GSSP for Gorstian Stage
Definition:
The base of the Gorstian Stage (Ludlow Series) is defined at Pitch Coppice Quarry near Ludlow, UK. It coincides with the rapid transition from the hard nodular limestones of the Much Wenlock Limestone Formation (Homerian) into the softer, predominantly argillaceous siltstones of the Lower Elton Formation (Gorstian).
Location:
The GSSP is located at Pitch Coppice Quarry (SO 4723 7298), a disused quarry about 4.5km west-south-west of Ludlow, UK, on the south side of the Ludlow-Wigmore road.
The Much Wenlock Limestone Formation (Homerian) consists mainly of nodular limestones. The GSSP of the Gorstian Stage coincides with the base of the Lower Elton Formation. The GSSP is defined at the rapid transition from the hard nodular limestones of the Much Wenlock Limestone Formation into the softer, predominantly argillaceous siltstones of the Lower Elton Formation.
Primary Markers:
Graptolites:Saetograptus (Colonograptus) varians and ?Neodiversograptus nilssoni occur 0.03m and 0.23m, respectively, above the base of Gorstian stage boundary. Acritarchs: The junction between Dorning's (1981) acritarch zones W3 and L1 is at 0.6m above the base of Gorstian stage boundary.
Correlation Events:
Graptolite FAD Saetograptus (Colonograptus) varians
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.