| Hettangian | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 201.4 ± 0.2 – 199.5 ± 0.3Ma | |||||||||
 Mollweide map of Earth 200 million years ago, with black outlines depicting countries in their locations | |||||||||
| Chronology | |||||||||
| |||||||||
| Etymology | |||||||||
| Name formality | Formal | ||||||||
| Usage information | |||||||||
| Celestial body | Earth | ||||||||
| Regional usage | Global (ICS) | ||||||||
| Time scale(s) used | ICS Time Scale | ||||||||
| Definition | |||||||||
| Chronological unit | Age | ||||||||
| Stratigraphic unit | Stage | ||||||||
| Time span formality | Formal | ||||||||
| Lower boundary definition | FAD of theAmmonitePsiloceras spelae tirolicum. | ||||||||
| Lower boundary GSSP | Kuhjoch section,Karwendel mountains,Northern Calcareous Alps,Austria 47°29′02″N11°31′50″E / 47.4839°N 11.5306°E /47.4839; 11.5306 | ||||||||
| Lower GSSP ratified | 2010[2] | ||||||||
| Upper boundary definition | FAD of the AmmonitesVermiceras quantoxense andVermiceras palmeri | ||||||||
| Upper boundary GSSP | East Quantoxhead,West Somerset,England,UK 51°11′27″N3°14′11″W / 51.1909°N 3.2364°W /51.1909; -3.2364 | ||||||||
| Upper GSSP ratified | 2000[3] | ||||||||
TheHettangian is the earliestage and loweststage of theJurassicPeriod of thegeologic timescale. It spans the time between 201.3 ± 0.2Ma and 199.3 ± 0.3 Ma (million years ago).[4] The Hettangian follows theRhaetian (part of theTriassic Period) and is followed by theSinemurian.[5]
In European stratigraphy the Hettangian is a part of the time span in which theLias was deposited. An example is the BritishBlue Lias, which has an upper Rhaetian to Sinemurian age. Another example is the lower Lias from theNorthern Limestone Alps where well-preserved but very rare ammonites, includingAlsatites, have been found.
The Hettangian was introduced in the literature by Swiss palaeontologist,Eugène Renevier, in 1864. The stage takes its name fromHettange-Grande, a town in north-easternFrance, just south of the border withLuxembourg on the main road fromLuxembourg City toMetz.
The base of the Hettangian Stage (which is also the base of the Lower JurassicSeries and the entire JurassicSystem) is defined as the place in the stratigraphic column where fossils of theammonitegenusPsiloceras first appear. A global reference profile (aGSSP) for the base was defined 2010 for an exposure of theKendlbach Formation at theKuhjoch section in theKarwendel Mountains of westernAustria.[6] The top of the Hettangian Stage (the base of the Sinemurian) is at the first appearances of ammonitegeneraVermiceras andMetophioceras.
The Hettangian contains three ammonitebiozones in theTethys domain:
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