Question 1

How do you say Toarcian?

Accepted Answer

Toarcian is pronounced toh-AR-see-an, with the stress on the second syllable. Break it down like this: 'toh' rhymes with 'go', then 'AR' like the letter R said loudly, then 'see', then 'an'. Say it all together quickly and you get toh-AR-see-an. It sounds fancy but once you practice it a couple of times it rolls off the tongue easily.

Question 2

What does Toarcian mean?

Accepted Answer

Toarcian is named after Thouars, a small town in western France. Scientists in the 1800s studied rock layers near that town and realized they represented a specific slice of Earth's history, so they named the time period after the place. The French paleontologist Alcide d'Orbigny officially named it in 1849. The '-ian' ending is a standard suffix in geological naming that means 'belonging to' or 'of' a particular place.

Question 3

When was the Toarcian period?

Accepted Answer

The Toarcian lasted from about 184.2 million years ago to 174.7 million years ago, making it roughly 9.5 million years long. It sits within the Early Jurassic, which means dinosaurs were already walking the Earth during this time, though they were not yet the massive giants of the later Jurassic. To put that in perspective, the Toarcian ended about 174 million years before humans appeared.

Question 4

What dinosaurs lived during the Toarcian?

Accepted Answer

During the Toarcian, dinosaurs were present but not yet dominating the planet the way they would later. Early sauropodomorphs, the ancestors of massive long-necked dinosaurs like Brachiosaurus, were growing larger. Theropod dinosaurs, which were the meat-eaters, were also diversifying during this time. However, the most spectacular animals of the Toarcian were not dinosaurs at all but marine reptiles like ichthyosaurs, which ruled the warm Toarcian seas in enormous numbers.

Question 5

What was the Toarcian extinction?

Accepted Answer

The Toarcian extinction, also called the Toarcian Oceanic Anoxic Event, was a major crisis that hit around 183 million years ago. Massive volcanic eruptions in what is now southern Africa and Antarctica pumped huge amounts of carbon dioxide and methane into the atmosphere, dramatically warming the planet and stripping oxygen from the oceans. Scientists estimate that up to 80 percent of marine species went extinct during this event. It is considered one of the five major extinction events of the Mesozoic Era.

Question 6

What caused the Toarcian Oceanic Anoxic Event?

Accepted Answer

The Toarcian Oceanic Anoxic Event was caused by a giant volcanic episode called the Karoo-Ferrar large igneous province, which erupted across what is now southern Africa and Antarctica around 183 million years ago. These eruptions released enormous quantities of greenhouse gases, especially carbon dioxide and methane, triggering rapid global warming. The warming caused ocean circulation to slow down and oxygen levels in seawater to drop, creating vast dead zones on the ocean floor. The organic material preserved in those oxygen-starved sediments became some of the world's important oil source rocks.

Question 7

Where did Toarcian fossils come from?

Accepted Answer

Some of the most famous Toarcian fossils come from the Posidonia Shale in southern Germany, which has yielded hundreds of beautifully preserved ichthyosaur skeletons, complete with soft tissue outlines. Important Toarcian rocks and fossils have also been found in England, France, Portugal, Spain, Argentina, and North Africa. The sheer quality of preservation in the Posidonia Shale is extraordinary, with some specimens showing stomach contents, skin impressions, and even unborn young still inside their mothers.

Question 8

How do scientists know when the Toarcian started and ended?

Accepted Answer

Scientists use a combination of fossil evidence and radiometric dating to pin down the boundaries of the Toarcian. Ammonites, coiled marine invertebrates that evolved rapidly, are the key fossils used to identify the start and end of the Toarcian because different species appeared and disappeared at very specific times. The official starting point of the Toarcian is defined by a rock exposure called a GSSP located at Ponta do Trovao near Peniche on the coast of Portugal. Radiometric dating of volcanic ash layers within these sequences gives the actual dates of around 184.2 to 174.7 million years ago.

Question 9

What was the ocean like during the Toarcian?

Accepted Answer

Toarcian oceans were warm, shallow in many areas, and teeming with life before the Oceanic Anoxic Event struck. Ichthyosaurs, plesiosaurs, and pliosaurs hunted in warm tropical seas that covered much of what is now Europe. Ammonites were extraordinarily abundant, and fish, belemnites, and marine invertebrates filled every ecological niche. During the Oceanic Anoxic Event, however, large parts of the ocean floor became completely devoid of oxygen, killing off huge numbers of species and leaving behind distinctive black shale layers that geologists can identify around the world today.

Question 10

What came before and after the Toarcian?

Accepted Answer

The Toarcian was preceded by the Pliensbachian Age, which lasted from about 190.8 to 184.2 million years ago, and it was followed by the Aalenian Age, which began around 174.7 million years ago. All three of these stages belong to the Jurassic Period. The Pliensbachian itself also ended with some environmental disruption, and the transition into the Toarcian brought further stresses that culminated in the dramatic Toarcian Oceanic Anoxic Event.

Question 11

Who named the Toarcian and when?

Accepted Answer

The Toarcian was named in 1849 by Alcide d'Orbigny, a French naturalist and paleontologist who is considered one of the founding figures of the science of using fossils to date rock layers. D'Orbigny based his definition on rock strata exposed near the town of Thouars in the Deux-Sevres region of western France, and he named the stage after that town. He was one of the first scientists to systematically use ammonite fossils to identify and correlate geological layers across large areas.

Question 12

Is the Toarcian part of the Jurassic?

Accepted Answer

Yes, the Toarcian is a stage within the Early Jurassic Epoch, which is itself part of the larger Jurassic Period. The Jurassic Period as a whole lasted from about 201 million to 145 million years ago, and the Toarcian sits in its earlier portion, from roughly 184 to 175 million years ago. So when you think of the classic Jurassic world of dinosaurs and giant sea creatures, the Toarcian is one of its first major chapters.

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