Rhuddanian

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.^[9] 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.^[10]

Rhuddanian
443.8 ± 1.5 – 440.8 ± 1.2 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Chronology
−444 — – −442 — – −440 — – −438 — – −436 — – −434 — – −432 — – −430 — – −428 — – −426 — – −424 — – −422 — – −420 — – −418 — Paleozoic O Silurian D L Llandovery Wenlock Ludlow Přídolí E Hirnantian Rhuddanian Aeronian Telychian Sheinwoodian Homerian Gorstian Ludfordian Lochkovian             ← Lau event ← Mulde event[1] ← Ireviken event[2] Subdivision of the Silurian according to the ICS, as of 2023.[3] Vertical axis scale: Millions of years ago
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. 55.4400°N 3.2700°W / 55.4400; -3.2700
Lower GSSP ratified	1984[4][5]
Upper boundary definition	FAD of the graptolite Demirastrites triangulatus
Upper boundary GSSP	Hlásná Třebaň section, Czech Republic 49.9230°N 14.2119°E / 49.9230; 14.2119[6]
Upper GSSP ratified	2024[7][8]

GSSP

The GSSP for the Silurian is located in a section at Dob's Linn, Scotland, in an artificial excavation created just north of the Linn Branch Stream. Two lithological units (formations) occur near the boundary.^[9] The lower is the Hartfell Shale (48 metres (157 ft) thick), consisting chiefly of pale gray mudstone with subordinate black shales and several interbedded meta-bentonites.^[9] Above this is the 43 metres (141 ft) thick Birkhill Shale, which consist predominantly of black graptolitic shale with subordinate gray mudstones and meta-bentonites.^[11]

The name is given after Cefn-Rhuddan Farm, Llandovery in Carmarthenshire, Wales.

See also

• Ordovician-Silurian extinction events
• Early Palaeozoic Icehouse

References

1. Jeppsson, L.; Calner, M. (2007). "The Silurian Mulde Event and a scenario for secundo—secundo events". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 93 (02): 135–154. doi:10.1017/S0263593300000377.
2. Munnecke, A.; Samtleben, C.; Bickert, T. (2003). "The Ireviken Event in the lower Silurian of Gotland, Sweden-relation to similar Palaeozoic and Proterozoic events". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (1): 99–124. doi:10.1016/S0031-0182(03)00304-3.
3. "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. September 2023. Retrieved December 16, 2024.
4. Lucas, Spencer (6 November 2018). "The GSSP Method of Chronostratigraphy: A Critical Review". Frontiers in Earth Science. 6: 191. Bibcode:2018FrEaS...6..191L. doi:10.3389/feart.2018.00191.
5. Holland, C. (June 1985). "Series and Stages of the Silurian System" (PDF). Episodes. 8 (2): 101–103. doi:10.18814/epiiugs/1985/v8i2/005. Retrieved 11 December 2020.
6. "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 3 August 2024.
7. "Silurian Telychian and Aeronian stage GSSPs have been relocated". stratigraphy.org. International Commission on Stratigraphy. Retrieved 1 March 2024.
8. Štorch, Petr. "Formal proposal for a new Global Boundary Stratotype Section and Point (GSSP) for the Aeronian Stage at Hlásná Třebaň, Czech Republic" (PDF). International Commission on Stratigraphy. Retrieved 16 April 2024.
9. Gradstein, Felix M.; Ogg, James G.; Smith, Alan G. (2004). A Geologic Time Scale 2004. Cambridge University Press. ISBN 9780521786737.
10. "GSSP Table - All Periods". International Commission on Stratigraphy. Retrieved 15 September 2018.
11. "GSSP for the Rhuddanian Stage". International Commission on Stratigraphy.