Rhuddanian
| Rhuddanian | |||||||||||||
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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 Akidograptus ascensus | ||||||||||||
| Lower boundary GSSP | Dob's Linn, Moffat, U.K. 55°26′24″N 3°16′12″W / 55.4400°N 3.2700°W | ||||||||||||
| Lower GSSP ratified | 1984 | ||||||||||||
| Upper boundary definition | FAD of the graptolite Demirastrites triangulatus | ||||||||||||
| Upper boundary GSSP | Hlásná Třebaň section, Czech Republic 49°55′23″N 14°12′43″E / 49.9230°N 14.2119°E | ||||||||||||
| Upper GSSP ratified | 2024 | ||||||||||||
In the geologic timescale, the Rhuddanian is the first age of the Silurian Period and of the Llandovery Epoch. The Silurian is in the Paleozoic Era of the Phanerozoic Eon. The Rhuddanian Age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma (million years ago). It succeeds the Hirnantian Age (the last age of the Ordovician Period) and precedes the Aeronian Age.