|
In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago.〔According to Gradstein ''et al.'' (2004); Brack ''et al.'' (2005) give 248 to 241 Ma〕 The Anisian age succeeds the Olenekian age (part of the Lower Triassic epoch) and precedes the Ladinian age. ==Stratigraphic definitions== The stage and its name were established by Austrian geologists Wilhelm Heinrich Waagen and Carl Diener in 1895. The name comes from ''Anisus'', the Latin name of the river Enns. The original type locality is at Großreifling in the Austrian state of Styria. 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. The global reference profile for the base (the GSSP or golden spike) is at a flank of the mountain Deşli Caira in the Romanian Dobruja.〔The GSSP was established by Grǎdinaru ''et al.'' (2007)〕 The top of the Anisian (the base of the Ladinian) is at the first appearance of ammonite species ''Eoprotrachyceras curionii'' and the ammonite family Trachyceratidae. The conodont species ''Neogondolella praehungarica'' appears at the same level. Sometimes (especially in Central Europe) the Anisian stage is 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'' 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「Anisian」の詳細全文を読む スポンサード リンク
|