Floian
The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from 477.7 to 470 million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.
| Floian | |||||||||||
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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 Graptolite Tetragraptus approximatus | ||||||||||
| Lower boundary GSSP | Diabasbrottet quarry, Västergötland, Sweden 58.3589°N 12.5024°E | ||||||||||
| Lower GSSP ratified | 2002 | ||||||||||
| Upper boundary definition | FAD of the Conodont Baltoniodus triangularis | ||||||||||
| Upper boundary GSSP | Huanghuachang section, Huanghuachang, Yichang, China 30.8605°N 111.3740°E | ||||||||||
| Upper GSSP ratified | 2007 | ||||||||||
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