Toarcian

The Toarcian is an important time period in Earth's history, part of what scientists call the Early or Lower Jurassic. It lasted from about 184.2 million years ago to 174.7 million years ago. This age comes after the Pliensbachian and before the Aalenian in the geologic timescale.

The Toarcian began with a big change called the Toarcian Oceanic Anoxic Event. During this time, the oceans had less oxygen, which caused many sea creatures to die out and the Earth to get warmer. Because of these changes, the fossils found from this time look different from those before it.

At the end of the Toarcian, scientists think there was a cooling period known as the Comptum Cooling Event. However, there is some debate about whether this cooling happened all around the world or just in some places.

Stratigraphic definitions

The Toarcian is a time period from long ago, named after the city of Thouars in France. A scientist first described it in 1842 after looking at old rocks near that city.

During this time, special fossils called ammonites appeared. Scientists use these fossils to mark the start and end of the Toarcian. In Europe, these rocks are part of a group called the Lias. Far away, in a place called the Tethys domain, more types of ammonites lived during this time.