Tremadocian
The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from 485.4 to 477.7 million years ago. The base of the Tremadocian is defined as the first appearance of the conodont species Iapetognathus fluctivagus at the Global Boundary Stratotype Section and Point (GSSP) section on Newfoundland.
| Tremadocian | |||||||||||
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| Chronology | |||||||||||
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| 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 the Conodont Iapetognathus fluctivagus. | ||||||||||
| Lower boundary GSSP | Greenpoint section, Green Point, Newfoundland, Canada 49.6829°N 57.9653°W | ||||||||||
| Lower GSSP ratified | 2000 | ||||||||||
| Upper boundary definition | FAD of the Graptolite Tetragraptus approximatus | ||||||||||
| Upper boundary GSSP | Diabasbrottet quarry, Västergötland, Sweden 58.3589°N 12.5024°E | ||||||||||
| Upper GSSP ratified | 2002 | ||||||||||
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