GSSP for the Base of Sheinwordian


Definition:

The base of the Wenlock Series coincides with the base of the Sheinwoodian Stage. The GSSP for the Sheinwoodian Stage is along the northern bank of Hughley Brook, 200m south-east of Leasows Farm. The GSSP is at the base of the Buildwas Formation.


Location:

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.
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Sedimentology:

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.
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Primary Markers:

The base of the Sheinwoodian Stage lies close to the base of the Cyrtograptus centrifugus Graptolite Biozone.

Secondary Markers:

Conodonts:
Basal beds of the Buildwas Formation contain diverse conodonts of the Pterospathodus amorphognathoides interval.

Other Locations around the World:

See: Holland, C. H. and Bassett, M. G. (eds.). A global standard for the Silurian System. National Museum of Wales, Geological Series 9, Cardiff.

References:

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.