| 翻訳と辞書 |
Hettangian
The Hettangian is the earliest age or lowest stage of the Jurassic period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triassic period) and is followed by the Sinemurian.〔For a detailed geologic timescale, see Gradstein ''et al.'' (2004)〕
In Europe stratigraphy the Hettangian is a part of the time span in which the Lias was deposited. An example is the British Blue Lias, which has an upper Rhaetian to Sinemurian age. Another example is the lower Lias from the northern calcarious alps where have been found well preserved but very rare ammonites like e.g. Alsatites.
==Stratigraphic definitions==
The Hettangian was introduced in the literature by Swiss palaeontologist, Eugène Renevier, in 1864. The stage takes its name from Hettange-Grande, a town in north-eastern France, just south of the border with Luxembourg on the main road from Luxembourg City to Metz.
The base of the Hettangian stage (which is also the base of the Lower Jurassic series and the entire Jurassic system) is defined as the place in the stratigraphic column where fossils of the ammonite genus ''Psiloceras'' first appear. A global reference profile (a GSSP) for the base was defined 2010 at the Kuhjoch in the Karwendel in western Austria.〔(GSSP Table )〕 The top of the Hettangian stage (the base of the Sinemurian) is at the first appearances of ammonite genera ''Vermiceras'' and ''Metophioceras''.
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「Hettangian」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|