Telychian

In the geologic timescale, the Telychian is the third and final age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon. The Telychian Age was between 438.5 ± 1.2 million years ago (Ma) and 433.4 ± 0.8 Ma. The Telychian Age succeeds the Aeronian Age and precedes the Sheinwoodian Age.^[8] The name of the interval is derived from the Pen-lan-Telych Farm near Llandovery, Powys, Wales.

Telychian
438.5 ± 1.1 – 433.4 ± 0.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Paleogeography of the Telychian, 435 Ma
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 Spirograptus guerichi
Lower boundary GSSP	El Pintado section, Seville, Spain 37.9853°N 5.9285°W / 37.9853; -5.9285[4]
Lower GSSP ratified	2024[5][6]
Upper boundary definition	Imprecise. Currently placed between acritarch biozone 5 and LAD of Pterospathodus amorphognathoides. See Llandovery for more info.
Upper boundary definition candidates	A conodont boundary (Ireviken datum 2) which is close to the murchisoni graptolite biozone.
Upper boundary GSSP candidate section(s)	None
Upper boundary GSSP	Hughley Brook, Apedale, UK 52.5811°N 2.6389°W / 52.5811; -2.6389
Upper GSSP ratified	1980[7]

It ended with the Ireviken event.

Ireviken event

Main article: Ireviken event

The Ireviken event was the first of three relatively minor extinction events (the Ireviken, Mulde, and Lau events) during the Silurian Period. It occurred at the Llandovery/Wenlock boundary (mid Silurian, 432.9 ± 1.2  million years ago). The event is best recorded at Ireviken, Gotland, where over 50% of trilobite species became extinct; 80% of the global conodont species also become extinct in this interval.