Llandovery (geology)

system	series	step	≈ age ( mya )
higher	higher	higher	younger
Silurian	Pridolium		419.2 ⬍ 423
	Ludlow	Ludfordium	423 ⬍ 425.6
		Gorstium	425.6 ⬍ 427.4
	Wenlock	Homerium	427.4 ⬍ 430.5
		Sheinwoodium	430.5 ⬍ 433.4
	Llandovery	Telychium	433.4 ⬍ 438.5
		Aeronium	438.5 ⬍ 440.8
		Rhuddanium	440.8 ⬍ 443.4
deeper	deeper	deeper	older

The Llandovery (according to convention correct, but completely uncommon, Llandoveryum or Llandoveryium ) is the chronostratigraphic series in the history of the earth with which the system of the Silurian began geochronologically about 443.4 million years ago . The Llandovery Series ended about 433.4 million years ago with the transition to Wenlock . It follows the Upper Ordovician series or the Hirnantium , the highest chronostratigraphic level of the Ordovician.

Naming and history

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

Definition and GSSP

The limits of the Llandovery are clearly defined by the already established limits of the levels of the Silurian. The series begins with the first appearance of the graptolite species Akidograptus ascensus ; the first appearance of the graptolite species 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 limit from the Telychium to the Sheinwoodium . This lies between the base of the Acritarchen biozone 5 and the extinction of the conodont species Pterospathodus amorphognathoides . The reference profile (GSSP = "Global Stratotype Section and Point") for the Llandovery series, the Rhuddanium stage and the Silurian is at Dob's Linn , Moffat ( Scotland ).

Breakdown

The Llandovery is divided into three stages:

• System : Silurian (443.4–419.2  mya )
  • Series : Pridolium (423–419.2 mya) (not subdivided into further stages)
  • Series: Ludlow (427.4–423 mya)
  • Series: Wenlock (433.4–427.4 mya)
  • Series: Llandovery (443.4-433.4 mya)
    • Stage: Telychium (438.5–433.4 mya)
    • Stage: Aeronium (440.8 to 438.5 mya)
    • Level: Rhuddanium (443.4–440.8 mya)

literature

• Felix Gradstein, Jim Ogg & Alan Smith: A Geologic timescale. Cambridge University Press 2004 ISBN 978-0-521-78673-7
• LR Cocks: The Ordovician-Silurian Boundary. Episodes, 8 (2): 98-100, Beijing 1985 ISSN  0705-3797 .
• MG Bassett: The Wenlock Series in the Wenlock Area. In: CH Holland and MG Bassett (eds.): A global standard for the Silurian System. National Museum of Wales, Geological Series 9: 51-73, Cardiff 1989 ZDB -ID & key = zdb 995874-5 .

Web links

• International Chronostratigraphic Chart 2012 (PDF)
• German Stratigraphic Commission, Manfred Menning (Hrsg.): Stratigraphische Tisch von Deutschland 2002 . Potsdam 2002, ISBN 3-00-010197-7 (1 sheet, Stratigraphie.de [PDF; 6.6 MB ]).
• Commission for the paleontological and stratigraphic research of Austria of the Austrian Academy of Sciences (Ed.): The Stratigraphic Table of Austria (sedimentary layer sequences). Vienna 2004 PDF (large)