The Gzhelian is an age in the ICS

International Commission on Stratigraphy

The International Commission on Stratigraphy , sometimes referred to by the unofficial "International Stratigraphic Commission" is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigraphy, geological, and geochronological matters on a global...

 geologic timescale or a stage in the stratigraphic column

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....

. It is the youngest stage of the Pennsylvanian

Pennsylvanian

The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...

, the youngest subsystem of the Carboniferous

Carboniferous

The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

. The Gzhelian lasted from 303.9 ± 0.9 to 299.0 ± 0.8 Ma. It follows the Kasimovian

Kasimovian

The Kasimovian is an geochronologic age or chronostratigraphic stage in the ICS geologic timescale. It is the third stage in the Pennsylvanian , lasting from 306.5 ± 1.0 to 303.9 ± 0.9 Ma. The Kasimovian stage follows the Moscovian and is followed by the Gzhelian.-Name and definition:The Kasimovian...

 age/stage and is followed by the Asselian

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 299.0 ± 0.8 and 294.6 ± 0.8 million years ago...

 age/stage, the oldest subdivision of the Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

 system.

The Gzhelian is more or less coeval with the Stephanian

Stephanian (stage)

The Stephanian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 304 and 299 Ma . It is a subdivision of the Carboniferous system or period and the regional Silesian series...

 stage of the regional stratigraphy of Europe.

Name and definition

The Gzhelian is named after the Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

n village of Gzhel

Gzhel (village)

Gzhel is the name of two rural localities in Ramensky District, Moscow Oblast, Russia, southeast from the center of Moscow. It gave its name to Gzhel ceramics as well as the Gzhelian age and stage in the ICS geologic timescale. In a broader sense, the name also refers to a cluster of villages and...

 , nearby Ramenskoye

Ramenskoye

Ramenskoye is a town and the administrative center of Ramensky District of Moscow Oblast, Russia, located southeast of Moscow. Population: 69,000 ; 28,000 ....

, not far from Moscow

Moscow

Moscow is the capital, the most populous city, and the most populous federal subject of Russia. The city is a major political, economic, cultural, scientific, religious, financial, educational, and transportation centre of Russia and the continent...

. The name and type locality

Type locality (geology)

Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....

 were defined by Sergei Nikitin (1850–1909) in 1890.

The base of the Gzhelian is at the first appearance of the Fusulinida genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

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

Conodont

Conodonts are extinct chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils now called conodont elements, found in isolation. Knowledge about soft tissues remains relatively sparse to this day...

 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

Golden spike

The "Golden Spike" is the ceremonial final spike driven by Leland Stanford to join the rails of the First Transcontinental Railroad across the United States connecting the Central Pacific and Union Pacific railroads on May 10, 1869, at Promontory Summit, Utah Territory...

 for the Gzhelian stage is yet lacking. A candidate is a section along the Ussolka river (a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Belaya river) at the edge of the hamlet of Krasnoussolsky, about 120 kilometres south-east of Ufa

Ufa

-Demographics:Nationally, dominated by Russian , Bashkirs and Tatars . In addition, numerous are Ukrainians , Chuvash , Mari , Belarusians , Mordovians , Armenian , Germans , Jews , Azeris .-Government and administration:Local...

 and 60 kilometres north-east of Sterlitamak

Sterlitamak

Sterlitamak is the second largest city in the Republic of Bashkortostan, Russia, located on the left bank of the Belaya River , from Ufa. The city's name comes from the Bashkir language and literally means "mouth of the river Sterlya". Population: Sterlitamak was founded in 1766 as a port for the...

 (in Bashkortostan

Bashkortostan

The Republic of Bashkortostan , also known as Bashkiria is a federal subject of Russia . It is located between the Volga River and the Ural Mountains. Its capital is the city of Ufa...

).

Biozones

The Gzhelian stage is subdivided into five biozone

Biozone

Biostratigraphic units or Biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa....

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

External links

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