In the

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 geochron ...

, the Asselian is the earliest geochronologic

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 ...

or lowermost chronostratigraphic

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 ...

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 ...

. It is a subdivision of the

Cisuralian The Cisuralian, also known as the Early Permian, is the first series/epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mou ...

Epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

Series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used i ...

. The Asselian lasted between and million years ago (Ma). It was preceded by the

Gzhelian The Gzhelian ( ) 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 to Ma. It follows the Ka ...

(the latest or uppermost subdivision in 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 ...

) and followed by the

Sakmarian In the geologic timescale, the Sakmarian is an age or stage of the Permian period. It is a subdivision of the Cisuralian Epoch or Series. The Sakmarian lasted between 293.52 and million years ago (Ma). It was preceded by the Asselian and fo ...

Stratigraphy

The Asselian Stage was introduced into scientific literature in 1954, when the Russian stratigrapher V.E. Ruzhenchev split it off from the

Artinskian In the geologic timescale, the Artinskian is an age (geology), age or stage (stratigraphy), stage of the Permian. It is a subdivision of the Cisuralian Epoch (geology), Epoch or series (stratigraphy), Series. The Artinskian likely lasted between ...

. 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 The Ural Mountains ( ),; , ; , or simply the Urals, are a mountain range in Eurasia that runs north–south mostly through Russia, from the coast of the Arctic Ocean to the river Ural (river), Ural and northwestern Kazakhstan.

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, small portion in Eastern Europe. It borders Russia to the Kazakhstan–Russia border, north and west, China to th ...

and

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 ...

. The base of the Asselian Stage is equivalent to the base of the Cisuralian Series and the Permian

System 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 open system (systems theory), environment, is described by its boundaries, str ...

. It is defined as the point in the stratigraphic record where

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s 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'' 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 Aktobe (, ; ) is a major city located on the Ilek River in western Kazakhstan. It serves as the administrative center of the Aktobe Region and is an important cultural, economic, and industrial hub in the region. As of 2023, the city has a popu ...

in the

.; 1998: ''Proposal of Aidaralash as Global Stratotype Section and Point (GSSP) for base of the Permian System'', Episodes 21(1): pp 11–18. Other reference species which approximate the base of the Asselian include ''Streptognathodus invaginatus'' and ''Str. nodulinearis'' (conodonts) and '' Sphaeroschwagerina vulgaris'' and ''Sph. fusiformis'' ( fusilinids). The top of the Asselian stage (the base of the Sakmarian stage) is at the first appearance of conodont species ''

Mesogondolella ''Mesogondolella'' is an extinct genus of conodonts. The species ''M. daheshenensis'' and ''M. subgracilis'' are from the Permian (probably Wordian) of the Daheshen Formation in China.The age of the Daheshen Formation in Jilin Province based o ...

monstra''. Asselian

biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. "Biostratigraphy." ''Oxford Reference: Dictionary of Biology ...

is mostly defined by the evolution of ''Streptognathodus''. There is some debate over the exact sequence of species; one option, according to Henderson (2018), 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 The Glass Mountains (also known as Gloss Mountains or Gloss Hills) are not actually mountains, but a series of mesas and buttes that are part of the Blaine Escarpment that extends from the Permian red beds of northwestern Oklahoma in Major Cou ...

of west Texas. In

South China South China ( zh, s=, p=Huá'nán, j=jyut6 naam4) is a geographical and cultural region that covers the southernmost part of China. Its precise meaning varies with context. A notable feature of South China in comparison to the rest of China is ...

, the Asselian is equivalent to at least the lower part of the regional Zisongian stage of the Chuanshanian Series. 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 The Rotliegend, Rotliegend Group or Rotliegendes () is a lithostratigraphic unit (a sequence of rock strata) of latest Carboniferous to Guadalupian (middle Permian) age that is found in the subsurface of large areas in western and central Europe ...

of Germany.

Notable formations

* Altenglan Formation (Germany) *

Archer City Formation The Archer City Formation is a Formation (geology), geological formation in north-central Texas, preserving fossils from the Asselian and early Sakmarian Stage (stratigraphy), stages of the Permian Period (geologic time), period. It is the earlie ...

(Texas, USA) * Council Grove Group (in part) (Kansas / Nebraska, USA) * Dunkard Group (in part) (West Virginia / Ohio / Pennsylvania, USA) *

Goldlauter Formation The Goldlauter Formation is a geologic formation in Germany. It preserves fossils dating back to the Permian period. See also * List of fossiliferous stratigraphic units in Germany See also * Lists of fossiliferous stratigraphic units in ...

(Germany) * Manebach Formation (Germany) * Meisenheim Formation (Germany) *

Muse Formation In ancient Greek religion and mythology, the Muses (, ) were the inspirational goddesses of literature, science, and the arts. They were considered the source of the knowledge embodied in the poetry, lyric songs, and myths that were related ora ...

(France)

References

External links

GeoWhen Database - AsselianUpper Paleozoic stratigraphic chart
at the website of the subcommission for stratigraphic information of the ICS {{Geological history, p, p Permian geochronology .