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Second age of the late Triassic
Norian −255 —
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−250 —
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−245 —
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−240 —
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−235 —
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−230 —
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−225 —
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−220 —
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−215 —
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−210 —
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−205 —
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−200 —
Stratigraphic unit Stage Time span formality Formal Lower boundary definition Not formally defined[6] Lower boundary definition candidates Base of Stikinoceras kerri ammonoid zone and near FAD of Metapolygnathus echinatus within the M. communisti Conodont zones[6] Lower boundary GSSP candidate section(s)
Upper boundary definition Not formally defined[6] Upper boundary definition candidates
Upper boundary GSSP candidate section(s)
The Norian is a division of the
Stratigraphic definitions
Cast of a tridactyl footprint of a theropod dinosaur from the Norian of the Czech Republic .
The Norian was named after the Noric Alps in Austria . 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
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 and the radiolarid species Proparvicingula moniliformis .
In the Tethys domain , the Norian Stage contains six ammonite biozones:
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
faunachron corresponds to part of the Norian.
[10]
Notable formations
* Tentatively assigned to the Norian; age estimated primarily via terrestrial tetrapod biostratigraphy (see Triassic land vertebrate faunachrons )
References
Notes
Literature
Brack, P.; Rieber, H.; Nicora, A. & Mundil, R. ; 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.
Gradstein, F.M.; Ogg, J.G. & Smith, A.G. ; 2004 : A Geologic Time Scale 2004 , Cambridge University Press .
Kielan-Jaworowska, Z. ; Cifelli, R. L.; Luo, Zhe-Xi ; 2004 : Mammals from the Age of Dinosaurs , Columbia University Press .
Martz, J.W. ; 2008 : Lithostratigraphy, chemostratigraphy, and vertebrate biostratigraphy of the Dockum Group (Upper Triassic), of southern Garza County, West Texas , Doctoral Dissertation, Texas Tech.
External links