a larger stream (''main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which they ...

of the Belaya river) at the edge of the hamlet of Krasnoussolsky, about southeast of Ufa and northeast of

Sterlitamak Sterlitamak ( rus, Стерлитама́к, p=stʲɪrlʲɪtɐˈmak; ; ) is the second largest types of inhabited localities in Russia, city in the Republic of Bashkortostan, Russia, located on the left bank of the Belaya River (Kama), Belaya ...

(in

Bashkortostan Bashkortostan, officially the Republic of Bashkortostan, sometimes also called Bashkiria, is a republic of Russia between the Volga river and the Ural Mountains in Eastern Europe. The republic borders Perm Krai to the north, Sverdlovsk Oblast ...

).; 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,

Biozones

The Gzhelian Stage is subdivided into five

biozone In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxon, taxa, as opposed to a Lithostratigraphy, lithostratigraphic unit which is defined by the ...

s, based on the conodont genus ''

'': * ''Streptognathodus wabaunsensis'' and ''Streptognathodus bellus'' Zone * ''Streptognathodus simplex'' Zone * ''Streptognathodus virgilicus'' Zone * ''Streptognathodus vitali'' Zone * ''Streptognathodus simulator'' Zone

References

External links

Carboniferous timescale
at the website of the Norwegian network of offshore records of geology and stratigraphy

{{Geological history, p, p, state=collapsed Pennsylvanian geochronology Geological ages