The Tournaisian is in the ICS

geologic timescale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochro ...

the lowest

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * St ...

or oldest

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

of the Mississippian, the oldest

subsystem A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and express ...

of the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous ...

. The Tournaisian age lasted from Ma to Ma. It is preceded by the

Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used b ...

(the uppermost stage of the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

) and is followed by the

Viséan The Visean, Viséan or Visian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem of the Carboniferous. The Visean lasted from to Ma. It follows th ...

Name and regional alternatives

The Tournaisian was named after the Belgian city of

Tournai Tournai or Tournay ( ; ; nl, Doornik ; pcd, Tornai; wa, Tornè ; la, Tornacum) is a city and municipality of Wallonia located in the province of Hainaut, Belgium. It lies southwest of Brussels on the river Scheldt. Tournai is part of Euromet ...

. It was introduced in scientific literature by Belgian geologist

André Hubert Dumont André — sometimes transliterated as Andre — is the French and Portuguese form of the name Andrew, and is now also used in the English-speaking world. It used in France, Quebec, Canada and other French-speaking countries. It is a variation ...

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 American Kinderhookian 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 (the upper part falls in the Viséan).

Stratigraphy

The base of the Tournaisian (which is also the base of the Carboniferous

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and express ...

) is at the first appearance of the

conodont Conodonts (Greek ''kōnos'', " cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, whic ...

Siphonodella ''Siphonodella'' is an extinct genus of conodonts. ''Siphonodella banraiensis'' is from the Late Devonian of Thailand. ''Siphonodella nandongensis'' is from the Early Carboniferous of the Baping Formation in China.New material of the Early Car ...

sulcata'' within the evolutionary lineage from ''Siphonodella praesulcata'' to ''Siphonodella sulcata''. The first appearance of

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish ...

species '' Gattendorfia subinvoluta'' is just above this and was used as a base for the Carboniferous in the past. The

GSSP A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted by ...

for the Tournaisian is near the summit of La Serre hill, in the Lydiennes Formation of the

commune A commune is an alternative term for an intentional community. Commune or comună or comune or other derivations may also refer to: Administrative-territorial entities * Commune (administrative division), a municipality or township ** Communes of ...

of Cabrières, in the

Montagne Noire The Montagne Noire ( oc, Montanha Negra, known as the 'Black Mountain' in English) is a mountain range in central southern France. It is located at the southwestern end of the Massif Central at the juncture of the Tarn, Hérault and Aude depart ...

(southern France).The GSSP was published by Paproth ''et al.'' (1991) 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 (the base of the Viséan) is at the first appearance of the

fusulinid The Fusulinida is an extinct order within the Foraminifera in which the tests are traditionally considered to have been composed of microgranular calcite. Like all forams, they were single-celled organisms. In advanced forms the test wall was di ...

species '' Eoparastaffella simplex'' (

morphotype In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative ''phenotypes'', in the population of a species. To be classified as such, morphs must occupy the same habitat at the s ...

1/morphotype 2). The Tournaisian contains eight conodont

biozone In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa, as opposed to a lithostratigraphic unit which is defined by the lithological properties o ...

s: *the zone of ''

Gnathodus ''Gnathodus'' is an extinct conodont genus in the family Idiognathodontidae. Use in stratigraphy The Tournaisian, the oldest age of the Mississippian (also known as Lower Carboniferous), contains eight conodont biozones, 3 of which are defin ...

pseudosemiglaber'' and '' Scaliognathus anchoralis'' *the zone of ''Gnathodus semiglaber'' and '' Polygnathus communis'' *the zone of '' Dollymae bouckaerti'' *the zone of ''Gnathodus typicus'' and ''

isosticha'' *the zone of ''Siphonodella quadruplicata'' and ''

Patrognathus ''Patrognathus'' is an extinct genus of conodonts. Use in stratigraphy The Tournaisian The Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The ...

andersoni'' (upper zone of ''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 Romer's gap is an example of an apparent gap in the tetrapod fossil record used in the study of evolutionary biology. Such gaps represent periods from which excavators have not yet found relevant fossils. Romer's gap is named after paleontologist ...

, a period of remarkable little terrestrial fossils, thus constituting a discontinuity between the

and the more modern terrestrial

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...

s of the Carboniferous.

References

Bibliography

* ; 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 (3), VII. * ; 2004: ''A Geologic Time Scale 2004'',

Cambridge University , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

Press * ; 2006: ''The Carboniferous system, use of the new official names for the subsystems, series and stages'', Geologica Acta 4(3), pp 403–407 * ; 2006: ''Global time scale and regional stratigraphic reference scales of Central and West Europe, East Europe, Tethys, South China, and North America as used in the Devonian–Carboniferous–Permian Correlation Chart 2003 (DCP 2003)'', Palaeogeography, Palaeoclimatology, Palaeoecology 240 (1-2): pp 318–372 * ; 1937: ''Die Devon-Karbon-Grenze'', Comptes Rendus (2) du Cinquième Congrès International de Stratigraphie et Géologie du Carbonifère, Heerlen 1935 (2), pp 703–714 * ; 1991: ''Decision on the Devonian–Carboniferous Boundary Stratotype'', Episodes 14 (4), pp 331–336

External links

Early Carboniferous timescale
at the website of the Norwegian network of offshore records of geology and stratigraphy

www.palaeos.com {{DEFAULTSORT:Tournaisian Mississippian geochronology Geological ages . Stratigraphy of Europe Tournai