Toarcian

The Toarcian is a time period from Earth's past. It was part of the Early Jurassic, and it lasted from about 184.2 million years ago to 174.7 million years ago. It came after the Pliensbachian and was followed by the Aalenian. Scientists study the Toarcian to learn about changes on Earth and its plants and animals from long ago.

The start of the Toarcian Age had a big change called the Toarcian Oceanic Anoxic Event. During this time, the oceans had less oxygen. This caused many sea creatures to die out and made the weather warmer around the world. Because of this event, fossils from this time look very different from fossils before it.

At the end of the Toarcian, Earth went through a cooler time called the Comptum Cooling Event. Scientists are still talking about whether this cooling happened everywhere or just in some places.

Stratigraphic definitions

The Toarcian gets its name from the city of Thouars in the Loire Valley of France. This time period was first described in 1842 by a scientist named Alcide d'Orbigny. He studied rock strata near Thouars.

In Europe, the Toarcian is part of a layer of rocks called the Lias. Scientists mark the beginning of the Toarcian by looking for the first appearance of a special type of fossil shell. This shell is called the ammonite genus Eodactylites. The end of the Toarcian is marked by the appearance of another ammonite genus called Leioceras.