GSSP for the Pragian - Emsian Stage Boundary


Definition:

The base of the Emsian Stage is located at the base of Bed 9/5 in the Zinzil'ban Gorge in the Kitab State Geological Reserve, 170km SSE of Samarkand, Uzbekistan. The GSSP for the Emsian Stage coincides with the first occurrence of the conodont Polygnathus kitabicus within the phylogenetic succession from Polygnathus pireneae to Polygnathus kitabicus.


Location:

The GSSP is located at the base of Bed 9/5 in the Zinzil'ban Gorge in the Kitab State Geological Reserve, 170km SSE of Samarkand, Uzbekistan. The GSSP is at a latitude of 39°12' North and a longitude of 67°18'20" E of Greenwich.
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Sedimentology:

The GSSP occurs in a relatively uniform sequence of dark micritic limestones, characterized by lack of significant abrupt faunal change. The GSSP at the base of Bed 9/5 is located 35cm above the top of the Madmon Formation on the western wall of the Zinzil'ban Gorge.
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Primary Markers:

The GSSP for the Emsian Stage coincides with the first occurrence of the conodont Polygnathus kitabicus within the phylogenetic succession from Polygnathus pireneae to Polygnathus kitabicus (formerly Polygnathus dehiscens). Because of uncertainties regarding the holotype of P. dehiscens a new specific name was proposed for a specimen from the GSSP section, Polygnathus kitabicus. Some conodont workers regard Polygnathus kitabicus as a junior synonym to Polygnathus dehiscens.

Other Locations around the World:

The phylogenetic lineage from Polygnathus pireneae to Polygnathus kitabicus can be recognized in Spain, Australia, North America, Tajikistan and China.

References:

Yolkin, E. A., Kim, A. I., Weddige, K., Talent, J. A., and House, M. R., 1997. Definition of the Pragian/Emsian Stage boundary. Episodes 20/4, p.235 240.