GSSP for Ludfordian Stage
Definition:
The base of the Ludfordian Stage is located at Sunnyhill Quarry, near Ludlow, Shropshire, UK.
Location:
The GSSP is located at Sunnyhill Quarry (SO 4950 7255) about 2.5km south-west of Ludlow town, Shropshire, UK. From Ludlow it is reached by the A49 and B4361 roads.
The Upper Bringewood Formation (Gorstian) consists of nodular silty limestone. The succeeding Lower Leintwardine Formation (Ludfordian) is lithological similar, but faunally distinct. The GSSP for the Ludfordian is represented as a thin shale seam, coincident with the base of the Leintwardine Formation.
Primary Markers:
Graptolites:
The most important incoming species above the GSSP is Saetograptus leintwardinensis leintwardinensis.
Secondary Markers:
Acritarchs:
Dorning's (1981) acritarch Biozone boundary L2/L3 is positioned slightly below the Gorstian-Ludfordian boundary. The incoming species of the L3 biozone are: Cymbosphaeridium pilaris, Leoniella carminae, Multiplicisphaeridium paraquaferum, Veryhachium leintwardinensis, and Leiofusa estrecha.
At or near the base of the Ludfordian Stage the following fossils either disappear or become very rare:
Brachiopods: Kirkidium knightii, Strophonella euglypha
Solitary corals: D. myops, P. globosa
Correlation Events:
Imprecise. May be near base of Saetograptus leintwardinensis Graptolite zone.
Other Locations around the World:
See:
Holland, C. H. and Bassett, M. G, 1989 (eds.). A global standard for the Silurian System. National Museum of Wales, Geological Series 9, Cardiff.
References:
Lethaia 14
Holland, C. H., 1982. The state of Silurian Stratigraphy. Episodes 5/3, p. 21-23, 1982.
Dorning, K. J., 1981. Silurian acritarchs from the type Wenlock and Ludlow of Shropshire, England. Review of Palaeobotany and Palynology 34, p. 175 - 203.
Lawson, J. D. and White, D. E., 1989. The Ludlow Series in the Ludlow Area. In: Holland, C. H. and Bassett, M. G. (eds.). A global standard for the Silurian System. National Museum of Wales, Geological Series 9, p. 73 - 90, Cardiff.