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In the geologic timescale the Bathonian is an age or stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian age succeeds the Bajocian age and precedes the Callovian age.〔For a detailed geologic timescale, see Gradstein ''et al.'' (2004)〕 ==Stratigraphic definitions== The Bathonian stage takes its name from Bath, a spa town in England built on Jurassic limestone (the Latinized form of the town name is ''Bathonium''). The name was introduced in scientific literature by Belgian geologist d'Omalius d'Halloy in 1843. The original type locality was located near Bath. The French palaeontologist Alcide d'Orbigny was in 1852 the first to define the exact length of the stage. The base of the Bathonian is at the first appearance of ammonite species ''Parkinsonia (Gonolkites) convergens'' in the stratigraphic column. The global reference profile for the base of the Bathonian (a GSSP) was ratified as Ravin du Bès, Bas-Auran area, Alpes de Haute Provence, France in 2009. The top of the Bathonian (the base of the Callovian stage) is at the first appearance of ammonite genus ''Kepplerites''. In the Tethys domain, the Bathonian contains eight ammonite biozones: *zone of ''Clydoniceras discus'' *zone of ''Hecticoceras retrocostatum'' *zone of ''Cadomites bremeri'' *zone of ''Morrisiceras morrisi'' *zone of ''Tulites subcontractus'' *zone of ''Procerites progracilis'' *zone of ''Procerites aurigerus'' *zone of ''Zigzagiceras zigzag'' 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「Bathonian」の詳細全文を読む スポンサード リンク
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