Silurian#Llandovery

The Llandovery ( by convention correct but completely into disuse in that Llandoveryum or Llandoveryium ) is in the geologic timescale, series, geochronological began the system of Silurian to the front of about 443 400 000 years. The Llandovery Series ended at about 433.4 million years ago with the transition to the Wenlock. It follows the Oberordovizium series or the Hirnantium, the highest chronostratigraphic stage of the Ordovician.

Naming and history

The name comes from the town of Llandovery ( Welsh: Llanymddyfri ) in Carmarthenshire (Wales ) ago. It was proposed in 1859 by Roderick Murchison.

Definition and GSSP

The boundaries of the Llandovery are uniquely defined by the already established boundaries of the stages of the Silurian. The series begins with the first appearance of the graptolite - type Akidograptus ascensus; the first appearance of the graptolite - type Parakidograptus acuminatus is only a little later (or higher in the stratigraphy ). The upper limit of the series is the ( according to recent studies ) somewhat imprecise border from Telychium to Sheinwoodium. This is between the base of acritarchs - Biozone 5 and the extinction of conodont species Pterospathodus amorphognathoides. The reference profile ( GSSP = " Global Stratotype Section and Point" ) for the Llandovery Series, which Rhuddanium - stage and the Silurian is Dob's Linn, Moffat (Scotland).

Subdivision

The Llandovery is divided into three stages:

• System: Silurian ( 443.4 to 419.2 mya ) Series: Pridolium ( 423 to 419.2 mya ) (not divided into more stages )
• Series: Ludlow ( 427.4 to 423 mya )
• Series: Wenlock ( 433.4 to 427.4 mya )
• Series: Llandovery ( 443.4 to 433.4 mya ) Level: Telychium ( 438.5 to 433.4 mya )
• Level: Aeronium ( 440.8 to 438.5 mya )
• Level: Rhuddanium ( 443.4 to 440.8 mya )