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GSSP for Sheinwoodian Stage

Definition:

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.

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. 		GSSP for Sheinwoodian Stage


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.


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.

Correlation Events:

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 Cyrtograptus murchisoni Graptolite Biozone

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.

Notes on Derivation of Age:

"

References:

Lethaia 14


Holland, C. H., 1982. The state of Silurian Stratigraphy. Episodes 5/3, p. 21-23, 1982.


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.

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