The Visean, Viséan or Visian 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 geochron ...

or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem 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 Visean lasted from to Ma. It follows the

Tournaisian The Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The Tournaisian age lasted from Ma to Ma. It is preceded by the Famennian (the uppermost st ...

age/stage and is followed by the Serpukhovian age/stage.

Name and definitions

The Viséan Stage was introduced by Belgian geologist André Dumont in 1832. Dumont named this stage after the city of Visé in Belgium's

Liège Province Liège ( ; ; ; ; ) is the easternmost province of the Wallonia region of Belgium. Liège Province is the only Belgian province that has borders with three countries. It borders (clockwise from the north) the Dutch province of Limburg, the ...

. Before being used as an international stage, the Viséan Stage was part of the (West) European regional geologic time scale, in which it followed the Tournaisian Stage and is followed by the Namurian Stage. In the North American regional scale, the Viséan Stage correlates with the upper

Osagean The Mississippian ( ), also known as Lower Carboniferous or Early Carboniferous, is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earlier of two subperiods of the Carboniferous period lasting from rou ...

, the Meramecian and lower Chesterian stages. In the Chinese regional time scale, it correlates with the lower and middle Tatangian series.; 2006: ''Global time scale and regional stratigraphic reference scales of Central and West Europe, East Europe, Tethys, South China, and North America as used in the Devonian–Carboniferous–Permian Correlation Chart 2003 (DCP 2003)'', Palaeogeography, Palaeoclimatology, Palaeoecology 240 (1-2): pp 318–372. The base of the Viséan Stage is at the first appearance of the fusulinid species '' Eoparastaffella simplex'' ( morphotype 1/morphotype 2). The type locality for the stage base used to be in a road section below the castle of Dinant in Belgium, but this type locality proved to be insufficient for the purpose of stratigraphic correlation. A

GSSP A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...

has been proposed in the Luzhai Formation near Penchong in the Chinese province of Guanxi. The top (the base of the Serpukhovian and Namurian) is laid at the first appearance of the conodont '' Lochriea ziegleri'', or at the base of the biozone of goniatite '' Cravenoceras leion''.

Biota

The Carboniferous-Earliest Permian Biodiversification Event began in the Viséan, coinciding with the start of the main phase of the Late Palaeozoic Ice Age. The late Viséan saw the widespread reappearance of metazoan

reef A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...

s after their devastation during the Hangenberg Event. One of the

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

s that lived during the Visean age was '' Westlothiana'', a

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

-like

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

. Though originally thought to be the earliest discovered

amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...

, more recent research has cast doubt on this interpretation.

Biostratigraphy

The Visean contains four conodont biozones: * '' Lochriea nodosa'' Zone * '' Lochriea mononodosa'' Zone * ''

Gnathodus ''Gnathodus'' is an extinct conodont genus in the family Idiognathodontidae. Use in stratigraphy The Tournaisian, the oldest age of the Mississippian (geology), Mississippian (also known as Lower Carboniferous), contains eight conodont biozon ...

bilineatus'' Zone * ''

texanus'' Zone In British stratigraphy, the Visean is subdivided into five substages. From youngest to oldest, these are:; 2006: ''The Carboniferous system, use of the new official names for the subsystems, series and stages'', Geologica Acta 4(3), pp 403–407. * Brigantian * Asbian * Holkerian * Arundian * Chadian (the lower part of this substage falls in the Tournaisian)

References

External links

Upper
an
lower
time scales for the Carboniferous at the website of the Norwegian network of offshore records of geology and stratigraphy

www.palaeos.com {{DEFAULTSORT:Visean Mississippian geochronology Geological ages . Stratigraphy of Europe

Name and definitions

Biota

Biostratigraphy

References

Further reading

External links