Darriwilian
The Darriwilian is the upper stage of the Middle Ordovician. It is preceded by the Dapingian and succeeded by the Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species Undulograptus austrodentatus around 467.3 million years ago. It lasted for about 8.9 million years until the beginning of the Sandbian around 458.4 million years ago. This stage of the Ordovician was marked by the beginning of the Andean-Saharan glaciation.
| Darriwilian | |||||||||||
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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 Graptolite Undulograptus austrodentatus | ||||||||||
| Lower boundary GSSP | Huangnitang Section, Huangnitang Village, Changshan, Zhejiang, China 28.8539°N 118.4897°E | ||||||||||
| Lower GSSP ratified | 1987 | ||||||||||
| Upper boundary definition | FAD of the Graptolite Nemagraptus gracilis | ||||||||||
| Upper boundary GSSP | Fågelsång section, Sularp Brook, Skåne, Sweden 55.7137°N 13.3255°E | ||||||||||
| Upper GSSP ratified | 2002 | ||||||||||
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