Late Triassic

Key takeaways

Late Triassic 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 Late Triassic to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Late Triassic from memory before moving on to harder problems.

Reference excerpt

The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between 237 Ma and 201.4 Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. The corresponding series of rock beds is known as the Upper Triassic. The Late Triassic is divided into the Carnian, Norian and Rhaetian ages. Many of the first dinosaurs evolved during the Late Triassic, including Plateosaurus, Coelophysis, Herrerasaurus, and Eoraptor. The Triassic–Jurassic extinction event began during this epoch and is one of the five major mass extinction events of the Earth.

Etymology The Triassic was named in 1834 by Friedrich August von Namoh, after a succession of three distinct rock layers (Greek triás meaning 'triad') that are widespread in southern Germany: the lower Buntsandstein (colourful sandstone), the middle Muschelkalk (shell-bearing limestone) and the upper Keuper (coloured clay). The Late Triassic Series corresponds approximately to the middle and upper Keuper.

Dating and subdivisions On the geologic time scale, the Late Triassic is usually divided into the Carnian, Norian, and Rhaetian ages, and the corresponding rocks are referred to as the Carnian, Norian, and Rhaetian stages. Triassic chronostratigraphy was originally based on ammonite fossils, beginning with the work of Edmund von Mojsisovics in the 1860s. The base of the Late Triassic (which is also the base of the Carnian) is set at the first appearance of an ammonite, Daxatina canadensis. In the 1990s, conodonts became increasingly important in the Triassic timescale, and the base of the Rhaetian is now set at the first appearance of a conodont, Misikella posthernsteini. As of 2010, the base of the Norian has not yet been established, but will likely be based on conodonts. The late Triassic is also divided into land-vertebrate faunachrons. These are, from oldest to youngest, the Berdyankian, Otischalkian, Adamanian, Revueltian and Apachean.

Late Triassic life

Following the Permian–Triassic extinction event, surviving organisms diversified. On land, archosauriforms, most notably the dinosaurs became an important faunal component in the Late Triassic. Likewise, bony fishes diversified in aquatic environments, most notably the Neopterygii, to which nearly all extant species of fish belong. Among the neopterygians, stem-group teleosts and the now extinct Pycnodontiformes became more abundant in the Late Triassic.

Carnian Age

The Carnian is the first age of the Late Triassic, covering the time interval from 237 to 227 million years ago. The earliest true dinosaurs likely appeared during the Carnian and rapidly diversified. They emerged in a world dominated by crurotarsan archosaurs (ancestors of crocodiles), predatory phytosaurs, herbivorous armored aetosaurs, and giant carnivorous rauisuchians, which the dinosaurs gradually began to displace. The emergence of the first dinosaurs came at about the same time as the Carnian pluvial episode, at 234 to 232 Ma. This was a humid interval in the generally arid Triassic. It was marked by high extinction rates in marine organisms, but may have opened niches for the radiation of the dinosaurs.

Norian Age

The Norian is the second age of the Late Triassic, covering the time interval from about 227 to 208.5 million years ago. During this age, herbivorous sauropodomorphs diversified and began to displace the large herbivorous therapsids, perhaps because they were better able to adapt to the increasingly arid climate. However crurotarsans continued to occupy more ecological niches than dinosaurs. In the oceans, neopterygian fish proliferated at the expense of ceratitid ammonites. The Manicouagan impact event occurred 214 million years ago. However, no extinction event is associated with this impact.

Rhaetian Age

The Rhaetian Age was the final age of the Late Triassic, following the Norian Age, and it included the last major disruption of life until the end-Cretaceous mass extinction. This age of the Triassic is known for its extinction of marine reptiles, such as nothosaurs and shastasaurs with the ichthyosaurs, similar to today's dolphin. This age was concluded with the disappearance of many species that removed types of plankton from the ocean, as well as some organisms known for reef-building, and the pelagic conodonts. In addition to these species that became extinct, the straight-shelled nautiloids, placodonts, bivalves, and many types of reptile did not survive through this age.

Climate and environment during the Triassic Period During the beginning of the Triassic Period, the Earth consisted of a giant landmass known as Pangea, which covered about a quarter of Earth's surface. Towards the end of the period, continental drift occurred which separated Pangea. At this time, polar ice was not present because of the large differences between the equator and the poles. A single, large landmass similar to Pangea would be expected to have extreme seasons; however, evidence offers contradictions. Evidence suggests that there is arid climate as well as proof of strong precipitation. The planet's atmosphere and temperature components were mainly warm and dry, with other seasonal changes in certain ranges. The Middle Triassic was known to have consistent intervals of high levels of humidity. The circulation and movement of these humidity patterns, geographically, are not known however. The major Carnian Pluvial Event stands as one focus point of many studies. Different hypotheses of the events occurrence include eruptions, monsoonal effects, and changes caused by plate tectonics. Continental deposits also support certain ideas relative to the Triassic Period. Sediments that include red beds, which are sandstones and shales of color, may suggest seasonal precipitation. Rocks also included dinosaur tracks, mudcracks, and fossils of crustaceans and fish, which provide climate evidence, since animals and plants can only live during periods of which they can survive through.

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Illustrations

Worked examples

Example 1 — a first encounter with Late Triassic

Start with the simplest possible case. Write down what Late Triassic 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 Late Triassic 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 Late Triassic 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 Late Triassic

In research: Late Triassic 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 Late Triassic 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: Late Triassic is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geological epochs, Late Triassic, Triassic, so understanding it makes those chapters shorter.
In everyday life: Look for Late Triassic 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.

How to study Late Triassic in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Late Triassic 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 Late Triassic out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Late Triassic in simple terms?

The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between 237 Ma and 201.4 Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch.

Why does Late Triassic 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 Late Triassic?

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 Late Triassic.