Wenlock Epoch

Wenlock
433.4 ± 0.8 – 427.4 ± 0.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Map of Earth as it appeared 430 million years ago during the Wenlock epoch, Homerian stage[citation needed]
Chronology
−444 — – −442 — – −440 — – −438 — – −436 — – −434 — – −432 — – −430 — – −428 — – −426 — – −424 — – −422 — – −420 — – −418 — Paleozoic O Silurian D Late O Llandovery Wenlock Ludlow Přídolí Early D Rhuddanian Aeronian Telychian Sheinwoodian Homerian Gorstian Ludfordian             ← Lau event ← Mulde event[1] ← Ireviken event[2] Subdivision of the Silurian according to the ICS, as of 2021.[3] Vertical axis scale: millions of years ago.
Etymology
Name formality	Formal
Name ratified	1980[4]
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Epoch
Stratigraphic unit	Series
Time span formality	Formal
Lower boundary definition	Imprecise. Currently placed between acritarch biozone 5 and last appearance of Pterospathodus amorphognathoides. See Llandovery for more info.
Lower boundary definition candidates	A conodont boundary (Ireviken datum 2) which is close to the murchisoni graptolite biozone.
Lower boundary GSSP candidate section(s)	None
Lower boundary GSSP	Hughley Brook, Apedale, U.K. 52°34′52″N 2°38′20″W / 52.5811°N 2.6389°W / 52.5811; -2.6389
Lower GSSP ratified	1980[4]
Upper boundary definition	FAD of the Graptolite Saetograptus (Colonograptus) varians
Upper boundary GSSP	Pitch Coppice, Ludlow, U.K. 52°21′33″N 2°46′38″W / 52.3592°N 2.7772°W / 52.3592; -2.7772
Upper GSSP ratified	1980[4]

The Wenlock (sometimes referred to as the Wenlockian) is the second epoch of the Silurian. It is preceded by the Llandovery Epoch and followed by the Ludlow Epoch. Radiometric dates constrain the Wenlockian between 433.4 and 427.4 million years ago.^[5]