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Encyclopedia > Trefawr Track

Trefawr Track, a forestry road north of Cwm-coed-Aeron Farm, Llandovery, Wales, is the location of the Global Boundary Stratotype Section and Point (GSSP) which marks the boundary between the Rhuddanian and Aeronian stages of the Silurian period on the geologic time scale. The GSSP was ratified in 1984. Llandovery (Welsh: Llanymddyfri) is a market town in Carmarthenshire, Wales, lying on the River Tywi and the A40 road. ... This article is about the country. ... A Global Boundary Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon stratigraphic section which serves as the reference section for a particular boundary on the geologic timescale. ... In the geologic timescale, the Rhuddanian is the age of the Llandovery epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that is comprehended between 443. ... In the geologic timescale, the Aeronian is the age of the Llandovery epoch of the Silurian period of the Paleozoic era of the Fanerozoic eon that is comprehended between 439 million and 436 million years ago, approximatedly. ... The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, about 443. ... // For other uses, see time scale. ...


The boundary is defined as the first appearance of the graptolite Monograptus austerus sequens (the base of the Monograptus triangulatus biozone). The section is primarily mudstone, which yields an abundance of shelly faunas. The graptolite Diplograptus elongatus occurs immediately below the boundary. First appearance datum is a term used by geologists and paleontologists to designate the first (oldest) appearance of a species in the geologic record. ... Graptolites (Graptolithina) are fossil colonial animals known chiefly from the Upper Cambrian through the Mississippian (Lower Carboniferous). ... Mudstone is a fine-grained sedimentary rock whose original constituents were clays or muds. ... Fauna is a collective term for animal life of any particular region or time. ...


References

  • Ogg, James. GSSP for the Base of Aeronian. Retrieved on 2006-07-01.

 
 

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