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 Anisian is the lower stage or earliest age of the Middle Triassic series or

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 ...

and lasted from million years ago until million years ago. The Anisian Age succeeds the

Olenekian In the geologic timescale, the Olenekian is an age (geology), age in the Early Triassic epoch (geology), epoch; in chronostratigraphy, it is a stage (stratigraphy), stage in the Lower Triassic series (stratigraphy), series. It spans the time betw ...

Age (part of the

Lower Triassic The Early Triassic is the first of three epoch (geology), epochs of the Triassic Period (geology), Period of the geologic timescale. It spans the time between 251.9 annum, Ma and Ma (million years ago). Rocks from this epoch are collectively kno ...

Epoch) and precedes the Ladinian Age.

Stratigraphic definitions

The stage and its name were established by

Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...

n geologists Wilhelm Heinrich Waagen and Carl Diener in 1895. The name comes from ''Anisus'', the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

name of the river Enns. The original type locality is at Großreifling in the Austrian state of

Styria Styria ( ; ; ; ) is an Austrian Federal states of Austria, state in the southeast of the country. With an area of approximately , Styria is Austria's second largest state, after Lower Austria. It is bordered to the south by Slovenia, and cloc ...

. The base of the Anisian Stage (also the base of the Middle Triassic series) is sometimes laid at the first appearance of conodont species '' Chiosella timorensis'' in the stratigraphic record. Other stratigraphers prefer to use the base of magnetic chronozone MT1n. There is no accepted global reference profile for the base, but one ( GSSP or golden spike) was proposed at a flank of the mountain Deșli Caira in the

Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...

Dobruja Dobruja or Dobrudja (; or ''Dobrudža''; , or ; ; Dobrujan Tatar: ''Tomrîğa''; Ukrainian language, Ukrainian and ) is a Geography, geographical and historical region in Southeastern Europe that has been divided since the 19th century betw ...

.The GSSP was proposed by Grădinaru ''et al.'' (2007) The top of the Anisian (the base of the Ladinian) is at the first appearance of

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

species '' Eoprotrachyceras curionii'' and the ammonite

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Trachyceratidae. The conodont species '' Neogondolella praehungarica'' appears at the same level. Especially in Central Europe the Anisian Stage is sometimes subdivided into four substages: Aegean, Bythinian, Pelsonian and Illyrian. The Anisian contains six ammonite biozones: *zone of '' Nevadites'' *zone of '' Hungarites'' *zone of '' Paraceratites'' *zone of '' Balatonites balatonicus'' *zone of '' Kocaelia'' *zone of '' Acrochordiceras''

Selected formations

* Ashfield Shale (

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, Australia) * Lower and middle Besano Formation (Switzerland and Italy) * Upper Ermaying Formation (

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and

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, China) * Favret Formation / Prida Formation ( Fossil Hill Member) (Nevada, US) * Grès à Voltzia (France) * Guanling Formation (

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and

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, China) * Moenkopi Formation (Holbrook and Anton Chico members) (SW US) * Lower and Middle

Muschelkalk The Muschelkalk (German for "shell-bearing limestone"; ) is a sequence of sedimentary rock, sedimentary rock strata (a lithostratigraphy, lithostratigraphic unit) in the geology of central and western Europe. It has a Middle Triassic (240 to 230 m ...

(central Europe) * Röt Formation / Upper Buntsandstein (Germany)

References

Sources

*; 2005: ''The Global boundary Stratotype Section and Point (GSSP) of the Ladinian Stage (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale'', Episodes 28(4), pp. 233–244. *; 2007: ''The Global Boundary Stratotype Section and Point (GSSP) for the base of the Anisian Stage: Deşli Caira Hill, North Dobrogea, Romania'', Albertiana 36, pp. 54–71. *; 2004: ''A Geologic Time Scale 2004'',

Cambridge University Press Cambridge University Press was the university press of the University of Cambridge. Granted a letters patent by King Henry VIII in 1534, it was the oldest university press in the world. Cambridge University Press merged with Cambridge Assessme ...

External links

GeoWhen Database - AnisianLower Triassic timescale
at the website of the subcommission for stratigraphic information of the ICS
Lower Triassic timescale
at the website of Norges Network of offshore records of geology and stratigraphy. {{coord, 45.0742, N, 28.8022, E, source:wikidata, display=title *01 Geological ages Triassic geochronology