Trefawr Track, a forestry road north of Cwm-coed-Aeron Farm,

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

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

, is the location of the

Global Boundary Stratotype Section and Point A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...

(GSSP) which marks the boundary between the

Rhuddanian In the geologic timescale, the Rhuddanian is the first age of the Silurian Period and of the Llandovery Epoch. The Silurian is in the Paleozoic Era of the Phanerozoic Eon. The Rhuddanian Age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma (mill ...

and

Aeronian In the geologic timescale, the Aeronian is an geologic age, age of the Llandovery Epoch of the Silurian geologic period, Period of the Paleozoic geologic era, Era of the Phanerozoic geologic eon, Eon that began 440.8 ± 1.2 annum, Ma and ended 43 ...

stages of the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 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 third and shortest period of t ...

period on the

geologic time scale 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 geochro ...

. The GSSP was ratified in 1984. The boundary is defined as the

first appearance In comic books and other stories with a long history, first appearance refers to the first issue to feature a fictional character. These issues are often highly valued by collectors due to their rarity and iconic status. Reader interest in fir ...

of the

graptolite Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian ( Miaolingian, Wuliuan) through t ...

''Monograptus austerus sequens'' (the base of the ''Monograptus triangulatus'' biozone). The section is primarily

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

, which yields an abundance of shelly

fauna Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...

s. The graptolite ''Diplograptus elongatus'' occurs immediately below the boundary.

References

* Geology of Wales Stratigraphy of the United Kingdom {{paleo-site-stub