In the

geologic timescale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochr ...

, the Telychian is the age of the Llandovery Epoch of the

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleoz ...

Period of the

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ...

Era of the

Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period, when anim ...

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 In the geologic timescale, the Sheinwoodian is the age of the Wenlock Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that is comprehended between 433.4 ± 0.8 Ma and 430.5 ± 0.7 Ma (million years ago), approximatel ...

Age. The name of the interval is derived from the Pen-lan-Telych Farm near

Llandovery Llandovery (; cy, Llanymddyfri ) is a market town and community in Carmarthenshire, Wales. It lies on the River Tywi and at the junction of the A40 and A483 roads, about north-east of Carmarthen, north of Swansea and west of Brecon. Hi ...

, Powys,

Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...

. The GSSP is located within the Wormwood Formation. It ended with the

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, ). The event is best recorded at Irevik ...

Ireviken event

The

was the first of three relatively minor

extinction event An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. I ...

s (the Ireviken, Mulde, and

Lau Lau or LAU may refer to: People * Lau (surname) * Liu (劉/刘), a common Chinese family name transliterated Lau in Cantonese and Hokkien * Lau clan, one of the Saraswat Brahmin clans of Punjab * LAU (musician): Laura Fares Places * Lebane ...

events) during the Silurian Period. It occurred at the

/ Wenlock boundary (mid Silurian, ). The event is best recorded at Ireviken,

Gotland Gotland (, ; ''Gutland'' in Gutnish), also historically spelled Gottland or Gothland (), is Sweden's largest island. It is also a province, county, municipality, and diocese. The province includes the islands of Fårö and Gotska Sandön to ...

, where over 50% of

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

species became extinct; 80% of the global

conodont Conodonts ( Greek ''kōnos'', " cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, whi ...

species also become extinct in this interval.

Anatomy of the event

The event lasted around 200,000 years, spanning the base of the Wenlock Epoch. It comprises eight extinction "datum points"—the first four being regularly spaced, every 30,797 years, and linked to the Milankovic obliquity cycle. The fifth and sixth probably reflect maxima in the precessional cycles, with periods of around 16.5 and 19 ka. The final two data are much further spaced, so harder to link with Milankovic changes.

Effects

The mechanism responsible for the event originated in the deep oceans, and made its way into the shallower shelf seas. Correspondingly, shallow-water reefs were barely affected, while

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

and hemipelagic organisms such as the graptolites, conodonts and trilobites were hit hardest.

Geochemistry

Subsequent to the first extinctions, excursions in the δ¹³C and δ¹⁸O records are observed; δ¹³C rises from +1.4‰ to +4.5‰, while δ¹⁸O increases from −5.6‰ to −5.0‰.

References

Llandovery epoch Silurian geochronology {{geochronology-stub