Ludfordian

Ludfordian
	425.6 ± 0.9 – 423.0 ± 2.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Chronology
	Epochs in the Silurian -444 — – -442 — – -440 — – -438 — – -436 — – -434 — – -432 — – -430 — – -428 — – -426 — – -424 — – -422 — – -420 — – -418 — P ; a ; l ; e ; o ; z ; o ; i ; c O S; i; l; u; r; i; a; n D L L; l; a; n; d; o; v; e; r; y W; e; n; l; o; c; k L; u; d; l; o; w Přídolí E Hirnantian Rhuddanian Aeronian Telychian Sheinwoodian Homerian Gorstian Ludfordian Lochkovian ← Lau event ← Mulde event[1] ← Ireviken; event[2] Epochs of the Silurian Period. ; Axis scale: millions of years ago.;
Etymology
Name formality	Formal
Name ratified	1980[3]
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	Imprecise. Near FAD of the Graptolite Saetograptus leintwardinensis
Lower boundary definition candidates	None
Lower boundary GSSP candidate section(s)	None
Lower boundary GSSP	Sunnyhill, Ludlow, England; 52.3592°N 2.7772°W
GSSP ratified	1980[3]
Upper boundary definition	FAD of the Graptolite Monograptus parultimus.
Upper boundary GSSP	Požáry Section, Řeporyje District, Prague, Czechia; 50.0277°N 14.3249°E
GSSP ratified	1984[4][5]

In the geologic timescale, the Ludfordian is the upper of two chronostratigraphic stages within the Ludlow Series. Its age is the late Silurian period, and within both the Palaeozoic era and Phanerozoic eon. The rocks assigned to the Ludfordian date to between 425.6 ± 0.9Ma and 423. ± 2.3 Ma (million years ago). The Ludfordian Stage succeeds the Gorstian Stage and precedes the Pridoli epoch. It is named for the village of Ludford in Shropshire, England.

The Lau event is a rapid pulse of cooling during the Ludfordian, about 424 million years ago; it is identified by a pulse of extinctions and oceanic changes. It is one of the series of fast sea-level and excursions in oxygen isotope ratios that signal fast switches between warm and cold climate states, characteristic of the Silurian climatic instability. The Lau Event occurred during an extended period of elevated seawater saturation state, explained by reservoirs of the planet's fresh water being locked up in massive polar ice caps. The sudden reappearance in normally saline marine environments of stromatolites and a mass occurrence of oncoids during the event suggested that minor extinction events like the Lau Event also resulted in periods of reduced grazing pressures on surviving "disaster biota", which can be compared to the aftermath of the more catastrophic end-Ordovician and end-Permian mass extinctions.[6]

Palaeontology

Arthropods

Arthropods of the Ludfordian
Taxa	Presence	Location	Description	Images
Brontoscorpio		Trimpley, Worcestershire, UK

Plants

Plants of the Ludfordian
Taxa	Presence	Location	Description	Images
Chaetocladus capitatus		Cornwallis Island, Northern Canada[7]
Eocladus		Cornwallis Island, Northern Canada[7]

References

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.
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.
Holland, C. (1982). "The State of Silurian Stratigraphy" (PDF). Episodes. 1982: 21–23. Retrieved 11 December 2020.
Lucas, Sepncer (6 November 2018). "The GSSP Method of Chronostratigraphy: A Critical Review". Frontiers in Earth Science. doi:10.3389/feart.2018.00191. Retrieved 11 December 2020.
Holland, C. (June 1985). "Series and Stages of the Silurian System" (PDF). Episodes. 8: 101–103. doi:10.18814/epiiugs/1985/v8i2/005. Retrieved 11 December 2020.
M. Calner, "A Late Silurian extinction event and anachronistic period" Geology 33, pp. 305–308; Geology On-line Forum: response to a reply.
Steven T. LoDuca, Michael J. Melchin & Heroen Verbruggen (2011). "Complex noncalcified macroalgae from the Silurian of Cornwallis Island, Arctic Canada" (PDF). Journal of Paleontology. 85 (1): 111–121. doi:10.1666/10-025.1. Archived from the original (PDF proofs) on 2011-07-22.

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[Jeppsson2007-1] 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.

[Munnecke2003-2] 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.

[silurianState-3] Holland, C. (1982). "The State of Silurian Stratigraphy" (PDF). Episodes. 1982: 21–23. Retrieved 11 December 2020.

[4] Lucas, Sepncer (6 November 2018). "The GSSP Method of Chronostratigraphy: A Critical Review". Frontiers in Earth Science. doi:10.3389/feart.2018.00191. Retrieved 11 December 2020.

[5] Holland, C. (June 1985). "Series and Stages of the Silurian System" (PDF). Episodes. 8: 101–103. doi:10.18814/epiiugs/1985/v8i2/005. Retrieved 11 December 2020.

[6] M. Calner, "A Late Silurian extinction event and anachronistic period" Geology 33, pp. 305–308; Geology On-line Forum: response to a reply.

[Complex-7] Steven T. LoDuca, Michael J. Melchin & Heroen Verbruggen (2011). "Complex noncalcified macroalgae from the Silurian of Cornwallis Island, Arctic Canada" (PDF). Journal of Paleontology. 85 (1): 111–121. doi:10.1666/10-025.1. Archived from the original (PDF proofs) on 2011-07-22.