GSSP for Sheinwoodian Stage
The base of the Wenlock Series and Sheinwoodian Stage is located at the base of the Buildwas Formation along the northern bank of Hughley Brook, 200m south-east of Leasows Farm.
The GSSP is located along the northern bank of Hughley Brook at SO 5688 9839, 200m south-east of Leasows Farm and 500m north-east of Hughley Church.
The GSSP lies at the base of Unit G of the Buildwas Formation. Unit G is comprised of grey-green mudstones at the base, becoming blue-grey upwards, with comminuted bryozoans, pelmatozoans, brachiopods, corals, etc.
The base of the Sheinwoodian Stage lies close to the base of the Cyrtograptus centrifugus Graptolite Biozone.
Basal beds of the Buildwas Formation contain diverse conodonts of the Pterospathodus amorphognathoides interval.
Imprecise. Between the base of acritarch biozone 5 and LAD of conodont Pterospathodus amorphognathoides. The current GSSP does not coincide with the base of the Cyrtograptus centrifugus Biozone, as was supposed when the GSSP was defined. Restudy recommends a slightly higher and correlatable level on condonts -- the Ireviken datum 2, which coincides approximately with the base of the murchisoni Graptolite Biozone
Other Locations around the World:
Holland, C. H. and Bassett, M. G., 1989 (eds.). A global standard for the Silurian System. National Museum of Wales, Geological Series 9, Cardiff.
Notes on Derivation of Age:
Bassett, M. G., 1989. The Wenlock Series in the Wenlock 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. 51-73, Cardiff.