The base of the Middle Devonian Series and Eifelian Stage is exposed in the Wetteldorf Richtschnitt at 21.25m above the base of the exposed section, near the town of Schönecken-Wetteldorf, Eifel Hills, Germany. The Emsian-Eifelian boundary coincides with the first occurrence of the conodont Polygnathus costatus partitus.
The GSSP is located in the Wetteldorf Richtschnitt, near the town of Schönecken-Wetteldorf, Eifel Hills, Germany (Schönecken mapsheet 1:25000, r 33 765; h 57 130). The boundary section is exposed for a length of 45m in a nearly N-S trench, situated about 650m SE of the Wetteldorf church.
The GSSP lies within the Upper Heisdorf Formation. The Upper Heisdorf Formation comprises grey and green mudstones and siltstones with little carbonate content and a few argillaceous limestone beds or calcareous sandstones. Toward the top there is a distinct increase of regularly interbedded carbonate beds. The GSSP lies within a 5cm thick layer of fine-grained crinoidal calcarenitic limestone, at 21.25m above the base of the exposed section, and just below the bentonite layer Horologium II. The GSSP is 1.9m below the base of the Lauch Formation.
The base of the Eifelian Stage coincides with the first occurrence of the conodont Polygnathus costatus partitus. Conodont Icriodus corniger retrodepressus enters low in the partitus Zone. This conodont is easily recognizable and permits correlations with sequences in the Ardennes, Spain, and England.
Conodont FAD Polygnathus costatus partitus
A parastratotype for the base of the Eifelian Stage is located within the pelagic Trebotov Limestone at Prastav Quarry, near Prague, Czech Republic.