Ludfordium

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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 Ludfordium is in the Earth's lower stratigraphic level of Ludlow - Series of the Silurian . Expressed in absolute numbers ( geochronologically ), the level ranges from about 425.6 million years to about 423 million years. The level follows the Gorstium and is replaced by the Pridolium series, which is not divided into levels.

Naming and history

The step is to Ludford Park and Ludford Bridge (over the River Teme ) near Ludlow ( Shropshire , England named). The name was suggested by English geologists Charles H. Holland , James D. Lawson , Victor G. Walmsley, and Dennis E. White in 1980. A small extinction event also began in the Ludfordium: the Lau event.

Definition and GSSP

The lower limit of the level is only imprecisely defined. It is located near the base of the Saetograptus leintwardinensis - graptolite zone. The upper limit (and at the same time the lower limit of the pridolium ) is determined by the first appearance of the graptolite species Monograptus parultimus . The official reference profile of the International Commission for Stratigraphy ( GSSP = "Global Stratotype Section and Point") is in the Sunnyhill quarry near Ludlow ( Shropshire , England ).

Breakdown

The Ludfordium can be subdivided into four conodont zones and three graptolite zones, which, however, have different ranges.

Conodonts:

Graptolites:

literature

  • Felix M. Gradstein, James G. Ogg, and Alan G. Smith (Eds.): A Geologic Time Scale 2004 . Cambridge University Press, Cambridge (UK) 2005. ISBN 0-521-78673-8
  • Charles H. Holland, James D. Lawson, Victor G. Walmsley & Dennis E. White: Ludlow Stages . In: Lethaia. 13: 268, Oslo 1980 ISSN  0024-1164
  • James D. Lawson and Dennis E. White: The Ludlow Series in the Ludlow Area. In: CH Holland and MG Bassett (eds.): A global standard for the Silurian System. In: National Museum of Wales, Geological Series. 9: 73-90, Cardiff 1989 ZDB -ID & key = zdb 995874-5 .

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