Gorstium

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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 Gorstium is the lower chronostratigraphic stage of the Ludlow series of the Silurian in geological history . Expressed in absolute numbers ( geochronologically ), the level ranges from about 427.4 to about 425.6 million years. The level follows the homerium and is replaced by the ludfordium .

Naming and history

The step is named after a farmhouse called Gorsty on the Ludlow to Wigmore road , approximately 4.5 km southwest of Ludlow, Shropshire , England . The name was suggested by English geologists Charles H. Holland , James D. Lawson , Victor G. Walmsley, and Dennis E. White in 1980.

Definition and GSSP

The lower limit of the level has so far only been determined imprecisely. It is located just below the base of the local Leptobrachion longhopense - Acritarchenzone and probably near the base of Neodiversograptus nils soni - Graptolithenzone . The upper limit of the level has so far only been defined imprecisely; it lies near the base of the Saetograptus leintwardinensis graptolite zone. As the official reference profile (GSSP = "Global Stratotype Section and Point") for the Gorstium, a profile in the abandoned quarry "Pitch Coppice", approximately 4.5 km southwest of Ludlow on the south side of the road from Ludlow to Wigmore was established.

Breakdown

The Gorstium can be subdivided into three conodont zones and two graptolite zones, with one conodont zone remaining unnamed and the upper conodont zone extending into the following stage of the Ludfordium.

Conodonts:

Graptolites:

literature

  • Felix Gradstein, Jim Ogg, Jim & Alan Smith: A Geologic timescale. Cambridge University Press 2004, ISBN 978-0-521-78673-7 .
  • 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 .

Web links