| System (period) | Series | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Devonian | Lower | Lochkovian | 419.2±3.2 | |
| Silurian | Pridoli |  423.0±2.3
| ||
| Ludlow | Ludfordian | 425.6±0.9
| ||
| Gorstian | 427.4±0.5
| |||
| Wenlock | Homerian | 430.5±0.7
| ||
| Sheinwoodian | 433.4±0.8
| |||
| Llandovery | Telychian | 438.5±1.1
| ||
| Aeronian | 440.8±1.2
| |||
| Rhuddanian | 443.8±1.5
| |||
| Ordovician | Upper | Hirnantian | older | |
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] | ||||
The Rhuddanian is the beginning age of the Silurian period and the Llandovery epoch. It began 443 million years ago and ended 440 million years ago. It is preceded by the Hirnantian age of the Ordovician era and is preceded by theAeronian.
GSSP[]
The GSSP for this age is located in Scotland. It can be found in a fake excavation just north of the Linn Branch Stream. There are also two geological units located nearby. The lower half consists mainly of pale gray mudstone with subordinate black shales and several interbedded meta-bentonites.
The upper half contains predominantly black graptolitic shale with subordinate gray mudstones and meta-bentonites.
Naming[]
It was named for the Cefn-Rhuddan Farm in Wales.
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.