Norian is a division of the Triassic geological period. It has the rank of an age ( geochronology) or stage ( chronostratigraphy). The Norian lasted from ~228 to ~208.5 million years ago. It was preceded by the [1 ] Carnian and succeeded by the Rhaetian. [2 ]
Stratigraphic definitions [ edit ]
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
ammonite biozones of and Klamathites macrolobatus , and at the base of the Stikinoceras kerri conodont biozones of and Metapolygnathus communisti . A global reference profile for the base (a Metapolygnathus primitius 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
. The base of the Rheatian is also close to the first appearance of conodont species Cochloceras amoenum and Misikella spp. and the Epigondolella mosheri radiolarid species . Proparvicingula moniliformis
Tethys domain, the Norian stage contains six ammonite biozones:
Palaeontology [ edit ]
Dinosaurs [ edit ]
†Pterosaurs [ edit ]
Crocodylomorphs [ edit ]
†Ichthyosaurs [ edit ]
†Dinosauromorphs (non-dinosaurian) [ edit ]
†Placodonts [ edit ]
†Crurotarsans (non-crocodylomorph) [ edit ]
Mammalia [ edit ]
†Ammonites [ edit ]
References [ edit ]
^ According to Gradstein et al. (2004). Brack et al. (2005) give 226 to 207 million years
^ See for a detailed geologic timescale Gradstein et al. (2004)
^ The genera listed are included in Mammalia by Kielan-Jaworowska et al. (2004) but not by those who restrict the taxon to the crown group.
Literature [ edit ]
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 [ edit ]