GSSP for Givetian Stage
Definition:
The GSSP for the Givetian Stage is placed at the base of Bed 123 in a section at Jebel Mech Irdane in the Tafilalt of Morocco. The Eifelian-Givetian boundary coincides with the level at which conodont Polygnathus pseudofoliatus changes to Polygnathus hemiansatus. The boundary corresponds closely with the base of the goniatite Maenioceras Stufe used as a Middle Devonian division, and the entry of the dacryoconarid Nowakia otomari.
Location:
The GSSP is located at Jebel Mech Irdane, 25 km SSW of Erfoud and 12km SW of Rissani, Morocco. 1:100 000 Carte du Maroc, Feuille NH-30-XX-2, Erfoud, Lambert's coordinates: x = 599 2, y = 470 6. The locality is about 6 km from the metalled Msissi road west of Rissani and easily reached by four-wheel-drive vehicles. The GSSP is at the base of Bed 123 in the succession.
The ridge of Jebel Mech Irdane is 4 km long and exposes a full and fossiliferous succession from the Emsian to the Frasnian. The GSSP section consists mainly of pelagic calcilutites and micrites with black shales at the Kacak Event level. The Kacak Event or otomari or rouvillei Event is a widespread hypoxic sedimentary perturbation near the Eifelian - Givetian Boundary.
Primary Markers:
The Eifelian-Givetian boundary coincides with the level (Bed 123) at which conodont Polygnathus pseudofoliatus changes to Polygnathus hemiansatus.
Secondary Markers:
Goniatites:
The base of the Maenioceras Stufe lies only fractionally below the GSSP.
Correlation Events:
Conodont FAD Polygnathus hemiansatus
Other Locations around the World:
Polygnathus hemiansatus can be recognized in the Cantabrian Mountains of Spain, in the Montagne Noir, France, in the Ardennes of Belgium, and the Rhenish and Eifel Mountains of Germany.