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Rhuddanian Age
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A detailed geologic time scale chart displaying Earth's history from the Hadean Eon over 4.5 billion years ago to the present, organized by eons, eras, periods, epochs, and ages with color-coded columns and corresponding dates in millions of years. A geologic time scale chart showing the Silurian period of the Paleozoic era, listing its epochs and stages with corresponding ages in millions of years ago, from 443.8 to 419.2 million years ago.
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Rhuddanian Age

geochronology
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A detailed geologic time scale chart displaying Earth's history from the Hadean Eon over 4.5 billion years ago to the present, organized by eons, eras, periods, epochs, and ages with color-coded columns and corresponding dates in millions of years.
geologic time The stratigraphic chart of geologic time.

The Rhuddanian Stage is the first of three stages within the Llandovery Series, which is the lowermost division of the Silurian Period. This stage encompasses rocks deposited between 443.4 and 440.8 million years ago, marking the beginning of the Silurian System. The Rhuddanian Stage is defined by the first appearance of specific graptolites, Akidograptus ascensus and Parakidograptus praematurus, found in the Birkhill Shale Formation in Scotland. It directly overlies the Hirnantian Stage of the Ordovician Period and precedes the Aeronian Stage. The name "Rhuddanian" originates from Cefn-Rhuddan Farm in Wales.12

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5 Britannica Sources
  1. Rhuddanian Stage
  2. Llandovery Series
  3. Rhaetian Stage
  4. geochronology - An absolute age framework for the stratigraphic time scale
  5. Carboniferous Period - Significant geologic events

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