Wenlock Epoch

The Wenlock Epoch (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 432.9 and 426.7 million years ago.^[5]

Wenlock
433.4 ± 0.8 – 427.4 ± 0.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N
A map of Earth as it appeared 430 million years ago during the Wenlock Epoch, Homerian Age
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 2023.[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. 52.5811°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. 52.3592°N 2.7772°W / 52.3592; -2.7772
Upper GSSP ratified	1980[4]

Naming and history

The Wenlock is named after Wenlock Edge, an outcrop of rocks near the town of Much Wenlock in Shropshire (West Midlands, United Kingdom).^[6] The name was first used in the term "Wenlock and Dudley rocks" by Roderick Murchison in 1834 to refer to the limestones and underlying shales that underlay what he termed the "Ludlow rocks".^[7] He later modified this term to simply the "Wenlock rocks" in his book, The Silurian System in 1839.^[8]

Definition and subdivision

The Wenlock's beginning is defined by the lower boundary (or GSSP) of the Sheinwoodian. The end is defined as the base (or GSSP) of the Gorstian.^[9]

The Wenlock is divided into the older Sheinwoodian and the younger Homerian stage. The Sheinwoodian lasted from 432.9 to 430.6 million years ago. The Homerian lasted from 430.6 to 426.7 million years ago.^[5]