GSSP for Emsian Stage
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 Eocostapolygnathus
kitabicus
within the phylogenetic succession from Eocostapolygnathus
pireneae to
Eocostapolygnathus 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 Eocostapolygnathus kitabicus within the
phylogenetic
succession from Eocostapolygnathus pireneae to
Eocostapolygnathus 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,
Eocostapolygnathus kitabicus. Some conodont workers regard
Eocostapolygnathus kitabicus as a junior synonym to
Polygnathus
dehiscens.
Correlation Events:
Conodont FAD Eocostapolygnathus kitabicus. New Emsian base under
discussion,
potentially FAD of Eocostapolygnathus excavatus
Other Locations around the World:
The phylogenetic lineage from Eocostapolygnathus
pireneae to
Eocostapolygnathus
kitabicus can be recognized in Spain, Australia,
North America, Tajikistan and China.
Additional Comments:
Name change from Polygnathus kitabicus to Eocostapolygnathus
kitabicus,
Name change from Polygnathus pireneae to Eocostapolygnathus
pireneae
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.
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