The Norian is a division of the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...

Period. It has the rank of an age ( geochronology) or stage (

chronostratigraphy Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geologic ...

). It lasted from ~227 to

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago ...

. It was preceded by the Carnian and succeeded by the

Rhaetian The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest a ...

Stratigraphic definitions

The Norian was named after the

Noric Alps Noric may refer to: * Noricum, an ancient region * Noric Alps *Noric language * Noric race *Noric steel Noric steel was a steel from Noricum, a Celtic kingdom located in modern Austria and Slovenia. The proverbial hardness of Noric steel is expr ...

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

. The stage was introduced into scientific literature by Austrian geologist Edmund Mojsisovics von Mojsvar in 1869. The Norian Stage begins at the base of the

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefis ...

biozones of '' Klamathites macrolobatus'' and '' Stikinoceras kerri'', and at the base of the

conodont Conodonts ( Greek ''kōnos'', " cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, whi ...

biozones of '' Metapolygnathus communisti'' and '' Metapolygnathus primitius''. A global reference profile for the base (a GSSP) had in 2009 not yet been appointed. The top of the Norian (the base of the Rhaetian) is at the first appearance of ammonite species '' Cochloceras amoenum''. The base of the Rheatian is also close to the first appearance of conodont species '' Misikella spp.'' and ''

Epigondolella mosheri ''Epigondolella'' is an extinct genus of conodonts in the family Gondolellidae. Synonyms '' Mazzaella'' is a new genus for ''Epigondolella carnica'' Krystyn (1975). Use in stratigraphy The top of the Norian (or the base of the Rhaetian, i ...

'' and the radiolarid species '' Proparvicingula moniliformis''. In the Tethys domain, the Norian Stage contains six ammonite biozones: *zone of '' Halorites macer'' *zone of '' Himavatites hogarti'' *zone of '' Cyrtopleurites bicrenatus'' *zone of '' Juvavites magnus'' *zone of '' Malayites paulckei'' *zone of '' Guembelites jandianus''

Subages

The Norian is divided into three global subages or substages: * Lacian (lower Norian) * Alaunian (middle Norian) * Sevatian (upper Norian) Many older studies considered the Rhaetian to be the uppermost substage of the Norian, though it has subsequently been raised to its own stage. The

Revueltian Land vertebrate faunachrons (LVFs) are biochronological units used to correlate and date terrestrial sediments and fossils based on their tetrapod faunas. First formulated on a global scale by Spencer G. Lucas in 1998, LVFs are primarily used with ...

land-vertebrate faunachron corresponds to part of the Norian.

References

Notes

Literature

*; 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. *; 2004: ''A Geologic Time Scale 2004'',

Cambridge University Press Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by King Henry VIII in 1534, it is the oldest university press in the world. It is also the King's Printer. Cambridge University Pr ...

. *; 2004: ''Mammals from the Age of Dinosaurs'',

Columbia University Press Columbia University Press is a university press based in New York City, and affiliated with Columbia University. It is currently directed by Jennifer Crewe (2014–present) and publishes titles in the humanities and sciences, including the fie ...

. *; 2008: ''Lithostratigraphy, chemostratigraphy, and vertebrate biostratigraphy of the Dockum Group (Upper Triassic), of southern Garza County, West Texas'', Doctoral Dissertation, Texas Tech.

External links

GeoWhen Database - NorianUpper Triassic timescale
at the website of the subcommission for stratigraphic information of the ICS *Norges Network of offshore records of geology and stratigraphy: ''Stratigraphic charts for the Triassic''

an

{{Geological history, p, m Norian, *02 Geological ages Triassic geochronology