The Tournaisian was named after the Belgiancity ofTournai. It was introduced in scientific literature by Belgian geologist André Hubert Dumont in 1832. Like many Devonian and lower Carboniferous stages, the Tournaisian is a unit from West European regional stratigraphy that is now used in the official international time scale. The Tournaisian correlates with the regional North AmericanKinderhookian and lower Osagean stages and the Chinese Tangbagouan regional stage. In British stratigraphy, the Tournaisian contains three substages: the Hastarian, Ivorian and lower part of the Chadian.
Stratigraphy
The base of the Tournaisian is at the first appearance of the conodontSiphonodella sulcata within the evolutionary lineage from Siphonodella praesulcata to Siphonodella sulcata. The first appearance of ammonite species Gattendorfia subinvoluta is just above this and was used as a base for the Carboniferous in the past. The GSSP for the Tournaisian is near the summit of La Serre hill, in the commune of Cabrières, in the Montagne Noire. The GSSP is in a section on the southern side of the hill, in an 80 cm deep trench, about 125 m south of the summit, 2.5 km southwest of the village of Cabrières and 2.5 km north of the hamlet of Fontès. The top of the Tournaisian is at the first appearance of the fusulinid species Eoparastaffella simplex. The Tournaisian contains eight conodont biozones:
the zone of Gnathodus pseudosemiglaber and Scaliognathus anchoralis
the zone of Gnathodus semiglaber and Polygnathus communis
the zone of Dollymae bouckaerti
the zone of Gnathodus typicus and Siphonodella isosticha
the zone of Siphonodella quadruplicata and Patrognathus andersoni
the lower zone of Patrognathus andersoni
the zone of Patrognathus variabilis
the zone of Patrognathus crassus
The Tournaisian coincides with Romer's gap, a period of remarkable little terrestrial fossils, thus constituting a discontinuity between the Devonian and the more modern terrestrial ecosystems of the Carboniferous.
Tournaisian life
Fish
Tetrapodomorpha
Literature
; 1832: Mémoire sur la constitution géologique de la province de Liège, Mémoires couronnés par l'Académie Royale des Sciences et Belles-Lettres de Bruxelles 8, VII.
; 1937: Die Devon-Karbon-Grenze, Comptes Rendus du Cinquième Congrès International de Stratigraphie et Géologie du Carbonifère, Heerlen 1935, pp 703–714.
; 1991: Decision on the Devonian–Carboniferous Boundary Stratotype, Episodes 14, pp 331–336.
