The Visean, Viséan or Visian is an
age in the
ICS geologic timescale or a
stage in the
stratigraphic column. It is the second stage of the
Mississippian, the lower
subsystem of the
Carboniferous. The Visean lasted from to
Ma.
It follows the
Tournaisian age/stage and is followed by the
Serpukhovian age/stage.
Name and definitions
The Viséan Stage was introduced by
Belgian geologist
André Dumont André Dumont may refer to:
* André Dumont (geologist)
* André Dumont (politician)
André Dumont (24 May 1764 at Oisemont – 19 October 1838 at Abbeville), was a French parliamentarian, a regicide, a deputy of the National Convention, Pre ...
in 1832. Dumont named this stage after the city of
Visé in Belgium's
Liège Province
Liège (; wa, Lîdje ; nl, Luik ; german: Lüttich ) 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 ...
. Before being used as an international stage, the Visean 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 Visean 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 roughly ...
, 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
In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative '' phenotypes'', in the population of a species. To be classified as such, morphs must occupy the same habitat at the ...
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 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
''Lochriea'' is an extinct genus of conodonts.
Use in stratigraphy
The Visean, the second age of the Mississippian, contains four conodont biozones, two of which are named after ''Lochriea'' species:
* the zone of ''Lochriea nodosa''
* the ...
'', or at the base of the
biozone of
goniatite ''
Cravenoceras leion''.
Biota
The
Carboniferous-Earliest Permian Biodiversification Event
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 ''Carboniferous ...
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 reefs after their devastation during the
Hangenberg Event.
One of the tetrapods that lived during the Visean age was ''
Westlothiana'', a reptile-like amphibian. Though originally thought to be the earliest discovered amniote,
more recent research has cast doubt on this interpretation.
Biostratigraphy
The Visean contains four conodont biozones:
* ''
Lochriea nodosa'' Zone
* ''
Lochriea mononodosa'' Zone
* ''
Gnathodus bilineatus'' Zone
* ''
Gnathodus texanus'' Zone
In British stratigraphy, the Visean is subdivided into five substages. These are from bottom to top: Chadian (the lower part of this substage falls in the Tournaisian),
Arundian,
Holkerian The Holkerian is a sub-stage of the Viséan stage of the International Commission on Stratigraphy (ICS) geological timescale. It is one of five sub-stages commonly used in the Viséan stage within stratigraphy by British, Irish and other geologists ...
, Asbian and Brigantian.
[; 2006: ''The Carboniferous system, use of the new official names for the subsystems, series and stages'', Geologica Acta 4(3), pp 403–407.]
References
Further reading
* ; 1832: ''Mémoire sur la constitution géologique de la province de Liège'', Mémoires couronnés par l'Académie Royale des Sciences et Belles-Lettres de Bruxelles 8 (3), VII.
External links
Upperan
lowertime 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