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GSSP for Hirnantian Stage


Definition:

The base of the Hirnantian Stage is defined at a point 0.39 m below the base of the Kuanyinchiao Bed in the Wangjiawan North Section, near Wangjiawan Village, 42 km north of Yichang City, western Hubei, China. The GSSP coincides with the first appearance datum of the graptolite Normalograptus extraordinarius.


Location:

The Wangjiawan North Section is located near Wangjiawan Village, 42 km north of Yichang City, western Hubei Province, China at a latitude of 30°58'56"N and a longitude of 111°25'10"E.
GSSP for Hirnantian Stage


Sedimentology:

At Wangjiawan the Wufeng Formation and the overlying Lungmachi Formation are characterized by black shales, dark brown siliceous shale and cherts. The Kuanyinchiao Bed consists of argillaceous limestone. The upper part of the Wufeng Formation containing the GSSP is comprised of dark brown siliceous shale.


Primary Markers:

First appearance of graptolite Normalograptus extraordinarius 0.39 m below the base of the Kuanyinchiao Bed.

Secondary Markers:

FAD of graptolite Normalograptus ojsuensis occurs 4cm below the FAD of Normalograptus extraordinarius. The Hirnantia Fauna, including trilobites, nautiloids and various microfossils, occurs in the Kuanyinchiao Bed, 39cm above the GSSP

Correlation Events:

Graptolite FAD Normalograptus extraordinarius

Other Locations around the World:

The base of the Hirnantian Stage at Wangjiawan North Section can be easily correlated with Nevada and S Kazakhstan.

References:

Chen, X., Rong, J., Fan, J., Zhan, R., Mitchell, C. E., Harper, D.A.T., Melchin, M. J., Peng, P., Finney, S. C., and Wang, X., 2006. The Global Boundary Stratotype Section and Point (GSSP) for the base of the Hirnantian Stage (the uppermost of the Ordovician System). Episodes 29/3, p. 183 - 196.



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