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The 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 million years ago.〔According to Gradstein ''et al.'' (2004). Brack ''et al.'' (2005) give 226 to 207 million years〕 It was preceded by the Carnian and succeeded by the Rhaetian.〔See for a detailed geologic timescale Gradstein ''et al.'' (2004)〕 ==Stratigraphic definitions== 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 ''Klamathites macrolobatus'' and ''Stikinoceras kerri'', and at the base of the conodont 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'' 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'' 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Norian」の詳細全文を読む スポンサード リンク
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