Hettangian
The Hettangian is the earliest age and 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.
| Hettangian | |||||||||
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| Chronology | |||||||||
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| Etymology | |||||||||
| Name formality | Formal | ||||||||
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| 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 the Ammonite Psiloceras spelae tirolicum. | ||||||||
| Lower boundary GSSP | Kuhjoch section, Karwendel mountains, Northern Calcareous Alps, Austria 47.4839°N 11.5306°E | ||||||||
| Lower GSSP ratified | 2010 | ||||||||
| Upper boundary definition | FAD of the Ammonites Vermiceras quantoxense and Vermiceras palmeri | ||||||||
| Upper boundary GSSP | East Quantoxhead, West Somerset, England, UK 51.1909°N 3.2364°W | ||||||||
| Upper GSSP ratified | 2000 | ||||||||
In European 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 Limestone Alps where well-preserved but very rare ammonites, including Alsatites, have been found.
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