Tournaisian

The Tournaisian is the oldest part of the Mississippian, which is the earliest part of the Carboniferous period. In geology, the Tournaisian is like the first chapter of an important book. It lasted from about 358.86 million years ago to 346.7 million years ago.

Before the Tournaisian was the Famennian, the last part of the Devonian period. After the Tournaisian, the next part of the Carboniferous began, called the Viséan.

Scientists split the Tournaisian into two smaller parts, called substages. The first is called the Hastarian, and the second is called the Ivorian. These names come from places in Europe where important rock layers from this time were first found. The Tournaisian helps us learn about how Earth’s surface and life changed long ago.

Name and regional alternatives

The Tournaisian was named after the city of Tournai in Belgium. A Belgian geologist named André Hubert Dumont first used this name in writing in 1832. This time period is part of the official timeline for Earth's history.

The Tournaisian has different names in different places. In North America, it is linked to the Kinderhookian and lower Osagean stages. In China, it matches the Tangbagouan stage. In the British Isles, people often call the Tournaisian the Courceyan stage.

Stratigraphy

The Tournaisian is the oldest part of the Carboniferous period. Scientists find its start by looking for a special tiny fossil called Siphonodella sulcata. These fossils help them know when this time period began.

The end of the Tournaisian is marked by another fossil called Eoparastaffella simplex. During this time, scientists found eight groups of tiny fossils. These groups help them study and split the Tournaisian into smaller parts.

Paleoenvironments

The Tournaisian period was a time of big changes for plants and animals on Earth. It matches a time called Romer's gap. During this time, scientists find very few fossils from land animals. This gap shows the difference between life forms from the Devonian period and those that came later.

A cold time called glaciation happened in the southern parts of the world. South America was near the South Pole and part of a large landmass called Gondwana. Coal was not very common yet and forests were not very thick, but some trees still grew very tall—up to 40 meters, or about 131 feet! The rivers looked different from today's rivers.

Notable formations

Some important rock layers from the Tournaisian time period include the Albert Formation in New Brunswick, Canada, and the Agua de Lucho Formation in Argentina. Other notable formations are the Ballagan Formation and Cementstone Group in Scotland, and the Herbesskaya Formation in Russia. Additional formations include the Horton Bluff Formation in Nova Scotia, Canada, the Mansfield Group in Australia, the Price Formation in West Virginia and Virginia, United States, and the Tournai Formation in Belgium.