GSSP for Famennian Stage
Definition:
The base of the Famennian Stage is defined in a section near the upper Coumiac Quarry, near Cessenon in southeastern Montagne Noire, France, where it coincides with the lower boundary of the lower Palmatolepis triangularis Zone. This is just above a major extinction horizon (Kellwasser Event), and coincides with the boundary between the Crickites holzapfeli Zone and the Phoenixites frechi Zone in the goniatite scale.
Location:
The GSSP section is located above the upper Coumiac Quarry, near Cessenon, Montagne Noire, France. The section is situated in the southeastern Montagne Noire, Department Hérault, District of Cessenon (topographic sheet 1:25 000, No. 2544 E, Murviellès-Béziers; Lambert's coordinates: x=130 375, y=658 55). It is adjacent to the southeastern border of the disused upper marble quarry of Coumiac, 175m WSW of the Les Granges farmhouse, about 1.5km NE of Cessenon village and 2100m SW of Causses et Veyran.
The sequence is one of pelagic calcilutites, mostly red tinted and well bedded, with bedding probably controlled by Milankovitch-Band climatic oscillations during sedimentation. The boundary is drawn between Beds 31g and 32a. Distinctive is Bed 31g which is correlated with the Upper Kellwasser Limestone of Germany and which is a hypoxic dark grey calilutite to calcarenite above which is the most marked faunal boundary.
Primary Markers:
The GSSP is defined by the abundant occurrence of the conodont species Palmatolepis triangularis in Bed 32a. The boundary corresponds to the extinction of all species of the conodonts Ancyrodella and Ozarkodina and the loss of all but a few species of Palmatolepis, Polygnathus and Ancyrognathus.
Secondary Markers:
Goniatites:
Goniatites of the Gephuroceratidae and Beloceratidae become extinct below the boundary. Crickites holzapfeli becomes extinct in Bed 31g and Phoenixites frechi has its first occurrence in Bed 32a.
Correlation Events:
Conodont FAD Palmatolepis triangularis, just above a major extinction horizon (Kellwasser Event) with conodont LADs Ancyrodella and Ozarkodina, and Goniatite LADs of Gephuroceratidae and Beloceratidae
Notes on Derivation of Age:
Devonian time scale is a statistical fit of a composite biostratigraphic zonation (based on Figure 8 of Williams et al., 2000) to selected radiometric ages