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The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series.〔See for a detailed geologic timescale Gradstein ''et al.'' (2004)〕 An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding age. Both age and stage bear the same name. As a unit of geologic time measure, the Cenomanian age spans the time between〔>〕 100.5 ± 0.9 and 93.9 ± 0.8 (million years ago). In the geologic timescale it is preceded by the Albian and is followed by the Turonian. The Cenomanian is coeval with the Woodbinian of the regional timescale of the Mexican Gulf and the Eaglefordian of the regional timescale of the US eastcoast. At the end of the Cenomanian an anoxic event took place, called the Cenomanian-Turonian boundary event or the "Bonarelli Event", that is associated with a minor extinction event for marine species. ==Stratigraphic definitions== The Cenomanian was introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1847. Its name comes from the New Latin name of the French city of Le Mans (département Sarthe), ''Cenomanum''. The base of the Cenomanian stage (which is also the base of the Upper Cretaceous series) is placed at the first appearance of foram species ''Rotalipora globotruncanoides'' in the stratigraphic record. An official reference profile for the base of the Cenomanian (a GSSP) is located in an outcrop at the western flank of Mont Risou, near the village of Rosans in the French Alps (département Hautes-Alpes, coordinates: 44°23'33"N, 5°30'43"E). The base is, in the reference profile, located 36 meters below the top of the Marnes Bleues Formation.〔The GSSP for the Cenomanian was established by Kennedy ''et al.'' (2004)〕 The top of the Cenomanian (the base of the Turonian) is at the first appearance of ammonite species ''Watinoceras devonense''. Important index fossils for the Cenomanian are the ammonites ''Calycoceras naviculare'', ''Acanthoceras rhotomagense'' and ''Mantelliceras mantelli''. 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「Cenomanian」の詳細全文を読む スポンサード リンク
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