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The Gzhelian ( ) is an age in the ICS
geologic timescale 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 geochr ...
or a stage 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 olde ...
. It is the youngest stage of the Pennsylvanian, 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 expres ...
of the
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonif ...
. 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 Univ ...
age/stage and is followed by the Asselian age/stage, the oldest subdivision of the
Permian The Permian ( ) is a geologic period and 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 251.9 Mya. It is the last period of the Paleoz ...
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 Russian village of
Gzhel Gzhel is a Russian style of blue and white ceramics which takes its name from the village of Gzhel and surrounding area, where it has been produced since 1802. Overview About thirty villages located southeast of Moscow produce pottery and shi ...
(russian: Гжель), nearby Ramenskoye, not far from
Moscow Moscow ( , US chiefly ; rus, links=no, Москва, r=Moskva, p=mɐskˈva, a=Москва.ogg) is the capital and largest city of Russia. The city stands on the Moskva River in Central Russia, with a population estimated at 13.0 millio ...
. The name and type locality were defined by Sergei Nikitin (1850–1909) in 1890. The base of the Gzhelian is at the first appearance of the Fusulinida
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencla ...
'' Daixina'', '' Jigulites'' and '' Rugosofusulina'', or at the first appearance of the
conodont Conodonts ( Greek ''kōnos'', " cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, whi ...
''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. Six meters higher in the reference profile, the Fusulinida species '' Sphaeroschwagerina vulgaris aktjubensis'' appears. At the moment (2008), a
golden spike The golden spike (also known as The Last Spike) is the ceremonial 17.6- karat gold final spike driven by Leland Stanford to join the rails of the first transcontinental railroad across the United States connecting the Central Pacific Railroa ...
for the Gzhelian Stage is yet lacking. A candidate is a section along the Ussolka river (a
tributary A tributary, or affluent, is a stream or river that flows into a larger stream or 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 drain the surrounding drai ...
of the Belaya river) at the edge of the hamlet of Krasnoussolsky, about 120 kilometres south-east of Ufa and 60 kilometres north-east of Sterlitamak (in
Bashkortostan The Republic of Bashkortostan or Bashkortostan ( ba, Башҡортостан Республикаһы, Bashqortostan Respublikahy; russian: Республика Башкортостан, Respublika Bashkortostan),; russian: Респу́блик� ...
).; 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 taxa, as opposed to a lithostratigraphic unit which is defined by the lithological properties ...
s, 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


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