GSSP for Frasnian Stage
Definition:
The base of the Frasnian Stage which coincides with the base of the Upper Devonian is defined at the base of Bed 42' at Col du Puech de la Suque section E in southeastern Montagne Noire, France. The GSSP also coincides with the lower boundary of the Lowerasymmetricus Zone which is defined by the first occurrence of the conodontAncyrodella rotundiloba.
Location:
The GSSP section is located at Col du Puech de la Suque section E in southeastern Montagne Noire, France. The section is located on the eastern slope of the hill 358, about 50m ENE from the crest, at 1.1km SE of St. Nazaire-de-Ladarez (1:25 000 Sheet St. Chinian, x = 660.67, y = 133.95).
Section E is characterized by a sequence of predominantly red and grey pelagic calcilutites, punctuated by hardgrounds that are mainly in the part of the sequence above the boundary level.
Primary Markers:
The GSSP coincides with the first occurrence of the conodont speciesAncyrodella rotundiloba.
There are 5 conodont associations recognizable in the section. In ascending order:
- an interval in the lowest part of the zone characterized by the early form ofAncyrodella rotundiloba.
- an interval with both early and late forms ofAncyrodella rotundiloba.
- an interval with the early form ofAncyrodella alata and late form ofAncyrodella rotundiloba.
- an interval withAncyrodella rugosa and the late forms ofAncyrodella alata andAncyrodella rotundiloba.
- an interval withAncyrodella africana, Ancyrodella pramosica, the late forms ofAncyrodella alata andAncyrodella rugosa (only in the lower part).
Secondary Markers:
Goniatites:
The goniatitesProbeloceras andPetteroceras feisti first appear low in the Lowerasymmetricus Zone.
Correlation Events:
Conodont FADAncyrodella rotundiloba