earth science

Tournaisian

Tournaisian is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tournaisian rather than just read about it. In short: The Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The Tournaisian age lasted from 358.86 Ma to 346.7 Ma.

Key takeaways

Tournaisian belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tournaisian to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tournaisian from memory before moving on to harder problems.

Reference excerpt

The Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The Tournaisian age lasted from 358.86 Ma to 346.7 Ma. It is preceded by the Famennian (the uppermost stage of the Devonian) and is followed by the Viséan. In global stratigraphy, the Tournaisian contains two substages: the Hastarian (lower Tournaisian) and Ivorian (upper Tournaisian). These two substages were originally designated as European regional stages.

Name and regional alternatives The Tournaisian was named after the Belgian city of Tournai. 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 American Kinderhookian and lower Osagean stages and the Chinese Tangbagouan regional stage. In the British Isles, where the Hastarian and Ivorian are difficult to distinguish, the entire Tournaisian was equivalent to the Courceyan regional stage.

Stratigraphy The base of the Tournaisian (which is also the base of the Carboniferous system) is at the first appearance of the conodont Siphonodella 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 Lydiennes Formation of the commune of Cabrières, in the Montagne Noire (southern France). 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 species Eoparastaffella simplex (morphotype 1/morphotype 2). 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 (upper zone of Patrognathus andersoni) the lower zone of Patrognathus andersoni the zone of Patrognathus variabilis the zone of Patrognathus crassus

Paleoenvironments The Tournaisian coincides with Romer's gap, a period of remarkably few terrestrial fossils, thus constituting a discontinuity between the Devonian and the more modern terrestrial ecosystems of the Carboniferous. The middle of the Tournaisian is marked by a southern glaciation event, of a slightly lesser extent than the glaciations which swept over Gondwana in the later Carboniferous and the very end of the Devonian. During the Tournaisian, South America was located at south polar latitudes and formed the westernmost part of the supercontinent Gondwana. The southwestern coastline of Gondwana was bustling with distinctive cold-water brachiopod and bivalve faunas. Coal is less common in the Tournaisian than in the rest of the Carboniferous, and forests and swamps were at low-density despite some trees reaching heights of up to 40 meters (131 feet). Anabranching channels and anastomosing rivers (with permanent channels splitting around large vegetated islands) would not develop until the Viséan, and river systems of the Tournaisian were more similar to those of the Late Devonian.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Tournaisian

Start with the simplest possible case. Write down what Tournaisian claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tournaisian before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tournaisian ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tournaisian

In research: Tournaisian appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tournaisian in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tournaisian is common in secondary-school and first-year university syllabi. It links to neighbouring topics Carboniferous Europe, Geological ages, Mississippian geochronology, so understanding it makes those chapters shorter.
In everyday life: Look for Tournaisian outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tournaisian in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tournaisian means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tournaisian out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tournaisian in simple terms?

The Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The Tournaisian age lasted from 358.86 Ma to 346.7 Ma.

Why does Tournaisian matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tournaisian?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tournaisian.